Astrofriend's homepage

www.astrofriend.eu
Share: Twitter Reddit Facebook Gmail Gmail Email
Search Astrofriend's homepage:

Valid CSS!

All pages shall now have been validated

Info Cookies (Kakor) / GDPR

Navigation

Advertisement /
Annons:

Advertisement / Annons:

My astronomy project:
Repair and adjusting focus friction
and
Develop a more advanced heavy load focuser


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. Ideas about 3D-print rack and pinion gears:

  8. 3D-Printing rack & pinion gears
  9. How to implement the rack & pinion into the focuser
  10. Combined rack & pinion and worm gear
  11. 3D CAD focus shaft holder and focus chassi
  12. 3D CAD and print of worm gear
  13. Implement of external push pull screws:

  14. New design with push pull screws
  15. Stabilization of the focuser draw tube
  16. Assembling the push pull system, 1
  17. Assembling the push pull system, 2
  18. To be continued

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


8: How to implement the rack & pinion into the focuser

Now when I have tested to 3D-print the rack & pinion gears with success I move to the next step. How to implement it into the 3" focuser I have. I could of course bought a new focuser which already have a rack & pinion and a stepper motor. But it had cost a lot of money and it's more fun to construct something by myself.


Focuser: 3D-Printing rack & pinion gears

I removed the focuser from the telescope, not the first time and now it doesn't take very long time for me.


Focuser: 3D-Printing rack & pinion gears

The other side, the grey part to the right is the steel friction plate, to increase the friction I have glued a sandpaper to it. It works well with no slipping but have to replace it with a new sandpaper once a year.


Focuser: 3D-Printing rack & pinion gears

The holder of the focuser shaft, the roller bearings are set under force by the top outer screws to have enough friction to not slip.


Focuser: 3D-Printing rack & pinion gears

Now when I have the parts dissembled I measure the weight of them. The focuser draw tube weight 0.75 kg, that was a lot more than I thought.


Focuser: 3D-Printing rack & pinion gears

The 3" field flattener weights 0.55 kg. Together 1.3 kg, to that I have to add the camera, about 1.5 kg, still no filter wheel or off-axis adapter with its guide camera. It's not hard to understand that the friction coupling slip sometimes.


Focuser: 3D-Printing rack & pinion gears

Inside the focuser, the four roller bearings that the focuser draw tube ride on. The force acting on the steel friction plate also hold the focuser draw tube in correct position. With a load of 4 kg It must have a high force to not come out of position.


Focuser: 3D-Printing rack & pinion gears

The draw tube and its holder. In my first attempt to implement the rack & pinion gears I try to keep these parts.


Focuser: 3D-Printing rack & pinion gears

The hole where the focus shaft was placed, now in someway I have to fit the helical gear inside this hole. It looks impossible.


Focuser: 3D-Printing rack & pinion gears

With the rack of module 0.5 mm put inside.


Focuser: 3D-Printing rack & pinion gears

Top view of the rack and focuser.


Focuser: 3D-Printing rack & pinion gears

At bottom the friction steel plate and above the shims, altogether 3 mm thick. The size of the steel friction plate is 114 mm long, 26 mm wide and 2 mm thick. The two small holes are 90 mm apart, two M2 screws hold it in place.


Focuser: 3D-Printing rack & pinion gears

The old bracket that hold the focus shaft and set it under tension.


Focuser: 3D-Printing rack & pinion gears

One of the ends of the bracket. The elongated hole is where the roller bearing sits. When it's adjusted up and down with the top screw the force on the friction shaft against the steel plate is adjusted.

Even if I can reuse this part I plan to 3D-print a more advanced bracket. It should also hold the stepper motor and the external gear box.


Focuser: 3D-Printing rack & pinion gears

The focus shaft with the prototype helical gear mounted. Looks good but next version of the rack will be much wider. When wider the helical gears works better, a lot of teeth is in contact all the time which makes a smother move.


Focuser: 3D-Printing rack & pinion gears

Helical gear installed into the focuser, here is very limited space. With fewer teeth the helical gear gets smaller, but also the strength of it decrease. I can mill the focuser house to get more space. But should I do that to a very expensive APO refractor ?

Go Back to content

Go Back
To page IX

Advertisement / Annons: