Focuser is stuffed

[MortonH]

Originally Posted by killswitch

Having a closer look, are the bearings supposed to be sticking out like that? It looks like it popped out of the housing.

Good question. I don't know!

[MattT]

Morton your focuser looks like the GSO types of which I have 5.....so having admitted that here is what I think.
The ball bearings on the fine focus are supposed to look like that. I have found the grindy thing happens every now and then with my GSO focuser's too. The grinding sound problem was solved by unscrewing the grub screw and moving the knobs out of the housing and the fine knob away from the corse knob giving them all a tiny bit of wiggle room.
Works for me, only discovered after pulling apart cleaning etc. I guess the tolerances GSO focusers are built to is good but not great. By contrast a Feather Touch on my Newt stored in the same place as my two refractors never has this problem.
Might work for yours
Matt

[MortonH]

Hi Matt.

In the last picture the fine focus knob is the only thing attached and it still grinds.

[MattT]

Three times every revolution must mean something that the 3 balls roll over. No dirt, grit or depressed insect that decided to end it all in the housing?
Thats all I can think of. Get rid of the grease and replace it with a small amount of Lithium grease.
Otherwise…a Feather Touch?
Matt

[MortonH]

Originally Posted by MattT

Three times every revolution must mean something that the 3 balls roll over. No dirt, grit or depressed insect that decided to end it all in the housing?
Thats all I can think of. Get rid of the grease and replace it with a small amount of Lithium grease.
Otherwise…a Feather Touch?
Matt

Yeah, reckon it's the bearings. Can't see any foreign matter but still have the feeling that the alignment is off a bit. Waiting for Stellarvue to reply - the owner is at a star party and won't be back for two more days.

Feather Touch isn't in the budget, but the excellent Stellarvue 2.5" focuser would be around $330 delivered, so we'll see.

[nebulosity. (Jo)]

Small bumps when turning ball bearings usually means one (or more) of the balls inside the bearing has a dent in it, this can easily happen if the centre part of the bearing has been nocked sideways somehow, which dents the balls.

Have had a lot of grief with this before when building focusers.

Jo

[MortonH]

Originally Posted by nebulosity.

Small bumps when turning ball bearings usually means one (or more) of the balls inside the bearing has a dent in it, this can easily happen if the centre part of the bearing has been nocked sideways somehow, which dents the balls.

Have had a lot of grief with this before when building focusers.

Jo

Is is possible to replace the dented ball in this scenario?

[MortonH]

Stellarvue have replied and commented that my pictures seem to show a lack of grease. They suggest the first step is to add some new grease and move it around to see if that helps. However, they also agree that the rotation axis looks to be slightly out of alignment and may need some attention.

Anyone know the best option for someone to check the focuser? Bintel or somewhere else?

[MortonH]

After discussing with Bintel it seems this issue is fairly common with cheap Crayfords and is a result of minor damage to the rotating pin and/or the bearings. Apparently the cost of trying to fix it wouldn't be viable, assuming I could even find someone to attempt it.

So I'm on the lookout for a replacement. Wonder what the chances are that someone has upgraded their Stellarvue focuser and kept the old one? Time to to post a Wanted ad...

[MortonH]

Have decided to order the Stellarvue 2.5" R&P focuser. My scope is out of warranty but they're giving me a discount

Will be putting the old one up for sale if anyone is interested in trying to fix it, or just using it as is. It still works, just not as nicely as it should.

[MrB (Simon)]

Hi Morton, just noticed this thread.
I bought a used SV70 here (described as good condition) with exactly the same issue.
I noticed the drawtube has been crushed in many places by the bearings, indicating that it has been overtightened. Nothing can be done about that but a new drawtube.
The 10:1 knob (actually closer to 11:1 from memory) has the exact same issue as yours and I couldn't see the cause either.
I gave up and replaced it with a Moonlite, never looked back.

[MortonH]

Sounds like these standard focusers aren't built to last, especially if you start hanging heavy imaging equipment on them (which I never have!).

I did strongly consider a Moonlite but they're another $100+ over the SV model. Plus I would have had to choose a colour and then live with that decision forever!

[MrB (Simon)]

Ah yeah I was fortunate in that a used Moonlite popped up here for a great price. I machined up an adaptor to suit which saved me about $100 I think. Not as nice finish as the Moonlite adaptor but perfectly functional, including rotation adjustment.