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Old 11-13-2016, 10:56 AM   #1 (permalink)
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Anti-Wrap Bar Q's

Building an anti-wrap bar, huge fan of Milikens Vehicle Suspension Dynamics book, so I have a bit of a background. I'm trying to come up with a rather slick setup for my transfer case mount and anti wrap mount to share a similar bracket in line with each other. Issue is, antiwrap bars are usually off center tho are centered as much as possible. Aside from strength issues (side load moments into the bar itself, why has nobody done a track bar as I have drawn below? This is a top view. I guess it would be an offset trackbar. The other issue is to make the tcase mount off center of the center of rotation from where the rear driveshaft is, which might cause some funky stress moments in the driveline.

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Old 11-13-2016, 04:38 PM   #2 (permalink)
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Not sure there is enough advantage to wahat you are drawing up to be worth the design challenges. A conventional bad light be what 6-8" off center? Shoot my current one was right next to the leaf for years and only once did the opposite side leaf suffer adverse effects. Now min is also as long as the d shaft and meets the shackle at the frame at th rear output area of the frame.
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Old 11-13-2016, 10:15 PM   #3 (permalink)
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You want the mount off to the passenger side on a conventional vehicle so the antisquat acting on a that side of the chassis can help counteract the driveshaft induced torque lean.
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Old 11-14-2016, 07:45 AM   #4 (permalink)
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It really depends on your suspension deisgn, but for compression style shackle, it's hard to beat the "Sam's Off road traction bar". Most call it that style as Sams was really the first to start making it.
I think Ruff stuff even sells the kit.
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Old 11-14-2016, 09:42 AM   #5 (permalink)
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It really depends on your suspension deisgn, but for compression style shackle, it's hard to beat the "Sam's Off road traction bar". Most call it that style as Sams was really the first to start making it.
I think Ruff stuff even sells the kit.
Yeh, mount it near the dif on the pass side and rock out.
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Old 11-14-2016, 10:36 AM   #6 (permalink)
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Yup - just match the shackle angle and enjoy. Very rewarding - I set mine up for lots of anti-squat - its nice to have the back end lift slightly on acceleration.
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Old 03-20-2017, 08:28 PM   #7 (permalink)
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Bumping this thread with my traction control design. I used to run the traditional Anti-wrap bar and noticed it caused a ton of bind. During droop it caused the front half of the springs to bind or become wavy. It also made the rear suspension very stiff feeling.

I used the 3 link calculator and spent some time under the Scout with a tape measure while raising and lowering the axle. I found that the natural movement of the leaf springs caused the pinion to change angle by 4 degrees from droop to compressed.
What I came up with is a two link traction control device. With this installed the pinion has the same change it had prior to installing it and it rides the same as without it other than I have no axle-wrap and the springs do not bind or get wavy.

I took it out wheeling this past weekend and it did great! Just thought I would share since I haven't seen anyone do this yet.
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Old 03-20-2017, 09:05 PM   #8 (permalink)
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Originally Posted by '71 800B View Post
Bumping this thread with my traction control design. I used to run the traditional Anti-wrap bar and noticed it caused a ton of bind. During droop it caused the front half of the springs to bind or become wavy. It also made the rear suspension very stiff feeling.

I used the 3 link calculator and spent some time under the Scout with a tape measure while raising and lowering the axle. I found that the natural movement of the leaf springs caused the pinion to change angle by 4 degrees from droop to compressed.
What I came up with is a two link traction control device. With this installed the pinion has the same change it had prior to installing it and it rides the same as without it other than I have no axle-wrap and the springs do not bind or get wavy.

I took it out wheeling this past weekend and it did great! Just thought I would share since I haven't seen anyone do this yet.
Judging by the type of shocks your running your not concerned about that bar binding and losing flex.
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Old 03-20-2017, 09:24 PM   #9 (permalink)
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Judging by the type of shocks your running your not concerned about that bar binding and losing flex.

I gained flex with this setup over the standard style bar. The springs are the limiting factor as the shocks still have plenty of travel left. I guess I could have put a small jack between the frame and axle to represent the weight of the wheels and tires for the picture.
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Old 03-20-2017, 11:40 PM   #10 (permalink)
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Originally Posted by '71 800B View Post
Bumping this thread with my traction control design. I used to run the traditional Anti-wrap bar and noticed it caused a ton of bind. During droop it caused the front half of the springs to bind or become wavy. It also made the rear suspension very stiff feeling.

I used the 3 link calculator and spent some time under the Scout with a tape measure while raising and lowering the axle. I found that the natural movement of the leaf springs caused the pinion to change angle by 4 degrees from droop to compressed.
What I came up with is a two link traction control device. With this installed the pinion has the same change it had prior to installing it and it rides the same as without it other than I have no axle-wrap and the springs do not bind or get wavy.

I took it out wheeling this past weekend and it did great! Just thought I would share since I haven't seen anyone do this yet.
Your driveshaft has a lot of slop in it.
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Old 03-21-2017, 05:42 AM   #11 (permalink)
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Quote:
Originally Posted by mrarmyant View Post
Building an anti-wrap bar, huge fan of Milikens Vehicle Suspension Dynamics book, so I have a bit of a background. I'm trying to come up with a rather slick setup for my transfer case mount and anti wrap mount to share a similar bracket in line with each other. Issue is, antiwrap bars are usually off center tho are centered as much as possible. Aside from strength issues (side load moments into the bar itself, why has nobody done a track bar as I have drawn below? This is a top view. I guess it would be an offset trackbar. The other issue is to make the tcase mount off center of the center of rotation from where the rear driveshaft is, which might cause some funky stress moments in the driveline.
There are already several good responses here, but let me add to this. I'm not familiar with Miliken's Vehicle Suspension Dynamics book, but many of these types of books usually deals with car based suspension systems. A 4wd suspension system maybe similar in design, but the dynamics are complicated by the fact that 4wd suspension systems operate thru a larger range of travel and must articulate. The anti wrap bar illustration you provided would work best in a car suspension system, but lacks the needed movement to allow the range of motion that a 4wd suspension is capable of.

In particular, the driveshaft requires a slip joint to allow the length to change as the suspension travels thru it's range of motion. The anti-wrap bar illustrated, runs virtually parallel to the driveshaft, but there is no provision for it to lengthen or shorten as the driveshaft does during suspension travel. The bar will cause bind. However there are some easy solutions and the idea can be effective. One solution is to add a slip joint in the bar, like that of a driveshaft. Another solution is to mount the forward end of the bar in a shackle, so that the swing of the shackle allows for differences in length. Both ideas will require a heim joint to allow some rotational travel, for axle articulation.

The offset of the bar as depicted isn't really necessary in a 4wd as it has plenty of clearance to allow for a straight bar between the differential and pivot point, at the front. A car's lower ground clearance puts the space for such a bar at a premium, therefore it tends to be offset to one side to clear the floor pan and exhaust system

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Last edited by RXT; 03-21-2017 at 05:43 AM.
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Old 03-21-2017, 06:27 AM   #12 (permalink)
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Your driveshaft has a lot of slop in it.
Good eye

The pictures were taken before I built longer ones.
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