Scopetech Zero Mount Slow Motion Problem

[tompato]

The slow motion cable breaking I don't mind too much, as I can just get a refund but it's now permanently stuck to my Scopetech Mount and I'm not sure what I can do to get it off tbh.

It's not like Skywatcher are going to refund me £375 for the fact they've potentially buggered my mount.

I could hope it loosens over time, or I could try drilling it but it's such a small screw I'm not sure I'd find much to screw into it to remove it. Maybe I could crack the metal casing at the end of the slow motion cables but although their screws are apparently made of butter the rest does not.

Ill move this to its own thread as it's not a problem with the mount anymore, just Skywatcher's shocking quality control.

Edited May 29, 2021 by tompato

[jock1958]

1 hour ago, tompato said:

So the slow motion cables arrived, they were great @jock1958, apart from the fact by hand tightening they kept undoing and so I went to tighten it a little bit and this happened (photo attached). To say I'm livid is an understatement, I've only had them for 5 minutes.

Ok that’s not good and very frustrating.
What did you use to tighten it up? If it’s a big screw driver it probably exerted too much torque and sheared the head off. There’s a few ways out of this but not sure what tools / expertise you have? 

[tompato]

It was only little, it wasn't even what I'd consider hand tight yet. It really has no business having a large flathead on it though because I could have been using a bigger screwdriver on it.

The whole design is poor tbh, I don't know why it doesn't just have a small Allen grub screw. The £5 aluminium knob from eBay had better which is a little bit alarming.

I'm not sure I'll even buy or get a replacement as I'd just be constantly worried it'll break off again. I'll have to try and find an alternative make of slow motion cable.

[jock1958]

There’s a small amount of thread protruding which you might be able to get some mole grips or pliers on, failing that cut a small slot with a junior hacksaw and use a screw driver to remove or drill a very small hole and use an easy out to remove what’s left of the sheared off screw. It’s a pain but it’s doable! 

[tompato]

Yeah I'll give both of those a go at some point. At least it's still attached so I can use the mount tonight 🤣

[jock1958]

Haven't been entirely satisfied with my slo mo controls especially in azimuth which has been intermittently stiff in operation even after adjusting the brass locknuts and tension screws on the worm drive housing,  so bit the bullet and stripped it down.  Note: mines second hand with no warranty!

Its fairly straight forward and only tools required were a small Allen key & torx bit.

On strip down I found all the components extremely well engineered and lubricated with either lithium or graphite grease mainly on the worm shaft and gear wheel and other specific areas. The design is clever and from what I can see it works on a simple slipper clutch design (with the aid of nylon washers) so when you tighten the friction knob it basically clamps the mechanism together which engages the slo mo control worm drive but also allows you to move the mount by hand. 

One thing I found there was no grease between the brass top hat bushes x2 and worm gear shaft which resulted in the shaft and top hat bushes rotating together in the shaft housing which was giving me the occasional stiffness that I mentioned above. This can be checked easily without stripping down by marking the top hat bushes (inside of white nylon washers) with a felt tip pen and rotate the slo mo control, worm shaft including locknuts should rotate top hats should remain stationary, see pic below.

 

Once stripped down I slid the two top hats inwards and greased the contact areas of the worm shaft and ensured the outside surfaces of the top hats and worm housing were de-greased. 

Before fitting the worm shaft into the housing I put a few drops of thread lock on the outside surface of the top hats to stop them rotating which so far has worked a treat.

Re-assembly is fairly straight forward, but take care that you don't over tighten the three small torx screws that holds the silver circular clamping plate in place, I tried it and axis was quite stiff to move (found these screws held in with thread lock).  I haven't any info on the torque loadings of these screws so I nipped them up with some more thread lock.

All in all I'm very happy with butter smooth operation but like I said I wouldn't have attempted this if I was the first owner with it still in warranty.

Some pics below of it stripped down.

  

 

 

Edited August 31, 2021 by jock1958

[JeremyS]

Glad to hear you’ve e solved your problem @jock1958

But what are the top hat bushes?

Is what I’ve marked one of them?

[jock1958]

34 minutes ago, JeremyS said:

Glad to hear you’ve e solved your problem @jock1958

But what are the top hat bushes?

Is what I’ve marked one of them?

Thanks Jeremy, that’s the top hats I should have marked them before I hit the send button.  Pic of typical top hat bush below 

Edited August 30, 2021 by jock1958

[jock1958]

Hi @JeremyS have marked & labelled the bits I mentioned in my post above, have also added some more thoughts on the design and operation which I hope will be of use to Scopetech Zero owners.

 

[JeremyS]

2 minutes ago, jock1958 said:

Hi @JeremyS have marked & labelled the bits I mentioned in my post above, have also added some more thoughts on the design and operation which I hope will be of use to Scopetech Zero owners.

 

Thanks for the update. I checked the top hats on my Zero and they were not rotating when I used the slo-mo, which is consistent with what you say should be the case.

[jock1958]

8 minutes ago, JeremyS said:

Thanks for the update. I checked the top hats on my Zero and they were not rotating when I used the slo-mo, which is consistent with what you say should be the case.

Great, if ain’t broke don’t fix it 👍