Posted by Sven Bring on February 24, 2003 at 09:50:10:
With rotary valves the bearing friction is augmented by sideways pressure to some degree, when the rotor shaft is pushed sideways by the link, and thereby pressed against the side of the bearings. The ideal would be if the only force applied was "rotational". I suppose that the string operated valves that some French horns use would be very close to this ideal.
What I'm wondering now is if it would be possible to minimize the sideways pressure by applying the pressure from the link as low (near to the rotor) as possible, or if the point on the shaft where the stop arm is situated is the only variable that matters. To illustrate, I wonder if a stop arm of type B in the picture would create less friction than type A. I feel that intuition isn't enough to answer this question, but maybe someone can help me?
If the picture doesn't appear in the message, it's at
w1.877.telia.com/~u87716654/pics/valves2.jpg
Sven