Dragster Chassis Length

[Tony Curcio]

Thanks, that is helpful.

[jmarkaudio]

http://www.landsharkdragsters.com/
185" running low 7's.

[BillyShope]

Yes, I can explain the long wheelbase business.

First, it must be recognized that the sanctioning outfits have specified minimums for the dragster classes. So, we couldn't go really short, even if we wanted.

The first hard tail dragsters had very short wheelbases and, in my opinion, were the best looking dragsters ever built. Mooneyes is my favorite. Still love to drive over to Garlits' museum and stare at it. But, that's just my opinion.

But, those early dragsters could be a little squirrely. So, someone got the idea that, if they were a bit longer, they might be more stable. And, whatta ya know, they were. But, there's an explanation...an engineering explanation...for what happened. Well, there's actually 2 engineering explanations, but one is of lesser importance. That one says that, yes, the dynamic equations indicate increased stability with a longer wheelbase. But, we know it can't be that simple, for there are short wheelbase open wheel race cars that handle very well...make that VERY well...at similar speeds.

Which brings us to the really important engineering explanation: Consider a conventional production car with rear wheel drive and a beam rear axle. As you're well aware, the driveshaft torque tends to unload the right rear tire on forward acceleration. The reaction to that torque is taken at the transmission/engine mounting points and is distributed...front-to-rear...in proportion to the front and rear roll stiffness. That portion which goes to the rear tends to cancel the unloading of the right rear. But, since some...usually most in a production car...goes to the front, the right rear is still light.

A solidly mounted rear axle has a very high...almost infinite...roll stiffness, so that was helpful to those early short wheelbase dragsters. But, there remained a great deal of torsional stiffness in the frame which extended to the front wheels. As a result, the rear tires were still far from equally loaded.

So, the major benefit of the long wheelbase is to essentially "decouple" the front end, causing essentially all of the reaction torque to feed to the rear, where it cancels the initial driveshaft torque and provides essentially equal rear tire loading (and increased safety).

Was there another option? Of course! Those early builders could have kept the front suspension and worked with it. But, that required development time and effort and...meanwhile...the long wheelbase dragsters were winning races.

(For the suspended full body cars, the anti-roll bar is the equivalent of the long wheelbase.)
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[david ring]

Originally Posted by Tony Curcio

Thanks, that is helpful.

Tony-you have a PM