The filter box is also manufactured in our machine shop. The design has been carefully verified and it is ready for fabrication. We also use aluminium avoiding contraction differences with the rest of the system.
The filter box includes 3 filter wheels with four filter spots in each one. The grism wheel also support 4 optical elements. The Lyot wheel is situated after the first filter wheel. Wheels are carved in a 48 pitch and 23.8cm diameter spur gears obtained from Ascent precission gear corporation.
Each wheel requires a switch, a motor and a mechanism turning mechanism. Switches are inserted in a piece that can be mounted separatly and then screwed to the filter box. Switches are standard actuator micro-switch JX-45. Motors are mounted in a holder that is attached to the filter box.
We choose regular motors and we clean the grease to adapt them to cryogenic temperatures. They are ""size"" motors and they were bought at Motors has been tested by Javier Cenarro under cryogenic temperatures. Following tests include wheel-motor coupling under cryogenic temperatures.