Yet ANOTHER anti-wrap bar question... (2 Viewers)

[potlatch4805]

Before you guys bite my head off, I searched, and read almost all of the posts pertaining to the anti-wrap bar on the 40. The problem is there are alot of different designs out there. I want to build it properly the first time. I made a drawing and I need to know if this is the CORRECT method of building one. I'm putting it on an FJ40 with 60 axles, built mainly for steep hillclimbs (loose dirt, shale, rocks ie; Canadian Rockies)


Thanks for the input,

Paul

 

[cruiserpilot]

What I did is turn your's over. The top tube doesn't need to be flat. The bottom tube should run as parallel to the driveshaft as possible. This will allow the antiwrap bar to move with the axle without binding. Try to build the point where the two tubes meet as close to the front pivot as possible. Check your driveshaft tube and see how much slip travel it incurrs, and try to see if you can limit the length of the shackle, yet still allow full travel. I didn't use a shackle on front, I made mine fixed using a spring bushing, and I have a slip tube inside the lower parallel tube that has the exact travel as my driveshaft.
I'll try to find a pic of mine here somewhere, FYI, mine is on a SOA FJ40.



I welded the front hanger to the round cross tube. This the way I did it, and I found it worked fantastic with a 351W up front, 4:88's and ARB's.

 

[Fast Eddy]

The top tube doesn't need to be flat. The bottom tube should run as parallel to the driveshaft as possible. This will allow the antiwrap bar to move with the axle without binding. Try to build the point where the two tubes meet as close to the front pivot as possible. Check your driveshaft tube and see how much slip travel it incurrs, and try to see if you can limit the length of the shackle, yet still allow full travel. I didn't use a shackle on front, I made mine fixed using a spring bushing, and I have a slip tube inside the lower parallel tube that has the exact travel as my driveshaft.
I'll try to find a pic of mine here somewhere,

Ouch. That's going to have all kinds of binding. Try jacking your rig up off the frame and see what happens with the bar and the rear end. The bar will keep the rear end from drooping as it should.

The rear end doesn't pivot along the driveshaft. It basically rides up and down in a vertical line and stays flat. If the anti-wrap bar is attached solidly to the rear end, like in cruiserpilot's pictures, the front of it also has to be able to not only twist, but travel straight up and down. The drive shaft has pivots (u-joints) at both ends and a slip joint in the middle, so it has totally different requirements.

Take a look at my anti-wrap bar in my after thread. There are some other pics and discussion in there, so you kind of have to sort through them. My bar has a slip joint that can twist and it has a shackle at the front that points straight backwards at rest, so the front of the bar can travel straight up and down like I have pointed out.

Anyone who says there's is "right", but not like I have described, jack up the frame with a jack and try to unbolt it. It will be bound up and you will not be able to remove it, which indicates that it can bind or break on the trail. The mount has to be strong, but I don't think "very strong". It doesn't have to support the whole weight of the truck, IMO. I use the stock fj40 round cross member with a sleeve around it.

Potlach, mine is about like your diagram, but with the shackle pointing straight back, and the joint at the end of the bar can pull in and out as the shackle swings up and down.

 

[cruiserpilot]

No binding, it rotates completely freely as the inner tube is greased and it is perfectly centered along the centerline of the truck. The advantage of an offset rear diff is being able to put a single antiwrap bar at the center of the axle. This worked perfectly for lots of miles and all conditions.

 

[zags]

Ouch. That's going to have all kinds of binding. Try jacking your rig up off the frame and see what happens with the bar and the rear end. The bar will keep the rear end from drooping as it should.

The rear end doesn't pivot along the driveshaft. It basically rides up and down in a vertical line and stays flat. If the anti-wrap bar is attached solidly to the rear end, like in cruiserpilot's pictures, the front of it also has to be able to not only twist, but travel straight up and down. The drive shaft has pivots (u-joints) at both ends and a slip joint in the middle, so it has totally different requirements.

While you are right about the axle not following the arc of the driveshaft, but it certainly does not travel straight up and down. The axle moves in an arc around the front spring eye.
.

 

[reddingcruiser]

It's actually more of an elliptical path, because as the spring compresses the axle moves away from the stationary mounting location. OOOH! Isn't suspension geometry fun.

 

[Fast Eddy]

No binding, it rotates completely freely as the inner tube is greased and it is perfectly centered along the centerline of the truck.

Rotates yes, but what effect does the bar have on the axle as the weight comes off of the suspension? Don't take my word for it. Jack up the frame from the center and watch. I'll bet the bar will lift the axle after only about 3-4" of jack height, then the bar will be bound up. If you then put it back down and disconnect the bar, you'll be able to jack it up 6-8" with the tires still on the ground.

The axle moves in an arc around the front spring eye.

Read below. It's not much of an arc. Don't take my word for it, measure it. The pinion angle changes very, very little as you lift the rear. It's more like an elevator than a pivot motion.

It's actually more of an elliptical path, because as the spring compresses the axle moves away from the stationary mounting location. OOOH! Isn't suspension geometry fun.

That is true, but it is more of a straight line than an ellipse, or an ellipse with a very large dimension. Mine goes about 10" up and down and at the pins probably only moves 1.5-2" forward and backwards.

 

[orangefj45]

Most of your suspension movement will not be "straight up and down" unless the vehicle is strictly street driven. And on the road it'll only travel 1-2" each way unless you jump the vehicle.
When you're dealing with an off road application, you need to worry about a traction device that can deal with suspension compression and droop as well as articulation.

The pic the OP posted is exactly what you want/need. We've been building them that way for years. It's a design perfected by FC187 and has been tried and tested on numerous cruisers. Including mine .......

Hth

Georg @ valley hybrids

 

[orangefj45]

Fwiw.....

1) you do want the top bar to be as close to horizontal as possible or you could run into issues with "dive" or "lift" under acceleration or braking.

2) you want the length of the bar to be as long as the rear driveline or slightly longer for the same reason.

3) the travel of the rear axle ( linear or elliptical ) depends on the arch of the springs and length of the rear shackles.

I know what this stuff looks like on paper. I did go to college for mechanical engineering. Who cares! Real world experience has taught me a lot more about things like traction bars ........


Georg

 

[potlatch4805]

The pic the OP posted is exactly what you want/need. We've been building them that way for years. It's a design perfected by FC187 and has been tried and tested on numerous cruisers. Including mine .......

Hth

Georg @ valley hybrids

Thank-you, this was the answer I was looking for!

Paul

 

[orangefj45]

We use 3/4"x3/4" heims on all three ends of the bar and bushings at the fixed end of the shackle.

Georg

 

[RockDoc]

Why is it that only the rear axle gets a track bar? Is it because acceleration/climbing shifts weight to the rear? Because spring wrap tends to make the rear axle "rear-up" as it loads and hop on release while it tends to make the front suspension squat down instead? Too difficult to fit one in front with the engine and tranny?

 

[Fast Eddy]

I know what this stuff looks like on paper. I did go to college for mechanical engineering. Who cares! Real world experience has taught me a lot more about things like traction bars ........

I would very much like to demonstrate to you and FC why you are wrong and I am right. If you used my design, you could probably make it out of lighter materials.

Try the experiment: jack your junk up off the frame in the center and see that the anti-wrap bar lifts the rear end.

The fact is that it may not usually matter in most off-road conditions, where you are twisting and not using much downtravel, but in the case where someone breaks their bar or the end mounts, this is why. I am convinced.

 

[chicago]

I built mine the same way Georg stated on two rig now and have not had a single issue.
Only difference is I used bushings at the rears in lieu of Heims.
Ruff stuff has a nice wrap bar bracket set for sale. Used this on both builds and would use it again.

 

[orangefj45]

I would very much like to demonstrate to you and FC why you are wrong and I am right. If you used my design, you could probably make it out of lighter materials.

Try the experiment: jack your junk up off the frame in the center and see that the anti-wrap bar lifts the rear end.

The fact is that it may not usually matter in most off-road conditions, where you are twisting and not using much downtravel, but in the case where someone breaks their bar or the end mounts, this is why. I am convinced.

fine. we don't know what the hell we're talking about. we've only been running trails including rubicon for 20 plus years and none of our bars have ever broken off the axle housing or the hanger mount. nevermind that we do this stuff for a living every day..............just a couple of idiots!


i just so happen to have one of quite a few SOA 40s in the shop right now that we built. with one of don's bars in it. i'll jack it up tomorrow and will post some pics.


georg @ valley hybrids



ps: one very simple question for you ed: when is the last time you drove your cruiser and the rear suspension dropped 8" on both sides?

 

[miker]

This topic is always fun.

 

[reddingcruiser]

Boys, boys play - nice with each other. Mine's still attached to the axle and hasn't ripped off just, and heaven knows I've tried! Used the RuffStuff 'Old Style" axle mounts, bushings on the back end and Heim's up front.

 

[orangefj45]

bawahahaha, if i was'nt playing nice you'd know it!



eddy is a friend of mine. i respect his opinion and him as a person. he does his homework and is a sharp cookie. and i think he feels the same way about me, or he would'nt have come to me for help with an issue he had after somebody else "fixed" it twice......


but i do like to poke fun at engineers!


mike, don't read into that too far. you know i admire your work.


georg

 

[Fast Eddy]

we've only been running trails including rubicon for 20 plus years and none of our bars have ever broken off the axle housing or the hanger mount. nevermind that we do this stuff for a living every day..

Your experience and success speaks for itself, of course. I'll bet you still learn something new every day, or at least every other day.

i just so happen to have one of quite a few SOA 40s in the shop right now that we built. with one of don's bars in it. i'll jack it up tomorrow and will post some pics.

Perfect. Don't waste a ton of time on it, but I'm curious about what you think after you try it.

one very simple question for you ed: when is the last time you drove your cruiser and the rear suspension dropped 8" on both sides?

That is totally true. You'd have to jump it, but a hard push over an obstacle with a load could result in a pretty good upward bounce.

eddy is a friend of mine. i respect his opinion and him as a person. he does his homework and is a sharp cookie. and i think he feels the same way about me,

Why thank you. If I didn't feel strongly about it, you are the last guy I would argue with.

i do like to poke fun at engineers!

You might look for a harder target than a software engineer.

 

[orangefj45]

engineer = engineer = engineer! ;p



there's more than one way to build a cruiser, just like there's more than one way to set up your suspension, your track bar, your steering, ........

none of them are perfect and a lot of them do work.

i see no reason why eddie's track bar should not work. but i also look at it this way: if i'm going to install something in my cruiser, then i want it to last as long as possible, require the least amount of "aftercare" and be repaired as easily as possible should the need arise.
what i'm getting at is that eddie's bar will require periodic maintenance since it has moving parts. the grease will need to be cleaned up and re-packed. that will require the bar to be removed if you want to do the job properly. if you don't maintain the greased slip-joint, then debris can and will get in there. that'll cause scratching, grinding, gauling and possible seizure of the "joint". and then you're left with a bar that still works but is essentially the same thing as the pic at the beginning of the thread.
furthermore, if the bar fails, then you might have to find another set of 80 series trailing arms to fix it. have fun!
last but not least, these bars do experience a tremendous amount of load put apon them when the pinion is trying to rotate up. i've seen bars built using .187" wall thickness tubing bend on a single climb. so we build ours using .250" DOM tubing. ain't gonna bend. yes, it weights a bit but the weight is down low in the vehicle so it does'nt hurt.

most sincerely!


georg