The tube assembly contains primary mirror assembly, secondary mirror assembly, aluminum extrusion structures and the guide wheels.
The main structure is supported by aluminum extrusion. The original design uses OpenBeam but I change it to EU standard. This is because I can't find OpenBeam vender in Taiwan. Btw, I also change the length to just 500mm.
Primary Mirror Assembly
The primary mirror support is redesigned. I add three clips to hold the mirror. The original design doesn't have clear documentation about axis adjustment. The selected primary mirror used in Ultrascope is 6" F/4 provided by Orion Optics.
Secondary Mirror Assembly
The original design use three additional additional bolts to adjust the light path offset. That means you have to adjust six bolts at the same.... that will be very difficult. So, I calculate the required offset and print the required structure directly. This will simplify the whole structure. It will also make axis collimation much easier.
There is a disadvantage of the new design. The selected secondary mirror is 50mm for 151mm F/6 primary mirror. If you change either one then you have to adjust the offset value and re-print the hexagon.
Guide wheels
Guide wheels are redesigned so that the diameter is smaller than the printable area of printer. The original design use laser cut but the cost of laser cut is pretty expensive in Taiwan. If it can be made by 3DP then we can modify the design as needed any time. Ultimaker 3 printable area is 215x215mm. The new design's dimension is 200x200mm.
The original design uses 250mm diameter. That means we loose 20% driving torque. If the torque generated by stepper motor is too small then we can use larger diameter, say 215x215mm for Ultimaker 3, or 223x223mm for Ultimaker 2.
The roller bearing should be assembled with guide wheels. The selected roller bearing can be found here.
The roller bearing should be assembled with guide wheels. The selected roller bearing can be found here.
