Rear engine drag chassis

[brechlrl]

My buddy built a hard tail rear engine dragster..150 inches wheelbase. The chassis is chrome moly, and he might have over built it a bit, so it is quite stiff. He is having trouble hooking up and experiencing wheel hop on launch. Could the chassis be too stiff?

[John Wallace]

I don't think you could be too stiff.

That's even shorter than my dragster. (180")
No suspension right?

What's the launch RPM?
Power Combo?
Slicks?

Mine hooks great and launchs good.

Also, what is the front to rear weight ratio?

[brechlrl]

Tire is 10.5 x 31 Engine is 340 cube 435 horse. 3 speed automatic.3.70 gear Launch at 3500. No rear suspension, solid axle with torsion suspension in front. We are going to scale it to see where the weight distribution shakes out. What should it be?

[582r10]

My buddy built a hard tail rear engine dragster..150 inches wheelbase. The chassis is chrome moly, and he might have over built it a bit, so it is quite stiff. He is having trouble hooking up and experiencing wheel hop on launch. Could the chassis be too stiff?

First thing I would suspect is too much air in the rear tires.




Roger
582r10

[BillyShope]

...solid axle with torsion suspension in front.

Use of a front suspension allows the chassis to be torsionally stiff and the wheelbase to be short. Good work! Keep the front wheel rate low. The early short wheelbase slingshots...such as the Mooneyes...would have had longer careers if they had included a front suspension.

If someone suggests a REAR suspension, pick up a tire iron and chase him away.
http://www.racetec.cc/shope

[BCLS776]

My buddy built a hard tail rear engine dragster..150 inches wheelbase. The chassis is chrome moly, and he might have over built it a bit, so it is quite stiff. He is having trouble hooking up and experiencing wheel hop on launch. Could the chassis be too stiff?

First thing I would suspect is too much air in the rear tires.




Roger
582r10

Try somewhere around 6 to 8 psi in the tires. It should hook with that and you can finesse it from there.

[John Wallace]

Billy any suggestions on the design of the front suspension?

[BillyShope]

Billy any suggestions on the design of the front suspension?

Nope. Well, if you have a clever way of increasing the wheel rate at the right front ONLY in rebound ONLY, it would be nice. The idea is to increase the weight pulled from the right front...so as to equalize rear tire loading...while maintaining equal spring rates during braking. Wait a minute! Wait a minute! This is a dragster, so you're using a chute. So, forget all that fancy stuff and simply use coil springs with a higher rate spring at the right front. There's a spreadsheet at my site to help in spring selection.
http://www.racetec.cc/shope