The word "efficiency" get's flashed around like a casual by-word. I have asked and asked yet no-one (so far) has been able to quote specific numbers or present graphical test results of the efficiency of the Fottinger hydraulic coupling. My general understanding from the automotive world is that it is unlikely to exceed much above ~80% whereas a well-designed fully-geared drive can exceed 90%. This is an important detail in respect of fuel consumption. My understanding is that ROLLS-ROYCE dyno tested salvaged DB's and analysed their supercharger drive design and efficiency. This must have generated an official report as this testing was commissioned by the R.A.E. I would like to see that report. It would go a long way toward explaining the mystery as to why R-R (and others) never copied it. Does any know for sure??
this looks like good engineering for certain applications, but I don't think it would work well for a vehicle transmission, because the forces are varied with such frequency that this would produce wear. Replacing a torque converter is not a fun thing to do. I can see how this could be very useful though in an industrial lathe, milling machine, or generator turbine where the forces tend to change more slowly, and at a more strictly controlled rate.
