Subscribed! As a design engineer and bike enthusiast I had usually separated one thing from the other, thinking of cycling as a separate hobby. Your channel has brought the two together for me and has made me more willing to apply engineering thinking to how I look at bikes. Keep up the good work dude.
I like how there's a Giant tcr in his video, for me Giant's the best brand on the planet !! Not because of the name Giant, not because of the look of Giant's bikes, not because of the country it comes from, not because of the color of their bikes, not because of etc. Many people do choose, like and say this or that brand is the best because of silly reasons and others like mentioned above, but because Giant is the only 100% themselves brand, big or small brand, they even make the carbon and the metal themselves. That's why it's the best. They're are some good brands like Allied cycle works (USA) and ax-lightness (Germany) which make everything themselves except the carbon and Lemond bikes (USA) which is in the process of becoming only the 2nd 100% themselves brand because they building their own carbon manufacturing facility and they design and make bikes themselves to.
simplicity is the best of everything! you have covered in 14min more than I remember from the school time (not being mechanical engineer) - super great! thank you!
Great video analysis. Would love to see this become a series of more bicycle truths. Im a design enthusiast (architecture student) and shop employee. I must constantly go against the industries lies to make sure customers get what is best for them and not believing the hype behind the marketing. Billions of dollars a year are used to fool good people into buying things that they do not need and do not affect their performance.
I’m no engineer but I have never been convinced by all the marketing BS from within the cycling industry, especially in regard to the subject covered in this video and the previous. Thank you!!
Correct me if I'm wrong: If there were 2 bikes, Bike A has standard 73 degree seat tube angle and Bike B has something steeper (say 75 degrees). If both had their saddles set up in the same position in relation to the BB, ie Bike A with an inline seatpost and Bike B with a set back seatpost, Bike B would have more compliance through the seatpost than Bike A? Because the steeper seat tube angle would mean that the seat tube/top tube joint is further forwards in Bike B, and thus the lever arm (L) for bending is longer? Assuming everything else, ie seatpost diameter, material, cross section, etc is constant, that is. That's for the great content! As a mechanical engineering student you brought learning out of the classroom for me.
Great video. Yourself & Luescher Teknik speak the most sense in the cycling industry Would you recommend replacing a standard 27.2mm carbon post with a 25.4mm post in an effort to improve comfort? My frame is a 1980s Tommasini with room for 25mm max. tyres and I find it a bit too harsh. If so, would a plastic be the best seat post shim material to use? I wouldn't fancy carbon (post) to a typical aluminium (shim) to steel (frame) for galvanic corrosion reasons
Hi Gary. Thanks for the comment. As for the shim, go ahead. I have also run a 25.4 in a 27.2 frame. At these small diameters, the difference in second moment of area is small however, so you may not feel a difference. I'd still recommend Alu for a shim, with a liberal coating of grease. Or even better, if you are custom making the shim, anodize it. Use 6000 series not a 7000 series as they tend to corrode less. You could try Delrin (an engineering plastic) but this may creep under clamp compression over time, meaning you may need to periodically tighten the seatpost clamp. Cheers
@@PeakTorque Thanks very much for the detailed reply. I was thinking of going from a standard stiff 27.2mm post to one with more engineered compliance (like the Cannondale ones), so going down in diameter at the same time would make sense. I'd probably draw the shim myself. I'm getting a stem face plate & Garmin mount made of 6082 aluminium and anodised soon, so I'll stick the shim on that order. Thanks again for the great advice
In fact, if you double the diameter of a tube with a fixed wall thickness, the second moment of area will not increase by a factor of 16. That's true for a solid rod, or when the wall thickness increases with the diameter. If the wall thickness is constant and small relative to the diameter of the tube, it will increase by a factor of around 8. This is since r^4 - (r-c)^4 is a cubic function of r, while r^4 - (0)^4 is quartic (here c represents the wall thickness). Of course, either way the point is that the diameter of the tubes is hugely important.
great video again, thank you for teaching me! I wonder for some time now, why there are no thru-axles for rim brakes available... As you pointed out in your videos, everybody's talking about stiffness when it comes to bicycles... So, it should be logical to offer thru-axles for rim brakes, wouldn't it? Can you explain the technical differences and hence the pros and cons for QRs and TAs? That is kind of a great favour, I'm asking for but I feel like this is a topic, which is quite neglected... Thank you in advance, greetings Markus
In the 90s when they relaxed the UCI rules a few bikes were made without seat stays. I have a superbike frame which was one of these designs, the Lotus bike was another. Shame the UCI has limited design so much, we could have had some really exciting bikes today.
I think the triangular frame is pretty much the best that you can possibly get in terms of weight/strength ratio. I am not sure about aerodynamics, maybe there might be some benefits to getting rid of the seat stays. In general, the double diamond frame is probably the best possible design. Deviate from it and you have to live with many drawbacks. That's the reason why most of these "fancy" looking frames like y shape or whatever never really caught on: they are mostly shit.
These videos (the two in this series, the TI bike video, and the Canyon seatpost video) are great. I know this was 2 years ago so not sure if you still check the comments, but it would be interesting to watch an overview video on stiffness of bicycle components to better understand which differences matter for riding and what is just marketing BS. Almost every bicycle component from frames to cranks to wheels is advertised partially based on stiffness.
As far as I understand, aluminium is far more “workable” than Titanium (triple butting, hydro/fluid-forming etc), so while Ti is a great material based on its properties... maybe the ability to create more refined shapes with aluminium actually make it a superior material to Ti? Or are Ti’s properties that good that it’s better than even a highly manipulated aluminium tube? Maybe a topic for a future vid... with a comparison grades of aluminium (6061, 6066, 6069) and cut through the BS on which might be “best”. Loving the channel!
Ti tubes are insanely thin. I was a field engineer for a well known laser manufacturer. A well know titanium bicycle company was looking at us to help with their production and so we were sent sample tubes. I never realized how paper thin the tubes are.
Loved the calm description at 2:00 regarding the manuf’s compliant stays - that said I rode a Ventum Tri bike on a test last year which is “stayless” (also downtubeless too a la Lotus) could get the tyre rubbing easily when powering out the saddle - takeaway good design but needs the engineering and structure to follow through - too many manuf’s are putting out rubbish and expensive rubbish too - same concept but rock solid but can’t buy one!! Diamondback’s Andean -
I’m really enjoying your content. I’m going to save these to she my sons in a few years to spark their imagination on how they can combine their school work and their passion. My wife is an oxbridge mathematician so hopefully they have mummy’s brains and daddy’s legs. Out of interest, what educational route did you take to get to where you are now? Keep up the great videos. P.S. don’t go too far down the Hambini swearing/slagging route. I ended up unsubscribing from him because of it. I think you have the balance just right at the moment.
Quite conventional STEM education really, but varied work experience. I studied physics, maths, chemistry, and design at college. I was terrible at Maths because i would often go to the boozer instead of lessons. I had some bad mates. But then i found MATLAB. I then did Mech Eng at university with a thought of going into finance. Deciding that was betrayal and too well paid i stuck to engineering. I started my career at the 2nd largest auto maker in the world, but since have had a varied career. Get your children to go for it. What it lacks in renumeration is made up for by achievements and specialty. I think its one of the few vocations where you can still really find a niche. It is not sitting in an office sending emails and quarrelling on Zoom.
First of all great video and good explanation on technical mechanics. Did you model all simulated seat posts as aluminium to show how the shape influences bending stiffness or did you model them in their real world material? Correct me if I am wrong. But since CFRP is an anisotropic material you can't use von mises stress to compare it with aluminium, since one criteria to use von mises stress is to have the same Poisson's ratio in all directions. Also, did you validate your simulation with real world testing?
I have a Thomson Elite for the Xc mtb , because it needs a long post without setback in 27.2,and yes,does not bend.(and saves weight)Tried it on the road bike,bit harsh,prefer the PNP ti post. Thanks,well explained.
Great video. In mtb they changed to 27.2 to 31.6 and the journalists says they are more compliant, on the other hand endurance road bikes use 27,2 seatpost for comfort... Seriously they just recite a poem given by the manifacturer these days...
Very nice video. What I'd like to know more of is things like fatigue life of various materials (steel vs carbon vs aluminium), things like manufacturing processes (carbon - classic pre-preg layup vs. RTM), aluminium (hydroforming vs normal butted tubes), as well as differences between joining techniques for steel, like TIG welding or filet brazing etc. Repairability of different materials would be a great subject too. Next I'd love to hear your thoughts about bikes which use hybrid or exotic materials, like magnesium, or Ti/Carbon hybrids - things like that... What would also interest me is the economics of manufacturing bikes - how can a motorcycle cost less than a high end bike? In terms of revenue, Ducati is only twice as big as Canyon so the old argument about economies of scale doesn't seem to be applicable... Also how close are Microshift to Shimano in terms of performance? Just my 2 cents
That's going to be difficult to discuss with any real world applicability as the different materials have different weaknesses to environmental damage (see the annual carbon fork recall by one or more of the big brands due to UV induced delamination). As far as econ, all that stuff is irrelevant. Marketing teams set a retail price. Accountants determine a production cost to maintain profit goals. Engineers then design a bike under that production cost limit. The consumer price of your bike isn't driven by production costs. Its marketing. Cost is determined, then the tech on your bike after. I notice no difference between MicroShift and Shimano, though I've not used the new hyperglide+
I wonder if tube shapes could be designed from the ground up from a stiffness standpoint and get the 'aero' treatment after the fact. I mean like thin plastic fairings over most of the tubes. Sounds a little old school but I think it would work well in this case.
Excelent video!! Ty for your work! It´s amazing how simple it is...Unfortunaly most of the people don´t have the knowledge to kill marketing! Keep on iwth your good work!
10:03: What makes you think that L is constant? Designers can opt to change the angle of the fork (and thus its length), or the length of the head tube (and thus the length of the fork)
L isn't fixed but compared to E and I it has much limited flexibility because it's driven by the bike geometry and kinematics rather than stiffness/compliance.
They DO NOT CARE. They make ‘truck loads’ of money from the BIG names in cycling. Otherwise what is stopping them from hiring/finding guys like this???
Great videos! I love your channel & factual/scientific basis of the information. This may be just me, but I'm unsure of the appeal of stiffness? Is it because of responsiveness in ride? Conservation of energy in peddling? I assume it works against comfort, hence the need for designing compliance into the bikes etc? The appeal of carbon for me personally had always been the allure of lightness/ aesthetics of the 'aero' designs; something that I have found a bit difficult to justify given my alu bike weighs less than 1kg more than the carbon bike I would have to spend £3-4k on... and as one of the humorous comments in your Ep1 video said, one can take a dump for the same weight gain... I wonder whether there'd be a market for Alu bikes that were designed to look more 'aero'- i/e/ not the conventional circular tube cross-sections? Or would they be too heavy?
Great video thanks ! I guess it was not really the point of the video but one little detail though : 1st moment of inertia != 2nd moment of area. They do have similar definitions but 1st moment of inertia has the dimension of kg/m², and it describes the mass distribution of an object relative to some chosen axis of rotation. You can get it from the second moment of area by multiplying by the surface density (assuming it is constant).
2:58 "Stiff, triangular structure. Not designed to bend." As a non-engineer, that is what I intuitively think when I consider Cannondale's goofy "kingping" contraption. I suppose the triangle and seat tube can pivot a bit, but it's clear they're trying MARKET the "comfort" geometry hype promoted by Trek and Specialized. I think I'd rather have a Ti frame anyway. What say ye?
How did you obtain a plausible FEA simulation for CF bending without having the correct E value entered into the software? That number depends on the layup - which you don't know
It is a triangle in the most general term, but you are missing details. The seat stays are not straight. They have curves or bends in them. You also have to consider the angle of the seat and chain stay. Granted, it won't deflect as much as the seat post is capable of, but there will still be some.
Hi there !! I have one question. In the last simulation, shouldn't the Thomson seatpost have been placed in the other direction? At first sight I would say that the stiffness of that geometry is higher if you rotate 90° the angle of the seatpost (or the angle of the force). Thanks for such a good content !! Keep pushing !! Cheers from Spain
The bike needs to be stiff enough to feel safe in handling. However wouldn’t all frames mor or less bend when pedalling? Some more some less, the question is if any energy is lost I.e. what is the frame’s efficiency. There will be heat losses, and this depends on the material.
What's the difference between automotive race f1/Gt4 and aerospatial grade carbon and carbon used in the top top top end from like the Tcr advanced sl, Emonda sl7 etc. You know the best highest end carbon from the highest end bikes from the top brands ? Ax-lightness which started out as a auto sport f1 carbon part manufacturer says the use automotive and aerospace grade carbon in their bikes like the Vial evo Ultra which can weigh between 4,4kg-4,8kg is it lighter and or stiffer or something ?
So, to keep the same stiffness but reduce weight. You can increase the diameter and reduce wall thickness to match the stiffness needed. Obviously, if you keep doing it, at some point the wall will be too thin and fragile. Why so many carbon gravel bike have more massive tube than a climbing road bike then? Gravel require more impact resistance and also more compliance to smooth out the road. Making tube diameter huge and thin doesn't achieve that.
Good explanation, I've never been interested enough to run any simulations myself or calculations (although im still riding an alu bike). What about the seat tubes with an offset to allow for compliance or even the Canyon Grail split thing.
Offset just increases the effective seat tube angle so when the load (that is generally vertical) is now further from the bottom bracket (in the direction perpendicular to the load), so the effective lever arm is longer so your deflection goes up. The split seatpost thing works by removing the sides of the seatpost and turning the whole thing into something like a leaf spring. The sides do most of the work here (think bending a ruler along its 2 different longitudinal axes, one is stiff, the other not, your taking the stiff parts out on the split seatpost).
haha, i was totally one of those people asking you about your stiffness ratings in one of your older videos! fwiw i was mostly just curious how you reached those figures plus i like to keep people honest!
l know you didnt intend to be funny in your commentary but you made me laugh alot thanks for calling out the BS !! l was surprised how much the different seat posts bend compared to each other WOW .l know now why my thompson rides so stiff and shocked how much flex a regular alloy post flex s
I might be super uninformed here, but it seems like steel has a roughly equivalent ratio of density to stiffness to both aluminum and titanium. First question would be what alloy of steel did you use for your numbers? Secondly, what is stopping steel frames from being exactly as light and stiff as aluminum and titanium frames, especially with modern alloys?
This would be a great project for aspiring engeneers graduates and high school students. However to many assumptions and more accurate modelling is needed to at the least ignite meaning discussions, beyond pub talk. All in all Good effort 👍
Would you be able to put together an analysis of oval chainrings versus traditional chainrings? Is there a real biomechanical advantage or is just a placebo effect? What is the impact of the degree of ovality? Chris Froome seems to believe in them, so would be helpful to have your view from an engineering perspective. Cheers!
I cant think of a reason to make a spaceframe out of cylindrical tubing other than for aesthetics and to make cutting of the tubes a royal pain in the ass for the poor buggers who have to make it :). If it's a proper spaceframe all the loads run axially down the tubes (in theory). As for compliance of seat stays ... I guess if they are spindly enough and possibly splayed then it will increase the deflection possibility ... if the chain stays are allowed to bend. I agree that it's a very stiff structure at the back and the only serious compliance is the seatpost ... a trusty cantilever in bending. Trek have a pretty good design with their isospeed system which has a genuine capability to modify the cantilever arm length and springiness. Keep the proper engineering stuff coming. You have a great knack for explaining stuff.
motorsport space frames get loaded in all sorts of crazy directions during unexpected departures from the racing line. So yes tubes are a good shape there. They aren't that hard to cut. and even easier on the high end stuff where a laser tube profiler just does it for you.
@@Cynyr good point on the laser cutting. I still dont get why round tubes in a spaceframe are better. By definition loads in a spaceframe member are axial or it ain't a spaceframe. Regardless of crazy loading, if the loads are going in through the suspension pickups and other major component mounts and these pickups and mounts are at a spaceframe joint and not slapped in the middle of a tube ... then everything is determinate. I'm not trying to score points here ... I genuinely dont get it.
@@stevecrabb1 think crash, not normal operation. Yes they probably are all mostly axial normally. But flip it through the infield, or so it around a tree, and good luck determining the loading. Also round tubes are ready to get.
@@stevecrabb1 interesting discussion here. Im actually fond of the latest isospeed spring concept on the madone. It is a neat and novel solution. Something seldom seen in road cycling design. I actually commend the designer on that. However, its a big spring with no damper. How does it feel at 110rpm trying to push 600w seated...who knows. I need to ride one. But I sure ain't buying a frame with that price tag. EVER. About the space frames, i can't actually think of a reasonably modern application where the loads are all axial. Especially not ground vehicles. Maybe there are some kit gliders/light aircraft that display this. I've seen some old old gliders where space frame members are just cables. If you take the wheels and a frame, and apply the static loads do you think the frame structure is determinate?.... I think this has confused the bike industry since day one.
@@Cynyr It's a bit like designing an aircraft to survive a crash :) not a lot of point. It depends on the formula and rules surrounding driver safety as to roll bars, leg protection etc. as to what you do. In any case smacking it into another car or wrapping it round a tree will involve a lot of tubes being put into bending as they get hit in the middle. A round tube is definitely not better in bending than a square/rectangular one. But its a bit hypothetical at that point. What I'm a little unsure of is whether a round tube in compression has a better strenght to weight ratio, if it has then it makes a lot of sense.
you mentioned you got rid of the thompson seat tube because it was too stiff, the giant TCR seems very similar. can you notice that difference when riding? thanks for the good video!
The Thomson elite was on my supersix. High top tube thus not much exposed seatpost. The TCR has a very long exposed seat post. Deflection goes up with free length to the power 3! So exposed length makes a huge difference.
@@PeakTorque Now I see why Cannondale have to make their small sizes SystemSix as ugly as it is. They need a lot of exposed seat post for the compliance to be acceptable for small riders. That make size 51 SystemSix Evo 's top tube slope a lot. (search for size 51 SystemSix, if you wonder).
am surprised this isn’t more popular, ok its semi technical but a) its visualized and b) presented in a human voice. regardless of bikes being one of the hottest subjects in sustainable mobile life those two factors should captivate a larger audience?
What software are you using for your simulations? Are your material properties all isotropic, or were you able to define a composite layup for an anisotropic material?
I thought the reason for going from steel to titanium to aluminium to carbon composite was because of beer canning. To get stiff and light the tube walls get too thin so less dense material is preferable as it preserves crush strength
Yes, so there is more than E an I. If not an alu bike could never be lighter than a steel bike. Since steel has higher E-modulus and yield strength, you could just match the diameter of the alu tube and reduce the wall thickness to reduce the weight. This is however limited by the local buckling strength of the tube wall.
hello mate, Thank you for your videos I'm a junior mechanical engineer, I work on my own bike project. Can you tell me what simulation software you use to simulate parts? Do you recommend a specific sheep one. Thank you
I would really if you could compare Allite magnesium alloy from Vaast bicycle against other materials ! Enjoy the information and education from your videos, cheers!
One thing I think about cycling is that we only ride double diamond frames because of the UCI. But ive never raced in UCI race so we are actually limiting ourselves by buying products that seldom need to be adhered to. So ok we're limting oursleves by frame shapes but to what degree? Listen to Mike Burrows occasionally when he's been interviewed and he'll say frame design is limiting bike speeds by a massive degree and the cycling industry is old fashioned, conservative and cannot think outside the box. And then I think about what Hambini says and he thinks the wheels make the biggest difference on a bike. So in his view the frame geometry must be ancillary. So I wonder what your thoughts are? Be good to get some discussion on that
Great video but in my opinion analysing a seatpost strength is a fairly moot point. The fact that the seatpost is inclined at an angle of 15-20 degrees from vertical means that most of the loading is the vertical axis and the tan of 15-20 is about 25-35%. For a 75kg rider that means that less than about 20kg of the riders weight is transferred into the angle in which the seatpost can deflect. There will be more deflection if the centre of mass of the cyclist is offset behind the centreline of the seatpost. Any "real" compliance from the rear end of the bike will be in the seat rails.
Yes the bending component is relatively small, but you have to treat the system dynamically. It's not a static problem. When you take into account bump inputs as dynamic forces and accelerations the rider weight is multiplied by a number of G. Even if just 1.5G, its significant.
Hi Alan. Significant compliance can and is engineered into some seatposts, even at a normal setback. One of the factors is how much of the seatpost is exposed. A tall rider like Peak Torque may have over 250 mm of exposed seatpost. (As he points out, bouncing can be an issue for compliant seatposts at high cadences.)
I have an steel Colnago Master Olympic. This frame has a crimped bottom , top and seat tube. Colnago claims, the the frame is stiffer with these crimbed tubes. Is that claim valid ?
Wait, what? How would higher stiffness negatively affect brake feel and modulation? Shouldn’t it be the other way around? Typically stiff things feel more responsive. Maybe too responsive? I’d like to understand this better.
Brandon Hicks yes it would feel more responsive and you would feel the ‘bite’ quicker. However, modulation is about adjustment of force. Softer springs provide slower acceleration/decelerations of forces therefore provide more compliance and adjustment. This is the reason why race cars are set up very softly sprung in wet conditions, to slow down the response of the brakes and cornering forces to prevent locking up etc.
My Colnago CLX 3.0 has all of the shapes that are supposedly too stiff and indeed it is stiff. Yet this is the bike I've set all of my best times for most of my courses. All of this is mediated with 28mm tires. Hambini argues that 23's are faster but he is an elf.
I often wonder why the stiffness (or lack there of) of the rear wheel is often ignored. I’m only 150lbs, but this is the only area I feel flexing under load.
If you weigh more and do jumping and tricks like I do you feel flex in wheels instantly! A great test of rear stiness of a bike is to do a 180 hop. If your bike can survive that its a stiff bike. If it can survive you doing it incorrectly and not breaking, well you got a tank! As a result when i get on a lighter bike feel genuinly scared the bike will just break cornering!
Very good my friend. I relish all your content. I like the tech stuff although i have zero knowlege. I hate maths physics and chem but i do ride and race bikes and have done so all my life. So i enjoy hearing about something i don't understand at all. Into my middle years i am currently thinking about electric bikes. I mean take my 400w and add about the same from an electric motor and riding a bike would be a new experience. I do like the look of that s works electric it looks the bizz. What's the engeneer's thoughts on that? Apart from the eleven grand price tag of course!
Anougher great video, thanks for keeping it simple. This is not a discussion what is better Carbon or Aluminum put how engineers can influence how a bike feels by making informed and intelligent decisions. It's just a shame that the marketing f#€€ whits get involved!
Tell the UCI to change their frame rules. They are based around the design of metal tubes not the properties of carbon fibre. Frame aerodynamics makes a lot more difference than the weight of frames but it way better to have monocoque carbon frames for its mechanical properties too.
This subject needs to be re-visited. I have 2 identical bikes, one disc, one rim. All parts & dimensions the same. Why is the rim bike so much more comfortable & generally livelier? Rim tyre pressures 95psi. Disc tyres 80 psi, & still the rim is more comfy. The only differences I can see are the beefed up front fork (obviously), & the thicker chain stays. Surely, the large difference in comfort & liveliness has to be down to the rear triangle, which seems to have more effect than you think.
The tension members stretch ever so slightly under load, and the compression members shrink in length, but there is no bending deflection on a well-designed truss.
Instead of focusing on seatpost compliance and comfort, you could as well have a more comfortable seat and pants. I have a comfort seat with a hole in the middle + the thickest possible seam in my pants (Bioracer and Assos). I have that aero seatpost and guess what? It is still very comfortable and as I hate flexy seatposts this really works best for me. And don't forget tire width and pressure... set priorities and stop talking about supermarginal gains in comfort of seatposts while it's really something marginal compared to all I mentioned in my comment.
If you buy your next bibshorts from Everve in Germany, you pick the thickness of the padding yourself, as they can be removed and altered to most thicknesses. You can have various pads, yes, in the same bibshort. Rtr
Your slide around 6min comparing a 40mm tube to a 60mm tube with constant wall thickness is interesting but not that usefull for the bike industry which is chasing weight. Going to a bigger tube at a constant wall thickness means heavier so one could easily say "of course heavier is stiffer". Same goes for your seat tubes shape comparaison actually. What would be the results with weight held constant accros shapes and materials ?
The seat stays on my carbon frame set have the shape of a sword with the flat parallel to the frame direction and are curved along their length in the accross frame direction, with no bridge for a rim brake caliper. So they don't form a triangular shape, as a triangle is a planar object, and the structure the rear "triangle" on my frame is, is not. So the bridge truss example is not applicable in this case as the truss members on the bridge, loaded with compression forces, likewise my seat stays, are not curvy, but are straight struts.
Great video demonstrating compliance compared to the cross-sectional area. Have watched alot of your videos since discovering this channel, really appreciate the engineering rigor behind your videos. I recently acquired a Supersix Evo Mod Team [same frame you had] and the first time I rode I, I noticed how little flex there was in the frame [especially the power transfer through the BB]. Coming from a CAAD12, this was a night and day difference. I came across this video from GCN that actually shows a surprising conclusion, that frame "stiffness" actually matters very little with regards to transfer, its mostly a perception of how immediate that power transfer occurs [Link to video: ua-cam.com/video/BH_AL4rxrp8/v-deo.html]. Curious as to what your take on this is. The test they conducted made sense and perhaps the perception in stiffness I'm feeling isn't actually resulting in more efficient power transfer, and more to the immediacy of that power transfer?
@UC08mbQ8UIX8DXSBFBO9VaZw curious about this as well. Does the deflection in the frame means that the energy is gone with a loss in power transfer? I am not sure about this. After deflection it will return back to its original position so no energy loss? On the other hand, descending @70kmph and making turns would be easier on a frame that flexes less in terms of handling, but thats another thing. I am not an engineer so curious on your take on this.
It seems to me that the bike industry is full of bs. I got into riding a few years ago and have upgraded my components on my aluminum frame and I love my cannondale synapse. Ive been looking at the new bikes and they all look the same and they all claim to be different, more aero, stiffer and better all around but the prices are ridiculous. Component prices are ridiculous for what they are as well.
The golf industry likes baffling its customers as well. It’s funny to hear consumers repeating the scientific tech jargon as they step up to the tee or during a cafe stop. I’m not innocent. Cool video.
We had many crazy shaped bike frames already in the 80/90ties-but i’m glad the UCI sticks to the 💎 diamond shape! In order to have fair races the rider‘s bikes should be similar in weight and performance. Plus not everything should be made of carbon fibre-it’s toxic waste and until today there’s no concept on how to recycle this shit-they still just burn it....
In your stiffness simulation, do all tubes have same wall thickness? The Elite seatpost has extra material in walls, so clearly extra material makes a difference. Also, that extra material in Elite seatpost is thickest in points which form a line parallel to the load. I wonder if you rotated that post 90 degrees, would it be even more resistant to flex. Towards the end of the video, you start talking about "compliance" and "feel" of the ride different seatpost materials/shapes provide, without backing those subjective terms with any data. Seems like a blemish on a series otherwise intended to dismiss marketing jargon.
Far yes the elite seatpost has non uniform thickness, measured and modelled from a real life example. Wall thickness and its distribution effects second moment of area (which the whole video is about). The orientation with respect to load (rider weight) is the same as it would be in real life with the saddle clamp fore-aft in line with the rider weight so i made sure of that. Simply put a seat post with a lower EI (stiffness) will be more compliant.
@@PeakTorque so, if looking for comfort. I should go with alloy seatpost with rather thin diameter thickness? My current carbon seatpost's weight (from merida) is 270g. Buying a Ritchey WCS AL2014 with 190g would be more compliant? Thank you
"If you double a tube's diameter, it gets 16 times stiffer." For thin wall tubes Ix = Iy ~= pi r3 t correct? So it gets 8 times stiffer, not 16 times. It would be nice to equalize the weights in the comparisons by adjusting the wall thickness.
In all the bikes I have ridden/raced over the last 30 years I have never thought any of them were not stiff enough. The problem has always been my legs! The cycle industry marketeers are so full of BS it is laughable.
Here are some stiffness measurements you can compare: Why It's Impossible For Steel Frames To Be More Comfortable Than Aluminium ua-cam.com/video/Lb4ktAbmr_4/v-deo.html
@@ChinaCycling LOL you may be good at Papier mache but you also work for Winspace now so I'm sure you could get it done. 😉 Just think, a bike that is actually as good as it supposed to be with no sudo engineering bs. 👍😁
Your engineering is good, but I’m not sure your application is at the same level. Some of this comes from youth and what has been lost regarding cycling history. If we ignore TT, especially on track, there’s not much to show that top level cyclists are faster than those who rode on bikes with steel “Standard Gauge” tubing. Which covers a long period of time which largely ended by the late ‘70s early 80s. So…. Let’s assume that TT gains are largely improved rider aero position (and I welcome any sound argument to the contrary). Ergo: large tubes, aero-tubes and components, non-round tubes, new materials, aero wheels,and so forth have essentially contributed nothing but marketing. That they’ve done in spades as you see the rampant inflation bicycling prices (even as it has been arguable that the cost of mfg. has gone down). Tire, fork, handlebars, seatpost, stem should be the primary sources of compliance, and in that order. Put on a set 21mm tires at 120 PSI, and on a smooth road you’ll feel the wing of a fly as you ride over it. Back in (I think) the mid-70s, there were successful Senior Tour riders on on Alan screwed and glued aluminum frames. These aluminum frames shared the same skinny tube diameters as the steel frames of the era. Your engineering will demonstrate how comparatively soft these bikes were. They saved weight. I doubt big sprinters could make use of them, but small climbers could. And for several years they were popular enough to also be sold under the branding of other bike manufacturers. Obviously this calls into question the idea that without stiffness, meaningful efficiency is lost. Despite rider preferences, I’d offer that if a frame is stiff enough to handle well, then it’s stiff enough to race. We don’t often hear much these days about being supple on the bike. This is probably a loss for all riders concerned. Why are you sensitive to seat-post stiffness? Do you bounce on your seat? Perhaps not, but if you haven’t considered it, we’ll maybe it’s time to. Also I’m not issue of braking difficulty when braking. Personally, I tend to take weight off the seat in any kind of challenging braking. This is both to facility shifty my weight as necessary and to radically reduce unsprung weight (which effectively is the whole bike rider combo). Maybe you can explain this one to me better. Anyhow just a few thought from the salt-mines.
@Peak Torque have you watched any cycling about videos? he has a video that's similar to this and gets to the same conclusion as you: ua-cam.com/video/Lb4ktAbmr_4/v-deo.html
Subscribed! As a design engineer and bike enthusiast I had usually separated one thing from the other, thinking of cycling as a separate hobby. Your channel has brought the two together for me and has made me more willing to apply engineering thinking to how I look at bikes. Keep up the good work dude.
As someone from an engineering background and who now works in the cycling industry I agree that titanium is a good choice for a frame.
I have a titanium frame and, well, I can't stop riding it.
They are building bike out of Bamboo these days : look them up : titanium is cool
I like how there's a Giant tcr in his video, for me Giant's the best brand on the planet !! Not because of the name Giant, not because of the look of Giant's bikes, not because of the country it comes from, not because of the color of their bikes, not because of etc. Many people do choose, like and say this or that brand is the best because of silly reasons and others like mentioned above, but because Giant is the only 100% themselves brand, big or small brand, they even make the carbon and the metal themselves. That's why it's the best. They're are some good brands like Allied cycle works (USA) and ax-lightness (Germany) which make everything themselves except the carbon and Lemond bikes (USA) which is in the process of becoming only the 2nd 100% themselves brand because they building their own carbon manufacturing facility and they design and make bikes themselves to.
I've returned to metal and titanium is fine with me.
Engineer here…. Agree 🚀
Ep 3. Joint Stiffness. Welded joints vs composite joints?
and lugged
@@31.8mm and fillet brazed :-)
up for this too
My joints are stiff.
simplicity is the best of everything! you have covered in 14min more than I remember from the school time (not being mechanical engineer) - super great! thank you!
Great video analysis. Would love to see this become a series of more bicycle truths. Im a design enthusiast (architecture student) and shop employee. I must constantly go against the industries lies to make sure customers get what is best for them and not believing the hype behind the marketing. Billions of dollars a year are used to fool good people into buying things that they do not need and do not affect their performance.
Your content is fantastic. Salad Fingers took it over the top - I haven't thought about grubby taps in years.
Worn cleats and rusty spoons feel the same to my fingers
The stiffness is between customer's ears...
Very well put together, and super informative. Thanks!
I’m no engineer but I have never been convinced by all the marketing BS from within the cycling industry, especially in regard to the subject covered in this video and the previous. Thank you!!
I really like the quality of your work!
Merci
Ditching seatstays sure would help with fitting belt drives.
Correct me if I'm wrong:
If there were 2 bikes, Bike A has standard 73 degree seat tube angle and Bike B has something steeper (say 75 degrees). If both had their saddles set up in the same position in relation to the BB, ie Bike A with an inline seatpost and Bike B with a set back seatpost, Bike B would have more compliance through the seatpost than Bike A? Because the steeper seat tube angle would mean that the seat tube/top tube joint is further forwards in Bike B, and thus the lever arm (L) for bending is longer? Assuming everything else, ie seatpost diameter, material, cross section, etc is constant, that is.
That's for the great content! As a mechanical engineering student you brought learning out of the classroom for me.
Great video. Yourself & Luescher Teknik speak the most sense in the cycling industry
Would you recommend replacing a standard 27.2mm carbon post with a 25.4mm post in an effort to improve comfort? My frame is a 1980s Tommasini with room for 25mm max. tyres and I find it a bit too harsh. If so, would a plastic be the best seat post shim material to use? I wouldn't fancy carbon (post) to a typical aluminium (shim) to steel (frame) for galvanic corrosion reasons
Hi Gary. Thanks for the comment. As for the shim, go ahead. I have also run a 25.4 in a 27.2 frame. At these small diameters, the difference in second moment of area is small however, so you may not feel a difference. I'd still recommend Alu for a shim, with a liberal coating of grease. Or even better, if you are custom making the shim, anodize it. Use 6000 series not a 7000 series as they tend to corrode less.
You could try Delrin (an engineering plastic) but this may creep under clamp compression over time, meaning you may need to periodically tighten the seatpost clamp.
Cheers
@@PeakTorque Thanks very much for the detailed reply. I was thinking of going from a standard stiff 27.2mm post to one with more engineered compliance (like the Cannondale ones), so going down in diameter at the same time would make sense. I'd probably draw the shim myself. I'm getting a stem face plate & Garmin mount made of 6082 aluminium and anodised soon, so I'll stick the shim on that order. Thanks again for the great advice
excellent - making the complex simple for basic understanding.
Jordan, i will reply to your email. Its on my list. Sorry
In fact, if you double the diameter of a tube with a fixed wall thickness, the second moment of area will not increase by a factor of 16. That's true for a solid rod, or when the wall thickness increases with the diameter. If the wall thickness is constant and small relative to the diameter of the tube, it will increase by a factor of around 8. This is since r^4 - (r-c)^4 is a cubic function of r, while r^4 - (0)^4 is quartic (here c represents the wall thickness). Of course, either way the point is that the diameter of the tubes is hugely important.
great video again, thank you for teaching me!
I wonder for some time now, why there are no thru-axles for rim brakes available... As you pointed out in your videos, everybody's talking about stiffness when it comes to bicycles... So, it should be logical to offer thru-axles for rim brakes, wouldn't it? Can you explain the technical differences and hence the pros and cons for QRs and TAs? That is kind of a great favour, I'm asking for but I feel like this is a topic, which is quite neglected...
Thank you in advance, greetings
Markus
Markus....theres a video coming up for you on that... In my opinion thru axles are not always stiffer...
In the 90s when they relaxed the UCI rules a few bikes were made without seat stays. I have a superbike frame which was one of these designs, the Lotus bike was another. Shame the UCI has limited design so much, we could have had some really exciting bikes today.
I think the triangular frame is pretty much the best that you can possibly get in terms of weight/strength ratio. I am not sure about aerodynamics, maybe there might be some benefits to getting rid of the seat stays. In general, the double diamond frame is probably the best possible design. Deviate from it and you have to live with many drawbacks. That's the reason why most of these "fancy" looking frames like y shape or whatever never really caught on: they are mostly shit.
These videos (the two in this series, the TI bike video, and the Canyon seatpost video) are great. I know this was 2 years ago so not sure if you still check the comments, but it would be interesting to watch an overview video on stiffness of bicycle components to better understand which differences matter for riding and what is just marketing BS. Almost every bicycle component from frames to cranks to wheels is advertised partially based on stiffness.
As far as I understand, aluminium is far more “workable” than Titanium (triple butting, hydro/fluid-forming etc), so while Ti is a great material based on its properties... maybe the ability to create more refined shapes with aluminium actually make it a superior material to Ti? Or are Ti’s properties that good that it’s better than even a highly manipulated aluminium tube? Maybe a topic for a future vid... with a comparison grades of aluminium (6061, 6066, 6069) and cut through the BS on which might be “best”. Loving the channel!
Reliable AL tube profiles are always larger. AL simply cannot bend very much before breaking, unlike carbon, ti or steel.
Ti tubes are insanely thin. I was a field engineer for a well known laser manufacturer. A well know titanium bicycle company was looking at us to help with their production and so we were sent sample tubes. I never realized how paper thin the tubes are.
longevity of aluminium bike frame is a problem. There's a reason several bicycle companies warranty their steel and titanium frames for life.
Loved the calm description at 2:00 regarding the manuf’s compliant stays - that said I rode a Ventum Tri bike on a test last year which is “stayless” (also downtubeless too a la Lotus) could get the tyre rubbing easily when powering out the saddle - takeaway good design but needs the engineering and structure to follow through - too many manuf’s are putting out rubbish and expensive rubbish too - same concept but rock solid but can’t buy one!! Diamondback’s Andean -
Cantilever chain stays can be really stiff is designed properly. I may show how in the next video.
I’m really enjoying your content. I’m going to save these to she my sons in a few years to spark their imagination on how they can combine their school work and their passion. My wife is an oxbridge mathematician so hopefully they have mummy’s brains and daddy’s legs. Out of interest, what educational route did you take to get to where you are now? Keep up the great videos. P.S. don’t go too far down the Hambini swearing/slagging route. I ended up unsubscribing from him because of it. I think you have the balance just right at the moment.
Quite conventional STEM education really, but varied work experience.
I studied physics, maths, chemistry, and design at college. I was terrible at Maths because i would often go to the boozer instead of lessons. I had some bad mates. But then i found MATLAB. I then did Mech Eng at university with a thought of going into finance. Deciding that was betrayal and too well paid i stuck to engineering. I started my career at the 2nd largest auto maker in the world, but since have had a varied career. Get your children to go for it. What it lacks in renumeration is made up for by achievements and specialty. I think its one of the few vocations where you can still really find a niche. It is not sitting in an office sending emails and quarrelling on Zoom.
Peak Torque Thanks for that. Really appreciate it. Keep up the good work.
People who have silver spoons in their mouths don't get far in the real world.
@@Hambini i dunno, i wouldn't mind a yacht.
First of all great video and good explanation on technical mechanics. Did you model all simulated seat posts as aluminium to show how the shape influences bending stiffness or did you model them in their real world material? Correct me if I am wrong. But since CFRP is an anisotropic material you can't use von mises stress to compare it with aluminium, since one criteria to use von mises stress is to have the same Poisson's ratio in all directions. Also, did you validate your simulation with real world testing?
I have a Thomson Elite for the Xc mtb , because it needs a long post without setback in 27.2,and yes,does not bend.(and saves weight)Tried it on the road bike,bit harsh,prefer the PNP ti post. Thanks,well explained.
Great video. In mtb they changed to 27.2 to 31.6 and the journalists says they are more compliant, on the other hand endurance road bikes use 27,2 seatpost for comfort... Seriously they just recite a poem given by the manifacturer these days...
31.6 will only be more compliant if the wall is made CONSIDERABLY thinner. At which case it's more at risk of crushing. Thanks
31.6 allows you to use a long dropper post. 27.2 is too narrow for that.
Very nice video. What I'd like to know more of is things like fatigue life of various materials (steel vs carbon vs aluminium), things like manufacturing processes (carbon - classic pre-preg layup vs. RTM), aluminium (hydroforming vs normal butted tubes), as well as differences between joining techniques for steel, like TIG welding or filet brazing etc. Repairability of different materials would be a great subject too.
Next I'd love to hear your thoughts about bikes which use hybrid or exotic materials, like magnesium, or Ti/Carbon hybrids - things like that...
What would also interest me is the economics of manufacturing bikes - how can a motorcycle cost less than a high end bike? In terms of revenue, Ducati is only twice as big as Canyon so the old argument about economies of scale doesn't seem to be applicable... Also how close are Microshift to Shimano in terms of performance?
Just my 2 cents
That's going to be difficult to discuss with any real world applicability as the different materials have different weaknesses to environmental damage (see the annual carbon fork recall by one or more of the big brands due to UV induced delamination). As far as econ, all that stuff is irrelevant. Marketing teams set a retail price. Accountants determine a production cost to maintain profit goals. Engineers then design a bike under that production cost limit. The consumer price of your bike isn't driven by production costs. Its marketing. Cost is determined, then the tech on your bike after. I notice no difference between MicroShift and Shimano, though I've not used the new hyperglide+
I wonder if tube shapes could be designed from the ground up from a stiffness standpoint and get the 'aero' treatment after the fact. I mean like thin plastic fairings over most of the tubes. Sounds a little old school but I think it would work well in this case.
Excelent video!! Ty for your work! It´s amazing how simple it is...Unfortunaly most of the people don´t have the knowledge to kill marketing! Keep on iwth your good work!
The aim of this channel is to change that statistic 👍
10:03: What makes you think that L is constant? Designers can opt to change the angle of the fork (and thus its length), or the length of the head tube (and thus the length of the fork)
L isn't fixed but compared to E and I it has much limited flexibility because it's driven by the bike geometry and kinematics rather than stiffness/compliance.
How do we send this to bike radar and gcn. hope they see this and the last video
there is no need - they are marketing driven ONLY ;-)
Bike Radar is a bit better. They have a great contributor called Seb Stott. He debunks a lot of MTB shite.
They DO NOT CARE. They make ‘truck loads’ of money from the BIG names in cycling. Otherwise what is stopping them from hiring/finding guys like this???
I think hambini already burned that bridge lol.
@@SprayIgniteBoom i don't think they make much money
Another great video, thanks 👍what software did you use to model the bending of the seat posts?
Yeah ditto. Having some nice side by sides is nice.
Great videos! I love your channel & factual/scientific basis of the information. This may be just me, but I'm unsure of the appeal of stiffness? Is it because of responsiveness in ride? Conservation of energy in peddling? I assume it works against comfort, hence the need for designing compliance into the bikes etc? The appeal of carbon for me personally had always been the allure of lightness/ aesthetics of the 'aero' designs; something that I have found a bit difficult to justify given my alu bike weighs less than 1kg more than the carbon bike I would have to spend £3-4k on... and as one of the humorous comments in your Ep1 video said, one can take a dump for the same weight gain... I wonder whether there'd be a market for Alu bikes that were designed to look more 'aero'- i/e/ not the conventional circular tube cross-sections? Or would they be too heavy?
Great video thanks ! I guess it was not really the point of the video but one little detail though : 1st moment of inertia != 2nd moment of area. They do have similar definitions but 1st moment of inertia has the dimension of kg/m², and it describes the mass distribution of an object relative to some chosen axis of rotation. You can get it from the second moment of area by multiplying by the surface density (assuming it is constant).
2:58
"Stiff, triangular structure. Not designed to bend."
As a non-engineer, that is what I intuitively think when I consider Cannondale's goofy "kingping" contraption. I suppose the triangle and seat tube can pivot a bit, but it's clear they're trying MARKET the "comfort" geometry hype promoted by Trek and Specialized. I think I'd rather have a Ti frame anyway.
What say ye?
How did you obtain a plausible FEA simulation for CF bending without having the correct E value entered into the software? That number depends on the layup - which you don't know
I would love to see titanium compared side by side to carbon as you think it's such a good frame material!
It is a triangle in the most general term, but you are missing details. The seat stays are not straight. They have curves or bends in them. You also have to consider the angle of the seat and chain stay. Granted, it won't deflect as much as the seat post is capable of, but there will still be some.
Excellent video, much appreciated.
Very interesting. Thanks a lot for sharing your knowledge 👍👍👍
I could be very wrong but I think its solidworks
Hi there !! I have one question. In the last simulation, shouldn't the Thomson seatpost have been placed in the other direction? At first sight I would say that the stiffness of that geometry is higher if you rotate 90° the angle of the seatpost (or the angle of the force). Thanks for such a good content !! Keep pushing !! Cheers from Spain
The subtle jab at hifi audio was quite nice to hear.
The bike needs to be stiff enough to feel safe in handling. However wouldn’t all frames mor or less bend when pedalling? Some more some less, the question is if any energy is lost I.e. what is the frame’s efficiency. There will be heat losses, and this depends on the material.
What's the difference between automotive race f1/Gt4 and aerospatial grade carbon and carbon used in the top top top end from like the Tcr advanced sl, Emonda sl7 etc. You know the best highest end carbon from the highest end bikes from the top brands ? Ax-lightness which started out as a auto sport f1 carbon part manufacturer says the use automotive and aerospace grade carbon in their bikes like the Vial evo Ultra which can weigh between 4,4kg-4,8kg is it lighter and or stiffer or something ?
So, to keep the same stiffness but reduce weight. You can increase the diameter and reduce wall thickness to match the stiffness needed. Obviously, if you keep doing it, at some point the wall will be too thin and fragile. Why so many carbon gravel bike have more massive tube than a climbing road bike then? Gravel require more impact resistance and also more compliance to smooth out the road. Making tube diameter huge and thin doesn't achieve that.
Good explanation, I've never been interested enough to run any simulations myself or calculations (although im still riding an alu bike). What about the seat tubes with an offset to allow for compliance or even the Canyon Grail split thing.
Offset just increases the effective seat tube angle so when the load (that is generally vertical) is now further from the bottom bracket (in the direction perpendicular to the load), so the effective lever arm is longer so your deflection goes up. The split seatpost thing works by removing the sides of the seatpost and turning the whole thing into something like a leaf spring. The sides do most of the work here (think bending a ruler along its 2 different longitudinal axes, one is stiff, the other not, your taking the stiff parts out on the split seatpost).
@@georgegrant6388 thank you! Correct.
haha, i was totally one of those people asking you about your stiffness ratings in one of your older videos! fwiw i was mostly just curious how you reached those figures plus i like to keep people honest!
l know you didnt intend to be funny in your commentary but you made me laugh alot thanks for calling out the BS !! l was surprised how much the different seat posts bend compared to each other WOW .l know now why my thompson rides so stiff and shocked how much flex a regular alloy post flex s
I might be super uninformed here, but it seems like steel has a roughly equivalent ratio of density to stiffness to both aluminum and titanium. First question would be what alloy of steel did you use for your numbers? Secondly, what is stopping steel frames from being exactly as light and stiff as aluminum and titanium frames, especially with modern alloys?
people who can weld super thin steels and corrosion/frame dings
This would be a great project for aspiring engeneers graduates and high school students. However to many assumptions and more accurate modelling is needed to at the least ignite meaning discussions, beyond pub talk. All in all Good effort 👍
Now you understand all there is to know about tube bending stiffness. lol
Well done, thanks
Would you be able to put together an analysis of oval chainrings versus traditional chainrings? Is there a real biomechanical advantage or is just a placebo effect? What is the impact of the degree of ovality? Chris Froome seems to believe in them, so would be helpful to have your view from an engineering perspective. Cheers!
I cant think of a reason to make a spaceframe out of cylindrical tubing other than for aesthetics and to make cutting of the tubes a royal pain in the ass for the poor buggers who have to make it :). If it's a proper spaceframe all the loads run axially down the tubes (in theory). As for compliance of seat stays ... I guess if they are spindly enough and possibly splayed then it will increase the deflection possibility ... if the chain stays are allowed to bend. I agree that it's a very stiff structure at the back and the only serious compliance is the seatpost ... a trusty cantilever in bending. Trek have a pretty good design with their isospeed system which has a genuine capability to modify the cantilever arm length and springiness. Keep the proper engineering stuff coming. You have a great knack for explaining stuff.
motorsport space frames get loaded in all sorts of crazy directions during unexpected departures from the racing line. So yes tubes are a good shape there. They aren't that hard to cut. and even easier on the high end stuff where a laser tube profiler just does it for you.
@@Cynyr good point on the laser cutting. I still dont get why round tubes in a spaceframe are better. By definition loads in a spaceframe member are axial or it ain't a spaceframe. Regardless of crazy loading, if the loads are going in through the suspension pickups and other major component mounts and these pickups and mounts are at a spaceframe joint and not slapped in the middle of a tube ... then everything is determinate. I'm not trying to score points here ... I genuinely dont get it.
@@stevecrabb1 think crash, not normal operation. Yes they probably are all mostly axial normally. But flip it through the infield, or so it around a tree, and good luck determining the loading.
Also round tubes are ready to get.
@@stevecrabb1 interesting discussion here. Im actually fond of the latest isospeed spring concept on the madone. It is a neat and novel solution. Something seldom seen in road cycling design. I actually commend the designer on that. However, its a big spring with no damper. How does it feel at 110rpm trying to push 600w seated...who knows. I need to ride one. But I sure ain't buying a frame with that price tag. EVER.
About the space frames, i can't actually think of a reasonably modern application where the loads are all axial. Especially not ground vehicles. Maybe there are some kit gliders/light aircraft that display this. I've seen some old old gliders where space frame members are just cables.
If you take the wheels and a frame, and apply the static loads do you think the frame structure is determinate?.... I think this has confused the bike industry since day one.
@@Cynyr It's a bit like designing an aircraft to survive a crash :) not a lot of point. It depends on the formula and rules surrounding driver safety as to roll bars, leg protection etc. as to what you do. In any case smacking it into another car or wrapping it round a tree will involve a lot of tubes being put into bending as they get hit in the middle. A round tube is definitely not better in bending than a square/rectangular one. But its a bit hypothetical at that point. What I'm a little unsure of is whether a round tube in compression has a better strenght to weight ratio, if it has then it makes a lot of sense.
you mentioned you got rid of the thompson seat tube because it was too stiff, the giant TCR seems very similar. can you notice that difference when riding?
thanks for the good video!
The Thomson elite was on my supersix. High top tube thus not much exposed seatpost. The TCR has a very long exposed seat post. Deflection goes up with free length to the power 3! So exposed length makes a huge difference.
@@PeakTorque i suspected that, thanks! probably makes the case for the aero shaped one even worse as it is less exposed than the TCR.
@@PeakTorque Now I see why Cannondale have to make their small sizes SystemSix as ugly as it is. They need a lot of exposed seat post for the compliance to be acceptable for small riders. That make size 51 SystemSix Evo 's top tube slope a lot. (search for size 51 SystemSix, if you wonder).
Very informative!
am surprised this isn’t more popular, ok its semi technical but a) its visualized and b) presented in a human voice. regardless of bikes being one of the hottest subjects in sustainable mobile life those two factors should captivate a larger audience?
What software are you using for your simulations? Are your material properties all isotropic, or were you able to define a composite layup for an anisotropic material?
I thought the reason for going from steel to titanium to aluminium to carbon composite was because of beer canning. To get stiff and light the tube walls get too thin so less dense material is preferable as it preserves crush strength
Yes, so there is more than E an I. If not an alu bike could never be lighter than a steel bike. Since steel has higher E-modulus and yield strength, you could just match the diameter of the alu tube and reduce the wall thickness to reduce the weight. This is however limited by the local buckling strength of the tube wall.
hello mate,
Thank you for your videos I'm a junior mechanical engineer, I work on my own bike project. Can you tell me what simulation software you use to simulate parts? Do you recommend a specific sheep one. Thank you
I would really if you could compare Allite magnesium alloy from Vaast bicycle against other materials ! Enjoy the information and education from your videos, cheers!
Are curved seat stays bollocks for increasing compliance?
One thing I think about cycling is that we only ride double diamond frames because of the UCI. But ive never raced in UCI race so we are actually limiting ourselves by buying products that seldom need to be adhered to. So ok we're limting oursleves by frame shapes but to what degree? Listen to Mike Burrows occasionally when he's been interviewed and he'll say frame design is limiting bike speeds by a massive degree and the cycling industry is old fashioned, conservative and cannot think outside the box. And then I think about what Hambini says and he thinks the wheels make the biggest difference on a bike. So in his view the frame geometry must be ancillary. So I wonder what your thoughts are? Be good to get some discussion on that
Giant like to use the D shaped seat post claiming it offers better compliance. Interesting to see this.
So a D fuse post flex s less than a round one??
Great video but in my opinion analysing a seatpost strength is a fairly moot point. The fact that the seatpost is inclined at an angle of 15-20 degrees from vertical means that most of the loading is the vertical axis and the tan of 15-20 is about 25-35%. For a 75kg rider that means that less than about 20kg of the riders weight is transferred into the angle in which the seatpost can deflect. There will be more deflection if the centre of mass of the cyclist is offset behind the centreline of the seatpost. Any "real" compliance from the rear end of the bike will be in the seat rails.
Yes the bending component is relatively small, but you have to treat the system dynamically. It's not a static problem. When you take into account bump inputs as dynamic forces and accelerations the rider weight is multiplied by a number of G. Even if just 1.5G, its significant.
Hi Alan. Significant compliance can and is engineered into some seatposts, even at a normal setback. One of the factors is how much of the seatpost is exposed. A tall rider like Peak Torque may have over 250 mm of exposed seatpost. (As he points out, bouncing can be an issue for compliant seatposts at high cadences.)
I have an steel Colnago Master Olympic. This frame has a crimped bottom , top and seat tube. Colnago claims, the the frame is stiffer with these crimbed tubes. Is that claim valid ?
Wait, what? How would higher stiffness negatively affect brake feel and modulation? Shouldn’t it be the other way around?
Typically stiff things feel more responsive. Maybe too responsive? I’d like to understand this better.
Brandon Hicks yes it would feel more responsive and you would feel the ‘bite’ quicker. However, modulation is about adjustment of force. Softer springs provide slower acceleration/decelerations of forces therefore provide more compliance and adjustment. This is the reason why race cars are set up very softly sprung in wet conditions, to slow down the response of the brakes and cornering forces to prevent locking up etc.
My Colnago CLX 3.0 has all of the shapes that are supposedly too stiff and indeed it is stiff. Yet this is the bike I've set all of my best times for most of my courses. All of this is mediated with 28mm tires. Hambini argues that 23's are faster but he is an elf.
I often wonder why the stiffness (or lack there of) of the rear wheel is often ignored. I’m only 150lbs, but this is the only area I feel flexing under load.
If you weigh more and do jumping and tricks like I do you feel flex in wheels instantly! A great test of rear stiness of a bike is to do a 180 hop. If your bike can survive that its a stiff bike. If it can survive you doing it incorrectly and not breaking, well you got a tank!
As a result when i get on a lighter bike feel genuinly scared the bike will just break cornering!
Very good my friend. I relish all your content. I like the tech stuff although i have zero knowlege. I hate maths physics and chem but i do ride and race bikes and have done so all my life. So i enjoy hearing about something i don't understand at all. Into my middle years i am currently thinking about electric bikes. I mean take my 400w and add about the same from an electric motor and riding a bike would be a new experience. I do like the look of that s works electric it looks the bizz. What's the engeneer's thoughts on that? Apart from the eleven grand price tag of course!
Great video! However I have a couple of rhetorical questions to your meshing technique...
Using tets for thin walls? Lol
@@PeakTorque Depends on the tets, first or second order? As this is a comparative example, I would not worry about it too much.
Anougher great video, thanks for keeping it simple. This is not a discussion what is better Carbon or Aluminum put how engineers can influence how a bike feels by making informed and intelligent decisions. It's just a shame that the marketing f#€€ whits get involved!
Tell the UCI to change their frame rules. They are based around the design of metal tubes not the properties of carbon fibre. Frame aerodynamics makes a lot more difference than the weight of frames but it way better to have monocoque carbon frames for its mechanical properties too.
“If you can’t dazzle them with deception, baffle them with bullshit.”
This subject needs to be re-visited. I have 2 identical bikes, one disc, one rim. All parts & dimensions the same. Why is the rim bike so much more comfortable & generally livelier? Rim tyre pressures 95psi. Disc tyres 80 psi, & still the rim is more comfy. The only differences I can see are the beefed up front fork (obviously), & the thicker chain stays. Surely, the large difference in comfort & liveliness has to be down to the rear triangle, which seems to have more effect than you think.
i enjoyed it! thanks!
Wait, don’t trusses still deflect under load? Been a while since I took structural..
The tension members stretch ever so slightly under load, and the compression members shrink in length, but there is no bending deflection on a well-designed truss.
Bravo
Are you saying the second seatpost, 27.2 in aluminium, bends more than 1st seatpost 27.2 in carbon?
I have that kind of seatpost and now I can see why my ride is so comfortable.
Instead of focusing on seatpost compliance and comfort, you could as well have a more comfortable seat and pants. I have a comfort seat with a hole in the middle + the thickest possible seam in my pants (Bioracer and Assos). I have that aero seatpost and guess what? It is still very comfortable and as I hate flexy seatposts this really works best for me. And don't forget tire width and pressure... set priorities and stop talking about supermarginal gains in comfort of seatposts while it's really something marginal compared to all I mentioned in my comment.
If you buy your next bibshorts from Everve in Germany, you pick the thickness of the padding yourself, as they can be removed and altered to most thicknesses. You can have various pads, yes, in the same bibshort. Rtr
@@borano2031 thanks, sounds interesting enough to give it a try!
Your slide around 6min comparing a 40mm tube to a 60mm tube with constant wall thickness is interesting but not that usefull for the bike industry which is chasing weight. Going to a bigger tube at a constant wall thickness means heavier so one could easily say "of course heavier is stiffer". Same goes for your seat tubes shape comparaison actually. What would be the results with weight held constant accros shapes and materials ?
Love it man! these engineering-driven videos! Is climate change a lie too? it might be :(
The seat stays on my carbon frame set have the shape of a sword with the flat parallel to the frame direction and are curved along their length in the accross frame direction, with no bridge for a rim brake caliper. So they don't form a triangular shape, as a triangle is a planar object, and the structure the rear "triangle" on my frame is, is not. So the bridge truss example is not applicable in this case as the truss members on the bridge, loaded with compression forces, likewise my seat stays, are not curvy, but are straight struts.
So, my steel racing bikes are stiffer than carbon wonder material???? :)
Great video demonstrating compliance compared to the cross-sectional area. Have watched alot of your videos since discovering this channel, really appreciate the engineering rigor behind your videos. I recently acquired a Supersix Evo Mod Team [same frame you had] and the first time I rode I, I noticed how little flex there was in the frame [especially the power transfer through the BB]. Coming from a CAAD12, this was a night and day difference. I came across this video from GCN that actually shows a surprising conclusion, that frame "stiffness" actually matters very little with regards to transfer, its mostly a perception of how immediate that power transfer occurs [Link to video: ua-cam.com/video/BH_AL4rxrp8/v-deo.html]. Curious as to what your take on this is. The test they conducted made sense and perhaps the perception in stiffness I'm feeling isn't actually resulting in more efficient power transfer, and more to the immediacy of that power transfer?
@UC08mbQ8UIX8DXSBFBO9VaZw curious about this as well. Does the deflection in the frame means that the energy is gone with a loss in power transfer? I am not sure about this. After deflection it will return back to its original position so no energy loss? On the other hand, descending @70kmph and making turns would be easier on a frame that flexes less in terms of handling, but thats another thing. I am not an engineer so curious on your take on this.
It seems to me that the bike industry is full of bs. I got into riding a few years ago and have upgraded my components on my aluminum frame and I love my cannondale synapse. Ive been looking at the new bikes and they all look the same and they all claim to be different, more aero, stiffer and better all around but the prices are ridiculous. Component prices are ridiculous for what they are as well.
The golf industry likes baffling its customers as well. It’s funny to hear consumers repeating the scientific tech jargon as they step up to the tee or during a cafe stop. I’m not innocent. Cool video.
Exactly the same
What bike is on the wall?
Ah Ok so you answered my question in your video ...thanks lol
We had many crazy shaped bike frames already in the 80/90ties-but i’m glad the UCI sticks to
the 💎 diamond shape!
In order to have fair races the rider‘s bikes should be similar in weight and performance.
Plus not everything should be made of carbon fibre-it’s toxic waste and until today there’s no concept
on how to recycle this shit-they still just burn it....
if the goal is like equipment, then just spec a single make bike and ballast the bike and rider up to some set minimum weight.
In your stiffness simulation, do all tubes have same wall thickness? The Elite seatpost has extra material in walls, so clearly extra material makes a difference. Also, that extra material in Elite seatpost is thickest in points which form a line parallel to the load. I wonder if you rotated that post 90 degrees, would it be even more resistant to flex.
Towards the end of the video, you start talking about "compliance" and "feel" of the ride different seatpost materials/shapes provide, without backing those subjective terms with any data. Seems like a blemish on a series otherwise intended to dismiss marketing jargon.
Far yes the elite seatpost has non uniform thickness, measured and modelled from a real life example. Wall thickness and its distribution effects second moment of area (which the whole video is about). The orientation with respect to load (rider weight) is the same as it would be in real life with the saddle clamp fore-aft in line with the rider weight so i made sure of that.
Simply put a seat post with a lower EI (stiffness) will be more compliant.
@@PeakTorque so, if looking for comfort. I should go with alloy seatpost with rather thin diameter thickness? My current carbon seatpost's weight (from merida) is 270g. Buying a Ritchey WCS AL2014 with 190g would be more compliant? Thank you
"If you double a tube's diameter, it gets 16 times stiffer." For thin wall tubes Ix = Iy ~= pi r3 t correct? So it gets 8 times stiffer, not 16 times. It would be nice to equalize the weights in the comparisons by adjusting the wall thickness.
very informative video as always
lot of echo in your sound, anyway great vidéo !
In all the bikes I have ridden/raced over the last 30 years I have never thought any of them were not stiff enough. The problem has always been my legs! The cycle industry marketeers are so full of BS it is laughable.
I still prefer high end modern day custom steel bikes.
Here are some stiffness measurements you can compare:
Why It's Impossible For Steel Frames To Be More Comfortable Than Aluminium
ua-cam.com/video/Lb4ktAbmr_4/v-deo.html
you've never ridden a bike with an aluminium fork have you ? Like a fucking jack hammer.
He made a Fred reference lmao
Yeah... who would make a bike that's not UCI compliant ;) ;)
I've got a 58cm 3D ready to go.
@@PeakTorque I'm pretty good at Papier-mâché if you wanna send it over. Will be compliant AF. Probably not best to ride it in the rain though.
@@ChinaCycling LOL you may be good at Papier mache but you also work for Winspace now so I'm sure you could get it done. 😉 Just think, a bike that is actually as good as it supposed to be with no sudo engineering bs. 👍😁
Give me the Bugatti Chiron of bikes.
Your engineering is good, but I’m not sure your application is at the same level. Some of this comes from youth and what has been lost regarding cycling history. If we ignore TT, especially on track, there’s not much to show that top level cyclists are faster than those who rode on bikes with steel “Standard Gauge” tubing. Which covers a long period of time which largely ended by the late ‘70s early 80s. So…. Let’s assume that TT gains are largely improved rider aero position (and I welcome any sound argument to the contrary). Ergo: large tubes, aero-tubes and components, non-round tubes, new materials, aero wheels,and so forth have essentially contributed nothing but marketing. That they’ve done in spades as you see the rampant inflation bicycling prices (even as it has been arguable that the cost of mfg. has gone down).
Tire, fork, handlebars, seatpost, stem should be the primary sources of compliance, and in that order. Put on a set 21mm tires at 120 PSI, and on a smooth road you’ll feel the wing of a fly as you ride over it.
Back in (I think) the mid-70s, there were successful Senior Tour riders on on Alan screwed and glued aluminum frames. These aluminum frames shared the same skinny tube diameters as the steel frames of the era. Your engineering will demonstrate how comparatively soft these bikes were. They saved weight. I doubt big sprinters could make use of them, but small climbers could. And for several years they were popular enough to also be sold under the branding of other bike manufacturers. Obviously this calls into question the idea that without stiffness, meaningful efficiency is lost. Despite rider preferences, I’d offer that if a frame is stiff enough to handle well, then it’s stiff enough to race.
We don’t often hear much these days about being supple on the bike. This is probably a loss for all riders concerned. Why are you sensitive to seat-post stiffness? Do you bounce on your seat? Perhaps not, but if you haven’t considered it, we’ll maybe it’s time to.
Also I’m not issue of braking difficulty when braking. Personally, I tend to take weight off the seat in any kind of challenging braking. This is both to facility shifty my weight as necessary and to radically reduce unsprung weight (which effectively is the whole bike rider combo). Maybe you can explain this one to me better.
Anyhow just a few thought from the salt-mines.
stiffness means nothing to %99.999 of riders.
@Peak Torque have you watched any cycling about videos? he has a video that's similar to this and gets to the same conclusion as you: ua-cam.com/video/Lb4ktAbmr_4/v-deo.html