Crayford or Rack and pinion for 80ED focuser replacement

[ollypenrice]

I'm a notorious doubter of the Crayford design in principle. Monty Python's Flying Focus...

nly joking!

Olly

[vlaiv]

4 hours ago, ollypenrice said:

I'm a notorious doubter of the Crayford design in principle. Monty Python's Flying Focus...

nly joking!

Olly

Yet you swear by Mesu - both being friction based products

[ollypenrice]

3 hours ago, vlaiv said:

Yet you swear by Mesu - both being friction based products

Heh heh, Steve Richards pointed this out many years ago! Guilty as charged.

Olly

[Skipper Billy]

14 minutes ago, ollypenrice said:

Yet you swear by Mesu - both being friction based products

If Mesu made focusers I would buy one in a heartbeat !! Until then R&P every time !!!

[ollypenrice]

2 minutes ago, Skipper Billy said:

If Mesu made focusers I would buy one in a heartbeat !! Until then R&P every time !!!

The difference may be that the friction drive of a well balanced mount is a fairly low-torque application. A focuser pointing at the zenith with a heavy CCD rig,  filterwheel and reducer-flattener is a pretty high torque application. I'm not an engineer but I have one staying and will see what he thinks. I'm certainly R and P for preference.

Olly

[johninderby]

Just get one of these and be done with it. 

[Skipper Billy]

1 hour ago, ollypenrice said:

The difference may be that the friction drive of a well balanced mount is a fairly low-torque application. A focuser pointing at the zenith with a heavy CCD rig,  filterwheel and reducer-flattener is a pretty high torque application. I'm not an engineer but I have one staying and will see what he thinks. I'm certainly R and P for preference.

True. I had a Moonlite on an ED80 loaded up with flattener, EFW2 and 7 filters and an Atik 460 and the focuser had to be tightened to almost cracking the bearings to stop it slipping.  

Its all down to design though - the clutch in my sports car is a friction drive and handles lots of  bhp being side stepped at full revs no problem ! 

[ollypenrice]

8 hours ago, Skipper Billy said:

True. I had a Moonlite on an ED80 loaded up with flattener, EFW2 and 7 filters and an Atik 460 and the focuser had to be tightened to almost cracking the bearings to stop it slipping.  

Its all down to design though - the clutch in my sports car is a friction drive and handles lots of  bhp being side stepped at full revs no problem ! 

Yes, I'm always amazed by clutches. It seems astonishing that they last more than ten minutes...

Olly