I have broke my sphon torque arm a half a dozen times now. Well this time around I lost the end of the arm that slips into the collar that mounts to the body. I was thinking since I lost it I want to fabricate it so the torque arm doesnt allow movement in that collar. Does anyone know the purpose of making the spohn torque arm 2 pieces besides the ease of install?

 

Do to the arc that the differential moves though as it goes up and down the arm has to be able to move in and out. This is the same reason why the drive shaft has a movable slip joint at the trans.
You should probably give it up and buy his new style one.

 

With that much Hp, you need to call Madman, you wont break his Tq arm.


David

 

Is this the older design with the slider, or the newer version where arm itself is one piece (plus the crossmember of course)?

 

That sounds like the original version of the Spohn TA... and that was not designed to support anything near 1,000rwHP. Many people broke them at 500HP. That's why he went to a different design. I've seen his current design handle a setup pushing 1,350 flywheelHP through a 3,525# 4th Gen chassis. For that particular arm, he added an extra diagonal brace or two between the upper and lower arms.

When his "old design" arms were still relatively new, he was strengthening them for free, by replacing the hollow rod that pushed into the slider with a chrome moly rod. He did that for mine. This is the old one, with the rubber bellows covering the slider joint:

http://members.aol.com/Fredrick518/Photos/TADS4in.jpg

New design:

http://cjcfo.fbody.com/members/injun.../DCP03248a.jpg

Given the fact that yours is so old, and given the fact that you're using it at power levels way beyond what anyone could reasonably anticipate, I'd just order a new design.

The version of the Madman arm that I saw did not have any provision for the changes in length, and ripped itself apart at the rear mount, on the same high HP car mentioned above (but when it was still under 1,000 flywheelHP). Maybe he's changed the design, but when I've questioned the lack of accomodation for changes in length, he did point out that people were running 1.2X 60-fts with the arm the way it was. Hard to argue with that.

 

Harlan's car put it to a pretty good test as well, 8.29 @ 166, and later on at 171mph. I trust my newer-style Spohn just fine.

 

It looks like if I just extend the arm and get away from the slider it will look like the new version. Maybe cut where it breaks away soon( before it goes in the slider) and extend the steel to where it would bolt to the tunnel brace it would be similar to the new version. What you guys think?

 

I broke my old style Spohn numerous time at 340 RWHP and a M6 and sticky tires. I redesigned the slider end with a larger diamter 4104 HT slip joint and corrected all of the problems on that end up to 390RWHP. But, then the other end, back by the rear, broke the top chrome moly tube right a a stiffener weld. Chrome moly isn't real terrific in terms of ductility so the failure was not just a bend. Fortunately enough of the arm stayed together that I didn't wrap the whole rear around at highspeed. I gave up and bought the latest generation Spohn. Only complaint with Gen II spohn is that he laser cuts all of the bolt holes in the connecting links and heim joint holes. The laser cut holes are way too big and allow additional slack and a hugh amount of noise. I ended up welding those holes shut and redrilling and reaming to a nice close fit. System is nice and quiet now.

Steve