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Rod ends in bending

Posted by Thomas Kimsey 
mekilljoydammit
Daniel DeRosia
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Re: Rod ends in bending
September 22, 2014 06:09AM
Quote
Cosworth
Quote
mekilljoydammit
...and when the bottom rod end is horizontal, how is hitting a bump not going to try to force the ball out of the cage?
Because there's no resistance forces... unless that specific arm has a shock attached to it, but even then its not the end of the world. And in my comment I didnt say it was all terrible.

Care to show those pics of the Riley MK3, I dont remember all GrandAm's but have worked with them for a long time, and even though DP's are a pile of garbage, I still think the Riley's had A arms, not the single arms like the Subaru.

Lower arm on the Lotus pic up above has the pushrod for the shocks attached to it.

As for the Riley, http://www.mulsannescorner.com/mkiiic-8.html (not mine) has a few pics of upper arms front and rear; I don't have my own webspace any more, much less one where I can cram all the photos I took at vintage races. The bottom links I annoyingly realize I don't have pictures of myself. I don't know what the DP ones are running, never seen up their skirts. Some of the prototype designers go to a lot further length to avoid it with shim adjustments for camber and all, but from what I've seen it's not like the ones that do use rod ends in bending are really associated with stuff that was unreliable on track.
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modernbeat
Jason McDaniel
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Re: Rod ends in bending
September 22, 2014 04:18PM
Bushrods and bellcranks to give a 1:1 tire to shock movement ratio.





Jason McDaniel
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Pete
Pete Remner
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Re: Rod ends in bending
September 22, 2014 06:03PM
Okay, dumb theory question. Do the top half of the shock and half of the rockers count as unsprung mass because they move with the suspension, or are they sprung mass because they are attached to the chassis? Or is it they are unsprung inertia but are sprung mass?

I ask only because I feel super light rallycross (SCCA) cars suck because the sprung:unsprung ratio is all out of whack, because people make the chassis lighter but the suspension stays the same if not slightly heavier, with the end result is the car gets to be uncontrollable over rough sections, which can be 80% of a course. And as I like to point out, if you can not lift, then you are automatically faster than people who do lift. So I wanna build a sub-2000lb car, while making unsprung weight as light as possible.

Disclaimer: I have Puhn's suspension book, but I don't recall seeing anything on the subject.



Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.
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mekilljoydammit
Daniel DeRosia
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Re: Rod ends in bending
September 22, 2014 06:33PM
They end up counting as unsprung mass. If it helps, think of "unsprung mass" as a shortcut for "unsprung inertia" because most of the time the differences between the two are mostly irrelevant... although frankly, compared to the mass of the wheel, tire, brake, upright etc I can't help but think the inertia from the bellcrank moving around is going to matter much either.

Also, I'm seeing a lot of details to like on that Lotus 7 clone, including the powerplant.
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Pete
Pete Remner
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Re: Rod ends in bending
September 22, 2014 07:30PM
Yeah, is what I had been thinking: it's the inertia itself that counts moreso than what is holding the weight up. But then I start overthinking again.

I really dig the huge travel my RX-7s new suspension has, so much that I'm trying to figure how to get 8-9" of travel in the front of the GTI, and I keep going back to ideas that rather require at least the spring to be on a bellcrank, because I don't have the resources to do a fancy WRC style upright.



Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.
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john vanlandingham
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Re: Rod ends in bending
September 22, 2014 09:42PM
Quote
Pete
Yeah, is what I had been thinking: it's the inertia itself that counts moreso than what is holding the weight up. But then I start overthinking again.

I really dig the huge travel my RX-7s new suspension has, so much that I'm trying to figure how to get 8-9" of travel in the front of the GTI, and I keep going back to ideas that rather require at least the spring to be on a bellcrank, because I don't have the resources to do a fancy WRC style upright.

It's the arc of the CV you have to pull hair about...8" is easy My normal VW stuff is 190mm or 7.5"
...done 8.25" also.
9" is getting way scary...
I do have 50mm inserts for 9"---ex Group A Lancia Delta Intergrale --surprising long for back then



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Pete
Pete Remner
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Re: Rod ends in bending
September 23, 2014 05:51AM
I have an easy solution for the CVs, that's no problem at all.



Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.
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