Broken Crayford focuser

[zumka]

:help:

Hi Everyone,

I need your help. While carrying back from the night Astrophotography session my trusted Skywatcher 72ED scope, I tripped and dropped it on the floor. As a result draw tube in the Crayford focuser became loose. After pulling the focuser apart, I have discovered that 2 out of 4 wheels that hold the draw tube in place are broken (see the attached images)

Do I need to buy a new focuser, or does anyone know where I can get the replacement wheels?

If I need a new focuser, can you please suggest which one I should get? I don't need anything advanced since I use ZWO EAF to focus.

Thank you

Daniel

[JA]

Hi Daniel,

IF all that is broken are the wheels (Ball Bearings) then a bearing supplier should be able to source replacements for you. Look for make and bearing numbers on the sides of the bearing races and/or take them in to your local bearing supplier and they should be able to provide a replacement. Fortunately there are many bearing suppliers in the Melbourne South East, Moorabbin, Clayton, Oakleigh. If you search Bearings in Moorabbin that should point you in the right direction.

ALSO Check carefully that it is only the bearings that are damaged and not the abutting rolling surface or any bearing holders, mounts. threads etc...



Best
JA

[Outcast]

I had a similar experience with the crayford focuser on my SW 72ED & took one of the bearings into allied bearings here in Cairns.

I took an intact bearing in to be measured & I was able to purchase replacements although they were fractionally wider but, importantly, same diameter.

In the end I purchased 4 & replaced all the bearings... job done...

Not sure if you have an Allied Bearings in Vic however, I'm sure you'd have a bearing business of some sort near where you are..

A quick google turned up Metro Bearings in Clayton South, Vic maybe give them a try...

https://metrobearings.com.au/

Cheers

[zumka]

Thank you,

It looks like the only damaged parts are the bearings.
I'll try the local suppliers

[Saturnine]

As others have pointed you in the direction to get new bearings I wont add to that but I'd be very surprised that any impact force that was enough to break bearings rings have not damaged the drawtube and / or focuser body. A careful inspection for dents or the focuser body or drawtube for being slightly out of round etc. If they are , that will impair the focusers movements and usability.

[zumka]

I'll do that tonight.

[zumka]

As option B which aftermarket focuser is compatible with 72ED?

[Bart]

Do yourself a favour and buy a good quality rack and pinion type. Feathertouch would be the go.

[zumka]

A focuser that is double the price of ED72?

[zumka]

I'm assuming this is the replacement focuser I need:

https://www.bintel.com.au/product/bintel-crayford-focuser-101-refractor-96mm-od/

[Saturnine]

Just measure the diameter of the broken focuser body where it attaches to the tube and buy the same size. Don't know what focuser Skywatcher use on the ED72, is it the same as in this picture.

https://www.bintel.com.au/product/evostar-ed72-guidescope/

If it is then there may not be a direct swap for a GSO focuser.

[zumka]

There are some minor scratches on the surface of the tube. See the attached photos

[JA]

The damage you have there could potentially affect the smoothness of the focuser, which is obviously a problem when trying to achieve fine focus.

The dints/gouges/scratches could carefully be filed and then sanded down, to remove any high spots, BUT be careful not go below the surface and thereby create a valley. I would try using a small fine flat metal file and then some sandpaper on a hard backing, BUT ONLY REMOVE THE HIGH SPOTS.

After that I would get the ball bearings as they're probably inexpensive and fit them to see if the focuser action is smooth or smooth enough. If it isn't then either buy a new focuser or possibly consider using some metal laden epoxy to fill the gouges file/sand back the tube to smooth.

You could also call Bintel and ask them whether they have an aftermarket replacement focuser for your scope or if they could supply you with the original focuser or parts of it as spare parts from Skywatcher.

Best
JA

[zumka]

Thank you for your advise bought 4 bearings from Metro Bearings. They were 1 mm wider. Worked without any issues.

[DaBris]

Hi, would your mind sharing what size the bearings you purchased from metro bearings are, I am in need of replacing mine for my ED72 also.
Thanks
Dan