Revelation focuser (minor) disassembly

[JamesF]

I wish to remove the non dual-speed knob from my Revelation dual-speed focuser:

I suspect the knob is fitted to the shaft using a screw through the end face of the shaft and that the slightly conical end of the knob comes off to allow access to this, but I am guessing.  At any rate, although there appears to be a join between the body of the knob and the end cap, I can't get anything in there to prise them apart.

Has anyone actually taken one of these knobs off?

My plan was to fit a motor drive either direct to the focuser shaft as I've seen done here or to put a pulley on the end of the shaft and drive it using a belt, but if all else fails I'll use a belt/o-ring drive over the knob.

James

[Davey-T]

No, just had a look at mine and it looks like a recipe for stabbing yourself with a sharp object trying to get the end cap off.

Dave

[JamesF]

That was exactly the conclusion I'd come to  I'd very much prefer to remove it non-destructively if possible, but at the moment I can't see how.

James

[Davey-T]

Try posting on that forum and ask Space Cowboy how he got it off.

Dave

[JamesF]

Try posting on that forum and ask Space Cowboy how he got it off.

PMed him a few days back but haven't had a response yet.  He's not been online for two months, so I'm not entirely hopeful.

James

[Davey-T]

Perhaps someone at FLO or Telescope House knows.

Dave

[JamesF]

I've found someone on astronomyshed who has done something very similar, so I've dropped them a PM too.  I'll get there one way or another

James

[Davey-T]

Put up a post if it works and I may do mine.

Dave

[Bizibilder]

I'd leave the knob in place and use a small timing belt to drive it  http://www.motionco.co.uk/timing-belts-timing-belts-c-25_38_27.html  I drive all my focussers on the fine adjustment knob using a modified servo.  It works very well and there is no perceptable slipping.  I have a plug in variable power supply that will work on any of my scopes.

[Scott]

it's no more than a guess really, but is it possible there's a retaining screw under the knerled rubber on the knob? just a thought really.

[JamesF]

Put up a post if it works and I may do mine.

Certainly.

James

[JamesF]

it's no more than a guess really, but is it possible there's a retaining screw under the knerled rubber on the knob? just a thought really.

Already removed that to look  There doesn't appear to be anything under it.

James

[JamesF]

I'd leave the knob in place and use a small timing belt to drive it  http://www.motionco.co.uk/timing-belts-timing-belts-c-25_38_27.html  I drive all my focussers on the fine adjustment knob using a modified servo.  It works very well and there is no perceptable slipping.  I have a plug in variable power supply that will work on any of my scopes.

That may well end up being the route I go.  It would have the advantage of allowing me to tuck the motor under the focuser body, too.

Come to think of it, that might be quite a neat way to motorise the tuner ring of my PST.

James

[Steve Ward]

I just fitted the motor on the other end ... 

[JamesF]

You mean on the dual speed end?

James

[Steve Ward]

Sorry James , will have to learn to read properly ... 

You'll need to remove the focuser assembly from underneath , the screw holding the end on is on the smaller part of the spindle hidden from normal view.

Can't remember fully but there may be some very small 'o' rings inside on the four fixing screws so be aware.

[Steve Ward]

[JamesF]

Oooh, now that's a cunning place to have hidden it.  Thanks Steve.

James

[Steve Ward]

You're very welcome , sorry for the previous stupidity ... 

Can't remember why I didn't fit mine to the 10:1 end but I'm sure there was a good reason , makes little difference with the f15 Mak as there's quite a big sweet spot so's to speak.

[ChrisLX200]

Fitted my drive to the 10:1 by removing the small knob and replacing it with a toothed pulley (although on my refractor I run the toothed belt directly on the focussing knob).

ChrisH

[JamesF]

Is that knurled brass nut a clutch mechanism, Chris?  Back it off and the driving pulley spins freely to allow the focuser to be moved by hand?

James

[JamesF]

Oh, and how did you mount the motor to the bottom of the focuser in that instance?  The Crayford SCT focuser has plenty of screws that can be used for mounting, but I'd not noticed that the R&P version (which I think that one is?) has any suitable mounting points.

James

[ChrisLX200]

Yes a simple clutch, just a half-turn to loosen for manual focusing. The motor bracket is an alloy channel which clamps to the focuser spindle housing using a few grub screws (not holes were drilled in the focuser!)

ChrisH

[JamesF]

A cunning and very neat solution  I may have to rethink my own plans now...

James

[ChrisLX200]

Well I really didn't want the focus motor sticking out the side by a several inches, so that's why it is slung underneath.

ChrisH