I saw this replica of a Bill Thomas Cheeta go across the block on BAT. I thought it interesting that they were using a TH-400 automatic.
https://bringatrailer.com/listing/1964-cheetah-coupe/
It brought to mind an interview I heard recently with Jim Hall the engineer and founder of Chaparral.
Jim said that they'd built a racecar in the mid-'60's for Can Am that was powered by a 327 Chevrolet and used a 3 speed automatic transmission (automatic because Chaparral was always thinking outside the box). After some initial testing it was discovered that they were experiencing significant wheel spin in any gear at almost any speed. The consummate engineer and perennial innovator, Hall scratched his head and asked "...why do we have a transmission?". They went to work and came up with a locking torque converter and direct drive. A few laps of the Rattlesnake (Hall's private test track) later confirmed that it was indeed faster.
My question is this: how would one easily duplicate that? It seems it would be a natural in something like this extremely lightweight Cheetah. I'm sure that when they built this Cheetah they just smashed down on the easy button. it's what I would have done had I not heard this very interesting interview.
Thanks
I guess the obvious answer, which I just thought of after I typed it out, is that it gives you reverse. But let's assume I'm building a competition car and don't care about backing up. That's what the crew is for.
Lots of stock cars use a two speed powerglide and a torque converter eliminator. Which is close to the same thing. But the reason for gears is to always be at the perfect place toque and horsepower wise, and wheelspin at any speed seems to me to be never in the perfect place. Not that that is necessarily a bad thing in a horsepower context....
That wasn't a true automatic it was a semi automatic. It was a conventional manual type transmission with a torque converter. The transmissions themselves were built by Chevrolet research which was headed by Frank winchell who later was the head of gm engineering. Before Chevrolet he had been an engineer at Allison.
unless you know how to design transmissions it would probably be very difficult.
During the early 60s some builders like Sadler etc experimented running high gear only transmissions.
here's the interview. Long but not short on interesting subject matter:
https://youtu.be/Z0rXyMwFMUI
Somebody knew the future was in automatics/DCTs . . . It's nice to be able to keep both hands on the wheel.
I always thought the semi auto was so your left foot could control the adjustable aero?
buzzboy said:
I always thought the semi auto was so your left foot could control the adjustable aero?
It came before that it debuted on the original Chaparral 2.
With direct drive, you'd want a torque converter so that you could pull out of the pits and out of super low speed corners. The locking ability would mainly get you a little bit less heat in the trans and a couple more MPH.
I THINK that GM made lockup versions of the TH200 and TH350. The easiest engineering is when it's been done for you already.
