Give me a quick schooling on going short, Medium, Long & longer Traction bars specifically for a '57 Chevy, Blown BBC, 2 dr. Sedan. Thanks!
Think of traction bars as a lever. A short bar that stops right at the front spring mount bracket should just limit spring wrap. That's kinda good. The longer they get the more lift is applied to the front of the car. Some of that helps weight transfer and plants the Tires on the Ground. The longer they get the more lift and wheel standers generally run the longest ones you see. Big Horse Power, wide tires and long bars and you're putting on a Show however, that costs you E.T. It's all physics.
If it's all physics, then I question that a longer bar applies more lift to the front of the car. The tires have a given amount of traction, which in turn torques the rear axle in the opposite direction of tire rotation. This rotation of the axle creates lift at the front of the traction bar. If a short bar/lever has X amount of lift at the end of, a lever twice as long will have 1/2 of X, but further towards the front of the car. The result, using physics/math, is the same amount of lift at the front of the car.
Ebbsspeed; Your statement is correct in that the tires can only make so much lift. It is the same no matter where the contact point is. The further forward it goes the easier it gets to lift the weight in front of the contact point. Think this way. You personally can only lift X lbs. with your hands off the ground. There's a 300lb slab of Steel Plate sitting on wood 2x4 and you need to move it sideways 6 inches. You can push on it by hand with all your strength, but your feet only slide away from you. You grab a 3 foot pry bar and try but it only wiggles. You then grab a 20-foot piece of pipe and you can move it wherever you want it. You still only can lift X number of Lbs. by hand. How can that be?
@Pist-n-Broke That would only apply if there was a fulcrum involved @Ebbsspeed is correct. As mentioned the traction bar should make contact at the spring eye to prevent spring wrap
Since we're probably talking ladder bars...? The fronts of the ladder bars should be mounted at the car's center of gravity. That will change depending on the drivetrain etc.
Do you want to go fast, or just "look Traditional" ? The theory behind Ladder Bar length, is the same as that for "Instant Center" location, on a modern 4 bar suspension. Only it is not adjustable, the "Instant Center" doesn't move as the suspension compresses, and the suspension binds in roll.
Just put some good springs under it, I am a fan of Chrysler SS springs. Put them under several cars over the years. With a automatic no other device needed , a 4 speed you need a snubber. They all have a 20 inch front segment and come for different weight cars. They are stiff and the right side of the car will sit higher than the left due to the bias but you won't deal with wheel hop. I have 002, 003 SS springs on the pile in my avatar and the right sits about a 1 inch higher on the right side. But it will plant the tires !
I don't believe Slapper bars or Traction bars use a fulcrum so why would I explain how to move weight using one when in asked application there isn't one? Go out in your shop (if you have one) and try it the way I explained it. See what happens.
Talking ladders here, going with a traditional look. Thanks for all the info, was just trying to refresh my memory!
Read this and it may help some. Its an older article. Also, it seems that the trend these days is not to make a car squat but to rise in back as it comes off the line. So might want to check a little further and see what gives. Might be you can find a way to get good traction by some slight mod to the ladder bar set up.
In your example of using a pry bar there are three points of contact. One is your hands on the bar, one is the slab of steel plate, and the third is the floor or the 2X4 or whatever else you are using to anchor the end of the bar. One of those three points is indeed a fulcrum. In a slapper/traction bar there are only two points of contact. Think of the slapper as a torque wrench instead of a lever. To apply 100 ft/lbs of torque to a bolt, you can either apply 100 lbs of force one foot away from the bolt, or 50 lbs of force two feet away from the bolt. Now reverse all the math, and think of the rear axle as the bolt applying torque to the slapper bar.
The car wants to rotate around the center of gravity. A short ladder bar, will try to lift the back of the car. A LONG ladder bar, attached to the chassis in front of the CG, will try to lift the front of the car. Exact same idea, as changing the Instant Center on a 4 bar.
Back in my dragging days, I had coil springs on the rear axle of my Olds, if I recall correctly. The slapper-looking "traction bars" I used kept the pinion more or less aligned with the plane of the drive shaft and helped eliminate wheel hop. I also had Air Shocks and a half dozen other little tricks, but the traction bars did most of the job...... and didn't cost a whole lot. They were painted black and weren't all that noticeable.
There is a whole lot of partial truths when talking about what causes what. 1st the car according to physics will want to rotate opposite of the wheels on the same center line (read that as along the axle). Now weight and balance affect how this is realized. You could get axle wrap, wheel chatter, the front end coming up, and even rear lift depending on how the suspension is setup. But throwing any one thing at the car won’t magically make the car hook. The best course is to figure out the basics of what you do and don’t want. Sit down with someone who is good at rigging for your desired goals and build it once, then tweak it for optimal performance. As stated there is a big difference between ladder bars and traction bars (aka slapper bars). Weight makes a huge difference as well. Remove or move 400 pounds and it will work very differently. Good luck.
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