3D CAD drawing:
Bracket for Pentax 645 300mm ED f/4 lens

Contents:

1. Draw a bracket for the back end of lens
2. Draw a bracket for the front end of lens
3. Draw a 180 teeth pulley for motor focus of the lens
4. To be continued

Note:
I take no responsibility or liability for what are written here, you use the information at your own risk!

3, CAD Draw a 180 teeth pulley for motor focus of the lens:

Information:

Even on this lens I want some sort of motor focus. I reuse the parts that I already have built to my Canon 300 mm lens. The idea is to have it very easy to shift between these two lenses or maybe other lenses in the future.

Pentax 645 300 mm 180 teeth pulley:

I used my earlier drawing for the Canon 300 mm lens, changed the dimension of the center hole. The clamp that hold it to the lens I draw with some other technique. The clamp screw I changed from M4 to M3 to have it more compact, no protruding parts that can cause problems.

I set the slicer to 2 mm walls, 30 % fill factor, no support.

Very good results from the 3D-printer, not much need to adjust it to get the finish. This is the side towards the camera. The center hole is 77.4 mm to fit the meter scale ring of the Pentax lens.

The other side, the surface in contact with the lens is 9 mm wide. The slit is 1 mm, the pulley is very stiff when I bend the slit apart to mount it on the lens..

The pulley mounted on the lens, it must line up with the focus motor and also the complete lens packet with camera must be in balance.

This lens' focus barrel rotate about 270 degrees from close to infinity focus.

I adjust the slit to correspond to zero focus, close distance, another mark will be made to know where the infinity focus is. Can't see the meter scale of the focus ring now when it's covered by the pulley. Have to very careful when I attach the motor focus because this lens doesn't have any friction coupling. If the motor doesn't stop at the ends something will be destroyed.