David Malicky wrote:
... For safety, I am thinking the tension device for the
1100rpm motor could trigger a switch that would shut off power to the
existing motor when the 1100rpm motor belt is under tension. Or a
Sprague clutch? Or hope I *always* remember. Any other ideas?

Put a double-throw switch between the current on-off switch and the 2
motors. Then only one motor can have power at a time:

/ .__________ motor
_____/ ._____/

.__________motor

Bob