Drobie
07-02-2002, 04:34 PM
What happens otherwise is that if it's at 50%, you have a full-wave tuning fork. It makes ALL KINDS of noise when you get to the magic frequency (speed of sound / length of shaft).
By setting it off-center, the two sides of the shaft oscillate at different natural frequencies and keep each other quiet.
If you skip the "center" bearing, it will run as a 1/2 wave tuning fork at a much lower frequency (1/4 of the frequency when set at 50%).
If you have a 9" long driveshaft (measured between end bearings) then put the center bearing 4" from the prop side, which means 5" from the motor side.
(Andy) I have a couple more questions about this.....
Is "noise" synonymous with vibration?
At what point (length) or under what conditions are 3 bearings preferable to 2?
By setting it off-center, the two sides of the shaft oscillate at different natural frequencies and keep each other quiet.
If you skip the "center" bearing, it will run as a 1/2 wave tuning fork at a much lower frequency (1/4 of the frequency when set at 50%).
If you have a 9" long driveshaft (measured between end bearings) then put the center bearing 4" from the prop side, which means 5" from the motor side.
(Andy) I have a couple more questions about this.....
Is "noise" synonymous with vibration?
At what point (length) or under what conditions are 3 bearings preferable to 2?