Pontiac "rope drive" Tempest
Posted: Wed Apr 30, 2014 7:38 pm
Here's another real odd-ball one. The so-called rope drive system, introduced in the 1961 Pontiac Tempest.
http://midsizebowties.net/articles/pont ... explained/
It starts with a rear mounted transmission connected to the engine via torque tube. This should sound familiar (C5 Corvette). This enabled a 50/50 weight bias, which is pretty incredible.
It would be novel enough if it was just the torque tube. But no. The engine for this car was a large 3.2L 4 banger, which was a cut-in-half Pontiac 389. Needless to say, it had vibes.
So aside from soft engine mounts, one clever technological marvel was the use of a flexible torque tube. It had a 3" bend at the center, supported by a carrier bearing. Due to the constant flex, it used no universal joints. How cool is that? If you still can't picture it, imagine a speedometer cable turning and it makes sense. It would act as a torsional damper for the engine.
Another interesting thing that I assume is also part of the C5+ torque tube design is that it is significantly narrower than a driveshaft. The Tempest shaft was 0.65" diameter for automatics and 0.75" for manuals, which seems small. But then it only transmits engine torque, not multiplied gearbox torque, so that makes sense.
http://midsizebowties.net/articles/pont ... explained/
It starts with a rear mounted transmission connected to the engine via torque tube. This should sound familiar (C5 Corvette). This enabled a 50/50 weight bias, which is pretty incredible.
It would be novel enough if it was just the torque tube. But no. The engine for this car was a large 3.2L 4 banger, which was a cut-in-half Pontiac 389. Needless to say, it had vibes.
So aside from soft engine mounts, one clever technological marvel was the use of a flexible torque tube. It had a 3" bend at the center, supported by a carrier bearing. Due to the constant flex, it used no universal joints. How cool is that? If you still can't picture it, imagine a speedometer cable turning and it makes sense. It would act as a torsional damper for the engine.
Another interesting thing that I assume is also part of the C5+ torque tube design is that it is significantly narrower than a driveshaft. The Tempest shaft was 0.65" diameter for automatics and 0.75" for manuals, which seems small. But then it only transmits engine torque, not multiplied gearbox torque, so that makes sense.