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Adjustable Rear LCA


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I have heard that you aren't supposed to weld chrome alloy with a mig welder from a friend of mine who works at art Morrison. However he is a very paranoid individual that enjoys finding things that may cause problems, he's a good friend of mine regardless but this the truth. With that being said has anyone that has put there chrome alloy mig welded control arms to use experienced any cracking or failure? Did you have to do any special heat treating? Or did you just weld it and you were good to go? That's what I'm really hoping for since I only have a mig welder.

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The originator of this design (myron, his thread is linked at the beginning, refer to page 4 of his thread) used chromoly. For the thickness of tube he was working with, his welding instructor informed him it would be alright to weld without any special pre-treating, I think if you step up from his wall thickness you have to pre heat-treat, so your friend is not wrong, as far as I know Myron has not had any problems and he has several track days on his car. In fact a company bought his design and started making them for market, although I have heard mixed reviews about their workmanship.

 

For my slightly altered design, I used regular DOM steel, of a larger diameter and of a thicker wall thickness following instruction from other members on this thread. I think Jmortenson mig'd his arms and they are also not chromoly.

Edited by seattlejester
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  • 1 month later...

So I am coming into this realizing I really don't know very much.

 

First off, finished product:

F15E2B1A-76DD-45E3-AF3A-94B6A02E5715_zps

Powdercoating place did real well. 

 

Something I am struggling to understand however is the forward to aft movement. Video for reference.

http://s639.photobucket.com/user/jesterjin/media/55A5E42F-991B-43B4-9EA8-D9BE273EB65A_zps0fzomrxj.mp4.html?o=0

 

With the axle and the strut installed is there enough rigidity in those two axes to prevent that twisting motion? I think TTT arms prevent this by having a fixed distance between the toe link and the A arm. Am I missing something here? Or is this how it is supposed to work?

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The strut top is in a fixed position and that's what holds the strut tube vertical. The difference between this design and mine with the toe link at the front is that the strut tube is on top of the rear pivot, so a simple push up or down on the hub (where the forces affect the suspension as the car goes over bumps and rolls) doesn't put a pivoting force (side load) on the strut tube as you show there if the toe link is in front. A solid control arm will deflect and that also puts load on the strut. The rear toe link design will put side load on the strut. The front toe link should put less than either because a vertical push to compress the strut won't twist things up as much. 

 

Check out posts 26 and 27:

http://forums.hybridz.org/topic/62776-yet-another-rear-control-arm-design/page-2 

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I see, I guess I got mixed up with 240zdan's recent thread calling for a pillow ball mount in the back as well. So the strut top is fixed and keeps that plane locked.

 

I'm going to have to look into more of the difference between the front and the rear toe link, I fear I'm still a bit lost. I will pour over your thread and the thread you linked once more.

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I can definitely see that, since for one thing your rearward rod end wouldn't have any play in it and your front one has a much shorter arm so it would deflect less. 

 

I wonder if on yours it would pivot backwards, granted the strut housing is right smack on top of the rear one so maybe not as much a concern. I think someone had a similar design as the one I ran except they used a solid bushing up front and two rod ends in the rear. I guess I won't know until it is on the car. 

 

Thanks for taking the time to sort me out, was pretty startled after I put it all together.

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Seattlejester, I am running a configuration just like yours (see pic) that has the toe link at the rear. I have been running it like this for 3 - 4 years and have never had any issues. But, if I ever build another set (and I am planning on doing so), I plan on moving the toe link to the front as Jon has done. It just looks like it would be more ridged. But, like I said, mine have worked just fine.

 

Mike Mileski

Tucson, AZ

post-116-0-79805400-1455042803_thumb.jpg

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AZC's setup is essentially solid.  Don't click on the link unless you have time and bandwidth, there seem to be a lot more pictures there now.  I pulled one out.

 

You could do similar but leave the rotating inner axis at its original position.

 

http://www.arizonazcar.com/cars.html

post-8864-0-70189500-1455048861_thumb.png

Edited by NewZed
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I thought with that style, they ended up adding a set screw to hold that original pivot in place as if it rotated at any time it would cause the arm length to shorten or lengthen.

 

I suppose I could have a delrin bushing made up, but I've cracked a couple delrin pieces so I'm not sure if that would be the ideal component. I've seen steel sleeves that peaked my interest.

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So I am coming into this realizing I really don't know very much.

 

First off, finished product:

F15E2B1A-76DD-45E3-AF3A-94B6A02E5715_zps

Powdercoating place did real well.

 

Something I am struggling to understand however is the forward to aft movement. Video for reference.

http://s639.photobucket.com/user/jesterjin/media/55A5E42F-991B-43B4-9EA8-D9BE273EB65A_zps0fzomrxj.mp4.html?o=0

 

With the axle and the strut installed is there enough rigidity in those two axes to prevent that twisting motion? I think TTT arms prevent this by having a fixed distance between the toe link and the A arm. Am I missing something here? Or is this how it is supposed to work?

What struts are you using as it apears you may have welded on an custom strut tube?

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