Technical UPDATE x2> Calling all suspension setup experts! real time axle wrap

traction masters are mostly parallel to the leaf springs.

 

Because few understand the basic laws of mechanics, and even fewer the laws of physics.

 

I of copied this from how to build hot rods. This does a good job of explaining traction bars, and a really nice explanation on Cal Tracs.

Traction Bars! The Way to Eliminate Axle Wrap!
Traction bars were created to cancel the effects of axle wrap. Axle wrap can happen to leaf springs under hard acceleration. (When you drop the hammer...) The torque from the rear axle can try to twist the leaf spring into an 'S' shape. As the spring snaps back, it can cause wheel hop. One way to fix this is to use traction or 'slapper' bars. Another method is to use the 'Caltrac' style traction bars.

'Slapper' bars work by stopping the twist of the rear axle. As the axle tries to twist, the bar twists up and comes into contact with the leaf spring 'eye'. This stops the twist of the axle and spring and makes the tires dig in and go.
The rubber snubber needs to contact the spring 'eye'. Some manufacturers just let them hit the spring, but that is the weak point of the spring we are trying to save... Many springs have been bent by incorrect snubber placement. So either get the right traction bars for your particular model, or you can lengthen or shorten yours to work correctly.

The distance from the rubber snubber to the spring eye can usually be adjusted. Taller or shorter snubbers can be bought or you can cut them shorter or add a spacer to make them longer.
The less gap you have between the snubber and the spring eye means the bar will react more quickly but less aggressively. It will also make the ride much firmer. The more gap you have the slower but more aggressive the traction bar will react. This also results in a much softer ride.
In drag racing there usually isn't any gap between the spring and the snubber because you want the traction bar to work as soon as you get on the gas. However this makes the rear suspension much more stiff. Not something you want on the street.
Adjust the rubber snubber for a softer or firmer ride. Start with a half-inch to an inch from the leaf spring. Then you can adjust from there.
'Caltrac' style bars work differently, but end up with the same reaction. They stop the twist of the axle and spring and make the tires dig in and go.
Basically, they use a lever and bellcrank system to 'push down' on the weak part of the spring, keeping it from twisting into an 'S' shape. This picture can explain it better:

Caltrac bars are more expensive and more complicated, but they do work great...
Now get out there and make those traction bars work for ya!
Don't forget! If you modify anything, make sure nothing hangs below the Scrub Line! Here's a picture to make it simple...

 

For the OP the above still does not really explain what is going on in the new set-up. The camera is a good way to watch what is going on, but to feel the bind and understand what is going mock up your set-up out of wood on a sheet of plywood, or even some cardboard.
I'll upload some pics from my phone...

 

Cut some cardboard like this



Drive thumb tacks through the front two pivot point into the paper.

Drive the rear thumb just through the two layers of cardboard.

While holding the front two tacks steady raise the rear tack and you will feel the bind,

In fact even if you make the front bars equal length you can still feel the bind, unless they are on the exact same bisecting point




Posted using the Full Custom H.A.M.B. App!

 

This still binds



Posted using the Full Custom H.A.M.B. App!

 

No bind, through the suspension travel, and you see how axle wrap torque would be transmitted to the front pivot



Posted using the Full Custom H.A.M.B. App!

 

I have a set of original " traction masters" on my gasser . The rear mount is 3"below the axle centerline the front is 3" below the front spring bolt .The bar is the same length as the front half of the spring . The bar and spring work together . The car hooks nice and brakes good too . It has an adjustable pinion snubber that I set about 1" at the track.

 

Ok, wow this thread has gotten interesting! I am so grateful for all input, because it makes me think, explore, expand my knowledge. I am 36 yrs old and just got bit by this bug a few years back, so its a learning curve.

"Roadsir" thank you for you cardboard diagrams, it really makes sense in theory and visually.

After all of this discussion, which led to confusion. I went back and looked again at my setup. The front mount is on the same level as where the front leaf mounts (pivot point). But, it's mounted around 3" shorter than where the leaf springs mount. (axle to leaf mount= 20", axle to traction stick=17")

I shot another video that captures the torque transfer more accurately. It is in slow motion, so you can really see what is happening. On my test drive, the ride is good. No Cadillac, but damn, its a 66 truck that is slammed!

 

Excellent suggestion, ran that for years on gasser 57. Hooked hard & no wheelhop ever.

 

Enlighten me

 

Check out the Ford Explorer traction bars and how they are mounted in relation to the spring. I narrowed one of those rear ends and mounted it in a 50 Ford traction bars and all.
Jim Ford

 

After spending 12-years in college?

You have to pay for that, son.

 

Roadsir: that is excellent advice! I like that a lot!
I've seen those slapper bars on squirrels Chevy 2 gasser, and been to stupid to figure them out, and to dumb to ask, but now I see. Thank you!!

 

If traction or reduced wrap is the goal of the work you want to do then all arcs of travel need to be considered. There's as many wrong ways and band-aid fixes as there are right ways. The 1st and most simple design can be found holding the rear axles in Mopar performance variants (and even their grocery getters), that being where the axle rests on the spring, which is considerably more forward than most leaf spring cars. As those got more powerful and tires got better they went to a 1/2 spring in the right front (rear leaf) and got away with pinion snubbers. The late great and beloved Bill "Grumpy" Jenkins was key in developing what we affectionately refer to as "slapper bars", Lakewood being among the best known and most efficient thanks to the Grump. I won't go into Cal-Tracs as they've been fairly well explained, and on a note of interest, something similar was available through your local Ford dealers and possibly Chevrolet dealers too. I've heard rumors on the Chevy deal but never cared to back em up.

As to "enlighten", all suspensions travel in an arc. Ladder Bar/Coil over, 4 Link, 3Bar (GM 'X' frames and a few others), even the primitive "Wishbone" found under Ford stuff until '48. That arc of travel can't suffer interference of any kind. While you can go bounce on a car, or even video what's happening as above, that arc of travel will certainly have occasion to maximize many times. Eventually parts fail either by bending, or worse yet, breaking in the least desirable position (up front) and dropping to the ground ready to pole vault the rear axle when it does. While that sounds extreme, you'll have to trust me that it isn't. If you've ever seen one break at speed on a drag strip you'll work real hard to make sure you don't have to suffer it. I watched a Monza break a ladder bar on a 2-3 shift and it launched the ass end straight up, did almost bumper-to-bumper rolls, then barrel rolled another 4-500'. Now imagine cruising a freeway at 65-70, hit a bump or a hole (full arc travel) and a bar breaks in front of the axle. I have this thing about embracing the basics. They will NEVER let you down. For an interesting and very understandable read on the topic I recommend "Doorslammers" by David Morgan.

http://www.amazon.com/Door-Slammers-The-Chassis-Book/dp/0963121707

 

at the very least, put a big U bolt under the front of the bar, to keep it from pole vaulting you. There are NHRA rules about this stuff, too.

 

So traction masters don't bind because you spent 12 years in college?

Thanks dad!

 

Never comment on Traction Masters, only the knowledge and wisdom of the common rabble.

The Highlander gave you the correct answer.