Quote:
Originally Posted by Rod
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