Which Rod Ends / Rose Joints to use in a (race) car ?
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- Опубліковано 3 лип 2024
- In this video I go a bit deeper into the issue why one of the rear suspension rose joints snapped. There is a bit of math in this video, however at the end I have some practical aspects .
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You never cease to amaze me with your excellent knowledge. Another great video. Thanks Steve 👍
So nice of you
FANTASTIC.
Myself, personally, I would like to see more videos such as this that are of a more technical approach to racing and racing components.
I also appreciated the mathematical calculations bases on the relevant formulae.
Thank you for the comments and yes , I understand . I will try to do so . But need to keep some common ground for others as well ... So , I do my best to satisfy everybody.
That was really interesting, thank you for sharing the knowledge. Also, I'm very glad that you avoided an accident and the people you race with look out for one another.
Thank you for the comments
Thanks for this video. I had a vintage Formula Ford which during an autocross event seemed to suddenly understeer resulting in me clipping a curb and pretty much tearing the left front suspension off and damaging the front left frame. A rose joint sheared in the same way as yours. I’ve always wondered if that was the cause or if it was driver error.
Thanks for the comments, I would say " most likely " either a radial dynamic load limit that was to low or metal fatigue .
@@D3SshooterIsn't that basically the same thing? Metal fatigue because of too high dynamic loading for the part.
@@tomiheinonen460 , yes it is kind of... its multiple high stress moments that slowly causes small cracks in t he structure of the metal and finally snaps... The more it is pushed at its limits , the faster the fatigue sets in.
❤ Very interesting and eye opening. Since life is on the line, every minute undertanding loads of vital parts is worth it!
Thanks for the comments
Excellent research, observations and reporting! Thank you! I suppose you will be checking and possibly replacing several Rose joints.
Thanks for the comments, and yes indeed that is on my list to do besides a new race clutch
Video was very interesting! Personally speaking I like to calculate what I need and then step up one model so I would probably have used a safety factor of 3 - now of course if you do that to everything on the car weight may be an issue.
Thank you for sharing your research! Math is always interesting!
Thanks for the comments
Hi 👋🏻 Steve. That was very interesting even though I’m not a racing driver but safety is paramount so sharing this sort of information will hopefully help someone else 🤩
Glad you enjoyed it
I had a class in college called "machine organs" where this type of calculation was done for almost all mechanical elements, nowadays most of these calculations are done in simulation on top of cad/cam... Now few people take the trouble to do a simple grocery bill to calculate anything... sensitivity and pride in designing something more complex is lost. And accidents can happen.
Well explained Steve,
By the way... this little car is really devilish!
I know you worked on this car before but wouldn't it be better to check the other suspension points too?!
Thanks for the comments, Indeed these calculations belong to the past in terms of manual/human work. Sadly as a lot of knowledge on how and why is lost in the mouse click lol
Hi Steve, I think I would replace them all just to be on the safe side. Great video🙋👍
You and me both!
Hi, I think this is a very important video. Sure parts should always be within specification with a safety factor. But you have me thinking about scrutineering and general maintenance of these types of racing cars. Depending on how much they are used, surely, parts like this require replacement at some time based on a safe life span for the part. Depending on how hard the car is used, I guess all parts have a life span and it is wise to replace them periodically. Again Steve you have got me thinking and learning. Thanks so much Marc.
Thank you for the comments Marc
Thanks for the video.
Thanks for the comments
I looked up the Fluro web site, but I didn't see anything about left hand thread rod ends. My old FF almost half of the rod ends were left hand thread. Is that a thing anymore?
That is still available, but you need to make the request to Fluro
I've been led to believe that a rose joint should be mounted in the flat position i.e. with the mounting bolt perpendicular (not parallel) to the ground. It would be a good question to ask Fluro.
According to the documentation, it does not matter as such and all depends on the two arms. In this case its a whishbone that goes up and down, so placing it in the vertical position is ok as it can pivot all around. If it was horizontal it would limit the whishbone movement up-down to the degrees it is specified ( these 13 degrees as far as recall)
As I said in the previous video, I suspect a design error with this overhanging screw which can induce parasitic vibrations which are reflected on the tail of the ball joint.
Thanks for the comments
Very interesting video. I have one question, are all the other rose joint type as the broken one or will you replace them all ?
Everything, so they will be replaced
Good points on the video but mostly all the math is useless since it's really hard to find out the forces existing in your suspension. This is only good for comparing two different joints, which you did. But you could do that by just comparing the dynamic values on the datasheet. Anyone please correct me if I missed something.
Thanks Tom, I have given the basics on the loads and forces on a rose joint and the base calculations for a common undertstanding. Followed by a practical look up of what is available and how to look and read the figures on data sheets. That was the intend, its is not to calculate the actual design and need on my specific race car. As that requires as you stated more details on the structure of the car and how it should witstand forces . That would be a chassis design session, and just maybe we do one to show the complexity in designing. Of course with CAD the design and calculations become easier. The only issue is , I need that software at home LOL
@@D3Sshooter Agreed, it's a fair explanation for common understanding. I have experienced similar failure of lower ball joint in MacPherson setup. It was an industrial grade joint. I replaced both sides with motorsport ones but after consideration left other similar joints in the system. The broken one was the only that sees shear force, others only push and pull in axial direction so it's much easier for them. The motorsport stuff costs 4 or 5 times more.
Another aspect which is hard to get real data for is, as Steve D3S mentions, is the dynamic loads seen by the suspension. It's not only a matter of speed and the bend radius, but the extra forces as the car skips and bounces on the uneven road surface. That can probably only be found by measurements on the car. Does anyone have any data for that?
Meanwhile, I seem to remember from engineering training years ago, that impact loads could be considered as three times static load and in a car weighing 500kg, impact loads of 1500kg (or 15000Newtons cornering at 1g) suggest these rose joint are in the right ballpark, particularly as the loads are shared between many more than one joint.
There are many variables at play in the construction of a chassis/suspension, but these variables can be suppressed or ignored, it all depends on what you want. In the case of a high-performance vehicle, a racing car... Everything will have to work to the limit and the safety coefficients will be extremely high. In Steve's case, i think he upgraded the suspension from ball joints to rose joint. I don't know if he took into account the characteristics of the original component and this may have contributed to the screw breaking. You can use SolidWorks to calculate complex structures like this, it will be like using a shotgun to catch flies, most builders develope and use their own software for this purpose.
@@nabsp It is indeed complex a good tool but expensive is autodesk inventor for all the calculations. For clarity , I did not build this race car, and rose joints are common on t he Formula Konig... smae as on Formula Ford. The Rose joints that were on the race car are of course 20 years old.. and not a MS type... So that is what is on the agenda change them out with MS rod ends... Thanks for the comments
Interesting video. I’m going to assume that your take away is to review all joints on your race cars and replace as needed. You don’t mention the cost differential between race designed parts and general. Is there a testing body to verify the manufacturer’s testing results? Also, this was not caught during tech inspection. Is there a requirement for documentation of parts used on the car? I know from past videos you have a time limit on seat belts.
Thanks for the comments, yes I will change all the suspension rose joints and associated bolds.. The price, yes those "no Maintenance, Motor Sport rated rods" are almost the double in cost. `An M12 as shown here runs at 60 euro plus... depending where you buy. Yes, thise are all tested based DIN norms and get a ISO approval number. Parts documentation is not easy for older or home build one off cars.. Some do,others don't
Any inspection before you enter the track could not prevent the snapping of the joint. If it was snapped, it should have been noticed. But not all trackday events have that sort of inspections.
About the limited life span on belts, fueltanks, seats and even racinggear for the driver are only mandatory when you enter a governed racing event. On trackdays it's up to the user if he thinks he is in need for new belts or any of the above, belts can be checked visually.
You started with the existing one as a reference so it gives you an idea of what you are looking for, but it would be nice to understand the maximum forces required by the car architecture. If you have a way to calculate that, I will be waiting the video on that topic :)
Another point, couldn't aging be another factor? Would your part still be able to handle those 13.5 kN as stated on the data sheet?
It would be really difficult as you would have to consider many hard to define parameters such as friction and dynamic impact forces. I'm sure there is software that can be used but not many hobby racers could get their hands on them, or know how to use them :) Fatigue lifetime can be considered as aging. If load is below certain limit the lifetime can be considered forever. When exceeding that limit it is finite number of load cycles.
@@tomiheinonen460 back then, I suppose that Autodesk Mechanical Desktop could handle that. I think that Inventor replaced it. SolidWorks should also handle it. "Benjamin Workshop" uses it for his projects (GT40 and Hypercar).
To provide and calculate all the forces that are at play and get the rigidity figures, shear point loads and more on the entire race car or any other car requires a lot of calculations and simulations. `there are software tools on the market for mechanical design (like 360, Inventor , CAD and others) that come near. However stress testing is at the end done in practice on test tracks etc... So for me to do so, that is kind of out of reach ( financially) . So we use common sense and over-dimension a bit, while doing some test runs.