quote:

Originally posted by jenavet:
When you start going really fast, you use the bars to control wheel speed. As you raise the wheelie bar up, you take wheel speed away. Lowering it adds wheel speed. It doesn’t allow the wheel to compress as far, which allows the tire to spin. A good race track will make the car faster by lowering the wheelie bars, but as the track goes away, raise the bar.”

Good explanation, but you have to be fairly close to the right wheel speed before using the bar to fine-tune it.

I have a couple things to offer.

I have run over 80 lbs in the nose of the old 225 hardtail and it kept going faster. This was to reduce load on the wheelie bar which was causing too much wheel speed going by the tree.

Also, if it's wheelstanding you need more power early. I could take weight out by being aggressive early. One time though I was setup aggressive (lots of power, light on the nose) but got scared of the track and turned it way down (knowing I couldn't turn it down just a little cuz it would wheelstand). Then at the last second I decided to turn my leanout timer back on which adds power around 0.8. So it drove out dead hooked on the bar until the leanout opened at which point it tried to rip the parachutes off.

quote:

Originally posted by "The Bender":
1° can make a huge difference.....

that's what she said....

quote:

Originally posted by Will Harrison:

quote:

Originally posted by "The Bender":
1° can make a huge difference.....

that's what she said....

Guess it depends where you start.

quote:

Originally posted by "The Bender":

quote:

Originally posted by jenavet:
When you start going really fast, you use the bars to control wheel speed. As you raise the wheelie bar up, you take wheel speed away. Lowering it adds wheel speed. It doesn’t allow the wheel to compress as far, which allows the tire to spin. A good race track will make the car faster by lowering the wheelie bars, but as the track goes away, raise the bar.”

Good explanation, but you have to be fairly close to the right wheel speed before using the bar to fine-tune it.

Completely agree. I have also found this only works if you have a bar that has some flex. When my Car is balanced correctly it will squat to where the bar just touches before the car moves. As the car starts to drive up on the tire a few rotations out thats where it will carry the wheels a little. Maybe 6 inches or so. With a real stiff wheelie bar ive found its too unforgiving. The window between unloading and coming up too high is just too small.

And that's where length comes into play.

The wheel height that works to prop up the leave is mostly independent of wheelie bar length because that motion is mostly downward (squat) and not rotation.

The height for the "prop up" is a great tuning tool to easily adjust wheel speed for changing track conditions.

Problem is, on a good track with a bar that is long enough to flex (~70 inches) the "prop up" height will unload the car as soon as it starts to rotate because it's too low now.

I think for a certain track condition there is a perfect length where you get the perfect "prop up" load and then can rotate the front end up ~18 inches on the way out. You really want to be able to adjust the "prop up" height while keeping the "drive out" height the same.

If I ever run another fast dragster I'll either figure out a way to easily adjust bar length or automate it to move up just after the hit. I did this to some extent with the first bar I built for my old 225 car but it took too long to adjust the difference between "prop up" and "drive out"

quote:

Originally posted by BJs Wild Ride:


If I ever run another fast dragster I'll either figure out a way to easily adjust bar length or automate it to move up just after the hit. I did this to some extent with the first bar I built for my old 225 car but it took too long to adjust the difference between "prop up" and "drive out"

I like the concept. Probably could be done with an air cylinder similar to the way timed shocks work. Have a cylinder dump a certain time into the run and allow the bar height setting to change.