8 replies to this topic

[ravajack]

A great moment for the Chaparral team.

 

 

 

 

[ravajack]

[Isaac S.]

 

A great moment for the Chaparral team.

 

A great moment for the Shelby team really. Sebring '64 is where the Daytona Coupe becomes a legend in racing. Then they went on to win Le mans (GT class, of course) and the World Manufacturers Championship in '65 (after Sebring) and that made Shelby American a legend in racing. 

[NSwanberg]

Does anybody know about the Chaparral's "automatic" transmision?

 

https://www.hotrod.c...r-aerodynamics/

[Dave Crevie]

The automatic Hall used in his car was Chevrolet Powerglide derived, with a manual shift valvebody developed in the Chevy "Skunkworks". He could shift up or down before the gear change was needed, something like a pre-selector. As far as I know, how that was done is still a secret, but I expect it was similar to what the drag racers were fiddling with at the same time.  

[Dave Crevie]

This question started me on a research quest. Being a 2016 issue, I don't have that one. So I started perusing my books which have info on the Chaparral, and found little about the automatics. In the Dave Friedman book there is a photo of it installed in the car, and it looks nothing like what is in that Hot Rod article. The one in that drawing looks more like your typical Colotti box with something added in the clutch area. The drawing doesn't show that area very well, but it could be a torque converter. My question is what is the additional crown gear shown in that area. An exploded view would have been far better. I see what appears to be shift bands for a planetary gear assembly, which might provide two different gear ratios just like a conventional automatic. If that is true, and the rest of the transaxle is a normal dog-ring unit, that means that there were two different input shaft speeds available. That would be something like an overdrive, but at the front of the trans rather than on the tailshaft or on the rear axle. If the planetary reduces input shaft speed, that also reduces rotational speed in the geartrain, and makes clutchless shifting easier. 

 

So, after trying to think that all out, I have to wonder why? Clutchless upshifts are fairly easy with a dog ring box, and become second nature after some time. A true automatic would eliminate that tiny split second when power would be broken to the rear wheels. Maybe, with all the shifts in a 12 hour race, that time might add a lap or two to your total. I know a guy who probably can straighten this all out for me, since he built transaxles for the USRRC and early Can-Am cars that used American V-8s. Would be a good excuse to call someone I haven't heard from in years.   

[NSwanberg]

The picture from the Hot Rod magazine article gave me fits. It looked like a convolution between a torque converter automatic and a manual gear box. Does clutchless dual clutch make any sense?

Is the crown ring your refering to what might be considered the flywheel or flex plate?

[Dave Crevie]

The crown gear appears to be inside the torque converter. The flywheel/flex plate/starter ring gear is ahead of it, and clearly visible. But the drawing doesn't show any other gear that would mesh with the crown gear. I'm thinking that just ahead of that crown gear is a planetary with the shift band around it, and at the bottom of the bellhousing is a servo for actuating it.  

[Ecurie Martini]

It was probably inevitable but Jim Hall was the first to make outsized wings successful so I blame him for the end of racing cars as beautiful sculptures leading us to where we are today with F1 cars that look like something that Jacques Cousteau might have found in the Mindanao Deep.  Never have and never will build a Chaparral model - to me they are simply ugly and life is too short.

 

EM