[ErroneousBosh]

Except a fluid clutch actually works, and a torque converter works even better and has three fans inside it ;-)

I can see the "passive" cylinder getting dragged around a little by viscosity but I don't see how this could transfer even the tiniest amount of power.

[yason]

Yeah, and like it's name a torque converter can actually not only transmit torque as well but also convert rpms to torque. Running the engine at high rpm at standstill converts revolutions of the input shaft to torque on the output shaft, thus allowing the car to start accelerating at slow speed but with high torque, operating without a clutch.

That's as close to fluid gearing as you can imagine.

[ErroneousBosh]

Yup. You can hold the RPM steady and watch the road speed climb as the inner blades "catch up" with the outer ones.

Not as funny as with CVTs though where you can have the road speed increasing as the engine RPM decreases. Or there was a guy about 20 years ago who had a Volvo 340 automatic fitted with a Volvo 760GLT 2.3 litre turbocharged engine, which he used to compete with at drag races at the local raceway. It did not too bad against similar vehicles in its class, but it sounded pretty funny because it would just race up to about 4500RPM and stay there for the whole run, as you had a rising howl from the drive belts at the back.

Of course my car has a torque converter and two viscous couplings - the TC between the engine and gearbox, one viscous coupling that makes the centre diff act like a very stiff LSD, and of course one that works the other way (eases off as it slips) to let the cooling fan stay at a steady speed.