Re: [Amc-list] truck arms

[Wrambler242@xxxxxxxxxxx]

Note; There are several designs of truckarms in use by NASCAR teams. 
I've seen square tube, rectangular tube and original I-beam types available from used race parts places.
Tube arms seem to be more common in the street scene and are big buck pieces.
I saw a set of I-beam type on ebay recently, I could not decide if they would be a good idea as while the pair was prices at $175 buyitnow and I-beam type they had Monoball ends. I would assume that the mono ball would make for a harsh noise/vibration issue right under the seats!
  Still thinking and reading and thinking!

--
Mark Price
Morgantown, WV
1969 AMC Rambler, 4.0L, EFI, T-5

 -------------- Original message ----------------------
From: "Swygert, Francis G MSgt 436 CES/CECM" <Francis.Swygert3@xxxxxxxxxxxx>
> Date: Tuesday, April 17, 2007 11:48 AM
> From: Tom Jennings <tomj@xxxxxxx>
> 
> Mark, one thing I don't see in a lot of these truck-arm schemes
> is explicitly allowing for roll. They all go up and down fine. I
> realize also that the angled arms helps, but a flat pivot that
> flexes in only one plane simply can't work.
> 
> ------------------------------
> 
> "Truck Arms" do allow for roll, but as you noted roll is limited. The
> angle of the arms and pivots allow for some roll motion, and the length
> of the arms. The original Chevy truck arms are I beams, not boxed. The
> beam itself twists as the vehicle rolls. It's designed specifically to
> twist. The beams are relatively heavy in cross section, but are made
> from 10-11 gauge material. They have a high resistance to bending in the
> vertical plane due to depth, but a low resistance to twisting in the
> horizontal plane. There is at least 6" of flex from one wheel to the
> other, though I believe it is more like 8" IIRC. One wheel can be jacked
> up for changing easily without affecting the other, or rather affecting
> it no more than it would a leaf spring or torque tube suspension. 
> 
> Boxed beams are used on NASCAR chassis. Those are much stiffer than the
> I beams used by Chevy and Hot Rods to Hell. HRTH sells the arms and
> other components for custom installations
> (http://www.hotrodstohell.net/catalog/catalog.htm). Stock Car Products
> (http://www.stockcarproducts.com/trkarm.htm) also sells them for about
> the same price (SCP $225 each, HRTH $220 each). SCP has a universal
> crossmember for $96, so it would be about $550 for the parts to put one
> in a 63-66 Classic (the most likely recipient) with a little welding.
> I'd cut the crossmember to the correct width and weld on end plates that
> would bolt under the car. 
> 
> I've though to build a set using 1"x3" 16 gauge rectangular tubing. That
> should handle moderate power (300-400 hp) and be thin enough to flex
> some. Not as much flex as an I beam, but should be enough to mimic a car
> with a rear roll bar. I just wonder if a length of tubing could be
> placed diagonally from one bar to the other to eliminate the need for a
> panhard rod. There would have to be rubber bushings or spherical rod
> ends to allow the arms to twist, but there's little enough movement and
> pressure on rod ends in that application that they should last. They
> won't last on the street when used to replace main suspension bushings,
> such as on strut rods and A-arms.  
> 
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