Pullrod adjustment, Spring preload?

[rjwoods77]

Hey guys,

If this is a repeat then show me the link because I cant find anything on it. I am making my pullrods as we speak. I had a funny question. I have been told that once you get the car done you balance the corner weights by adjusting the pullrods/pushrods. What is the difference between that and turning the spanner wrench on the shock. I am understanding things wrong? What excatly is a zps(zero preload system)?

Also I think I have seen this before and I wonder why it isnt done more? Instead of 2 rod ends, 2 jam nuts, 2 threaded inserts and a tube.

Can you do 2 spericals, 2 weld in holders, 2 jam nuts , 2 pipes with threaded ends that accept a lh,rh threaded union? I guess the though behind this is to keep the force off the small shank of a rod end?

Comments appreciated.

[rjwoods77]

Hey guys,

If this is a repeat then show me the link because I cant find anything on it. I am making my pullrods as we speak. I had a funny question. I have been told that once you get the car done you balance the corner weights by adjusting the pullrods/pushrods. What is the difference between that and turning the spanner wrench on the shock. I am understanding things wrong? What excatly is a zps(zero preload system)?

Also I think I have seen this before and I wonder why it isnt done more? Instead of 2 rod ends, 2 jam nuts, 2 threaded inserts and a tube.

Can you do 2 spericals, 2 weld in holders, 2 jam nuts , 2 pipes with threaded ends that accept a lh,rh threaded union? I guess the though behind this is to keep the force off the small shank of a rod end?

Comments appreciated.

[murpia]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Rob Woods:
I have been told that once you get the car done you balance the corner weights by adjusting the pullrods/pushrods. What is the difference between that and turning the spanner wrench on the shock. </div></BLOCKQUOTE>

You should do both. That way you can cornerweight your car AND place your static position within the damper travel range exactly as you want.

Ian

[Jersey Tom]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Can you do 2 spericals, 2 weld in holders, 2 jam nuts , 2 pipes with threaded ends that accept a lh,rh threaded union? I guess the though behind this is to keep the force off the small shank of a rod end? </div></BLOCKQUOTE>

I'm sure you could.. but that's more parts to assemble *and* fabricate. Getting that union thing goin might be diffficult, getting the right tap drill hole given your tube size, then hand tapping it in a lathe. And as if pullrod tubes weren't thin-walled enough, tapping them is going to make some super thin sections, combined with the stress rising effect of cut threads.

Those 'small' rod end shanks are still pretty strong. They're designed for this.

[Marshall Grice]

the big difference is static shock length. If you change the length of your shocks to change corner weights the motion ratios could/will be different for each wheel. depending on the suspension design they could be significantly different.

With regards to redesigning a pullrod, why? are you really going to gain anything out of doing that? Have you measured the deflections of the clasic pullrod design and decided that it's not stiff enough for your application? Is your pullrod seeing some sort of bending loads? Personally it sounds like a waste of time to me, but if you're that bored have at it.

btw, most of the big time race cars i've seen don't use rodends, they use clevises(clevii?) and put the sphericals in the rocker/a arm.

[rjwoods77]

Thanks. Makes sense. Wasnt really looking at it hard. Just seen a couple pics of it but the obvious is the obvious.

[Erich Ohlde]

The main reason for adjusting pull/push rods instead of spring preload is that changing the former has no effect on wheel rate. spring preload changes ur bellcrank position thus changing ur carefully designed wheelrate curve.

[D J Yates]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Marshall Grice:
btw, most of the big time race cars i've seen don't use rodends, they use clevises(clevii?) and put the sphericals in the rocker/a arm. </div></BLOCKQUOTE>

That's a nice idea. Can't belive i never thought of it before. I'll have to investigate.

[James Morrison]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Marshall Grice:
btw, most of the big time race cars i've seen don't use rodends, they use clevises(clevii?) and put the sphericals in the rocker/a arm. </div></BLOCKQUOTE>

I have been noticing myself how big time race cars (i.e. Aston Martin DBR9) use clevisis for connecting steering arms and a-arms. Any idea on the advantages over rod ends?

[Marshall Grice]

stiffness.

[Lukin]

Not to mention quick geometry changes if you make the clevis 'long' enough.

[Buckingham]

Even good rod ends will have just a tad bit more radial slop than a ball joint. On a push/pull rod where the rod is always in compression/tension, this isn't much of a problem, on A-arms and tie-rods it can be.