Motor Mount
The T/R switch drive motor spins the rotating mirror at 20 Hz, or 1200 RPM in a software-programmable way. Due to space constraints (and also as a means to reduce vibrational coupling), the motor will drive the mirror via a belt-frive in a 1:1 configuration. The 1:1 is important because the laser is slaved to fire off of the motor's encoder. This task is much simpler if the once-per-rotation pulse is phased with the physical mirror.
The motor position is indicated below, but the following PDF hidden-line drawings from above and from the side are probably more useful.
The competitors for space are the New Focus 9855 mirror mount that sits below the motor, and the CCD camera, whose mounting arrangement also needs to be worked out. Both the motor and CCD camera will utilize the tapped holes along the corner of the table, but this sharing will be tight and must be coordinated.
The motor shaft is to be parallel to the shaft of the mirror, so that an in-plane belt can connect the two. The motor mount ought to have some tension adjustment built-in.