Skytee II - movement when axis locks applied

[John]

Overall I'm a big fan of the Skytee II mount and have enjoyed using mine with a variety of scopes for quite a few years now.

I've got the slow motions adjusted nicely so there is practically no backlash on either axis.

The only remaining gripe that I have with the mount is a small movement around an axis (alt and azimuth) when I lock it.

The amount of movement is quite small but it is enough to push a target just out of the field of view when using high magnifications (eg: 200x plus).

I've been scratching my head over what might be causing this

I've tried removing and checking the locking levers and the brass inserts that they tighten. There is a brass plug / bush below each one that bears against the axis shaft but I assume that is normal. The levers seem in good order and I keep the small screws that hold them in place tight.

The axis of the mount are well lubricated and the mount moves very smoothly when the locks are loose and also when they are tight and the slow motion knobs are used.

I can't understand why increasing the pressure of the locking screw against the axis shaft, to lock it, should result in this small rotation of the shaft 

Has anyone else experienced this and, if so, does anyone know of an adjustment that stops it happening or at least reduces it to a minimum ?

Many thanks

 

Edited May 19, 2021 by John

[banjaxed]

16 hours ago, John said:

Overall I'm a big fan of the Skytee II mount and have enjoyed using mine with a variety of scopes for quite a few years now.

I've got the slow motions adjusted nicely so there is practically no backlash on either axis.

The only remaining gripe that I have with the mount is a small movement around an axis (alt and azimuth) when I lock it.

The amount of movement is quite small but it is enough to push a target just out of the field of view when using high magnifications (eg: 200x plus).

I've been scratching my head over what might be causing this

I've tried removing and checking the locking levers and the brass inserts that they tighten. There is a brass plug / bush below each one that bears against the axis shaft but I assume that is normal. The levers seem in good order and I keep the small screws that hold them in place tight.

The axis of the mount are well lubricated and the mount moves very smoothly when the locks are loose and also when they are tight and the slow motion knobs are used.

I can't understand why increasing the pressure of the locking screw against the axis shaft, to lock it, should result in this small rotation of the shaft 

Has anyone else experienced this and, if so, does anyone know of an adjustment that stops it happening or at least reduces it to a minimum ?

Many thanks

 

I am not familiar with this mount but notice you have owned it for “quite a few years “. Could it possibly be worn or has it always had this problem.

[John]

52 minutes ago, banjaxed said:

I am not familiar with this mount but notice you have owned it for “quite a few years “. Could it possibly be worn or has it always had this problem.

Thanks for the reply. This issue seems to have become more noticeable over the past few months.

It could be a case of wear but I'm trying to work out where that could be happening. The locking mechanism is very simple - just the pressure exerted by a screw on the axis shaft with a brass plug / bush in between the end of the screw and the axis shaft surface.

 

 

[jock1958]

Hi @John I’ve just had a look at my ST 2 and apart from a small amount of backlash when the axis are locked there’s no additional movement. 
If it’s a fairly recent thing just wondering if the locking collars at the end of the rotational shafts have worked loose?  from memory they are held in place by 3 grub screws.

Last time I stripped mine down I also ensured the contact areas of the Alt & Az shafts and locking lever bushes were thoroughly de-greased. 

Edited May 21, 2021 by jock1958

[John]

10 minutes ago, jock1958 said:

Hi @John I’ve just had a look at my ST 2 and apart from a small amount of backlash when the axis are locked there’s no additional movement. 
 

 

Thanks for the reply.

Maybe that small amount of backlash is what I'm noticing ?

It is slight but just enough to move a target out of a high power field of view as the lock is applied.

Maybe I'm getting a bit fussy !

 

 

Edited May 20, 2021 by John

[jock1958]

Hi @John you probably know this already but if you can’t see anything obvious you can always adjust the slo mo worm gear housings. I did this on a number of occasions to get rid of some backlash and am happy with it as is (with a bit of backlash) 

Edited May 20, 2021 by jock1958

[chiltonstar]

John - I wonder, did the solution above solve your problem? I too have slight movement on the azimuth axis, which isn't removed by adjusting the worm against the gear wheel - my assumption is that this is due to the gear itself moving slightly on the shaft. Clearly, I need to carry out a complete stripdown (there's a post from BomberBaz with details I believe).

Chris

[John]

1 hour ago, chiltonstar said:

John - I wonder, did the solution above solve your problem? I too have slight movement on the azimuth axis, which isn't removed by adjusting the worm against the gear wheel - my assumption is that this is due to the gear itself moving slightly on the shaft. Clearly, I need to carry out a complete stripdown (there's a post from BomberBaz with details I believe).

Chris

Hi Chris,

I've not had the chance to try it out yet. I'll post back on here with the results when I have