Trac Bars / Track Bars / Anti wrap bars

[greg]

Check out the new JP magazine - it has a good writeup on spring over conversions and part of this includes some detail on trac bars etc...

i'm aware of two solutions to avoid the spring bind (with keeping the springs)

1. run a shackle at both ends of the spring (this involves a lot of work though).

2. (unproven) run a track bar that provides no restriction when being compressed, but does provide restriction under tension.

you could always run more leaves in your springs

[greg]

i used to have an overkill one on my old zuk

worked welll dont have pics of it any more

given the size of your tyres tim, i think that a traction bar was overkill on your car (pun intended)

[roc box]

Quote from 4wd monthly August 2004 page 119 "article Track bar design and construction" Most traction bars under leaf sprung vehicles have three things in common:a shackle of equal length to the shackle fitted to the spring; a high-flex joint that allows the axle to articulate without bind; and two links that triangulate to control the axle. Without these three elements your traction bar will do more harm than good to your ride and suspension performance.

ok 4wd monthly knows everything

we have 3 examples in this thread that shows otherwise

maybe if there was a foot difference between the shackle length it might hurt but when ur talkin 1 2 or 3 inch it wont effect it

i agree tim ps pete it was cheap but it was all i had

[germo]

ok
I have a theory, have a think about it and get back to me.

the problem with the trac bar rotating the diff as it drops or compresses (as I tried to show in a pic but it won't work) has been talked about.

and the use of shackles and slip joints to allow some degree of play, or movement has been discussed.

now I have a theory which may or may not work. I have not tried it, but it uses elements we may already know.

a four link (five link) using parallel arms causes no pinion movement, ie it stays on the same angle in droop and compression.


OK I HAVE THOUGHT ABOUT MY THEORY AS i'M WRITTING AND HAVE ALREADY BLOWN IT OUT OF THE WATER!

I thought that by using two arms that are parallel to each other, this would stop pinion twisting on the way down. it would however also make the pinion stay at the angle set. still causing resistance against the way the sring will arch and want to roll the diff.

the second element to the design would be to ad two slip joints (as covered above) to each arm to stop the diff being pulled/ pushed in an arc!

this in theory would allow diff to travel up and down as the leaves would want, by not rotating the pinion angle/diff on leaves, and by not having an arc due to the slip joints.

DOES ANYONE SEE THE PROBLEM I CREATED.

the trac bar MAY move easier. but what happens when under accelleration?
the bars won't stop anything as the top one will compress, the the bottem will extend. thus allowing the diff too rotate.

I SUCK.

maybe this is the reason I have not seen such a design

maybe if they both had small shackles on them they may work, only letting the diff rotate a tiny bit, before taking effect, but still giving some of the benefits as stated above.
it would still suck. just a normal one would be could.

so would coils!!

[redzook]

ok
I have a theory, have a think about it and get back to me.

the problem with the trac bar rotating the diff as it drops or compresses (as I tried to show in a pic but it won't work) has been talked about.

and the use of shackles and slip joints to allow some degree of play, or movement has been discussed.

now I have a theory which may or may not work. I have not tried it, but it uses elements we may already know.

a four link (five link) using parallel arms causes no pinion movement, ie it stays on the same angle in droop and compression.


OK I HAVE THOUGHT ABOUT MY THEORY AS i'M WRITTING AND HAVE ALREADY BLOWN IT OUT OF THE WATER!

I thought that by using two arms that are parallel to each other, this would stop pinion twisting on the way down. it would however also make the pinion stay at the angle set. still causing resistance against the way the sring will arch and want to roll the diff.

the second element to the design would be to ad two slip joints (as covered above) to each arm to stop the diff being pulled/ pushed in an arc!

this in theory would allow diff to travel up and down as the leaves would want, by not rotating the pinion angle/diff on leaves, and by not having an arc due to the slip joints.

DOES ANYONE SEE THE PROBLEM I CREATED.

the trac bar MAY move easier. but what happens when under accelleration?
the bars won't stop anything as the top one will compress, the the bottem will extend. thus allowing the diff too rotate.

I SUCK.

maybe this is the reason I have not seen such a design

maybe if they both had small shackles on them they may work, only letting the diff rotate a tiny bit, before taking effect, but still giving some of the benefits as stated above.
it would still suck. just a normal one would be could.

so would coils!!

so ur saying
2 parrallel arms both with slip forward and backwards?

that means when u get on the gas the top one will extend and the lower shorten = axel wrap

[Gwagensteve]

I seem to have lost the issue now (most unlike me... I have petersens back to 1991) but on the cover of 4WD sport utility mag, maybe early last year there was a jeep with some very trick sunray engineering built (I think) traction bars on the front. They looked like shark fins with slots in them and there was a roller on the chassis. The "fin" moved up and down on the roller so fore/aft movement was controlled. these were pivoted on the axle so articulation was unhindered.

This was in a SPOA application, and it had relatively limited travel - I think around 10".

We looked very hard at this for Greg's car, but I wasn't really feasible in our application.

It would be very, very noisy IMHO, but effective. Of course, in the rear, it is harder to do and will start coming through the floor etc.

I guess the real problem is that it is easier to do coils badly than it is to do a traction bar well, and as most people think leaves suck and coils rule, very few people spend much time trying to fix these problems.

Steve.

[alien]

talk about a can of worms! haha

whats this about using a cable??? *hides the can opener*

[Gwagensteve]

Greg and I are working on a VERY BAD IDEA.

Basically the engineer for Gregs new project has said that all conventional traction bars tend to influence the springs, and as such, we will have to present him with a design that doesn't for him to sign off on it as part of the cert.

We can't.

What we did do is heaps of work to get the theoretically best position for a single bar. (i.e on top of the diff to behind the transfer case.)

Instead of fitting a single solid bar though (because this will influence the springs, we will be using a cable. This will allow the whole shebang to go slack when the suspension droops, but at or around ride height, it will be
almost tight, so it will prevent axle wrap.

It won't work for many applications - gregs car is bumstop spaced, SPUA and has the shackles moved to promote squat, and we have already had discussions about noise, harshness and all sorts of other problems, but the engineer WILL sign off on it. (I suspect because he thinks it is useless) I believe that where we have our mounts situated, we could almost use a solid one piece bar and get away with it, as the total variation in length from full comp to full droop (about 180mm @ the diff) is around 13mm in our application.

I am sure that in a SPOA application, a cable wouldn't work any better than a single bar or any other design.

You will find if you draw out the arc that a leaf sprung diff moves through when it travels, it is impossible to perfectly emulate with any device fixed at two or three points.

Steve.

[MY45]

I vote for the "slip and twist" mounted to the centre of the diff there should be no influence (binding) on the springs. If i was to do mine again i would just use 3 rubber bush's and no heim as its not needed.

[zookjedi]

might be a stupid question but why don't people run a single bar opossed to the triangulated system dont hilux front diffs run a short single bar ? what would be the disadvantage between the triangulated bar mounted on two places on the diff and one on a cross member opposed to the straight single bar mounted with one mount on the diff and one to a cross member .

is it that with the single system the diff would still attemp to rotate under the pivot point effectively trying to still bend the leafs but to a lesser extend than no bar at all , where as the triangulated bar holds the diff in a set postion unabling it to tilt at all , is that correct ?

or am i missing something ?

jai

[Rhett]

I have been running a single bar for the last six months and have been through 3 tail shafts. I am now in the process of designing my new track bar. It will be mounted at two points at the diff and ajusable at each corner for fine tuning.

[muppet_man67]

whats the effect on tailshafts of a single bar? is it interfering. (mounted so it comes in contact?)

[Rhett]

At times it has wraped engough to bind the unis then bust the shaft. This has only happened when doing silly things such as lighting up all 4 tires when hooked to a stuck patrol on rock.

[muppet_man67]

At times it has wraped engough to bind the unis then bust the shaft. This has only happened when doing silly things such as lighting up all 4 tires when hooked to a stuck patrol on rock.

so its not effective. how does it still get that much wrap? does compress the springs?

[droopypete]

At times it has wraped engough to bind the unis then bust the shaft. This has only happened when doing silly things such as lighting up all 4 tires when hooked to a stuck patrol on rock.

so its not effective. how does it still get that much wrap? does compress the springs?

It tortures them, winds them up on exceleration and then winds them the other way on hard braking, it send the pinion up and down all over the shop with suspension travel and stuffs your uni's, I know because I have one too
Peter.

[lay80n]

Zuki jedi, the hilux front trac bar is realted to the steering style on a live axle models. Because the drag link runs along the side of the chassis rail lengthways the the j-arm on the RHF knuckle, if the front axle was allowed to wrap, then the wheels would be turned. So by stopping axle wrap, the steering is kept under control. I cant find a picture of a solid axle lux with std steering on it on this machine, but if you can find one look at it and you will see what i am talking about. Sorry if my description is a bit average.
Layto....

[NIK]

I was looking through some old american 4wd mags recently and saw a neat idea for a traction bar. Havnt tried it yet but looks good in theory.
It was a link mounted to a bracket welded to the u bolt plate ( flipped above spring ) that ran to the rear shackle and attached to the centre bolt. Obviously you would need extended shackles but what are peoples thoughts on this? It may limit spring compression and droop which in turn would limit flex, not sure how they over come this.
Nik

[alien]

pics? sounds kinda weird! =)

I like the cable idea myself - just sounds funky!

[NIK]

Sorry cant seem to post pix from hard drive to net

[alien]

the bar idea may work if you used like, a giant sized bed spring on the single fixed point... so it has some stretch and some compression... dunno if it'd work but in theory it sounds kinda alright?

[NIK]

Just dragged the mag out to re look, its jan 98 four wheeler.
The bar is ona hilux and it has flat rear springs. It looks like its got heim joints at both ends but no other movement built in.
Another idea Im looking into is instead of the second leaf in the pack wrapping around the spring eye and stopping (milatry wrap?) it extends and is secured by the centre pin. So it has goes from eye to eye under the main leave then wraps over the fixed eye and runs back to the centre. Hope that makes sense. It should minimise wrap not sure how it affects flex.
Nik