Different Idea for Traction Bars

[Cooker]

I was surfing another site today and came across a link to these traction bars.



They don't offer a kit for the Dana axles, and it looks a little weak to support the power of the Cummins anyway, but I thought they were interesting enough to post here so others could check them out and/or build their own.



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Here is a link to their site: http://www.azkickin.com/antiwrap.htm

 

[WadePatton]

cool, another skint cat.

 

[HoleshotHolset]

Check out this pic - look at the upper right hand side of the pic...



The bracket that bolts to the frame looks a bit skimpy... .

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Like Ryan said... it might not hold up to a Cummins... but it is an interesting design. It would be neat if someone could incorporate driveshaft loops into the design... .



Matt

 

[Extreme1]

I agree that the frame brackets look light. They should have a larger frame span as well.



If the attachment to the crossmember is allowed to pivot on the crossmember, these might actually work without binding and potentially causing damage. The best/easiest traction bars for leaf sprung vehicals are still the snubber bars.



Edit: The best set up for drag racing would be to float the axle and use real ladder bars. Ladder bars without floating the axle will bind and may cause damage.

 

[BigBadDodge]

I can't wait to post pics of mine completed

 

[NVR FNSH]

Originally posted by Extreme1

I agree that the frame brackets look light. They should have a larger frame span as well.

Please explain why - with any data/assumptions to back it up.



It appears to me that the 'shackle' can rotate about the tubular cross member and that the only load that heavy wall tube will see is bending if they got the geometry right and don't let the heim joint in the end of the control arm bottom out and bind.



I would have mounted it inboard of the frame rails and minimized the loss of ground clearance as much as possible.



It may be undersized but w/o knowing more about it - thickness, bolt spacing, loading assumptions etc I'll hold off on design critique.





Brian

 

[Hammer]

Edit: The best set up for drag racing would be to float the axle and use real ladder bars. Ladder bars without floating the axle will bind and may cause damage.

Man what a great comment and most will completely miss it. I am glad to see someone else has the same thoughts and views as me. Way too many time I see people who are working on their "trick" suspensions and have put no thought or done any research on how it can be made to assist your traction problems instead they create more than they had before. Suspensions that are not free create more bind and cost HP/tq,most here do not understand it,nor are they willing to accept the cost which will incurred to free the rear suspension's up to allow their "trick" bars to work. So what do they have then,lots of stuff for others to go... . "Wow,now thats cool. ".



NVR FNSH...

You ask many deep questions in a short time. First off what your looking at is nothing more than a glorified pinion snubber. Anyone who knows suspensions knows this will not work on a vehicle with the springs centered like our trucks have. If you ever seen the damage from a snubber in a older HP Mopar after a period of time you'd not even think of running one. That setup there will cause much more damage than you would expect. Look at the pics carefully and ask yourself this... What is going to carry the load and what damages can be done because of this?.



You want a better place for suspension basics and what works and what does not I'll give you a book to look for,read it,save it near your work bench,there is way more than we can get into here... ...



"Doorslammers"... . By Dave Morgan



Hope this helps... ... ... . Andy



on edit...

I fogot to address one more thing which I see alot... Ladder Bars Vs 4 Links

Pro Stock racers Reher-Morrison years ago did a test with a ladder bar car and their newly designed 4 link set-up when Lee Shepard was alive. What they inturn found out about the 4 link setups after a 1000 runs was there was a 1000 ways to run the same number. True a link car is more tunable and may give you that extra hundreth needed in a heads-up class race,BUT,just when you think your ride is fast with a link chassis a ladder bar car will fly by you.

 

[Rotty]

it may look weak but you have to run the numbers.

Say you had 1000 lbs of rotational force probably realistic on the rear axel.

If the piviot point was 1 foot away, you would have to hold 1000 lbs.

but is that pivot point was say 3 feet away then you only need to hold 333. 33333lbs.

just like a torque wrench but with a HP cummins trying to twist things.

The real trick is to have the pivot point at the front universal joint along with the front joint of the leaf springs, then no binding.

If you have binding then your forces will exploded as well as parts.

Steel does not compress or stretch very well. This is over simplified but it will get you in the ball park.

 

[Steve St.Laurent]

The real trick is to have the pivot point at the front universal joint along with the front joint of the leaf springs, then no binding.

Actually, that isn't correct. On our trucks the front eye of the leaf springs is in a fixed location. The rear leaf spring eye moves rearward and down as the suspension compresses due to the shackle at that point. Therefore as the suspension compresses the axle has to move rearward and also has to rotate rearward. In other words the straight line distance between the forward leaf spring mount and the center of the axle is longer as the suspension compresses and the leaf springs flatten. If you have a solid bar that is the same length as from the axle centerline to the front spring perch when the suspension cycles then you are trying to bend the front half of the spring pack thereby binding the suspension up.



The problem with a ladder bar setup that connects at two points on the axle such as this one is that it will not allow the axle to rotate as the suspension compresses (remember that as the leaf springs flatten the spring eye on the rear of the leaf spring move rear and DOWN - thereby changing the pinion angle of the rear axle). This causes some bind in the suspension. In order for a solid ladder bar design to work with no suspension bind it has to be designed properly to allow for the axle to move rearward and rotate to the rear the proper amount as the suspension cycles. For a design like this (2 attachment points) to work with no bind you need to have two bars (one on each side of the axle) and you need to put a shackle both at the front and at the rear of the leaf springs so that the axle can freely float in relation to the bars.



Just my $. 02

 

[BigBadDodge]

Steve, that is exactly why I am getting rid of the leafs and installing firestone moble home air bags with my 4 link.



Some pics HERE



BBD

 

[NVR FNSH]

Originally posted by Hammer

NVR FNSH...

... First off what your looking at is nothing more than a glorified pinion snubber.



You want a better place for suspension basics and what works and what does not I'll give you a book to look for,read it,save it near your work bench,there is way more than we can get into here... ...



"Doorslammers"... . By Dave Morgan

IIRC the pinion snubber on a Mopar just slammed up against the bottom of the unibody. It didn't prevent axle wrap it just limited how far the springs would twist.



Thanks for the book recommendation. I may have to add it to my collection of engineering textbooks from college My degree is in Mechanical engineering, my senior project was a remote actuator arm for the rear suspension on a SCORE Trophy truck that I helped design while doing a 6 month contract job at a small off-road race truck design shop. We did the design work but not the fabrication. My interest is mostly off-road stuff so I'm not well versed in what works best on the drag strip. Again, thanks for the book recommendation I'll see if I can find it locally.

Originally posted by Steve St. Laurent

For a design like this (2 attachment points) to work with no bind you need to have two bars (one on each side of the axle) and you need to put a shackle both at the front and at the rear of the leaf springs so that the axle can freely float in relation to the bars.

Steve,

It appears to me that the front end of the link is mounted to a pivoting shackle and this will allow the springs to follow their arc without binding up. This type of set-up is preventing axle wrap only it is not positively locating the axle. When the pinion starts to lift the front of the link will lift and put the shackle in tension regardles of it's position on the heavy walled tubular crossmember. The shackle is a two force member as long as the front eye on the link doesn't bind up and the only force the heavy walled cross member will see is bending.



Jeeps with spring-over suspension have been running this type of set-up for a while now and it works well.



For his senior project a friend of mine designed a traction bar set-up like this for his '79 4wd F-350 flatbed and it worked out very well. When you analyze the forces involved the bottom line sometimes turns out to be that you don't need 1/8" wall but it's just easier to work with. 1/8" wall is just an example I don't remember what the real numbers were.



Brian

 

[SRadke]

Originally posted by Steve St. Laurent





The problem with a ladder bar setup that connects at two points on the axle such as this one is that it will not allow the axle to rotate as the suspension compresses (remember that as the leaf springs flatten the spring eye on the rear of the leaf spring move rear and DOWN - thereby changing the pinion angle of the rear axle). This causes some bind in the suspension.

This is the big point I see here. This system will allow the axle to follow it's natural arc in suspension travel but as the axle tries to naturally rotate the traction bar setup prevents it. That will cause a bind.



-Scott

 

[Steve St.Laurent]

I should have worded that differently. The first part of my post I was just replying to Rotty's comment about the front pivot point. What I did miss saying is that in order to take care of the axle rotation problem along with having a shackle at the front and rear of the leafs the front of the ladder bar also has to be fixed - not a shackle. Another thing I just noticed with this design is that there doesn't seem to be any allowance for articulation - although the specifically state that it doesn't elminate articulation. Looking at it, it looks to me like the only articulation it would allow is deflection in the bushings at the rear and bending of the bars.

 

[ECappleman]

Originally posted by NVR FNSH



Steve,

It appears to me that the front end of the link is mounted to a pivoting shackle and this will allow the springs to follow their arc without binding up. This type of set-up is preventing axle wrap only it is not positively locating the axle. When the pinion starts to lift the front of the link will lift and put the shackle in tension regardles of it's position on the heavy walled tubular crossmember. The shackle is a two force member as long as the front eye on the link doesn't bind up and the only force the heavy walled cross member will see is bending.



Jeeps with spring-over suspension have been running this type of set-up for a while now and it works well.



For his senior project a friend of mine designed a traction bar set-up like this for his '79 4wd F-350 flatbed and it worked out very well. When you analyze the forces involved the bottom line sometimes turns out to be that you don't need 1/8" wall but it's just easier to work with. 1/8" wall is just an example I don't remember what the real numbers were.



Brian

Finally someone hit it. The design looks good except for the axle end. Relying on the 14B pinion bolts is a mistake. I would also like to see a little better job of attaaching it to the frame. It should be attached to brackets that are welded to the axle itself. Numerous off road vehicles are running this setup and are achieving over 2 feet of travel. They are also cpable of putting more torque to the ground than a diesel due to the fact that a 100:1 crawl ratio is commonplace.



Here's a good example. #ad

 

[SMorneau]

I don't think I get this design. The attachment to the axle housing is a bad idea. The attachment to the frame is a complete disaster waiting to happen. Look at the holes drilled all in a line way off center from the neutral axis of the frame members. Even if the design transfers no load to the mounts the mounting holes are poorly chosen. It looks like designer is trying to preserve some articulation by working in the center.

 

[NVR FNSH]

Upon closer inspection I think I'm wrong ... ...



I thought the link was welded at the shackle end to form a 'Y' and there was a heim joint/spherical bearing at that end. I looked closer at the picture from the website and it appears to be two straight tubes with a clevis at the shackle end and a poly bushing at the axle end. This thing is a disaster... . The heavy wall tubular crossmember will see considerably higher loads - a moment due to any axle articulation - than I originally thought and the give is in the bushings at the axle end.



Bottom line? I wouldn't touch this thing with somebody else's truck.



Brian

 

[willyslover]

Brian. . take a look at mine when we see each other soon

 

[NVR FNSH]

What bar do you have?



Brian

 

[Hammer]

IIRC the pinion snubber on a Mopar just slammed up against the bottom of the unibody. It didn't prevent axle wrap it just limited how far the springs would twist.

Think about that now...

If you understand Ma Mopars suspension then you will understand that spring twist does not happen. With the suspension located front of center on a HP Mopar all the snubber did was make a very poor attempt at controlling axle wrap.



BBD...

Scott ,the setup you are designing is a very nice unit and its easy to see alot of work and time are evident. BUT it is not a true 4-link its a 4-bar suspension. 4-bar suspensions have been around a long time and have alot of travel but no adjustment to control top and bottom hit of suspensions to allow the vehicle to obtain maximum traction on marginal surfaces.



Steve...

While its a given axle wrap kills power in these trucks the way you describe how a ''ladder bar'' setup need to be mounted is a little off base. The ones you have designed are nothing more than a simple 2 bar setup. While a setup like this is good for helping to limit axle wrap it will not assist in helping to control or add hook which is a much bigger problem.



One thing I continuously see with all the ladder bar/4-link aftermarket manufacturers for our trucks is their uncanny ability to only aid in slowing axle wrap,adding to suspension bind and taking money from our wallets for products that do not help in creating hook. No One who makes a product for these trucks even considers that the owners may wish to do more than control wrap. Its easy to see this just by the locating points they use for the front of their suspension parts they built to help us. Always they are designed with the attachment points so high that it kills the instant center and moves the true hook point to a area that can never be attained.



To effectively use the ''ladder bar or 4 link'' the rear housing needs to be made a full floater and only use the rear springs for supporting the vehicle. The most common design of this you could see is to look at a older super-stocker suspension with their ladder link suspension. It used the factory springs,axle housing on full floaters allowing for some front to rear movement, and a good set of double adjustable shocks to help control top and bottom hit. With a ladder link deal instant center was limited(which was the reason for the 4-link designs now popular) and only could be raised up or down slightly. Most good hooking ladder link rides like the front hook points between 2-5 degrees below the pinion angle and the lower in the front the better the axis rotation was helping to create hook. 4-link instant centers are a different animal and are applied differently depending on who designed the system. Most good working 4-link setups have equal length bars and are located outside the frame rails to allow for infinite adjustments. Remember that with a 4-link the closer to the rear you make the instant center the harder it will hook. Move the instant center further away(spreading the bars apart) and it softens the hook. NEITHER suspension will work effectively on a solid mounted spring set-up or will work without the use of a quality double adjustable shock to control top and bottom hit.

 

[willyslover]

Brian. . I have the bars Steve made up for a few of us. .