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Traction bar with shackle mount useage in HIGH torqe applications...

sled_dog

sled_dog

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Long story short, there is an 05 Twin Turbo Cummins powered Dodge that needs a traction bar system. Due to a few constraints my thought of what to do is running either one of two setups:

1004AR_bar_5.jpg


or:
Shop+pics+004.jpg


So many big Diesels run the simple 2 straight bar setups, and I see so many of them bent, twisted, or broken. The friend of mine who used to own the truck in question has built 2 traction bar systems. Both failed. One bent when put under strong use(pulling a sled at a competition), and the other ripped off of the frame (weld failure).

I really think it can all be done better. Just the simple addition of a shackle should give it less bind.

My main worry however is that it would have to be a very strong shackle setup, and the bolt through the bushing end of the shackle would have to be strong. My wonder is, what size bolt to go with and where to get bushings to match. I'd think at least 5/8" bolt if not 3/4". The truck is at over an estimated 1000 ft-lbs so its doing some damage.
 
I think you are on the right track and 3/4" bolts should be strong enough (better to overbuild than underbuild). I don't know what to tell you about the bushings.
 
I would build something like the second one, with gussets and make it long so there wont be so much stress on the frame. He has a crew cab right? I would make it at least 1/3 of the trucks length.
 
The upper one is mine, and the shackle bolt is a 3/4" grade 8 monster. The bars themselves are 1.5" X .375" wall DOM (as is the crossmember bar). The diff mount plates are 3/4" and are bolted on with grade 8's as well. It's beef...probably the weakest point is the frame it's bolted to. :doah:

Rene
 
I just can't decide whether a single link is good enough(like Rene's setup). Or if the torque is going to require 2 like Ryan's setup...

I took the truck out last night, and with me speed shifting it I chirped 4th.... the thing NEEDS traction assitance.
 
we installed a lift kit at work in a built to the hill 02 ext cab long bed dodge with cummins nv4500. he is running 3" body and 10" suspension lift. he had the 2nd set like you posted. but thay are the ones like natinal tire and wheel sells that bolt in. and are 5ft long. he modifyed them to have 2 mounts on the axle and he is spinning 46" claws with detroit in the back end. he loves it and said no rear movment much over stock.

i would say with that much power best to do 2 bars in line with the springs like he did. works good for him . i have seen him get on it. and no wheel hop.

found pic before modded. he just added a second mount at the bottom. like your bars posted in pic 2.

fabstg2bars.jpg
 
Since articulation doens't appear to be high on the list of goals I'd go with two links. That way each is only working 1/2 as hard as a single link would be.

I would use a design similar to the second pic, but dump the sheetmetal plating. Go with diagonals like a Roof Truss or similar.
Triangles are your friend. :D
Notch to intersect the centerlines of all of the tubes.
Also dump the urethane bushes on the axle end and go with rod ends. NOT Spherical rod ends, plain rod ends. They look like a clevis w/o the center slot. Somewhat common in drag racing ladder bars & 4 links.

Unless you're willing to spend the time to find the sweet spot of the travel arc within the expected range of motion, I'd go with the shackles. Best would be to put the shackles in tension. Won't require nearly as much mass to get the strength needed as compressoin shackles would require.
Remember that your tab thickness and the radius around the hole should both increase as the hole size increases. A decent ROT for the radius is to use the OD of a USS washer for the bolt in question as the minimum diameter around the hole. I would guess that the minimum tab thickness should be at least 1/3 of the bolt's OD.

EDIT: The reason for dumping the urethane bushes is b/c they allow compliance. Normally this might be a good thing, but in the sort of use implied they use up valuable time in distorting, and given that much distortion their lifespan isn't likely to be all that great.
 
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I would do two bars but I would not put a bend in them I would use straight bars and brace inbetween them, like has been said traingles are your freind. As far as bolts go I would use bushing at one end of the bar and some type of heim at the other. My prefrence is one heim at the shackle end and the bushing at the axle end. If you want bigger bolts drill the bushing so you can fit a bigger bolt in them. Most definatly on the right track though.
 
for a truck witht hat much power the 2nd pic would do better, i'd just go a tad big longer for the added wheel base.
 
ntsqd said:
EDIT: The reason for dumping the urethane bushes is b/c they allow compliance. Normally this might be a good thing, but in the sort of use implied they use up valuable time in distorting, and given that much distortion their lifespan isn't likely to be all that great.
Click to expand...
I'm unfamiliar with solid rod ends. I was thinking today, what about going simple to replace. Namely, weld a piece of something like 1.5x.120 DOM to the end of the links(at the axle end) and machine up a couple of steel bushings to press fit in. If they happen to wear out over time(doubtful) they could be replaced.

As I look at them on FK's site this makes sense. Would allow for pinion angle adjustment to run those on the upper portion of the link.
 
Found them on Alston's Chassisworks page They make two sizes, 1"-14 x 5/8" bore and 3/4" x 1/2" bore; p/n's 1203 & 1204 respectively. Had to d/l their 14 Mb catalog pdf to find them. They are in the middle of the second picture on page 63
 
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