Skytee 2 - another design flaw

[RobertI]

I was on holiday in North Norfolk last week and looking forward to making use of the dark skies to do some visual observing. Sadly all I got was seven nights of solid cloud, which was a great disappointment, although North Norfolk itself was superb . One cloudy evening, I decided to take the Skytee apart to see how it worked. I felt a bit like Alan Partridge sitting in the Lintern Travel Tavern dismantling his Corby Trouser Press. Anyway it all seemed very straightforward so I tightened a ring to try and reduce the play in the vertical axis. It didn't really work and I think the play will remain due to the low tolerances of the manufacture. However encouraged by my success in re-assembling it (unlike Alan Partridge) I decided to see whether I could reduce the backlash in one of the axes. I set about adjusting the worm, a procedure I have performed successfully many times on the CG5's I have had. To my dismay I stripped a thread on the central bolt - I couldn't believe it as I had applied very little pressure. Closer inspection revealed yet another flaw in the design; the screw was not long enough and only a couple of threads were able to make contact. The slightest pressure caused the aluminium threads of the work housing to disintigrate:

 

Not sure how I am going to resolve this yet - I am sure it will be a painful process though. Any thoughts appreciated.

For those that are interested here is the setup I was planning on using:

 

[Chris]

Hey Rob, not great by the sounds of it, I can't believe you didn't get at least one clear night either

The only thing I can think to resolve the stripped thread is to use a thread repair insert similar to the one in the link below:

http://www.pvrdirect.co.uk/sealey-vs311-01-thread-inserts-m8-x-1mm-for-vs311-pack-of-5/?CAGPSPN=pla&CAAGID=25337172250&CATCI=pla-54458723577&catargetid=120134430000000121&cadevice=c&gclid=CjwKEAjwya-6BRDR3p6FuY2-u3MSJAD1paxTy6SWD_1CpKYwcPeJIRRHgb4QtNF0kUJ_WrMzud2ekRoCSnnw_wcB

What a pain for you though. It would be interesting to know if other Skytee users have a foreshortened central bolt? (Ooh-err!).

I don't know why all these mounts come with tons of backlash as standard? The one I had cetainly had plenty on the alt axis. I know they are made to a price point but I'm sure most would pay an extra 20 quid or so for a mount that is better tuned.

[RobertI]

Thanks Chris, the thread repair option looks promising although I guess I would still need to source a longer bolt? Not too difficult I guess. Thanks for the link.

Although I like the Skytee 2, I don't think I would recommend one as a new purchase; better to get one with upgraded thumbscrews/saddle  (as the threads strip on the factory thumbscrews as I discovered) and all the other problems 'tuned out' by the seller. In many ways perhaps they should sell the mount without saddles at all (like certain other altaz mounts) and that might allow them to produce a higher quality mount at the same price point. Just a thought....  

Rob

 

[Stu]

Bit of a nightmare Rob, I hope you get it sorted. I've never tried a SkyTee, but I must say they look a little over complicated for the job they do, and the feedback on them is quite mixed. I do prefer the simplicity of the Ercole mount, but then I'm not a fan of slo mo controls so I know this is an issue for some.

[RobertI]

Thanks Stu. Normally I don't bother with all the counterweights and just stick a scope on one or both sides like the ercole. But I thought as I had time on my hands I would give it a go and see what the experience was like. As my main aim was to to compare objects see n through both scopes I was especially interested in the ability to accurately align the scopes with each other for comparison of views at higher power. Never got to find out! My next purchase is probably a Giro Mini or Berlebach Castor for lightweight grab and go viewing. Looking forward to some precision German engineering!

[spaceboy]

Personally I would tap the stripped thread and buy the next bolt up to the length required. If the unthinkable was to happen again in the future then a thread repair insert would drop nicely into the now larger hole.Taps can be purchased single or in a tap and die set from machine mart, tool station and the like. Again personally I'd get the set as they are handy for all sorts of things. As long as you drop a little oil on the tap and thread a little at a time not going gung ho wrenching on them they will last ages.

[RobertI]

Thanks Spaceboy. I do actually have a tap and die set so could do this. There is not a lot of depth to play with so I may have to remove the shaft to allow the tap to go deep enough and potentially out the other side. Also the head of an larger bolt (eg: M8) will not fit into the existing gap so I would have to expand that too, but it's doable, just finding the time.... Thanks again.

[Merlin]

Use paraffin as a lubricant for the taps. Oil isn't suitable for aluminium.

[spaceboy]

7 hours ago, RobertI said:

Also the head of an larger bolt (eg: M8) will not fit into the existing gap so I would have to expand that too,

Could you not use a hex cap bolt instead ?

 

2 hours ago, Merlin said:

Use paraffin as a lubricant for the taps. Oil isn't suitable for aluminium.

Are sky-watcher mounts aluminium? I'd always thought they were cast zinc ??  

[Dave Lloyd]

28 minutes ago, spaceboy said:

Could you not use a hex cap bolt instead ?

 

Are sky-watcher mounts aluminium? I'd always thought they were cast zinc ??  

They might be a zinc alloy, I don't think pure zinc would be strong enough.

[Macavity]

Had troubles in the same general area. Can't remember quite why, but I need to put
a washer under one of the bolts on either side of your "problem" one. One of the
TINY hex grub screw adjusters has stuck fast too! There's a good mount struggling
to get out IMO though. But it's finding the TIME to fix all these things, innit, Eh?

Nil desperandum? "Chin up" lads / lasses etc. etc. 

[RobertI]

36 minutes ago, spaceboy said:

Could you not use a hex cap bolt instead ?

 

Are sky-watcher mounts aluminium? I'd always thought they were cast zinc ??  

The existing bolt is hex cap and quite narrow so I think an larger bolt will be too big unfortunately. Thanks for the idea though.

 

5 minutes ago, Macavity said:

Had troubles in the same general area. Can't remember quite why, but I need to put
a washer under one of the bolts on either side of your "problem" one. One of the
TINY hex grub screw adjusters has stuck fast too! There's a good mount struggling
to get out IMO though. But it's finding the TIME to do all these things, innit, Eh?

Nil desperandum?

Time...if I could have one wish it would be for more time....   I guess this is what precision engineering buys you, extra time in that you don't have to fiddle and fix things!