The correct way to make welded splice joints in chassis members

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  • Опубліковано 28 вер 2024
  • In this video I debunk the myth that the correct way to make splice joints in chassis members is with an inclined or Z cut. These are scarf joints which have been used for centuries in timber structures but have no place in welded steel structures.
    I also address the supposed regulatory requirements about this which apply in certain parts of the world.
    Of necessity this is a technical video although I have tried to make the concepts understandable to non-engineers.
    This is a re-posted video with the new content appearing at 16.30.
    This video builds on ideas introduced in my earlier video on chassis repairs (please watch this first)
    • Rustproofing and chass...
    Those who want to learn more about the methods used in this video are encouraged to look at the following videos:
    Beam stresses • Understanding Stresses...
    Mohr's circle • 08.2 Mohr's circle for...
    Failure theories • Understanding Failure ...
    Mohr's circle and failure theories • Yield Criteria for Duc...

КОМЕНТАРІ • 594

  • @johna7661
    @johna7661 8 місяців тому +68

    As a young welder I worked at an outfit that repaired tankers that had been damaged or needed refurbishing. We lengthened frames, sometimes on brand new trucks. We cut the frame 90 degrees and butt spliced the extension piece. We backed it up with plates on the sides and stress relieved the area. That’s all we did, right or wrong and never had a problem.

    • @defendermodsandtravels
      @defendermodsandtravels  8 місяців тому +13

      All very good but why did the reinforcing plates go on the sides (webs) where the stresses are lowest.
      Stress relieving is great but very unusual on thin sections.

    • @modquad18
      @modquad18 8 місяців тому +6

      How did you stress relieve?

    • @johna7661
      @johna7661 8 місяців тому +16

      We heated the area evenly with a rosebud and let it cool. I was following the boss’s instructions, 1970, I didn’t know jack about it at the time. Still don’t…

    • @Bighorn_built
      @Bighorn_built 7 місяців тому +9

      ​@johna7661 I have heard of that referred to as normalizing, it does exactly what you were told it does. It allows the grain of the steel relax and find the spot it wants to be in. Just be weary of warpage in longer parts.

    • @GenasysMech
      @GenasysMech 7 місяців тому +3

      Spot on in my opinion.

  • @fk4515
    @fk4515 8 місяців тому +25

    I am a welder for a Recreational Vehicle manufacturer in the USA. The plant I work at does predominantly motor homes. On some of the class A and Class C units we modify the frames by cutting them in half and adding or removing sections of the frame. When we cut a frame the cut is straight across the frame at a 90 degree angle or straight up and down much like you are advocating here. When the frame is welded back together there is a section of metal that fits on the inside of the "C" channel much like a sister rafter welded in place on the inside of the frame and if the chassis is shortened the two frame halfs are butt welded together. If the chassis is being lengthened than there is a section of steel of the same profile butt welded to the frame halfs on each end. The only reason I could see using an angle cut like you have discussed is if it is a tubular or box section frame and you make the cuts in opposite direction on the inside and outside. But I was also taught on most steel if the weld is done correctly it should be stronger than the metal itself. I've welded a few things together only to have them break in an area adjacent to the weld, but this is on repair work, not new fabrication. Sometimes we welders like to layout the weld and make it more complicated than it has to be if for no other reason to show off our skills and convince those looking at the weld in the future that we knew what we were doing when we did it.

    • @TheRoadhammer379
      @TheRoadhammer379 8 місяців тому +2

      Well, RVs do not have to abide by Federal Motor Carrier standards, but we lengthen semi truck frames and the FMCSA DOES NOT recognize or approve of vertical butt welds. We use the Z cut only.

    • @defendermodsandtravels
      @defendermodsandtravels  Місяць тому +2

      @@TheRoadhammer379 I'd be very interested to engage with the FMCSA engineers who drafted their regs to understand why they are at odds with the rest of the structural fabrication industry. Or maybe the regs were drafted by unqualfied amateurs like the NZ Hot Rod Association (as related to me by a NZ Engineer).

  • @GordonBuck-y4s
    @GordonBuck-y4s 8 місяців тому +29

    As a retired mechanical engineer it was wonderful to be reminded of Mohr’s circle which I studied 45 years ago as part of Statics, which is the realm of Civil Engineers who design and build structures where the dynamic load s are small compared with the static loads.
    For statically loaded structures the failure mode you considered, plastic deformation is appropriate. However, dynamically loaded structures often fail catastrophically by fatigue cracking.
    Design and fabrication of joints to be resistant to fatigue cracking is a specialised discipline that is suggest you investigate further, perhaps in your next video.
    In light duty motor vehicles, particularly the off-road variants, it is not uncommon for fatigue to be the most relevant design failure mode.

    • @defendermodsandtravels
      @defendermodsandtravels  8 місяців тому +16

      Hi, pleased to have you on board. You are preaching to the converted when talking about fatigue (my background - PhD in Fracture Mechanics and more than 4 decades in offshore engineering where everything gets fatigued 24/7).
      The dudes who promote the / and Z profile joints generally say they are "way stronger" so I decided to refute the argument based on static strength. To keep it simple I didn't get into fatigue and torsion but maybe I should make a second video to cover these too.
      I think the statistics are that about 90% of all failures in metal structures and components across the board are due to fatigue.

    • @tomasbengtsson5157
      @tomasbengtsson5157 5 місяців тому +3

      Hello! Interesting discussion. You have a lot more experience than I have so feel free to correct me if I’m wrong. I fail to see how a Z-joint or an angular joint would make a structure more fatigue resistant. In my experience the fatigue cracks start at either a defect or at the point of highest stress concentration. I fail to see how a Z-joint or any other shape would help with that. As pointed out in other comments a longer weld only increases the risk of defects. A correctly performed weld is as strong or stronger than the base material. A longer weld on the side of the member as a z- or angular joint will do nothing to improve the fatigue or yield strength.
      The only reliable way I know of is to avoid sharp corners, add re-enforcing plates where the stress is highest (top and bottom as shown in this case) and make sure you have a flawless weld.
      I don’t work as a mechanical engineer so even though I have studied mechanical engineering a long time ago, it’s not my profession. I do however work in the aerospace industry, and I know for a fact that we use riveted butt joints with splice plates to join members because, among other reasons, it’s difficult to guarantee the quality of a welded joint and fatigue cracking is a major concern.
      I have never seen a z- or angular joint in an airframe.

    • @defendermodsandtravels
      @defendermodsandtravels  5 місяців тому +1

      @@tomasbengtsson5157 Agree with everything you say.

    • @Errol.C-nz
      @Errol.C-nz 5 місяців тому

      A significant factor not considered at all in this academic exercise is heat stress & that effect on fatigue already built in with the welding.. nothing quite like a REAL test.. engineers! & their bloody maths.. they need to learn to weld themselves & understand the materials in reality.. double plating is a sticking plaster solution to piss poor work & design

    • @defendermodsandtravels
      @defendermodsandtravels  5 місяців тому +4

      @@Errol.C-nz So you don't need engineers with their bloody maths to design anything. Just leave it to welders to get on with fabricating things and it'll be OK then.

  • @graemewhite5029
    @graemewhite5029 11 місяців тому +17

    I'd forgotten all the techy stuff I learned at college and the equations were going over my head a bit, but I was just starting to think "I bet this is a hangover from those 'wood botherers' habits ?" and had a little chuckle when you came to the same conclusion !

    • @defendermodsandtravels
      @defendermodsandtravels  11 місяців тому +6

      Yup so it is. A carpenters' joint which got adopted by the chassis welding dudes.

    • @yonmusak
      @yonmusak Місяць тому

      @@defendermodsandtravels You only have to look at how the Ironbridge in Telford was built (the first major bridge to be built with cast iron), to see how much influence the chippies had in the joint work. You can also see how over-engineered it was, given their limited understanding of cast iron's performance.

  • @mikeitsprobablyfine
    @mikeitsprobablyfine Рік тому +51

    I Stumbled on this video, Its nice to see someone using Mohr's circle in a practical example! I primarily use EC (Euro Code) myself and think the joint configuration has more to do with the allowable fatigue stress. The maximum stresses, as you very nicely calculated and presented, are irrelevant of the joint cut. However the fatigue stress is greatly dependent on the joint used. According to detail categories within the tables of chapter 8 in EN1993-1-9, longitudinal welds in joined members will have a higher Δσ (allowable fatigue stress range) than perpendicular (butt) welds. Using cover plates (fish plates or stretcher plates) further increases the fatigue resistance of the joint. Furthermore, i think the welding requirements for a full section butt weld are often neglected and dictate greatly the final strength of the joint (and for closed sections is nearly impossible to properly implement). The joint configuration to use is for me debatable, but to me the problem is more to do with fatigue resistance rather than strength analysis

    • @defendermodsandtravels
      @defendermodsandtravels  Рік тому +18

      The purpose of this video was to debunk the myth touted by the chassis welding dudes that those exotic joint configurations are somehow "stronger" than conventonal butt welds. Given the lack of disagreement in the comments I think that has largely been achieved.
      You are of course correct that in practice fatigue will govern. Clearly a longitudinal butt weld will have better performance than a transverse butt weld but this isn't going to help much when you need to splice two lengths of beam together.
      In a new build the manufacturer will locate the weld in a low stress location (ideally at a point of contraflexure) and will have no problems.
      If the weld has to go into a high stress location then it needs to be very sound and suitably detailed. A double sided butt weld free from defects with modest weld reinforcement of smooth profile will perform almost as well as the parent metal. This can be achieved with a single sided weld but is much harder (all offshore platforms made from tubulars have these welds and they perform well). A practical solution as you say is to use reinforcing plates to reduce the general stress level but these must be suitably detailed too.
      I hope we agree on this.

    • @thabob1267
      @thabob1267 10 місяців тому +1

      Mike should respond to this one.

    • @DMJ52
      @DMJ52 8 місяців тому +2

      Brilliant answer and one of the few people that have mentioned fatigue. BS5400 is another good reference on log/log curves for classes of weld.

    • @aussiedrifter
      @aussiedrifter 8 місяців тому

      G'day Mate, No the fracture was a direct result of severe corrugations over a long period of time & a reluctance of the previous owner to deflate the tyre pressure. I have not had any trouble since purchasing the truck & carrying out the repairs, plus even though we run on 10 X 20" split rims I always reduce our tire pressure from 100 Psi down to 70 Psi to help cushion the vibracions.

    • @JD-ub5ic
      @JD-ub5ic 8 місяців тому +6

      ​@@defendermodsandtravels it may perform as well as the parent material with regards to strength, but not with regards to fatigue. A welded joint increases fatigue since the weld material is a different tensile strength, and there will always be a heat affected zone that partially anneals the material, so there are discontinuities along and near the weld. A welded joint puts a low ductility weld next to a high ductility heat affected zone which is a recipe for fatigue.
      Fatigue in bending like this would want to follow a vertical line down the chassis rail. Welding vertically gives a crack a path to follow along the highest stress plane. A Z profile gives a hard barrier to crack propagation, and keeps less of the joint within the highest stress plane.
      It seems to me that fatigue is a convincing argument, especially once you consider that this is for chassis modifications on existing structures where you can't assume perfect material, perfect weld, perfect joint, etc. It doesn't help that as far as I'm aware these welds aren't tested other than visually.
      All that being said, a simple vertical butt joint is probably perfectly acceptable, especially on a passenger vehicle. Personally, I think fishplating is more important than the actual joint geometry.

  • @davidjohnson242
    @davidjohnson242 8 місяців тому +14

    Well done. As a welder/fabricator (also with a math degree) I fully support your findings. I also appreciate your simplified direct presentation.

    • @TheRoadhammer379
      @TheRoadhammer379 8 місяців тому +1

      You can support his findings but you would be proven wrong. Why does the federal agency that oversees semi truck regulations and inspections not approve of vertical butt welds for semi truck frame splices? Our facility has performed over 5000 frame lengthening splices and all require a Z cut. But hey, you are a welder and math genius, and I perform frame splices in real world day to day work, so I guess hauling 80,000lbs, over hundreds of thousands of miles, withstanding tens of thousands of pounds of torsional frame twist from torque with zero failure is in significant.

    • @tandemwings4733
      @tandemwings4733 8 місяців тому +4

      @@TheRoadhammer379 Perhaps because they follow some old wives tale and "that's how we've always done it", without coming up with any real engineering standards.

    • @davidjohnson242
      @davidjohnson242 8 місяців тому +2

      ​@@TheRoadhammer379 ... the effective use of an equally strong cut and weld is not a counter example. It's an example of what also works - but requires extra cutting and fitting.
      As a result, you should feel very confident that the method you are using is just as right as any other.

    • @paulnewton943
      @paulnewton943 8 місяців тому

      I'm confused, all truck frames/chassis say DO NOT WELD. We would strip the truck down to just a chassis and the run it through the crush until back to speck, but not all were repairable. As far as lengthening they would be done along the rows of multiple holes in the chassis. Two plates one either side (along a vertical plane) and the next hour or so of nipping and then tensioning them down. Over the years I have seen so many different ways of doing this on boxed chassis . What I can't understand is why we don't use a process of drawing back the welded area. A 1943 GMC 6x6 weapons carrier had been modified by the armed forces in 1944. It had been cut 18°from vertical with a fish plate ( stick welded) on the inside and a boxed channel on the inside of the chassis 6" past the fish plate, but the ends had 2" holes and they been cut through the centers. They then used a drawing back chalk with oxy acetylene. I had a lengthy chat with the chap who built it and restored it after it had seen action in Europe. There was quite a storey that went with the modification. The kit was sent from the States and fitted in the UK in under a few hours.

    • @1crazypj
      @1crazypj 7 місяців тому

      ​@@TheRoadhammer379
      Great to have someone who actually does this chime in.
      As far as I'm concerned, over built is better than theoretically correct. (but, I'm just a mechanic so my opinion is worthless)
      I've had to repair far too much stuff that met engineering standards and design protocols which 'should not break until xxxxx hours/miles/Km', but, it does, sometimes within hours of putting in service
      I'm sure most engineers know they are not infallible and can't think of everything, but, I have met a few who think like surgeons - no one can possibly know any better than they do. ( like the joke, what 's the difference between God and a surgeon? - - - - - - - God doesn't think he's a surgeon)

  • @stephenhans189
    @stephenhans189 8 місяців тому +13

    You are correct! Look at oil ships construction . Rarely do you see anything other than a vertical or horizontal be weld . ships must flex loaded or unloaded must be loaded and unload due stress on cargo areas. But at Sea they encounter forces that are incredible from multiple directions at the same time. Thank you for the time explaining stress and showing the process of figuring out.❤❤❤❤

    • @defendermodsandtravels
      @defendermodsandtravels  8 місяців тому +7

      Yes I am right. I have been involved in steel framed buildings, bridges, fixed offshore platforms and floating offshore platforms (converted tankers) for decades. I have never seen one of these exotic joint configurations proposed by the chassis welding dudes. They seem to know something the structural engineering industry doesn't. I wait to hear their technical case.

  • @colvinator1611
    @colvinator1611 8 місяців тому +4

    Well ! Very interesting indeed. Whilst I have a 50 year history of electronic and electrical engineering, I'm convinced by your analysis of the chassis joints. I would have thought an angle joint would be required. Not any more !. Thanks a lot for the video. Colin ( Wakefield )

  • @briangough30
    @briangough30 8 місяців тому +12

    I agree with you. I have extended a truck chassis using a square butt joint. This happened in Queensland, Australia. about 1970. Preheating (warming) , and low hydrogen electrodes used.

    • @andretorben9995
      @andretorben9995 Місяць тому

      Its more a case of quality of work. I've seen some shocking welds on structural items.

  • @daviddroescher
    @daviddroescher 8 місяців тому +5

    Square cut seams to be top notch for stationary items. Avation chassis repairs, eg dented portion of tube, are called out for angle cuts and fish plates.
    This is where some of the idea that angle cuts are better. The problem i see with this approach is that round tube , Square and c channels are different in there bending properties.
    Thank you for the clear explanation. It will beapplyed when i splice a chevy diesel 4x4 front frame section into my 2wd 1st gen dodge Cummins

  • @kevinmartin9432
    @kevinmartin9432 8 місяців тому +12

    I served my apprenticeship in the 70s on Foden trucks, and their inhouse built chassis were legendry. The only inclined joint in the chassis was for flitch plates ends, and these were only bolted in. So I have always butt welded my chassis repairs!

    • @Hitman-ds1ei
      @Hitman-ds1ei 8 місяців тому +2

      As good a reason as I can think, the test of time is always my consideration and seldom do manufacturers continue to use a flawed design if it results in warranty claims against faulty products !

  • @timothywilliams2021
    @timothywilliams2021 8 місяців тому +5

    With the correct filler and proper welding techniques you are right. The reason some area's do this is because poor and improper welding. More overlap gives more weld area to bind it together. Also long term fatigue is probably being considered.
    In my area it's also common to see reinforcing plates welded on over the joint.

    • @martin-vv9lf
      @martin-vv9lf 4 місяці тому

      if you don't remove the chassis it can be difficult to weld vertically. the overlapping splice gives a greater horizontal area to weld on.

  • @BasementEngineer
    @BasementEngineer 8 місяців тому +4

    Hmmm, allow me to chime in here with my experience as a DIY and Professional Engineer now retired.
    I had a case where an overhead travelling crane was shut down by the DoL and I got a call for rescuing the little fabricator.
    To cut a long story short, the main beam of the overhead travelling hoist had a perpendicular "square" welded joint in the middle of its 30 ft span!
    I advised the owner to contact an inspection firm that specialized in structural steel examination and have them do a magnetic particle examination of the weld on all surfaces of the beam, and to evaluate any indications in compliance with the appropriate code.
    If all was well with this examination, it was to be followed by radiographic examination of the weld to insure that the weld interior was also sound metal (No partial penetration welds here!). Again, any indications were to be evaluated in accordance with the applicable code.
    Only with this examination and sound results would I certify the load capacity of this hoist.
    Moral of the story: For a butt joint to be of the same or better strength than the parent metal, the weld must be examined to ensure its quality.
    And structural welds for buildings, bridges, oil platforms etc. are thusly examined to ensure this required quality.
    The same cannot be said for DIY work on automotive frames. Here a longer weld with greater cross sectional area is worthwhile to make up for lower quality welding and unknown steel properties.
    As an aside, LENGTHENING a chassis without due analysis using known values as shown herein, is wrought with its own difficulties.

  • @tractorsandmachines
    @tractorsandmachines 8 місяців тому +4

    Excellent presentation. I, too, believe the idea of angle splice joints originated from using scarf joints to join wood members in structures. For wood spars in aircraft, this is still common practice. Wood and metal are disimilar materials, as are the bonding mechanics. In the end, the calculations say it all. Thanks for sharing your knowledge.

    • @blanchae
      @blanchae 6 місяців тому

      I was thinking the same thing that the idea originated from scarf joints for wood. Which I happened to use to fix the rotten ends of my front porch joists a couple of years back.

  • @mrman1536
    @mrman1536 8 місяців тому +3

    Early in my apprenticeship 70s there wasn't much general metal engineering knowledge amongst mechanical engineers i could call on . Kenworth had chassis repair configerative data scenarios in their workshop manuals , all of which had angle welded joints with in and out gusset plates . All truck manufacturer's stated do not weld top and bottom flanges. As an Aussie i wrote BHP and asked their engineers opinion quite comprehensively butt joint with specific rods and welding process All of the chassis i welded were butt welded and crack repairs were x-ray checked for welding defects.

  • @miketrusky476
    @miketrusky476 8 місяців тому +22

    All Class 8 truck manufactures have bulletins on how to repair their frames. Great place to learn what they recommend.

  • @Byzmax
    @Byzmax 8 місяців тому +1

    As the man who started all this materials testing said "Facts, Not Opinions" .
    Your observation around the reason this is so made think of the first Iron bridge. Yes it was cast, but look at the jointing method. It's all woodwork joints.
    Great video that follows that principle.

  • @ShaunHensley
    @ShaunHensley 4 місяці тому +1

    Every structural iron job I have been on utilized splice plates. 0:47 It’s crazy seeing all these projects without them.

  • @johnsmith-z8y
    @johnsmith-z8y 8 місяців тому +6

    Nice one good to know, thank you. I'm not an expert, just an industrial designer who has worked several years in metal fabricating (designing) the only reason I can think of for staggered joints is that in some cases it helped for alignment, but then again as you say not for the final strength of the joint. I agree, weird joint shapes - scarfing, etc. - are a left over from timber joints, which were in the old days not even glued but pegged (trenails).

  • @raymacklures5899
    @raymacklures5899 8 місяців тому +3

    You are correct in your calculations and the result of the forces involved if you loaded a fresh chassis to failure. So a 90 degree welded joints with full penetration and ground flat with no imperfections should show almost no real change in performance from the tons of load to fail
    It is vibration induced fatigue, the changes in the steels grain sizes of the welded joint is the reason for the inclined joint as you pointed out the load will induce a failure at 90 degrees so a tear begining at a flange will want to take the shortest route across the member in the loads plane. If a weld is there,,, it will not crack in the center of the weld but at the interface between the fine grained filler metal and the enlarged grains in the heat affected zone parent metal.
    Now vehical manufactures have the opportunity to test there chassis for harmonic hot spots generated by real world use. And they can put 90 degrees joints if required away from these areas if they land to close to these areas so it is crack propagation the inclined joint is trying to defeat in a one off application and bridging across a potential harmonic hot spot..

    • @PumpkinBMW
      @PumpkinBMW 7 місяців тому

      This!

    • @Warrior_Resisting_Colonialism
      @Warrior_Resisting_Colonialism 6 місяців тому

      You're forgetting something......... Bridges and boats using butt connections, flex and vibrate all the time too......Also remember, just SAYING it, doesn't make it true. The man asked you to present your case with the source to back it up. Where's your source?

  • @Equiluxe1
    @Equiluxe1 8 місяців тому +3

    I think this comes from the days of wrought iron construction which was at first carried out as if it was wood using mortice and tenon type joints and wedges, later on when rivets were used they still used much the same as wrought iron has a grain just like wood, so two beams would be riveted together using fish plates which looked like two fish tails back to back. The idea here was that the greatest stress raiser area was in the neutral zone, this practice is still used on Lorries where chassis sections are joined or reinforced and riveted or bolted together, as to whether the term fish plate is due to its shape or not I have no idea but fish plates were used to join railway lines before other large iron or steel construction took off. I have extended lorry chassis in the past with the plug and plate method where the extension is then bolted to the vertical plates, also I have used the overlap and reinforce method with fish plates and in this case used traditional shape fish plates as it looks nice. I have never hear of the angled splice though.

  • @tano1747
    @tano1747 8 місяців тому +2

    As an engineer, I entirely agree from a stress analysis point of view.
    I suspect that the guys advocating for splice style joints are doing so more because (in a "working in your shed" context)
    1) the longer joint offers more opportunities to clamp the two sides to ensure good alignment, which would not so much make it stronger than a properly executed full penetration butt weld, but reduce the risk of misalignment between the two sides that would introduce various problems with stress concentrations and load eccentricity etc that would weaken it,
    and
    2) a longer weld at a gentle angle is closer to a horizontal position weld (and is therefore easier for an amateur to get a good weld) than the vertical up or vertical down alternative for welding the beam web. Obviously this isn't a concern in a factory for a properly trained welder, but for the guy in his shed working in an awkward position it may be easier, and therefore it may reduce the risk of a poor weld, and again this would potentially reduce risk of failure from introduced defects. Not so much making it stronger as reducing risk of making it weaker.
    Of course, I am not advocating for back yard DIYers to attempt chassis mods; I can't think of a more dangerous field of endeavour for an MBA (mediocre but ambitious) welder... but people do try it, and in that backyard world, the splice joint might in fact have a slightly lower chance of failure and hence be part of the accepted wisdom for a reason. But (to repeat for emphasis) obviously I would infinitely prefer the DIY guy to use some common-sense and bring in a qualified welder for the frame splice welding at least.

    • @defendermodsandtravels
      @defendermodsandtravels  8 місяців тому

      I would point out yet again that any failure is likely to emanate from the top or bottom flange where the highest stresses will be (unless there are attachments to the web with high local stresses). If you can get the flange welds right then the web butt shouldn't be a problem.
      I think the reasoning is simply that if the weld is longer then it must be stronger, which is a seductive if erroneous argument.

  • @audunorrestad5482
    @audunorrestad5482 Рік тому +5

    I really like your videos and the effort put into counter some of the diy "engineers" on youtube! Only reason I find for angled welds would be as a design feature to prevent stress concentration in the chassis from plates welded on to strengthen the frame.

    • @defendermodsandtravels
      @defendermodsandtravels  Рік тому +3

      Audun, there's little reason ever to add cheek plates to the (side) of a chassis member.

  • @insolentstickleback3266
    @insolentstickleback3266 8 місяців тому +1

    You Sir, are a very watchable guy. I of course could not follow the equations exactly, but was able to follow the context. The end conclusion, transition from wood to steel construction. 👍🏻

  • @midnighttutor
    @midnighttutor 10 місяців тому +16

    Very interesting presentation. I am wondering if you have perhaps made any assumptions in your analysis which were not apparent or included in your calculations. The one I am thinking of is the tensile and shear strength of a welded joint versus pristine metal. Given that you cannot account for the quality of the weld itself in your calculations, is it possible that an angled interface offers a greater factor of safety just because the surface area of the weld is greater and could mitigate less than optimal weld penetration etc? Thank you.

    • @warrenarthur5629
      @warrenarthur5629 8 місяців тому

      In the bending moment sections there is no increase in weld surface area, only in the shear sections, which are not the failure point in such members.

    • @midnighttutor
      @midnighttutor 8 місяців тому

      Thank you for clarifying. In this case what would you suggest is the best option to mitigate less than optimal welds? I think I am a great tig welder but without xrays or cutting the joint open there is no way to be sure of integrity. @@warrenarthur5629

    • @defendermodsandtravels
      @defendermodsandtravels  8 місяців тому

      The AISC code (American Institute for Steel Construction) states that for a weld without defects in structural steel one may assume the weld is as strong as the parent material. This obviously doesn't apply to defective welds or to all types of metals and alloys but it covers the cases we are looking at.
      The AISC code is the most widely used in the world and few people would question their recommendations.

  • @carmelpule8493
    @carmelpule8493 3 місяці тому

    You are correct about the timber relations to people's way of thinking when it comes to welding metallic joints,
    A good weld produces a homogeneous joint which is as good as the original material,
    I used backing plates inside the rectangular section of the chassis and rose welded them in addition to the butt weld. Never had any problem. When the local inspector/examiner saw the joints, he just smiled and said, "Well , it is never too late to learn from others!"

    • @defendermodsandtravels
      @defendermodsandtravels  3 місяці тому

      You clearly did a very good welding job. In industry we use the necessary welds, as defined in the design codes, but without extra reinforcement etc. If you do that your profit is gone.

  • @selrahc2061
    @selrahc2061 8 місяців тому +3

    I actually had to weld a frame recently. Before I go further I am a engineer so I follow your math. Your using ideals thoughout your calculations. What I found fatigue cracking by most of the mounts. This involved stress relief and overly of better material to transfer the load to good material. But excellent analysis.

  • @stuartbell7078
    @stuartbell7078 Рік тому +2

    You are producing great videos, and I like the way you are challenging "established" methods and principles, when they are clearly wrong. I think it is far better to think about each and every thing you do from first-principles, rather than blindly following convention; 20years in Automotive design and development has taught me that much. In the case of this specific analysis, the unstated but clear conclusion is that repair of chassis longitudinals must be done in a way that allows the top and bottom faces to be repaired robustly - not as-per many Series LR chassis I have seen where a repair has been made with the rear body-tub in-situ, and the welding has been very much at arm's length, blind, and at the wrong torch-angle. One chassis had a top-face joint that was nothing but a tangle of MiG-wire projection-welded either side of the repair!

    • @defendermodsandtravels
      @defendermodsandtravels  Рік тому +7

      Weld the top and bottom flanges correctly and chassis will do the job. And no, you simply cannot weld the top flange of a chassis rail if the tub is in place, period.
      I cringe when I see dudes spending a huge amount of time reinforcing the webs, claiming to be "doing the job right", when that isn't where the critical stresses are. That may earn them a load of extra subscribers but it isn't based on fact.
      I don't actually set out to challenge anyone. I just approach things from first principles, as an engineer, and if that conflicts with others' opinions I'm sorry but I can't do anything about it.

  • @billshiff2060
    @billshiff2060 11 місяців тому +1

    Great info. I would say that with some alloys where the HAZ might be a problem that you could make a joint such that the stressed flanges are V shaped like so... (looking down on the flange) Left member flange]]]]]] >>[[[[[[[right member flange ( hard to draw)
    Or maybe (looking down on the flange) Left member flange]]]]]]//[[[[[[[right member flange (flipping the scarf on it's side to increase the welded areas length)
    So that at no point on the stressed flange is the entire weld subjected @ 90deg to the stress at one point and one time. It would also distribute the loads over a longer welded area reducing the effect of any defect.

  • @lucky7s94
    @lucky7s94 8 місяців тому

    At work, I'm building a massively overbuilt towing rig chassis for my boss out of salvaged pieces of different vehicles starting with a 79 Ford L700 frame. We grafted an engine crossmember, springs, and 4wd axle beams from a Gen 9 92-96 super duty, it's going to relieve a 6.2 Ls/Lt (whatever it is) with a 6L80 behind it. The frame will have a 73 F-100 body dropped onto it. We have found a tongue and groove pattern would be an appropriate pattern if we needed to shorten the frame. Obviously, with this type of build, we have areas where there is no real stress plus, the frame is not your typical frame. It's easily twice as thick as a typical passenger vehicle. This will be our second hand built towing rig. The first one, we learned critical lessons. The second one, we are eliminating those problems and making it far more capable.

  • @ReduxGarage
    @ReduxGarage 9 місяців тому +1

    All I know is the two main chassis rails on my 1976 VW type 2 have one vertical welded joint each. …still connected.
    When facing a problem, those of us who don’t have the technical expertise, look at the possible solutions and take our best guess at what would be stronger, in this case. And I suspect the solution that gets selected the most becomes THE solution.
    Great video!

  • @perstaffanlundgren
    @perstaffanlundgren 8 місяців тому +1

    Regarding timber joinery, there are also more than one wood peg or big nail scerw in them to take upp linear tension in the joint. This is used in in the ones that has "hooks " also
    One "simple" joint that can take bending forces on itself is
    This variant of the half half split joint . (Note the angled tungs) this joint can be used in boat bow /sterns also, a wodden peg is then put in the joining planes to prevent leaks.
    Sometimes the joining surface is at an angle but the butt ends should be done in the same way on does too.
    _____________________
    /_________
    _____________ /________
    In modern timber houses you sometimes butt joint with a joining plate put in sawn groove that goes into both the joining members.
    This is often only for joining logs in a solid wall , with overlap in the logs above under . This can be achieved with "tung and grove" also.
    _____________________
    ___|___
    ___________ |_________
    When we want linear tension to be absorbed we use lark tail
    Joining , often to prevent walls from buckling out join inner walls to outside walls or to prevent floor beams from creeping out of there mouting holes in the timber wall.
    The beams often hold the walls together to prevent buckling out in between the gavel gavel walls from the weit of the roof , this can happen if the roof is supported by top and side beams logs only and roof joists laid in lateral to them.
    (Sorry if some terms are not corect/ hard to understand ,
    I am not American / English,
    English is not my native language. )

    • @philhealey4443
      @philhealey4443 7 місяців тому

      I've put in a comment above in relation to zig zag bracing in long span floor joists which would prevent twisting. The Japanese seem to be masters of timber joints that seem impossible to assemble !

  • @RickKerner
    @RickKerner 8 місяців тому +1

    The time taken to evaluate the stress levels in the chassis beam are demonstrated very well. What might be missed is by applying a building structure weld code to an automotive chassis, in my opinion. Welds, or more accurately, the junction of weld and the heat affected zone (HAZ) are sensitive and need to be addressed properly. If you examine BS7608 and its associated S-N curves of the myriad welded joints, you'll see that the strength of the welded joint does not approach the strength of the parent material. In fact, for most of the included materials, a plot of the test coupon results reveals a common stress level that a welded joint should not exceed. If acknowledgement of BS7608 is applied, one would use the tensile stress level in bending or the tensile stress in the moment near the spring perch to use as a guide for creating a joint that minimizes these stresses and keeps them below that for infinite life as seen in the S-N curve. If the stress levels in the welds on the top and bottom surfaces of the beam show risk of not meeting infinite life, then proper doublers* need to be applied in order to add cross section to the high stress junctions and to create a tapered weld that doesn't run 90* to the top or bottom of the beam. To stretch a chassis by using vertical "bologna" cuts and just welding them back together is a recipe for later sadness, in my experience.
    *You can see several examples in the attached link on how to address tensile stresses in welds on the top of a chassis beam that undergoes loads of several G's in normal operation. Of course, known load cases and significant amounts of FEA and results interpretation led to this successful chassis design by our team.
    patents.google.com/patent/US10507870B2/en?inventor=chang&assignee=CNH

    • @defendermodsandtravels
      @defendermodsandtravels  8 місяців тому

      I will reply to the fatigue question in a subsequent video. The dudes who promote the weird weld details claim they are "way stronger" so I chose to refute it based on static strength.
      Yes SN curves with any sort of weld are worse than unwelded steel however this depends on the type of detail. Simple butt welds give the best performance of any type of welded joint and the fact is that if a butt weld is well made and has a good profile it will perform excellently in fatigue.
      My field is offshore structures which are largely made of short lengths of rolled tubulars (or cans) welded together with single sided butt welds. They are subject to fatigue loading 24/7 for their design lives of typically 30 years - orders of magnitude worse than any vehicle chassis. Cases of failure at the butt welds are almost unheard of. If there are fatigue cracks they are invariably at the joints where the stress concentration factors are commonly in the range 5-10.
      Be careful about doublers; they reduce the general stress level but increase the SCF and put you onto a lower S-N curve.

  • @grinchthe8469
    @grinchthe8469 8 місяців тому

    Excellent decription of findings, sir.
    I am a spray painter, and used to work in Alberta where truck mounted drill rigs were made to order. They were very heavy, some not road legal.
    When they shortened frames on transport trucks, they cut the frame on a 45% or so angle, and this was beveled and welded together. After that another rectangular shaped length would be added to the outside, AND DRILLED AND BOLTED OVER WELDED AREA(overlapping side to side).
    This was called fish plating.
    🇨🇦🤔

    • @defendermodsandtravels
      @defendermodsandtravels  8 місяців тому +1

      That's a battleship mod in my book.
      All they needed to do was a competent butt weld with a bit of reinforcement (I.e. the weld cap proud of the surrounding base metal) and it would have been full strength. Easy to do on open sections where one has access to both sides of the weld, harder but doable for single sided welds.
      There's an interesting point about bolted fish plates. Unless one makes proper friction grip connections they will have limited effect. If the bolts are acting in shear (especially in single shear) there will be movement and the stress will be taken by the weld instead of being shared; if this starts to crack then the whole joint will start to fail.
      It sounds as if the company you refer to didn't have proper engineers on their staff.

    • @ronblack7870
      @ronblack7870 8 місяців тому

      @@defendermodsandtravels perhaps there was a fatigue issue where the adjoining base metal would crack as the weld was stronger and stiffer. doing what they did may have spread the stress more.

    • @defendermodsandtravels
      @defendermodsandtravels  8 місяців тому

      @@ronblack7870 No given that any fatigue crack is likely to emanate from the flange welds.

  • @jimf671
    @jimf671 8 місяців тому +1

    Where angled joints come into there own is in the repair of metallic or non-metallic components using adhesive, braze or solder. That may have found its way into the mindset of repairers. Typically, there used to be a common apprentice workshop lesson involving cutting a 10mm mild steel square bar into two pieces. The bar was cut with an angled joint to provide a joint surface of three times the area of the cross-section of the bar (10x30) and it was then brazed back together. Attempts to make it fail in bending resulted in failure of the steel and not the brazing. It is a pretty convincing lesson and can be usefully applied in many situations. However, it has no relevance to the chassis welding task considered here.

  • @parrotraiser6541
    @parrotraiser6541 8 місяців тому +1

    Early iron structures were built using wooden-structure techniques. (This tendency for practices that made sense in older technologies, even when the original need has completely disappeared could be called Technological Cheshire Cats; the cat has disapeared, but the grin remains. There's a similar phenomenon in language; Diesel engined steamships set sail; that's two generations in one phrase. Scarph joints in wood offer a larger surfaces for the application of glue than buttj oints.

  • @ihdieselman
    @ihdieselman 8 місяців тому +2

    That seems rather strange that you would consult leading experts on stationary buildings when trying to make an argument about why you should not avoid a abrupt point of failure along the heat affected zone of a weld on a vehicle chassis that is going to be twisted and torqued repeatedly as it drives down the road. This is especially true for heat treated steel frames used on heavy trucks. That's not even the same material that they use in structural steel construction. Even with a perfect weld you are still going to have a heat affected zone on either side of the weld where the parent metal is affected in its strength. On paper this doesn't seem to make any difference at all but the main difference in theory and practice Is that in theory there is no difference. In reality truck frames are rarely treated so kindly has to not be overloaded. And when they are the stresses are concentrated on certain points in the frame and it is best to try to distribute these points as far as possible as to not create a stress riser where it is more likely that a crack will begin. The point of the diagonal cut is not so that it has the same strength that it originally did. It is to minimize the effect of the stress riser that you have created by making the joint in the first place. On a light duty vehicle like a defender, it probably doesn't make any difference. But when you're talking about a log truck that's traveling down the highway next to your family. Do you really want to take a chance on that or do you want to give it the best chance possible to avoid unnecessary deaths?

  • @davidkelly9218
    @davidkelly9218 8 місяців тому +1

    The amount of time one could put into a discussion on rights and wrongs is crazy. Being a welder/fabricator/Welding engineering technologist/ instructor and general jack of all trades I for one agree with your points. However I do have a couple of thoughts on this, not necessarily agreeing or disagreeing with them. I think (not know) from a lot of discussions I have had over the years that by angling the cut and weld a lot of people tend to believe they are accounting for any metallurgical issues that may arise from welding on a frame that may have been heat treated to get the mechanical properties required in the frame when manufactured. Some of this being that they simply do not know how their weld has affected the base metal and not knowing how to compensate in any other way for perceived potential problems. Sometimes I have seen it done simply for accommodating bolts holes into the equation to help with alignment issues( ie. making it easier to align and measure). I for one do not believe in cheek plates. If a weld has been done with the proper procedures and filler metal then the properties of the filler metals should be higher than the base metal. The structural ductility in the heat affected zone is the question. In every weld proper preheat, interpass temperatures, and post weld treatment is probably the biggest thing to think about but is generally unknown or not thought about by the average garage mechanic. I welded a crack in an excavator (hitachi 450) boom one night in an open field on a mound of dirt 20 feet in the air at minus 35 degrees C. One inch plate cracked across the top and 3/4 inch plate cracked all the way down one side and all by myself. Preheat consisted of a tiger torch trying to keep this warm then 1/8" 9018 electrodes in a properly prepped open root weld joint. I could preheat all I wanted (not enough) then weld and I could still take my glove off and touch the weld as soon as i finished running the bead. Just a huge metal heat sink. There was no scenario in my mind that this wasn't going to break as soon as they started working with it. Can you imagine the crystalline structure of the heat affected zone. I did not put on cheek plates as what was the point to adding stress risers outside of the broken area.
    Did my best and 4 years later it was still working in a rock quarry with an operator trying to beat it to death.

    • @defendermodsandtravels
      @defendermodsandtravels  8 місяців тому

      Although I can design welds I am not a welder myself and I have great respect for those who can do it. You have clearly put a lot of thought into your trade as well as practising it. We need more like you around.

    • @davidkelly9218
      @davidkelly9218 8 місяців тому

      @@defendermodsandtravels Thank you I appreciate your thoughts. I take great pride in my workmanship and I truly love what I do. I should point out however that when doing frame rail repairs or extending the rails on a transport truck I still prefer to do an inclined joint. This is partly for ease of alignment and the fact that we are not able to easily test for any changes in the grain structure in the heat affected zone of the weld. The weld itself will seldom fail but the original frame next to the weld is the issue. By having that inclined cut we can often have a bolted member such as a spring hanger attached to both sections. On something like a frame, which is a dynamically loaded structure and as such is in constant movement and vibration going down the road, the inclined angle would put the stress as you calculated crossing the weld zone and not running alongside the heat affected zone. The vertical(web) in this case is really not the issue as any cracking that might occur would most likely start at each end of the weld on the flange. An easy experiment to try is to take a piece of material and put a radius on the edge (ground lengthwise to the flat bar) and bend it and then bend a piece with a sharp corner (grinding marks across the flat bar). The sharp corner will crack and cracks the will propagate across the flange. Most failures that I have witnessed in my experience happen when the weld start/stop areas have not been properly ground and blended with the base metal. Engineering aside there are so variables to consider if you truly want to look at every scenario. One little variable can change an outcome. Too much heat in the weld zone or somebody cooling their weld with water can drastically change that grain structure for example. Unfortunately this can not be taken in by those calculations. Knowledge of the theory and the practical are both required for a safe and efficient outcome.

    • @davidkelly9218
      @davidkelly9218 8 місяців тому +1

      @@defendermodsandtravels in my previous post I should mention that these are my thoughts on heavy truck frames not on passenger vehicles. I have seen a lot of welds that should not be on the roads. I love these discussions and often look forward to a differing point of view. As well as educating and being educated by someone with a differing view. Too many people these days take some of these differing points of view too critically and fail to look at the big picture. I look forward to learning everyday. I have fun knowing there is more than one way to get aa job done.

    • @defendermodsandtravels
      @defendermodsandtravels  8 місяців тому

      @@davidkelly9218 We all learn from each other, agreed.

  • @PauloNeuenschwander
    @PauloNeuenschwander 8 місяців тому

    First I'd like to say that this video is great. Congratulations!!!
    I agree with you, the direction of the cut should not influence the results. In Eurocode EN 1993-1-8, that deals with joints calculation, just mention that full penetration welds have the same resistance as the weakest material in the joint. Exactly like you said.
    A 45 degree (more like a zig zag) weld can be used as a crack arrester for fatigue purposes in other situations. But it's clearly not the case in this video.
    Very nice approach!

    • @defendermodsandtravels
      @defendermodsandtravels  8 місяців тому

      Sorry but welds aren't good crack arrestors, a fatigue crack will go right through if the weld is in the way (it takes the path which releases most strain energy). This is my specialist field. Happy to debate it if you have any doubts.

  • @steinmargunnarsson3709
    @steinmargunnarsson3709 8 місяців тому

    Very good explanation on the subject. The only thing I can add to this is that when I was studying, we were only allowed to load the welds to 60% of the allowed stress of the beam material (I think I remember this correctly) I agree on the timberframe explanation as no-one has been able to weld timber, not that I know of.

    • @defendermodsandtravels
      @defendermodsandtravels  8 місяців тому +1

      I don't think you remember it quite correctly. A full strength butt weld is just that. However a single sided butt weld, where full penetration cannot be guaranteed, must operate at reduced stresses (5/8 was specified in BS449).

    • @steinmargunnarsson3709
      @steinmargunnarsson3709 8 місяців тому

      I belive you are correct. Thank you Sir@@defendermodsandtravels

    • @trevthetroll
      @trevthetroll 8 місяців тому

      Woodcraft rods...

  • @stefanandersson9616
    @stefanandersson9616 5 місяців тому

    Very interesting video (makes me nostalgic over my past as a welder). If not mentioned yet it seems to be easier to get the two parts straight to each other with an alongated fit rather than a cut fit (like a pair of light beacons used in navigation). Elongatet fit only for measuring purpose(?)

    • @defendermodsandtravels
      @defendermodsandtravels  5 місяців тому

      If it makes it easier to align cut it how you wish, but don't think it will be stronger.

    • @stefanandersson9616
      @stefanandersson9616 5 місяців тому

      @@defendermodsandtravels As he says in the video, if it were wood the need of transfering shear strength to the other part would need an elongated joint. It's not necessary when welding metal.

  • @gcaustin12
    @gcaustin12 8 місяців тому +2

    I agree with everything you say regarding the joint and how to weld it back together. I do however, have one comment and that is crack propagation. I used to work on some highly loaded beams that flexed depending on the way the operators loaded or used them. Once a crack is initiated in the beam the crack would travel in a straight line typically from the bottom flange to the top flange in a simply supported beam where the load hung between equidistant lifting points. The idea of angling the joints comes from the fact that it’s harder for cracks to change direction and usually take the least resistive path of a straight line.
    I agree the cracks have to start somewhere but the case where you are making a field repair and you add scab plates on the repaired crack we usually cut the ends of the scab plates with a large radius or a forward then backward angle. This type of repair tended to be long lasting as compared to scab plates that had plain vertical welds which tended to easily propagate cracks.

    • @dave4737
      @dave4737 8 місяців тому

      That's what I do

  • @genelong203
    @genelong203 5 днів тому

    I am no engineer by any means but from those that I have seen do this they gave some explanation that at the time made sense to me at least. More weld surface and to help prevent a potential crack to keep going and would be stopped by the change in direction. I don't think it had anything to do with the joint itself being stronger.

    • @defendermodsandtravels
      @defendermodsandtravels  4 дні тому

      That isn't reality. If you have a crack starting from the highest stressed location (top or bottom flange) it will then propagate through the member. It won't follow the weld, it'll be equally happy to go through parent metal. A change of direction of weld won't stop it.
      If you watch the videos published by the chassis welding guys they invariably say that the fancy joints are "way stronger". I have never seen anyone justify their weld details by arguing about crack propagation.

    • @n2sport1
      @n2sport1 4 дні тому

      Well I've seen many welders on big equipment say it but I guess because you haven't I must be wrong.
      Thanks for correcting me.

  • @bud-in-pa589
    @bud-in-pa589 8 місяців тому

    I believe you are correct that it doesn't matter if you use a vertical weld joint in the web of the frame. The problem, as I see it, is the welds you make in the frame flanges. These need to be reinforced or you may well end up with cracks forming in the HAZ of the welds as a result of fatigue loads. After all, automotive frames are continually flexing over the open road and for trucks in particular that are heavily loaded, the stresses in the frame flanges can be quite high and when you superimpose fatigue (flexing) loads as well you may eventually end up with cracks forming in the flange welds. The solution is to weld reinforcing plates over the flange welds. Ideally, the reinforcing plates should be 4 to 6 inches long and be skip welded to the flange (in tension) along the longitudinal axis of the plates. Most importantly, DO NOT weld the ends of the reinforcing plates. Using doublers or fish plates over the web welds really isn't necessary.

  • @peterblake548
    @peterblake548 8 місяців тому

    This was an outstanding presentation with some very in-depth analysis. However, something you might consider is fatigue failure. Auto chassis are subjected to all manner of impact forces and vibration from rotating, and possibly out of balance, elements. Architectural constructions are not subjected to much of this except low frequency wind loads. However, a high-rise apartment building near a supersonic test sight would certainly expose the building to square wave events. A Fourier analysis of these waves will disclose that something in the design will likely go into resonance and possibly fail by the members exceeding their elastic limit. It might be instructive to analyze wrecked automobiles that had square cut modifications to try to determine if the square cut was a contributing factor. In addition, an in-dept look at Formula one racing cars and inquire about the protocols they employ for builds and the numerous modifications.

    • @defendermodsandtravels
      @defendermodsandtravels  8 місяців тому +1

      Clearly fatigue will most likely be the cause of any failure Dynamics associated with the suspension will be a factor (which is why I applied a simple DAF to the static load however the dynamics associated with the body and chassis will be minor.
      The guys who propose those exotic joint profiles claim they are "way stronger" so I refuted that argument based on static strength.

    • @peterblake548
      @peterblake548 8 місяців тому

      @@defendermodsandtravels I loved your very in-depth analysis ...we don't see much of that on UA-cam from people who actually work on cars. I hope Elon considers fatigue issues for his interplanetary missions where vibration damping i is most likely totally absent due to the absence of air. I have visions of some of the proposed structures flying apart from resonant vibrations. I sleep well at night because I have a three wheel car !!!

  • @fredmercury1314
    @fredmercury1314 8 місяців тому +11

    This is all nonsense. Everyone who knows anything, knows the best way to join a chassis rail is with JB Weld.

    • @ItreboR63I
      @ItreboR63I Місяць тому +1

      That's posh. Just use flex-tape™

    • @heathkill4821
      @heathkill4821 24 дні тому +1

      Bro thats nothing… use Super glue

  • @husq2100
    @husq2100 Рік тому +3

    Good video.
    I think the scarf style joint could actually be worse than a straight butt joint. Surly the forces don’t like the welds changing at 90 degrees…
    I wonder if there has been some confusion with the welding joint of the chassis rail and the welding of fish plates, or doublers on to chassis rails?

    • @defendermodsandtravels
      @defendermodsandtravels  Рік тому +2

      As I tried to explain in the video the member will fail (if overloaded) by bending, and all that really matters is the strength of the top and bottom flanges. If you want to make it stronger add some material to the flanges, not to the web.
      Don't think of lines of force following the line of the weld - it doesn't work like that. There will be a stress field which is in equilibrium with the external loads and this will flow through whatever material is there (either the base metal or the weld metal). It doesn't follow the weld.

    • @husq2100
      @husq2100 Рік тому

      @@defendermodsandtravels I didn’t mean the line of force would change due to the joint shape. I ment the forces flowing through a change in direction of the weld.
      Fish plates or doublers are added for many reasons other than bending of the chassis in the vertical plane. You might be attaching link mounts or a cross member to the webs….

    • @OzSafe1
      @OzSafe1 8 місяців тому

      I extended my caravan chassis rails by 1 metre. The two rails were 50mm x 100mm x 4mm RHS. I used a butt joint weld and then welded angled fishplates either side and only welded the top and bottom edges of the plates, leaving the side faces ‘angled at 45 degrees’ free from welding. I hope this is OK because we used to extend truck chassis this way years ago.

  • @harry8506
    @harry8506 8 місяців тому

    The angular or complicated joint looks pretty . Tradition may be the main reason for this type of joint, that is this is the way it has always been done where you worked or learned your trade. I just think it looks better.

  • @peternewman958
    @peternewman958 8 місяців тому

    One thing you seem to have forgotten is torsional stress that a chassis undergoes.
    As someone who was studying mechanical engineering and doing a lot of truck chassis work, i know from experience that with a conventional chassis shape of top and bottom flange with one web , and no matter how many inner channels that you have to do a 45deg cut on the web and depending on what the truck will be doing quite often a 45deg cut on top and bottom.
    I had to do this with many 6 wheel drive Isuzu trucks that were going from Brisbane to Papua New Guinea for mining exploration.
    They had a nest of 3 channels . Cow of a job they were.
    In the end though it comes down to whether the person welding is capable of 100% penetration with no inclusions.
    Generally I would grind out then needle gun each weld, usually doing one side then the other to prevent overheating the steel.
    The needle gun does assist in stress relief.

    • @defendermodsandtravels
      @defendermodsandtravels  8 місяців тому

      And if I am going to look at torsion should i also look at section warping and associated stresses? I haven't forgotten them but I must keep the concepts simple so people can follow them otherwise the only people who will watch it are qualified engineers.
      I take it you are familiar with the fundamental difference in torsional stresses in open and closed sections? How am I going to explain that to viewers in a short video?
      The fact is that if the as-designed member resists applied torsion then it will continue to do so with a competent butt joint.

  • @Russ-jk6tt
    @Russ-jk6tt Рік тому

    Wow, some real engineering analysis. I like everything in the analysis but take exception to the fundamental assumption of uniform loading along the frame span where in actuality we have four point loads, two on the front hangers and two on the back. It will precipitate different stress values but the analysis will be the same.

    • @defendermodsandtravels
      @defendermodsandtravels  Рік тому +1

      It makes little difference in fact. With a UDL the bending moment diagram will be a parabola whereas with point loads it will consist of a series of straight lines between the loading points but with a similar max value. I was hardly going to bother to do a detailed survey to measure the individual body and engine / transmission mounting points, and then to estimate the point load at each location. A lot of work for a small improvement in accuracy (although you would do that if you were doing a real design).
      You will note that I calculated the equivalent UDLs to give the correct axle loads so they can't be far wrong.
      I take it you aren't an engineer because any engineer would have made the same approximation as me.

  • @bcubed72
    @bcubed72 5 місяців тому

    The reason is the same reason bicycle lugs are scalloped: if you change the stiffness of the frame ABRUPTLY, then you create a "stress riser" as the frame flexes in use, setting yourself for fatigue failure at the discontinuity
    The bridge you referenced earlier has a far more static load.
    SEE ALSO: DeHavilland Comet and square windows.

    • @defendermodsandtravels
      @defendermodsandtravels  5 місяців тому

      I am well aware of stress raisers and fatigue failures.
      I am not sure what your point is though. If you are referring to butt welds there will be a notch stress at the weld toe if the weld hasn't been profiled. I didn't consider the case of welded attachments.

  • @LTVoyager
    @LTVoyager 8 місяців тому

    I suspect the angled cut is a carryover from the days of wooden structural members such as frames and airplane wing spars. Wood is generally joined with a scarf joint to maximize the surface area available for gluing.

  • @stevenginnever5343
    @stevenginnever5343 9 місяців тому +1

    Hi
    Interesting video, didn't understand most of it. But at the end you referred to carpenters joints, so after a quick Google I found this info. First chassis frames between 1896 - 1910 , were made almost entirely from wood. Joints were reinforced by wrought iron. Maybe this is why the confusion.

    • @defendermodsandtravels
      @defendermodsandtravels  9 місяців тому

      No confusion in my mind. Scarf joints were used by carpenters and joiners to transfer shear forces which was always a problem with timber until the invention of gang nail plates. However these joints have no place in steel structures.

    • @stevenginnever5343
      @stevenginnever5343 9 місяців тому +1

      @@defendermodsandtravels My apologies for the confusion remark, it was aimed at the Australian and Canadian authorities insisting on these joints, and not at you. As you said in your video, these special joints are not needed with steel chassis .

    • @defendermodsandtravels
      @defendermodsandtravels  9 місяців тому

      If the Australian and Canadian authorities demand scarf joints they should revisit their pointless regulations. Why demand something the vehicle manufacturers don't practise? They could start by looking at my video and learn a bit of basic engineering :-)

  • @alext8828
    @alext8828 5 місяців тому

    Inclined and Z joints are appropriate for wooden glue-ups where the glue line length needs to be long enough and/or a mechanical "trick" like a scarf joint needs to be produced. Metal is different. The assumption is that the welded joint approximates any other part of the metal in terms of strength.

  • @johnbarker419
    @johnbarker419 4 місяці тому

    This video has come up in me feed multiple times over a span of months. I've always walked away from it a bit troubled despite the fact that your arguments are correct. A properly executed butt weld on a straight, vertical line should be as strong as the metal on either side. Should, and a substantial number of comments have leaned into the fact that bad welders produce bad welds. That's true, but I simply couldn't shake the belief that there's more to it than that. I've finally put together the words to express why I'm uncomfortable with the thesis.
    Let's say you have the money to hire the best welders, give them the best equipment, pair them with engineers to cross check their thinking, and supply them with the best materials. Given all this and the understanding that a properly executed weld should be as strong as the parent material, you decide to lengthen the steering shaft on your car. Chances are, you'll be fine. In fact, UA-cam is filled with people lengthening and shortening steering shafts in their sheds, and as far as we know, it usually works out fine.
    And when it doesn't? Well, that's when you're Frank Williams, explaining to the world's press why Ayrton Senna is dead. Is anyone here a better engineer than those on an F1 team? Unlikely. Is anyone here a better welder than you'll find on an F1 team? Certainly I'm not, and it would be a pretty arrogant assumption to call the people on those teams hacks. None of us are likely working with better tools or materials, either.
    That's why people in the real world incorporate extra weld area, fishplates, sleeves in the case of a shaft, and other reinforcements. Because "as strong as the parent material" only holds true if everything is perfect. When it isn't, you really aren't sure how much room for margin for error is left, or how much you've compromised the parent material. The unknowns can kill you just as effectively as the knowns.

    • @defendermodsandtravels
      @defendermodsandtravels  4 місяці тому

      You seem to be very anxious on this subject.
      Never forget that failure will start in the flanges where the stresses are highest. Adding fish plates to the webs achieves nothing. Using a slant or Zed profile splice joint similarly achieves nothing.

    • @johnbarker419
      @johnbarker419 4 місяці тому

      @@defendermodsandtravels so you claim. I disagree, and there are plenty of others who also disagree. You're welcome to do as you wish, but there's ample evidence your method requires the work to be perfect. Good luck with perfection. if it were easy or simple, these other methods would not be so common.

    • @defendermodsandtravels
      @defendermodsandtravels  4 місяці тому

      @@johnbarker419 "Perfection" is an unbelievable weld quality, necessary for nuclear pressure vessels and the tendons of TLPs (tension leg platforms). The welds don't need to be perfect, just good or competent. I think I give a definition of the requirements in the video. Any half decent welder will be able to do this.
      If your approach is to tolerate dodgy welds and to compensate by adding more weld metal and reinforcing plates that's fine but I don't subscribe to it.

  • @petercunningham3469
    @petercunningham3469 8 місяців тому +1

    I think if you look closely at heavy vehicle frames you will see doubled panels In welded sections, you should realise that twisting forces are just as destructive to a chassis than shear forces I've worked on many large sections of chassis and construction machinery and I can tell you butt welds diagonals and any combination there of don't last without adding doublers of correct length and layout the welded heat affected area will crack when twisting force is applied to it.

    • @TheRoadhammer379
      @TheRoadhammer379 8 місяців тому

      Don't waste your breath, the video creator just discredits any other methods beside his, yet he's oblivious to regulations in other countries and he's definitely not an expert in frame splices.

  • @shutupstoopid4518
    @shutupstoopid4518 8 місяців тому

    I know you work like heck to put a flange on a pipe square and straight and I've seen serious pipe hammer from fluid in them ...all straight welds....thanks

  • @wayneriedlinger
    @wayneriedlinger 8 місяців тому

    Here in the Alberta oilfield many of the bigger heavy trucks used for moving drilling rigs had the chassis lengthen. Nowadays it is always a straight or 90 degree joint and has been for about 30 years now. But years ago I was always told by some of the older men I worked with that it had to be an angled joint.

    • @defendermodsandtravels
      @defendermodsandtravels  8 місяців тому

      Very interestng to hear that. The older guys will have had it fixed in their minds that an angled weld is better without being able to explain why (except perhaps with a lot of arm waving).
      Conditions where you live are particularly harsh because of the low temperatures.
      Thanks for the comment.

    • @TheRoadhammer379
      @TheRoadhammer379 8 місяців тому

      ​@@defendermodsandtravelsoh stop with the condescending bullshit. You neither live in Canada or the united states, so you are oblivious to the federal regulations on frame splices. How many comments do I have to reply to make you understand that you are not an expert in this field. Aside from the arm waving, please explain why federal regulations only approve the Z cut. Also, please explain why numerous states in the US WILL NOT PASS A MOTOR VEHICLE FOR ANNUAL SAFETY INSPECTION with a vertical frame weld repair...oh because that repair is suseptible to cracking.

    • @defendermodsandtravels
      @defendermodsandtravels  8 місяців тому +1

      @@TheRoadhammer379 I made it clear in the video that I know nothing about local regulations on chassis welding however I'd like to have a conversation with those who drafted them.
      You are very quick to assume that I nothing about engineering in North America. I have an engineering degree from Washington University; I am a professional member of ASME and ASCE; the design codes I have always worked to are API, AISC and AWS; I have worked on projects in the USA, principally in Houston.
      The comment I would make is that there's a disconnect between practice in the Civil, Structural and Energy industries on the one side and those involved in chassis repairs on the other.

  • @KurNorock
    @KurNorock 8 місяців тому

    People assume you need slanted or stepped joints in welded steel because you you need them when gluing other materials such as wood or plastic, where the glue may not be as strong as the base material.

  • @williebosman8056
    @williebosman8056 8 місяців тому

    Very educational, there is still a Mercedes structural guide for chassis modification that requires or suggests the angled joint. It would be interesting to find out why they recommend it.

    • @defendermodsandtravels
      @defendermodsandtravels  8 місяців тому +1

      Yes it would. Out of interest I looked at the chasses of a number of trucks and semi-trailers, incliding Mercedes, and all of the butts were straight cut.
      I wull have to take your word for it about the manual. I find it odd that there's a factory manual on chassis mods.

    • @marioreali5925
      @marioreali5925 8 місяців тому +1

      From the trucking viewpoint. Vocational truck frames are modified all the time when new for various jobs. The U.S manufacturers do provide guidelines for what can and shouldn't be done when welding on frames. The manuals will claim you shouldn't weld frames and then tell you how.

    • @TheRoadhammer379
      @TheRoadhammer379 8 місяців тому

      ​@@marioreali5925read more closely, the manufacturer clearly states "do not weld or drill on frame FLANGES". The flange being the top and bottom of the C channel. In the United States, the Federal DOT ONLY approves of the Z cut but this guy is an expert on torsional twisting force in the tens of thousands of pounds of torque on semi truck frames, oh wait he isn't.

  • @norduferhandel4512
    @norduferhandel4512 8 місяців тому

    I worked for a tier 1 company and in the mid 80's to the mid 90's both General Motors and Ford switched from a one piece frame rail on their pickup trucks.
    The GM frame was a "C" channel rear section and a welded box forward stub frame. These sections were joined and welded straight down the side of the rail, one side only.
    Then the overlap had upper and lower "fingers" that were also welded.
    I agree that all the BS with angle cuts and Z cuts are a waste of time.

    • @TheRoadhammer379
      @TheRoadhammer379 8 місяців тому

      Except you'd be wrong. I assume you are American, so I'm going to assume you know what the DOT is, more precisely the Federal DOT that oversees semi trucks. The "silly" angle or Z cut you so quickly shit on is the ONLY approved method of frame splicing by the Feds.

    • @norduferhandel4512
      @norduferhandel4512 8 місяців тому

      @@TheRoadhammer379 which is kind of funny since the OEM's who engineered and tested these frames, and which we did long term cycle testing in facility for the OEM's.
      Pretty much did a vertical splice weld with horizontal top and bottom channel welds.

  • @gilesyful
    @gilesyful 8 місяців тому

    A factory chassis is normalised eliminating stress at the welds that is hard to achieve in the home workshop. Is this a factor where fatigue is an issue

  • @markwinton4827
    @markwinton4827 7 місяців тому

    The dominant stress in a beam is the Principal Stress which is parallel to the longitudinal axis. When assessing the weld for fatigue if the joint is oblique then the component normal to the weld is the sine of the angle to the axis times the longitudinal stress. Therefore, for say a 45-degree splice the stress normal to the weld that initiates fatigue is approximately 70% of that for a vertical (90 degree) splice.

    • @defendermodsandtravels
      @defendermodsandtravels  7 місяців тому

      It appears you have got some engineering knowledge (maybe a professional engineer?) but you have unfortunately missed the main point like many other viewers.
      If you are looking at a fatigue failure (which wasn't the subject of this video) it will start in one of the flanges which is where the highest bending stresses are. As soon as the crack has gone through thickness it will propagate very quickly into the web and failure will follow immediately. The angle of the web weld will have virtually no effect on the fatigue life.

  • @romantkachuk168
    @romantkachuk168 Рік тому +2

    I've heard that the steel gets weak close to the welding points due to high temperature exposure and potential damage from the welding itself. So by making a longer cut the weakness gets distributed across longer joint. It might only apply to a non professional welding though. Does it make sense?

    • @defendermodsandtravels
      @defendermodsandtravels  Рік тому +6

      You are referring to the HAZ (heat affected zone) properties. The HAZ should have a yield stress at least as high as the base metal but it can be more brittle if a poor welding technique is used.
      However you are missing the main point; bending failure will start when the top and bottom flanges get overstressed. Putting an angled joint in the web is irrelevant.

    • @romantkachuk168
      @romantkachuk168 Рік тому

      @@defendermodsandtravels thanks for reply. I really enjoy your channel

  • @donsmith9081
    @donsmith9081 8 місяців тому

    Thanks for doing all the calculations.

  • @jackrichards1863
    @jackrichards1863 5 місяців тому

    Fear. Without your skills and understanding the assembler is attempting to make the best connection possible. Life may hang in the balance on the integrity of this joint. In our mind, the longer connection is probably the stronger? We surmise. I don't but the evidence is visible. Hence the stepped vertical joint. Below a writer says a longer bad weld is better than a shorter piece the same. Qualified and studied welder operaters know only a good weld of the appropriate filler mate is acceptable. In NZ these joints are scrutinised by a book of rules. Visually i see a fish plate bolted in and a vertical welded seam to remove fretting. Thanks for a very practical view of the process.

  • @NollEngineeringPerformance
    @NollEngineeringPerformance 8 місяців тому

    It’s easier to get a good horizontal weld than vertical and you can’t always flip a truck frame up in the air to keep the puddle from falling out of it. Those who think it’s easy to weld a vertical on a truck frame aren’t doing it in the field, regularly, with a body on it and fuel tank straps/body mounts/crossmembers/exhaust/hangers/etc in the way. I’ll take a 45 to lay my weld into all day over a straight cut

  • @francoisroos2014
    @francoisroos2014 7 місяців тому

    Could not read all the comments, maybe mentioned, the reasons offered, fatigue and bad welding is true, you also have to consider the welding material strength. A chassis is regularly made of 350MPa material and your weld could be less, in addition the area where materials mix might have completely different properties. My welding instructor used to say before you weld ask, can you not bolt, rivet or glue. His argument was that on unsure materials the effect of welding can be very unpredictable and you have to be aware of this.

  • @davidfrick383
    @davidfrick383 8 місяців тому

    Generally in my experience , when one welds a straight line in a chassis ie. a truck in an off road configuration it creates a weakening effect to the frame. The weld won't break, just alongside the weld in the parent metal will though . So often a triangle or diamond patch is welded and plug welded over the top of said joint as a reinforcement and miraculously no breaks occur. So yes in an on road car a single weld could work perhaps forever. Would you like to bet your life on it though in catastrophic high stress off road situations? Everyone has seen frames break as constructed by a manufacturer. which is why one often sees on off road vehicles frame metal welded boxing a frame or welded right over the top of existing frames, thicker frames to stiffen and resist breakage out in the back country.

  • @raytaylor4421
    @raytaylor4421 8 місяців тому

    I checked the 'NATIONAL GUIDELINES FOR THE CONSTRUCTION AND MODIFICATION OF STREET RODS IN AUSTRALIA '. It makes no mention of chassis joint types.

  • @MitzvosGolem1
    @MitzvosGolem1 Рік тому +1

    Torsion and fatigue crack propagation?

  • @pettingellhammer
    @pettingellhammer 8 місяців тому

    Welds shrink as they cool leaving the area right alongside the weld in stress. That’s why weld repairs usually fail at the edge of the weld, it’s rare for decent welds to actually in the weld bead. The idea of the more complicated joints is with the longer welds there’s more area that has to crack before failure. As a maintenance welder with over 50 years’ experience I like to fishplate my weld jobs on frames to avoid any future failures. I use plates at least 3 times longer than the height of the frame rails and attach the fishplates with only horizontal welds. The mistake that I’ve seen several times is welders will run vertical welds at the ends of the fishplate, figuring it’s stronger but in actuality they are only causing 2 more vertical stressed areas in the frame. Vertical welds on frames should be avoided if possible, especially on highly stressed truck frames.

  • @woodennecktie
    @woodennecktie 6 місяців тому

    you are absolutely right , but if your goal is to fight car backbenchers logic on how everybody is doing it wrong , you need an extra lifetime. but thank you for this efford.

    • @defendermodsandtravels
      @defendermodsandtravels  6 місяців тому

      My aim is to put the information out there for anyone who is interested. I really don't mind if viewers choose to accept it or not.

  • @johnallen3555
    @johnallen3555 Рік тому +1

    mmm
    - the issue with both the inclined and the z cuts is that on the top and bottom flanges, the weld, with its stress concentrations and potential defects are right angles to the principle bending stresses in the chassis ( yup in the very direction that the flange would crack if it were going to crack)
    - there is no dispute that a factory butt weld is good and can be full strength, it would be a very exceptional automotive workshop that would subject its welds to the level of testing that woud be applied to say a steel bridge, or oil rig fabrication
    = the assurace of a theory compliant, defect free weld is just not commonplace in the automotive repair industry as it is in other industries. ((yes, we would should send a steering component away for xray testing, not so much for chassis work. yes there are other test options, good luck finding a shop that has a quality process that includes NDT (no distructive test) on the landrover chassis repair.
    - there is a shop in my town that I have no doubt does have these quality management processes as they build and export modified vehicles of a very very high standard all over the world. This is well above the standard of the majority of shops that do chassis works
    Toilet paper tears along the dotted (stress concentation) line when it exposed to principle stress that is at perpendicular to the peforation line.

    • @defendermodsandtravels
      @defendermodsandtravels  Рік тому +2

      A competent double sided butt weld with a bit of reinforcement (i.e. overfill) will be full strength. One can make full strength single sided butt welds (as in all tubular structures) but the measures required to achieve this are beyond the capabilities of most workshops so I'd recommend a reinforcing plate, suitably profiled at the ends.
      The toilet paper analogy is unhelpful unless you have a weld like a dotted line. Yielding will start when the effective stress (or von Mises stress) exceeds the yield stress of the steel irrespective of the direction (the effective stress is a scalar quantity, not a vector). Putting the weld at an angle to the principal stress makes no difference.

    • @johnallen3555
      @johnallen3555 Рік тому

      I always approach repairs (well, field repairs anyway) as dodgy welds, (not wisthanding that we used the very best and highly competent trades available so to achieve high quality welds, theny were untested and often done under difficult circumstances (upside down in a confined space, in the middle of the night, whilst putting out grass fires under a failed machine)
      If a crack were to initiate in the weld area (due to small defect say), the jolly crack will naturally want to go (unlike Star Trekenterprise), where its predecessord have been before (given the same sort of loadings) and have a field day with any weld defects, stress concentrations and the like
      The above concerns in no way relate to the normal theory and assessment of defect free tested good welds and assemblies done under controlled conditions..
      I guess this highlights an aspect of my background that lived and breathed engineering and maintenance in a less that ideal world.
      I really appriciate the view on things and expertiese that you have to share :)

  • @drew79s
    @drew79s 8 місяців тому

    This is an interesting one because most of the analysis and the underlying reasoning are wrong.
    In Australia and New Zealand the reason that legislation refers to a requirement to scarf or fish mouth joints is because it's instructed inside of manufacturers body builders instructions and repair instructions.
    Manufacturers are quite clear on this for two reasons; the first is that welds frequently underperform in shear in the real world, certainly in situations where you have a plain butt joint without reinforcement, the material properties of the weld material, parent material and HAZ all vary progressively along the weld zone. This makes the area very sensitive to cracking, so increasing the joint area helps a lot, this is accomplished by diagonal cutting the weld area.
    The second is that the section changes thoughout the weld, which leads to stress concentration due to material thickness variation throughout the region. This also leads to risk of cracking in the same way.
    Most manufactories (all who authorise weld repairs in loaded areas that I'm aware of) instruct that you must create a diagonal cut with at least a 3:1 length to height ratio and, ideally, fish plate with an extension over the repaired structure and taper down over that same 3:1 ratio in both directions past the repair area. This is to ensure that you don't get localised cracking in the repair zone, which is a frequent issue.
    The other thing is that your bending moment diagram grossly oversimplifies the vehicle structure and the loads are grossly underestimated which leads to some odd conclusions.
    The reason the spring hats are integrated into the chassis the way they are is to create a local reinforcement and a stiffness gradient away from those interfaces, same for the body mounts. Similarly the body mounts are isolated for two reasons; sound and to prevent stress being passed through the body.
    Finally, all the joints you illustrated are civil construction joints and designed specifically to avoid this problem, all of the joints you presented are end features terminating into another structure, none are a mid span repair.
    Finally, if you're experiencing bending in your chassis rails you're doing something very wrong. I've only ever seen that in crash. The mode you're trying to avoid is fatigue failure from high cyclic loads, which usually occur at points of high stiffness variation or where initiating weaknesses exist... As outlined above.

  • @neilthomas649
    @neilthomas649 8 місяців тому

    Very interesting analysis. I do however think that unless you grossly overload the vehicle, chassis failure will be caused by fatigue and dynamic loading. Under such a failure mode the quality of the weld is vitally important. Manufacturers usually have their weld procedures and quality checks in place hence you only see vertical welds. A poor vertical weld together with fatigue failure can result in catastrophic failure. The longer weld may first give an indication of failure. A modified chassis weld will more than likely have many inclusions worsening the fatigue strength.

    • @defendermodsandtravels
      @defendermodsandtravels  8 місяців тому

      Something like 90% of failures in metal structures are due to fatigue which emanate in the zone of highest fluctuating stress usually initiating at a defect or stress raiser. For most bending members this will be in one of the flanges. Once the crack has started it'll just grow at an accelerating rate until fast fracture takes place. Angling the web weld at 45 deg will make no difference.

  • @Buildituniversity
    @Buildituniversity 4 місяці тому

    With a Z notch running longer than the frame is deep (let’s say a 12”splice on a 6” C channel) wouldn’t having more continuous base metal crossing the joint spread more of the load of the weld into the centre of the channel where the load is basically zero? It may not change the tension on the bottom or the compression on the top welds, but not cutting the base metal completely horizontally would mean the forces that do apply are spread between half welded steel and half I disturbed steel. Wouldn’t that decrease the chances of a catastrophic failure?

  • @ronaldstrother6693
    @ronaldstrother6693 Рік тому +1

    Do you have a working example applied to a vehicle to show?

    • @defendermodsandtravels
      @defendermodsandtravels  Рік тому +1

      No I have demonstrated what the best weld configuration is and leave it to others to show how to lay the weld metal. I may do more on this later in the year.

  • @andynicoll8566
    @andynicoll8566 5 місяців тому

    In wood we're using glue rather than a weld and we know for sure that end grain to end grain does not bond well so we increase the gluing surface of the joint by a scarf joint a step joint or an interlocking joint.

  • @malcolmyoung7866
    @malcolmyoung7866 7 місяців тому +1

    Technically ‘smoke and mirrors’ to me but way more than enough layman jargon for me to understand. Just what the internet needs and absolutely great info for starting a bar brawl(quite a big bar brawl) if one wanted to. I watch a lot of ‘fab’ videos and if any chassis welding is occurring.. it’s all cut at 45 degs etc. The reasons being to carpentry and wood structures.. hits you right on the end of the nose(that bar brawl is still happening) and your explanation showing there is ‘no difference’ in the outcomes means that both sides of the argument can go home to their wives(bloodied and bruised) suitably justified in their own minds to who was ‘right’.. one half of the ‘argument’ spending more time in the pub due to a more efficient method of joining chassis.. possibly with more clients and more money in their pockets..

    • @defendermodsandtravels
      @defendermodsandtravels  7 місяців тому

      Yes the bar brawl has been quite fun. I am very happy to debate different opinions but the few really abusive comments get deleted.

  • @WilliamProsser-v2m
    @WilliamProsser-v2m 5 місяців тому

    Whilst working in Alaska, I noted that the usual railway welded joint failed vertically, especially in extreme cold weather. So I concluded that metal behave in extreme cold conditions. A crack about 45 degree to the joint then formed, due to the rail being flexed up and down, a lump the size of a small loaf of bread would eventually break-off and all traffic stopped. Do you think this failure could have been avoided, if the rail had been supported under the joint? This was a frequent field failure. WDP

    • @defendermodsandtravels
      @defendermodsandtravels  5 місяців тому

      I can't envisage what you mean when you say, "the rail supported under the joint".
      Extreme cold weather raises different problems. It is vital for all of the zones (base metal, HAZ and weld metal) to have good low temperature toughness. If this isn't the case you can get fractures from quite small defects. I'd expect such falures ro emanate from welded attachments to the top or bottom flange.

  • @andrewiannello6548
    @andrewiannello6548 8 місяців тому

    You just explained the reason you don't weld vertical butts. Because the load is greatest at the top and bottom flange. If the weld fails, the chassis separates. If you inclined it, the top and bottom welds are offset and the inclined weld is longer, hence stronger.
    If you look at heavy plant equipment many connections are sleeved and the welds are inclined or a wave shape, designed to reduce the heat on the original member in the vertical direction and distributing the weld load over a larger area.

    • @defendermodsandtravels
      @defendermodsandtravels  8 місяців тому

      It doesn't matter if the flange welds are offset. If you get a crack in either of those welds it will propagate through the web until failure occurs irrespective of how the web has been welded.
      The argument that the weld is stronger if longer is seductive but erroneous. The steel (whether welded or not) will start to yield when the effective stress is greater than the yield stress. As the load is increased the area of yielding increases until plastic collapse occurs (in practice the chassis member fails when it gets a permanent set and is no longer fit for purpose). The weld length doesn't come into it.

  • @WilliamMoser
    @WilliamMoser 8 місяців тому

    Im fairly sure ive seen a z spliced beam in industry, i will ask a structural engineer. I find this pretty interesting as i dont trust my welds as far as i can throw my MIG welder - i could throw my inverter stick welder way further.

  • @anthonylimjoco5958
    @anthonylimjoco5958 8 місяців тому

    From the offroad racing side I was thought to splice with a semi circle weld. We were shown failures with the straight vertical splice. I've always wondered if there was other factors involved to the vertical splice failure. Unfortunately, I weld based on designed drawings and do not have much data.

    • @defendermodsandtravels
      @defendermodsandtravels  8 місяців тому +1

      I can assure you the weld didn't fail solely because it was a vertical splice. As I have tried to demonstrate other weld profiles are no stronger. It's a mistake to look at a failure and to attribute it to one cause unless you know the story.

  • @louisvanrijn3964
    @louisvanrijn3964 8 місяців тому

    Dear Defender mods. Interesting, and mostly correct. But never compare steel with wood structurally using the same stress formula's
    Wood is anisotropic. Steel is isotropic: same properties are in all directions.
    Aircraft Fir wood example: 50 Mpa compression strength grain wise, and 5 Mpa shear strength along the grain. Ratio = 1:10 , so a glued scarf joint must be 1:10 at least.
    The repair manuals suscribe however 1:20 scarf joints in wooden aircraft girders, if the same bending has to be transferred.
    Concerning the steel welded joints: fatique tests on welded joints (repeated loads hence, very often repeated) show a stress concentration of 2.2 in such a weld.
    Otherwise said: the weld behaves if a groove with a 2.2 local stress increase is added. Local stress increase, only present near the weld.
    So: if fatique is the sole design criterion, the weld must be 2.2 times stronger than the surrounding.
    Hence it is wise to add the joint in a low loaded area, you showed so nicely in the Moment line. That was a solid begin of the video.
    If a joint is placed in a highly loaded area, reinforcent plates must be added. But the have their own stress concentration factors where they begin, and end. It is not so easy to design a fatique resilient repair. Static strength is never a topic on a chassis, except in a crash situation.

  • @smjones4238
    @smjones4238 6 місяців тому

    Quite possibly if the frame was heat treated after all factory welds were done the new cut+weld would somehow be compromised. Putting in a stepped or angled joint would spread out the stresses and make it last?

    • @defendermodsandtravels
      @defendermodsandtravels  6 місяців тому

      Quite wrong I regret to say. The stress field in the beam is in equilibrium wither applied forces. Using an angled or stepped weld doesn't magically reduce them. This would violate the laws of physics.
      Also thin sections like this aren't heat treated.

  • @angelsierra1988
    @angelsierra1988 Рік тому +1

    Fantastic Informative Video !! Thx !

  • @christopherbuckley7544
    @christopherbuckley7544 5 місяців тому

    Okay, novice here, and I'd have to say the advantage to an angle weld is a longer weld length, which can compensate for margins of error in workmanship, i.e. sloppy cuts, sloppy welding, inadequate alignment. This theory seems to have been confirmed by other comments from experienced and informed persons.

  • @anomamos9095
    @anomamos9095 6 місяців тому

    The purpose of fish mouth zigzag or angled joins is not because they are in anyway particularly stronger in a static load but because chassis flex and bend they are far less likely to propagate a fracture.
    The engineering requirements may vary but generally you need an overlap of six to eight inches with riveting or rosette welds, a fish mouth or similar plus a diamond plate covering the main joint.
    The strength gain is in not putting a brittle weld joint in a flex line.

    • @defendermodsandtravels
      @defendermodsandtravels  6 місяців тому

      Are you a structural engineer?
      I don't know where your theory has come from. It is certainly not in accord with any of the recognised international design codes (e.g. AWS or AISC).

    • @anomamos9095
      @anomamos9095 6 місяців тому

      @@defendermodsandtravels automotive engineer, computer engineer. Auto mechanic.
      I have not been in the auto field for thirty years but the one thing I definitely remember is but joints are not allowed and will fail inspection and get your vehicle defected off the road

    • @defendermodsandtravels
      @defendermodsandtravels  6 місяців тому

      @@anomamos9095 If you can point me to the design code or regulation which states that I'll look at it.
      We also need to alert the semi-trailer manufacturers. You'll find that where there's a change in section in the chassis rails a straight butt weld is used (certainly in Europe and in Asia).

    • @anomamos9095
      @anomamos9095 6 місяців тому

      @@defendermodsandtravels .
      It’s been thirty years since I was involved in the automotive field so I don’t remember exactly where to find the regs but you can try searching the hot rod design specifications or vehicle modifications rules from Australia (New South Wales department of motor transport port).
      Trucks are not the same as cars and 4x4 light vehicles so depending on the country there may be different standards applied especially In laxer places.

  • @HamiltonSRink
    @HamiltonSRink 8 місяців тому

    I personally have seen a warning label applied to truck chassis: "Do Not Weld". Which tells me there are things going on in a chassis that the O E manufacturers want to distance themselves from any legal liabilities. On the other hand, there are videos from Pakistan open air repair projects doing mind blowing alterations and repairs on truck chassis.

    • @TheRoadhammer379
      @TheRoadhammer379 8 місяців тому

      You should read a little more closely... DO NOT WELD OR DRILL ON Flanges, that's what the manufacturer decal ACTUALLY states. The flange being the top and bottom of the C channel frame. Do you realize, we'll probably not, but manufacturers of semi trucks in the United States drill and weld on semi truck frames to install step boxes, chain carriers, and brackets??? Our facility lengthens semi truck frames, you are talking about a vehicle that hauls 40 tons over hundreds of thousands of miles, withstanding immense torsional torque twisting under load. Do you know what the torque output is in first gear of a 550hp semi truck once torque multiplication of gears is factored in... a caterpillar diesel producing 2050lbs-ft of torque at the crankshaft is putting 118,000lbs of torque to the ground in first gear. And Z spliced frames are holding up to that force. But hey, he's an expert and I just do frame splices under federal government scrutiny, what would I know.

    • @HamiltonSRink
      @HamiltonSRink 8 місяців тому

      @@TheRoadhammer379 Did you read the part of my comment after" on the other hand,"?

  • @guypehaim1080
    @guypehaim1080 8 місяців тому

    Many fabricators use fish plates to reinforce chassis joints when modifying the chassis. Sometimes they are employed when joining two different chassis to form a new vehicle. Is this endeavor worth while?

    • @defendermodsandtravels
      @defendermodsandtravels  8 місяців тому

      Shouldn't be necessary but if there's any doubt about the strength of the welds use reinforcing plates but remember the highest stresses are likely to be in the top and bottom flanges.

    • @guypehaim1080
      @guypehaim1080 8 місяців тому

      Thank you for answering my question. It makes sense that if the original chassis was made without reinforcements then the modified chassis would not require them except possibly where the chassis is to used beyond its original design parameters.@@defendermodsandtravels

  • @mhughes1160
    @mhughes1160 8 місяців тому

    Very interesting 🤔
    Thank you for sharing your knowledge 👍

  • @donsmith9081
    @donsmith9081 8 місяців тому

    I have always heard that it makes the material harder in the heat affected zone-more prone to cracking. Apologize in advance for not having a chance to watch full video.

    • @defendermodsandtravels
      @defendermodsandtravels  8 місяців тому +1

      The HAZ can be more prone to cracking under certain circumstances e.g. if there's moisture present during welding causing the release of hydrogen. This will of course happen irrespective of the joint configuration.

  • @s7courier
    @s7courier 8 місяців тому

    Just a curiosity question. Why is a fish-type patch also included in most of the UA-cam videos on chassis modifications to any type of reconnection joint? Is it for lack of confidence of the welder? or what else?

    • @s7courier
      @s7courier 8 місяців тому

      BTW: I enjoyed your analysis in terms of statics and dynamics.

  • @servicetrucker5564
    @servicetrucker5564 8 місяців тому

    I have a tow truck that my dad doubled and boxed the frame and everything is straight across and wrapped around the flanges. Pretty much a big C on a little c then boxed into a D. He wasn’t an engineer but it ain’t broke yet

  • @electronsmove
    @electronsmove Рік тому +2

    Weld up two C channels taken from old trucks and use each weld shape on a different sample and then load test them under bending and torsional loads against a none spliced frame rail and see what happens. Easy youtube video for you.

  • @GWAYGWAY1
    @GWAYGWAY1 6 місяців тому

    The inclined splice is used in joining wooden structures , but that is because of the perceived weakness of glues and the base materials. With modern glue a butt joint is also working because the large area of the end sections and the absorbency of the end grains. Early preconception for welding comes from the wooden model and the desire for as big a weld as possible because of poor materials of the welding rods and poor fusion capabilities. 😊

  • @dmc5681
    @dmc5681 8 місяців тому

    Dynamically loaded structures e.g. I beam fabricated with top flange, bottom flange a web are often done in a manner to stagger the welds to try and provide a means to arrest a possible fatigue crack as there is no pure vertical weld fracture plane. Not seen angled ones though. Search for skeletal railway wagons

  • @roadkisserful
    @roadkisserful 8 місяців тому

    I like it and as they say "proof is in the pudding" to construct it and stress it that is what Greek philosphers have done 🙂

  • @paladin0654
    @paladin0654 8 місяців тому

    Angled welds: more joint area than 90 degree joints and spreads stress along the weld line instead of the corners.