I'm going to have my 65 strut rods cut / threaded

691 Views 9 Replies 4 Participants Last post by Dinosawnj, Jun 18, 2002

Hottarod

Discussion Starter · Jun 17, 2002

After a few discussions with a drag racer friend from way back and talking to a local machine shop everybody believes that cutting extra threads in these will work fine. The cut will not be abrupt but tapered up to the thicker part of the rod. Tapering instead of an abrupt cut line will help prevent it from fracturing at this point. I believe that 1.5 inches of extra thread will be enough. I may devise some sort of sleeve to go inside the bushing to help strenghten it where the strut rod goes through. This is done on the later adjustable rods. Another thing that we will do is loosen the control arm bolts when pulling the caster. This should prevent any kink or bind from being set up by pulling the strut rods forward some. Now what do you all think of this?

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Dinosawnj

· #2 · Jun 17, 2002

Why not cut the strut shorter and thread the strut to accept a beefy rod end. You then can drill a hole thru the sides of the strut rod frame member and weld in reinforcing body washers. This way your free of the big bushing a get better range of motion up and down. This way somewhat common in the 70's and 80's before the TCP arms.

Bob.

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camachinist

· #3 · Jun 17, 2002

I believe it was I who suggested it the other day, yes?

I wouldn't do it on a street car, for liability reasons, but see no reason why you can't do it to a race car...

I'm assuming that, instead of going to a shoulder, you'll be putting a nut on the back side to locate the biscuits....that method will make it much more adjustable and more forgiving of design tolerances...

Good luck!

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66benchcoupe

· #4 · Jun 18, 2002

I don't see why you would need to loosen the control arm when you adjust the new rod. What could possibly bind?

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Hottarod

Discussion Starter · #5 · Jun 18, 2002

I don't know, LOL. I guess I was thinking that the control arm would rotate on its axis and do something like try and make the tip of the strut rod turn inwards a little.

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Hottarod

Discussion Starter · #6 · Jun 18, 2002

Sometimes I have trouble understanding what language you are speaking, LOL. I've been told before that putting the extra threads in these makes them prone to breaking which is why I've been reluctant to do it. I think this taper thing is the fix for that problem.

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66benchcoupe

· #7 · Jun 18, 2002

It will, a little, but not enough to cause a problem, IMO. I would watch the lower control arm where it bolts to the frame while you're adjusting the new rod. If you moved the lower arm forward enough then you could possibly have some binding there since it wasn't designed to be adjusted that way. You'd have to be adding a lot of positive caster to do that, I'd think, so much your front tires would end up rubbing the front of the wheel well.

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Hottarod

Discussion Starter · #8 · Jun 18, 2002

I'm not sure I follow what you said. Getting rid of the bushing seems like to me would be a big problem because there would be no give at all then. I can see that breaking a strut rod or bending the lower control arm. Even the Nasa(TCP) ones have a kevlar bushing on the end. Somebody else makes a heim joint strut rod that requires you to reverse the direction of the hole(cutting and welding required). They were expensive too and I didn't want to cut up my strut rod frame brackets.
.

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camachinist

· #9 · Jun 18, 2002

Sometimes I have trouble understanding what language you are speaking, LOL

hehehe...sorry 'bout that...

The only time you should be concerned about the strut rods breaking (after a modification which you have described) would be if they're case hardened steel and you cut through the case hardening when doing the machine work....generally, tempering goes deeper and won't be as affected.

Given that the struts operate in tension during their periods of highest loading, generally, I wouldn't be too worried about it. The lower control arms on the race car are mild steel and use SS heim ends and I've been pretty abusive of them in the lights over the years (bracket racing) and haven't seen any signs of fatigue.

Before I put struts on the car, I had trailing arms instead of strut rods (because of the RP geometry) and never had any problems with those either, and they were in compression and bending under high braking forces. I had more problems with the shock towers cracking around the upper spring seat (from wheelstands)

A taper will do the job but, IME, and .060"-.080" root radius at the end of the threaded area will serve the same purpose. I've made hundreds of hydraulic rods in my career and make them exactly the same way and have never had a root radius failure to date. They're (and your strut rods) are more likely to fail in the root (minor diameter) of the thread pitch unless care is taken (with tooling) to impart a small radius to the root of the thread. Die-cut threads are often sharp in this area, which can promote stress raisers under heavy loading/stress and ultimately lead to failure.

Hope I'm not jabbering too much in machinist-speak...*G*

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Dinosawnj

· #10 · Jun 18, 2002

Sorry for any confusion. I use the word bushing for any hard rubber or poly component and rod end or sperical bearing for componets meant to allow movement without bind except for perpendicular to the mounting bolt arrangement. What I was saying was to remove the rubber (or Poly) bushing your using and replacing it with a beefy rod end (just as in the TCP application, can be teflon or kevlar coated). The rod end will allow for movement in all directions accept for straight forward (which is what your after). There will be considerably less bind than with a stock type bushing.

You could make one a little fancier (and similiar to TCP's) by buying a right and left hand thread steel training arm sleeve (page 180 of the 2002 Coeman catalog or similiar - TCP uses Aftco) a puting the rod end on the front side and the threaded strut rod (cut down considerably) into the other end. By twisting the trailing arm tube. you can now easily adjust the rods length (and lock down with jam nuts).

Bob.

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