Alex with the almost fully assembled filter wheel stack. At top is the POL wheel, with FW1 just behind it. Then, there is a large gap followed by FW2 and FW3
Fully assembled filter wheel stack, showing the four drive gears. The four stepper motors engage these gears to move the desired wheel in the stack. The stack contains several bearing races and wave washers to provide reference surfaces and expansion room for cooling/warming.
Side view of almost completed filter wheel stack. The hub is actually a set of four nested cylinders.
Front view of hub, with only a single gear attached, so the nested hub cylinders can be seen.
View with two gears attached, two yet to be attached.
To keep the MLI wrap on the G10 shell from adsorbing water, we kept the whole assembly inside the cryostat shell, made a flat front cover, and vacuum pumped the whole system.
Detail of the vacuum pumping set up. Thermocouple gauge allowed monitoring the internal pressure over time. Rotary valve to turbo allowed removal of pumping system after reaching adequate vacuum.