over-engineering is not engineering

 

race car (tubular) suspension and "bending" (of thin rod heim joints). whew a simple link would have been more productive.

https://www.formulastudent.de/pr/new...-of-fs-design/



no math. car salesmen mumbling/punching the numbers to arrive at an answer is not cool lol

 

It's not over engineering, when you engineer something you don't design to the failure point, have a safety factor that you shoot for. Depending on how critical the part in question is determines how high of a safety factor you need to shoot for. When you're talking about a part that keeps the car traveling in a straight line when it's supposed to be, it's a pretty important part.

Tensile strength means nothing to this arm because the concern is in a bending or shear load condition. Rule of thumb is that usually shear strength is only 1/3 to 1/2 of the tensile strength.

If you look at race cars they do use rod ends. They use them everywhere. But none of them will be used in bending conditions.

If you have no option and MUST put a threaded fastener in a bend/shear condition they it must be very very oversized for the application.

I wouldn't take what Dallas has said with a grain of salt, he's right on everything he's said.

None of these rod ends are undergoing bending loads...

 

come on. even i can see it

 

using larger heim joints would solve the 'issue'. its not engineering. just some type of no drama compromise

 

unbolt one end of the lower arm and drop ur car back down onto its wheels and watch which way the wheel goes.

Also how many months of the year do u keep your car underwater to make ur hardrace arms go like that that is impressive lol

 

let me help you, so you dont get verbally abused by tech



thats an opposite scenario from evo aftermarket control arms and looks quite problematic. it actually experiences a higher force since wheel has leverage.



this seems like typical topic for FSAE/mech eng'g, they use the tiniest parts. we dont use those tiny heim joints, not even on swaybars

 

Whut ! I can't even troll like this if I tried.

 

Dallas groupie? lol what you mean? or whats the point of saying that?

 

another angle so you might see 'rod ends in bending'



another pic i found googling this topic/ (another engineer's design)


I'm not defending STM's new control arm. I'm never buying that since it has their logo and has too much exposed threads

 

Dallas already showed you the math. Your FSAE example has almost no moment length acting on it. It's also a low bend angle, which lowers the total bending load going through that joint..

I'm going to see myself out of this convo now, like everyone else has. Everyone seems to be on the same page about this except you, and if what's already been said here isn't registering for you then there's nothing more I can say to convince you otherwise.

 

I've been running those exact Momentum's for 2 years now. Hard bounces, full send it mode especially the forces it saw at Daytona and the bus stop, including 1 off road there, 0 issues and still straight as an arrow.

Now, that's not to say Dallas's observation is wrong, it isn't, but proof is in the pudding and the paper is just a proof. I took the risk even though he yelled at me for it, likely just to annoy him haha. "I" would recommend them. But I'm just a different type of engineer

If he were to ...I dunno..make the right one then I would have bought it in a heartbeat LoL. The adjust-ability combined with Austin's E bolt deletes is king. One COULD produce a threaded rod that had the same tensile strength of a cast alum chunk of metal no, if we're all talking theory here.

 

And thats fair. My point is that these style of arms are so close to the limit and threads in bending are just bad design (Regardless of what the ignorant one wants to believe). The other ones I linked with the coupler sleeve is a better alternative. But the other issue is that solid bushing on the outside. Thats another huge source of stiction and bending loads. Any time you take a factory spherical and replace it with a urethane bushing its a step backwards.

 

I just wanted to bring this to light. I never understood probably because a lack of deep technical knowledge, but I've always seen heim or spherical bearings radially loaded in off road racing like Baja and so on, but axially loaded in power sports. Ie snowmobiles, quads, etc . . . Are they technically different joints? Different coverage of the hemisphere ?

 

I just wanted to bring this to light. I never understood probably because a lack of deep technical knowledge, but I've always seen heim or spherical bearings radially loaded in off road racing like Baja and so on, but axially loaded in power sports. Ie snowmobiles, quads, etc . . . Are they technically different joints? Different coverage of the hemisphere ?