my best with my cal tracs was a 1.777 60 ft. 11.5x16x26 mt et streets and stock torque convertor also. I also was spinning a bit.

 

No flames intended, just physics

I hope I can shed some light on the "slapper bar" style of traction bar.

The entire theory behind the "slapper bar", is to limit rotation of the rear end and provide lift to the front end of the truck.

1. Limiting rotation of the rear end does two things. First, it eliminates driveshaft breakage due to binding. This doesn't mean that you won't break driveshafts. If you have enough traction and enough torque, you can still break the driveshaft.

2. The "slapper bar" is simply a lever. It turns rotation of the rear axle/spring ***'y, into lift at the contact point of the snubber. This makes the length of the lever roughly 24" long (centerline of the axle to the snubber contact point). What you feel when the slapper bar hits the spring is lift, not squat. If you are getting a significant amount of squat, the rear springs or shock rates need to be adjusted to minimize this. A set of adjustable shocks will be more than adequate to dial this out. The decrease in ET will be insignificant, meaning you won't get much reduction if any.

If you lift the rear end, you are not getting maximum weight transfer. The opposite is true also. If you squat the rear end too much, you are lengthening the reaction time of the chassis, and absorbing the energy of the vehicle through spring movement. It's a very delicate balancing act.

This is why Professional drag classes leave the line just barely carrying the front wheels. This is 100% weight transfer, minus a slight amount of upward movement.

Racing broken down to physics, is a game of weight transfer. It's a simple fact that you must have weight on the tires that you want to do the work. If you want to accelerate a rear wheel drive vehicle, you must transfer the weight to the rear.

Conversely, if you want to turn the vehicle, you must the have weight transferred to the front tires. Just ask any road racer who has accelerated too early out of a turn (its called massive understeer, or power oversteer, depending on how much acc. is applied).

 

Simple physics...

Weight transfer from front to rear due to acceleration is simple to determine. It is based on the height of the center of gravity (C.G.) of your vehicle, how much it weighs, your acceleration rate, and the wheelbase length.

You can pretty much ignore the vehicle weight part since any increase in weight transfer due to vehicle weight simply loses out when it tries to accelerate the increased vehicle weight.

C. G. height is an easy thing to mess with. Think of the old dragsters you see in pictures. They used to raise their cars to increase weight transfer. Now that the drag tires are stickier, they don't need to, but if you're running F1s...

The Lightning wheelbase is set so you can't really mess with it easily, but it's helpful to know that longer wheelbases DECREASE weight transfer. If you could find a way to move the rear axle forward on your truck, you'd not only have more initial weight on the rear, but you'd transfer more there when you accelerated.

It's interesting to note that the harder you accelerate, the more weight you transfer. At some point you transfer too much weight, pull the front tires off the ground, and you start looking for ways to maintain traction but decrease weight transfer. Right, 1BADTK?

Good traction devices lift the entire vehicle upon acceleration. For relatively lower powered vehicles, they lift mainly the rear. They do this to increase the downward pressure of the tires on the track. F=ma, so if the mass of the vehicle is moving up, there has to be a force making this happen. This force is coming from the tires and the tire downward pressure is increasing. Keep in mind that it only increases while the vehicle is being lifted. Once it reaches it's max height, there isn't any extra lifting force on the tires. BUT, there is extra force because now you've raised the vehicle C.G. The danger in lifting too much/too fast is that when the rear stops going up and the lifting force on the tires is eliminated, the tires spin.

JDM's bars are too long to do much lifting. They are nearly parallel to the ground. The twisting force of the axle will push forward on the bars and push against the frame, but they don't push up, only forward. They'll work great for eliminating wind-up.

Jay's bars push up near the front of the spring when the axle tries to wind-up. The physics of the bars should allow them to do more lifting.

This is probably getting long and boring so I'll stop now...

 

Yep, Yep, Ahuh, Ah Huh I like it, I like it......
Gotta Love those slapper's.

I will say one thing about 60ft's, BS. I pulled a 1.51 on a 11.41 pass spraying a 90 HP wet shot with nothing more than a pair of exhaust clamps holding the springs together. Where am I going with this? Heck I don't know but I love these slappers.

 

Andre, I love it . LOL

The poor man's traction device, and old drag racers trick. Clamping the springs.

 

I got a 1.767 60 foot et with Truck-Traks and ET streets at 18 psi. This first run also gave me my new best et of 12.662(still behind CC's 12.631 but he got that et in the cold air--I think.)

Dan