My astronomy project:
Repair and adjusting focus friction

Content:

Repair the friction coupling:

1. Introduction focuser
2. Disassembling the focuser
3. The friction parts
4. Assembling focuser together
5. Implement of high friction surface
6. Spring compensation load
7. To be continued

Related projects:

• Repair and adjusting focus friction
• Tangent arm focuser
• Rack and Pinion focuser
• Push and Pull focuser
• Focus and camera rotator
• Focus and temperature drift

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

6: Spring compensation load

Problem and more problems, will it never stop? Now when I fixed the slip in the focuser I can still see that the start position and parking position of the focuser isn't the same. Strange because I can both see and feel that it doesn't occur any slip in the focuser anymore. What could it be then? After consulting the forums around the world I got a lot of tips, one was that the motor is too weak when the telescope is pointing upwards. No... no... I thought, my motor is the medium size and has a strong torque, now when I have the telescope indoors again after the season is over I could took a deeper look.

What did I found? Oh... yes the motor is on the limit to stall when driving the focuser draw tube in the upwards direction. The motor has high torque but after I increased the force adjustment of the focuser friction coupling all the torque is used to overcome the friction and no extra left to lift the focuser, the field flatter and the camera. What can I do to fix that, some balance weight or similar ? In the forums they talked about spring loads, maybe that is a way to solve this problem easy, at least for the moment.

After thinking about the problem and looking after what I have in the boxes at home I came to this solution:

A quick and dirty solution, a spring that compensate for the weight of the focuser and the camera. The needed force will of course be different with the angle the telescope is pointing at, I have the spring force balanced with the weight at 45 degree telescope angle. Not very nice looking but indoors test show that it works, maybe I have a better solution when the new season starts a half year later now when I know what's the problem. If I just could replace the friction bearing to the screw adjuster that apply the force on the axis it should work without this spring, but it is very limited space inside the focuser.

I have now solved the problem temporarily, but later I must construct something that really works. My plans are a Rack and Pinion or a Push Pull design. Have a look in the content above.