I'm probably going to fab up my own custom torque arm because I haven't found anything that I like.

I've got a Spohn torque arm right now, and I'm going to get rid of everything but the axle yoke. I'm just unsure if I should use Chromoly cylindrilical or rectangular tubing for fabbing up the new design.

Any ideas on which is stiffer with regards to shock loading?

Weight for weight, the material needs to be able to be stiff, yet flex at the limit and not catostrophically fold up & fail.

 

Contrary to popular belief alloy will not change the stiffness of a material.

It will change utimate strength but you should not be near that anyway.

Avoid Chromemoly unless you have a heat treatment oven.

Square tubing puts more metal in about the same space as a tube. 1" square tube with the same wall will be stiffer in bending than 1" tube. It will weigh more per foot but it will be stiffer also.

Either approach will work, I think square would be better top and bottom and easier to work with.

Large tube / square at top and bottom combined with a diagonal web of smaller tube in the center is a good approach. You are building a truss like you see in a house.

Most likely cheaper to buy one with these design features, rather than spend time and money on a DIY.

But good Luck.

Z28

 

Thanks. No one is currently building one with the design features I want. I want a decoupled torque arm design with the ability to adjust both pinion angle, instant center of acceleration and instant center of braking. I also want a quality upper slider link with integrated shock damper. In addition, I want a striker plate that gets attached to the transmission tunnel and doubles as a driveshaft loop. The striker also needs to be attached at the top of the transmission tunnel such that it transfers torque into the roll bar assembly.

Lastly, I will be modifying my subframe and moving the transmission crossmember mounting holes backwards to enable me to run a simple and lightweight transmission crossmember that does NOT exert a torque on the existing bolts. Under hard acceleration I can get as much as 1/2 inch upwards deflection from my Spohn piece, and it's not the crossmember that's flexing, it's my subframe.

The Spohn T56 retrofit torque arm is strong and rigid, but noisy and exerts a bending force onto the crossmember fasteners. It also weighs fourty pounds. I want to trim the weight of my torque arm and crossmember to twenty-five pounds or less.

Jason Swindell of Unbalanced Engineering has not returned any of my emails so I guess I'll have to design and fabricate my own.

Oh, and I *do* have a heat treatment oven for stress relieving welds. As long as the assembly isn't too long, I should be able to heat it up to 700 degrees or so. I've gone as high as 1600, but I'm not sure that heating stuff to cherry-red hot is necessary.

 

Hi,

Sounds like a serious project.

I was looking under a dirt track car that was being shown at a car dealership promotion.

It had solid rear suspension with a torque arm. Very much like the camaro setup.

They had used a small coil over shock at the end of the torque arm. It was mounted almost vertically. No room to do that on a camaro, but the idea was interesting.

The setup could be tuned in a number of ways, spring rate, preload, rebound and compression dampening. Perhaps a rear shock off of a motorcycle, or a small air shock.

You might want to spend some time and see what the dirt track guys are up too.

Jason uses square and round tube, I like his design but it looks tricky to setup right.

I don't have enough power to bend my stock arm so I was thinking about GW front arms and T2R as my next step.

The decoupled design looks like a great idea to me, better than anything I have seen from anybody else.

Happy Tinkering

Z28

 

Thanks,

Hey I met the owner of Detroit Locker last night and discovered that he's a certified gearhead and projaholic. He was telling me about their Trutrac differential, and suggested I call Moser engineering on getting one put into a new 12-bolt axle assembly. It's supposed to also have a 250 lb preload, but feature three sets of torque balancing gears versus the Torsen's two sets. I was intrigued, but then this morning I decided to just readjust my gear lash on my H.D. Torsen / Richmond gearset and run it till it breaks. It frees up $2200 for my suspension development and maybe even two new sets of race tires

 

rectangular tube turned on it's side is the stiffest thing without going to some sort of h beam welded billet plate

 

Round will have more strength at a given crossection.

 

Round however is not as strong flexion wise. A 5 foot piece of round and a 5 foot piece of squared turned on it's side, next to eacother, with the same load bearing force right on the middle of the bar, would cause the round to flex more then the rectangle.