- Oct 18, 2003
- Saline Michigan
I recommend you visit the equations for viscous forces between flowing fluids in contact with stationary surfaces. Any good introductory fluids textbook should do. Then you can postulate radii, clearances, how much area is needed to generate how much torque capacity, and how much energy is lost in a viscous drive. Then your can also go to a heat transfer text, and figure out how much area and delta T it would take to passively cool these things.I was thinking that if the concentric shafts were both rather long, the surface area the fluid is in contact with would provide sufficient "grip" to keep slippage down to a reasonable level and give enough external surface area via the outer shaft to cool it enough.
I should clarify that I mean having only a millimeter or so of clearance between the inner and outer shafts.
I will tell you it is not really practical for our levels of power and weight sensitivity. If you do not believe me, knock yourself out with the fluids and heat transfer books. I will help you get the math straight if you want, but it won't change the fact that a 200 hp engine will lose a bunch of energy and that you won't be able to make a practical device for a flying airplane this way.