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Adjustable Rear Control Arms: Anyone Interested?

Guest Anonymous

By Guest Anonymous
in Brakes, Wheels, Suspension and Chassis

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Guest Anonymous

Guest Anonymous

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They are reversable like the stock units. The pin doesn't need to be pulled for the arms to be adjusted. The Rod Ends are threaded into the main shafts and are set with roll pins so they can't move. The main shafts are threaded and slide inside the outer housing. The nuts on the main shafts are loosened and tightened to adjust the length of the main shafts. The nut just behind the Rod End is to hold the shaft straight while adjusting the length. When adjusted to the proper length the nuts on the mainshaft are torqued to prevent the shaft from moving. Very simple and very fast for adjustments. Pics on the car will follw within the next week.

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Guest Anonymous

Guest Anonymous

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Please explain why the pin needs to be pulled and then I can give you the reason it doesn't. I will follow up with more pics that show instalation and adjustability as I install them on my car. At this point there are less than 5 people that have shown interest so I'm not not real sure how much work I want to put into documenting everything. I might just start with my car and then show them to the members of the local club and start that way.

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TimZ Newbie

TimZ

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Please explain why the pin needs to be pulled and then I can give you the reason it doesn't.

 

I think that the confusion (at least for me) comes from the fact that you said that the rod ends were secured in the main shaft with roll pins. If this is corect, then it looks like you would have to rotate the whole assembly (including the rod ends) to make length adjustments.

 

Now after reading your description for the fourth time and looking at the picture, I think I see what is going on - the mainshaft is threaded on both ends of the tube that it slides in, but the tube is not threaded. The jam nuts on both ends are what do the adjusting. Is this correct?

 

My only concern with this would be whether you have made any provisions to keep the threaded shaft from abrading the inside of the tube, and eventually enlarging the id of the tube to the point that the shaft can wobble enough that the jam nuts will no longer remain tight.

 

This is the same issue that makes it desireable to use a bolt with a long unthreaded portion as opposed to one with threads all the way. The unthreaded portion keeps the bolt centered in the hole (assuming the hole is the proper size for the bolt), and keeps the threads from chewing up the bore.

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Guest Anonymous

Guest Anonymous

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That is exactly how it works. The clearance on the threaded shaft inside the housing is about 20/1000s. The shaft is 1" B7 alloy fine thread and the housing is seamless pipe. I understand your concern and only time will tell. I have given some thought to recessing the threded shaft in the center and mounting a set screw to the outer housing or machining a key way. I'm not sure it is necessary given how tight it is when everything is torqued

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TimZ Newbie

TimZ

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I understand your concern and only time will tell. I have given some thought to recessing the threded shaft in the center and mounting a set screw to the outer housing or machining a key way. I'm not sure it is necessary given how tight it is when everything is torqued

 

Given the side loads and vibrations that you are going to see in that location, it's probably not a question of whether it will be a problem, but more one of how soon.

 

I think this should be a fairly easy problem to address. I would think that given the dimensions of the main shaft, you almost certainly are having the threads cut on this anyway, right? I can't imagine this being an off the shelf piece. If this is the case, all you need to do is determine a reasonable range of adjustment, and only cut the threads in the shaft on the ends instead of the whole shaft, leaving an unthreaded portion in the middle that slides in the tube.

 

I do like the design, BTW - it looks very nice, and I may very well be interested in a set. It would probably have to be next winter's project, though - I've already spent WAY too much money this winter :shock: ...

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johnc Newbie

johnc

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I'm always surprised how simple things can be made complicated. All you really need to add the threaded rod ends to the main shaft is a simple threaded insert that fits about 2" into the end of the outer housing and is welded in place. You're just building a tubular control arm so why not use the same design as on TransAm and NASCAR stock cars for the threaded ends.

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TimZ Newbie

TimZ

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All you really need to add the threaded rod ends to the main shaft is a simple threaded insert that fits about 2" into the end of the outer housing and is welded in place.

 

John - am I missing something, or wouldn't this require removal of the infamous spindle pin to allow adjustment?

 

Two things I like about BeastZ's design are the ability to adjust it without disassembly, and the fact that it's impossible for an inexperienced customer to adjust the rod end out so far that there is insufficient thread left to retain it safely. NASCAR and TransAm pit crews know exactly how far they can safely go. I'd be willing to bet that this would not even occur to 80% of the backyard wrenches out there. Until their wheel was dragging by the brake lines, that is... :eek2:

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johnc Newbie

johnc

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wouldn't this require removal of the infamous spindle pin to allow adjustment?

 

Not at all. The rod end setup would be the same as in the picture above except you wouldn't have the threaded end going all the way through what Beastz calls the main shaft(s).

 

Another point I would like to make - rear toe is not something you adjust all the time. Even racing monthly I adjust rear toe, maybe, once per year.

 

it's impossible for an inexperienced customer to adjust the rod end out so far that there is insufficient thread left to retain it safely.

 

Nothing is impossible for a determined idiot. But with a minimum 2" of thread even a determined idiot would get the alignment so out of whack that the car couldn't be driven safely. He'll wreck before a rod end even has a chance of falling out.

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TimZ Newbie

TimZ

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Okay, I'll buy that, but the threads on the rod ends will have to be opposite that on the shaft/insert (right hand/left hand).

 

Nothing is impossible for a determined idiot. But with a minimum 2" of thread even a determined idiot would get the alignment so out of whack that the car couldn't be driven safely. He'll wreck before a rod end even has a chance of falling out.

 

If it were used for both camber and toe adjustment, it might not be as impossible as you think, and possibly not unstable. You could end up with a crapload of camber, but if the toe was reasonable, it would be driveable.

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Guest Anonymous

Guest Anonymous

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It looks like there is some solid debate on my control arms and it is good to read other peoples thought processes. All of the adjustment comes from the 1" main shafts. The Rod Ends could be LH threads to give some adjusabilty but I don't see the advantage. I have them threaded all the and roll pinned so they can't move inside the main shaft. I want to keep the shaft from being able to spin at all therfore reducing the chance of the touqued jam nuts from coming loose. I will try these as they appear in the pic. At this stage I can hand tighten the jam nuts and take all play out of the main shafts. I dont think it's going to move once it's torqued into place. There is no doubt witrh the adjusabilty they give I can get my rear specs right where I want them. I'll be getting rid of my camber bushings and going to poly. If the shaft play becomes an issue I'll just set it up where I want it and drill a hole through the the outer housing and main shaft and run a bolt through it. That will lock it into place and remove all doubt of it moving. Thanks for all of the input. This project is more complcated than it would first appear. Keep the thoughts coming

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TimZ Newbie

TimZ

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The Rod Ends could be LH threads to give some adjusabilty but I don't see the advantage.

 

The reason I mentioned that was that John had mentioned the idea of leaving the rod end unpinned, and making the shaft such that it just screws into the tube itself, instead of just riding in it. The idea was that the adjustment could then be made by screwing the shaft in and out of the tube (which would now be threaded on the inside).

 

For this to work, the rod end would need to be the opposite-handedness from the shaft's outer threads. Otherwise, when you screwed the shaft out of the tube, the rod end would screw into the tube, which would negate the adjustment.

 

Hopefully that made sense...

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Guest racerxlite

Guest racerxlite

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I am very interested in your rear control arms. I've been looking for replacements from stock that allows me to adjust camber on the control arm vs. installing the camber plates on the towers. Not much room on IMSA fender flares w/ the 275/40/17"s on the car. Looking to go 16X10 or 16X12's next year for purposes of slicks.

 

My concern would be reliability. The car was built for auto-x, road racing & hill climbs. I am concerned with failure at 100+ heading up a mountain. I would love some additional info on the control arms, as well as some background to your experience building suspension components.

 

Thanks,

Matthew Benson

matt_benson@hotmail.com

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