View Single Post
  #27  
Old 24-06-2008, 09:11 PM
tnott's Avatar
tnott
Oblonnygox

tnott is offline
 
Join Date: Aug 2006
Location: Adelaide
Posts: 221
Quote:
Originally Posted by Rod View Post
Hi Tim,



I have been following your articles about your tri-dob. It looks great! Could you explain a little more about the cable drive on the altitude. I have read about cable drives but can't visualise how they work.

Regards,

Rod.
The driven altitude fin has a 1.2 mm cable screwed onto one end which runs along the curved length then wraps around a roller twice. It then connects to a spring, which is connected to a small toggle lever.

When the lever is engaged the friction of the cable around the roller drives the scope (like a horse's reigns outside a saloon in a Western). When the lever is disengaged the cable slips so the scope can be moved manually. A notch is made in each end of the bearing (to stop it slipping off) and a channel made in the teflon it sits on.

The cable also winds from side to side a precise amount depending on the width of the cable, as well as the circumference roller and the alt bearing. Mine needed a custom one.

Attached are some photos of more "standard" scopes
Attached Thumbnails
Click for full-size image (111-1123_IMG.jpg)
40.3 KB40 views
Click for full-size image (Jnr-Alt.jpg)
18.9 KB44 views
Reply With Quote