Shaun.Hendricks@bergenbrunswig.com wrote:
>
> Uh, having just watched a show on modern "Top Fuel" dragsters, all three
> 'cars' (if that's what you call them things) only had 1 (one) gear, there was
> no shifting at all. They just slipped an automatic clutch until the vehicles
> speed got up high enough to fully "catch". If the automatic clutch was set
> too tight it'd smoke the tires, too loose and you got a poor take off. They
> replaced the clutch after each race they could manage it. The driver
> controlled the slip as well by the throttle. Watching the video, the drivers
> usually started at about 3/4 throttle and pushed it up from there as the
> dragster rocketed down the track. (I don't think you can call a car like this
> a "manual" since theres not shift at all)
> I'm certainly no expert on this, so if the show was wrong forgive me, but
> it all made sense the way it was set up. I do know that drag bikes have push
> button transmissions and they rocket through the gears so fast it's almost as
> fast as the driver can push the button.
>
> Shaun H.
>
> ---original message---
> Pro Stocks DO NOT have autos!!! They are all 5 speeds, and starting next
> season,t he drivers have to shift em with a lever, not a button. Also Top
> Fuel, F/C, All Alky cars, and majority of the comp cars are all clutch cars.
>
> Brad
Pro Stocks or at least most of the winning ones use a Lenco 5 speed. Up
till last year they were using a Lenco 4 speed. The Lenco (I may be
spelling it wrong) transmission uses planetary gear sets just like the
modern automatic transmission. The difference is that the passenger
car/truck automatic uses a computer or a governor to controller the
hydraulic line pressures that control shifting and Lenco uses mechanical
linkage to control the shifting. The air solenoid is just taking the
place of the driver's arm moving the mechanical linkage. In a planetary
gear set transmission gears do not move when you shift like in a manual
transmission, rather bands are tighten or release or clutch packs are
engaged.
With a Lenco the only time a clutch is used is when the car is setting
still. On a Pro Stock once the clutch is released and the car is
launched the clutch is not touched again until the race is over or the
engine blew. The Lencos are shifted without releasing the clutch.
On a street type drag car or any drag car running slower than 10 seconds
in the quarter the manual transmission is faster then an automatic, but
it doesn't win races. Consistency win races and the automatic is
consistence. I'll give away .2 any day if I can run the same thing run
after run, never varying more than .005. I love a manual transmission
car and they are fun to drive on test and tune night but they don't win
races. Now once you get below 10 seconds the manual is no longer
faster, the Lenco is the best with a highly modified automatic coming in
second. Here the amount of time that the engine is disconnected from the
power train when you shift comes into play.
With a 5 speed how much time does it take to shift 5 times, half a
second if you are real good. Now if you're runnin 8.5 ET you have a
half second that your car wasn't under power while the Lenco and
automatic cars were under power the full 8.5 seconds. With an automatic
and a Lenco power is still being applied while shifting, the gears
aren't being move, another band is just suddenly tighten.
Bob
In modern drag racing that's a lot more to it then meets the eye.
This archive was generated by hypermail 2b29 : Fri Jun 20 2003 - 12:10:45 EDT