Yet another Rear control arm design

[JMortensen]

Ok, so here's where I'm at. I have the main tube that connects the inners ready to weld up. I have one complete triangle with no inner bracing mocked up, and it looks as though it's going to be TIGHT between the control arm and the tiny little tie rod. In the last picture I have two 3/4" rod ends end to end, I was trying to figure out how long the tie rod would end up. You can see if you look closely that I've spaced the rod end away from the end of the strut housing. With this tie rod end length of only 2 3/4" and using 3/4" rod ends, you have to do this. I don't know that this would be particularly harmful, but that's where I'm at right now.

 

Alternatively I could cut some length off of the shank of the rod end. That's not a very desirable way to get this done for me, but it may be the only choice. If I cut them down a bit then I could use an even shorter turnbuckle, maybe 2 1/2" or something like that. The next problem will be finding the turnbuckle. I know Coleman makes custom lengths so they'll be my first stop. I guess the question is do they turn the threads on a lathe, because if they tap them then they won't be able to make a turnbuckle that short.

 

 

 

[74_5.0L_Z]

First, the toe link does not need to be perpendicular to the strut housing. So you can gain a little length by moving the inboard end of the toe link toward the front of the car. Second, you might try 5/8" rod end for the toe links. The 5/8" rod ends are a bit shorter than the 3/4" rod ends. Besides, the toe link will not be nearly as stressed as the fixed rod end.

 

As far as turnbuckles go, make your own using these weld-in end from ChassisShop:

http://secure.chassisshop.com/partlist/502/

 

 

Be sure to buy matching left hand and right hand adapters, cut your tube, weld them up, and Voila. You've got a turnbuckle.

 

[JMortensen]

Because I'm using the 3/4" rod end with the 5/8" hole, the link does have to be close to perpendicular, otherwise the frame around the ball may contact the strut housing. Actually now that you mention it, I haven't checked for clearance, maybe the frame would miss the strut housing.

 

The reason I'm using the 3/4" rod ends is because Cary wore out a set of 5/8" rod ends on his control arms very quickly.

[EMWHYR0HEN]

I remember Cary mentioning that the rod ends were cheapo ones used on a V8 application.

 

If clearence is an issue i'm sure some high quality 5/8 rod ends will do just fine.

 

I don't think your going to be able to buy a turnbucle that short. Your best bet is to just use round tubing and get creative with a way to hold/turn the tube.

 

I was considering finding a nut large enough and welding it around the outside of the tube. However, it may not look pretty.

 

All you really need is 2 flat surfaces that run paralell on the tube to get an ajustable wrench on.

[JMortensen]

Cary and I are both using QA-1 XM rod ends. Certainly not top of the line, but they aren't the cheapest ones you can find either. The load ratings on them are really good for the price. Teflon lined, chromoly ball, etc.

 

Here's the description from Pit Stop USA:

Description: Unsurpassed Performance! The Best Rod Ends for Racing! XM Series Features: • 52100 Bearing Steel • Teflon® / Kevlar® • Chrome Moly Steel • Metal to Metal Support for • Heat Treated • Self-Lubricating • Heat Treated Heavy Shock Loads • Hard Chrome Plated • Self-Sealing • Protective Coated for • Increased Cross-Sectional Thickness • Precision Ground Corrosion Resistance for Greater Tensile Strength Benefits: • Heavy duty. • Metal to metal for heavy shock loads. • Increased cross-sectional thickness for greater tensile strength. • Commonly used on 4-Link and Ladder Bars. • Self-sealing race keeps dirt out. • Self-lubricating liner won't pound out like other styles.

 

As to the turnbuckles, I know I can get a 4" from Coleman. Not sure how far in they're threaded. I know they do custom lengths, I guess I'll have to call them to see if they can do something that short. Not doing the nut thing. In my opinion that's not enough thread engagement for the rod end. It may be that I could get away with less because I'm using a larger thread diameter, but I have a pretty strong inclination not to do that.

[JMortensen]

Called Coleman this morning. They are able to make turnbuckles for about $35 each. Looking at the link that Dan provided, the cost for the tube ends and tubing is almost the same. I went ahead and bought the prefabbed units just to save hassle.

[johnc]

Is the jig you have on the bench your welding fixture? That part needs to be tightly bolted in place before welding and a stress relieving step after welding and before unbolting would be a good idea.

[JMortensen]

Is the jig you have on the bench your welding fixture? That part needs to be tightly bolted in place before welding and a stress relieving step after welding and before unbolting would be a good idea.

That was the plan. How would you suggest stress relieving?

[johnc]

First, let the part cool completely after welding.

 

Use a torch with a rosebud tip and get a 900F temperature crayon (Tempilstik). Mark each side of each welded joint with the crayon 1" from the weld. Use the torch to heat a joint until the crayon marks melt. Cover the joint with a heat blanket or something to slow the cooling process down. Proceed to the next joint. If you're really anal, heat all the joints equally and at the same time before letting the part cool down.

 

What you're trying to accomplish is to relieve any stress buildup and resulting distortion from the welding process.

 

EDIT: Before you go through all of this, you can take the part out of the welding jig and see how much distortion exists. If its just a little bit, I probably wouldn't worry about stress relieving the part.

[JMortensen]

Looks like I'll be crossing my fingers and hoping it doesn't warp too badly.

[tube80z]

Cary and I are both using QA-1 XM rod ends. Certainly not top of the line, but they aren't the cheapest ones you can find either. The load ratings on them are really good for the price. Teflon lined, chromoly ball, etc.

 

These lasted about three events before pounding out the liners. We switched to Aurora bearings, AM series if I remember correctly, and they are doing better. But even these are taking a lot of abuse. They were very stiff when put on the car and now are very easy to move.

 

I recommend the 3/4 rod ends to Jon because they have a lot more bearing surface area and the price difference isn't that much. I would have thought the front would take more of the load too. It was a 3/4 QA-1 part and it had no slop and was still pretty tight. The same batch of 5/8 QA-1s were used in the lower front control arms and for TC rods. These are holding up fine. So I do think there's a lot of stress back here.

 

Of course this is a V8 car driven by a couple of immature adults that giggle everytime they see 14 inch black marks get laid down.

 

Cary

[blueovalz]

Jon, have you thought about swapping the adjustable link to the rear side of the arm? This would allow a lot more length for the link. Plus, you'd avoid the torque force from being placed in the middle of that front tube (or wherever it will connect on that front tube). With the rear link, you could attach the link adjacent to the rear bushing support and eliminate any forces acting on an unsupported member (or eliminate more structure to support the connection up front).

 

[JMortensen]

Go back a couple pages and you'll see why Dan and I wanted to go this route. I believe this will put much less side load on the strut shaft than the arm as you've drawn it, because the fixed point is directly under the strut shaft.

[JMortensen]

Several weeks later and more progress. The turnbuckles from Coleman came. I had ordered them at 3" and had to cut them down to 2 1/2, which also required cutting down some of the rod end shank as well. Theoretically this weakens the rod end, but I'm using oversized ends here so I don't think it will be a problem.

 

I had drawn the control arm like this:

 

 

Now I'm thinking that I should only use one brace like this:

 

 

And here is the arm with the bracket for the toe link mocked up. I'll have to take a look at Emwhyrohen's bracket again, he shaped his so they look pretty...

 

 

The brace that is in line with the toe link goes straight to the center of the inner tube, and that just doesn't seem like a good way to try and strengthen the control arm. I'm also considering gusseting all the corners with .060 sheet taco gussets for good measure.

[EMWHYR0HEN]

Your arms are looking great Jon. To make it easier on the eyes I just took some random round curves to get rid of the sharp corners on the clevices.

 

 

After you weld it all up, including that brace that splits it into 2 triangles, you'l be amazed how ridged the arm will be and might not need to add any gussets.

[JMortensen]

I forgot to get stylish with the brackets. Once I had finally cut and notched and drilled and plug welded the fittings and everything was ready I just started welding them up.

 

I'm going with no gussets as suggested. I was curious as to the weight of these and was pleasantly surprised, 8 lbs with the toe link and rear rod end and a much larger than necessary bolt for the toe link.

 

Any suggestions before I rattle can these guys and make them pretty?

 

[1 tuff z]

yes, weld in a little 'z' between the tubes for the ultimate in style!

 

just kidding, they look great jon!

[EMWHYR0HEN]

Any suggestions before I rattle can these guys and make them pretty?

 

 

Yeah weld the other side!

[z-spec]

There are different ways to do it i,i made them with fixed track and just adjustable toe in/out they are made from thin wall 4130 tube

[Flexicoker]

Make sure you guys are looking at the axial load ratings for the rod-ends you're using. The bearings are loaded axially under accel and braking on most of your control arms, and the axial load rating is significantly lower than the radial load rating.