How to - replace nlyon slider in AutodomeII motor dome for Sirius Labs dome

[g__day (Matthew)]

So I need to swap over a nylon spacer in my astrolab - that ensures the Dome rotation motor's gear is in the right position on the track. It sits in a metal housing held in blace to a steel bracket attache to the motor by 3 horizontal and 2 vertical bolts.

I am trying to understand how to replace the two vertical bolts. The horizontal ones seem accessible through the motor housing itself - so very simple to get to. The two vertical bolts seem much harder to access.

Does anyone have or know where to find installation instructions? Is it like detach the three horizontal bolts - slide the whole housing unit along the track so its easy to access - then remove the two vertical bolts - swap over the nylon slider and then reverse the process?

I mounted this on a dome ring on my own 2.2 metre square dome; so if it requires detaching the motor unit then this won't be simple - it would involve removing steel roofing and tearing walls.

If it is a special tool or long philips screwdriver or a right angle screw bit then I can look for one of these.

The first step before I fiddle around is ask if anyone here has the replacement instructions or know how the job is mean to be done. I have reached out to the seller, MaxDome forums and Sirius Labs - and am awaiting feedback.

Many thanks,

Matthew

PS

I will check tomorrow - but I really hope it is as easy as the top slide comes off with by undoing the three bolts - that would really be a logical design - fingers crossed. Amazing that it is so hard to find the assembly instructions!

PPS

Going through my original MaxDome set up posts of 2015 - I see HOughty, wOmbat, Jase and Peter Ward use these dome control set up - guys do any of you change the nylon slider or have dissassembly / reassembly - or original installation documentation you could share please?

[Leo.G (Leo)]

Matthew you've probably already looked at the facebook page I found through CloudyNights but here's a link in case it helps.
I can't check, I don't have an FB account.


https://www.facebook.com/siriusdomes/?_rdr


I will however see if I can find instructions anywhere online, I have the time.


There may be something in these older IIS threads:


https://www.iceinspace.com.au/forum/...d.php?t=200529


https://www.iceinspace.com.au/forum/...d.php?t=111503




Some other possibly non related finds:



https://www.beckstromobservatory.com...lable-options/


https://shoalhavenastronomers.asn.au...01/Maxdome.pdf


https://stargazerslounge.com/topic/3...ather-monitor/

[g__day (Matthew)]

Excellent links thank you!

I have seen many of these links but my search so far is fruitless!


When I feel a bit better I will inspect it and see if I am lucky and if it dismantles the way I imagine it will!

[g__day (Matthew)]

Well success - my initial insight seems correct! The nylon slider is mounted in a upside down U shaped metal holder and this is held by three bolts to the motor unit. So I just have to get to these bolts - and a magnetic screwdriver should be able to do this (I just checked) with a normal one - I just have to be careful not to drop the bolts!

So tomorrow when I should be feeling a bit more healthy I will give it a go!

Thanks all,

Matthew

[g__day (Matthew)]

Thanks again for trying Leo!

I hope the bolts are steel (and thus magnetic) - not stainless steel - as two are rather close to the motor so hard to get at; I may end up putting a clear tube over the screwdriver head and shaft - so if the bolt drops its gets held in the tube rather than fall down into the gear!

[g__day (Matthew)]

Does anyone have hints for how to confirm the optimal distance from nylon slide to the rotator gear?

I noticed the new track has a wider tooth and valley design - and I think the gear wheel sits deeper in it -so I wonder if it sits a 0.5 mm or deeper into the track - meaning the nylon slide may need a packing piece to sit the correct distance from gear wheel?

Owen from Sirius Domes said you may need to put a bit of carboard in - I wonder does he mean between the metal housing of the slider and the nylon - to make it sit lower and closer to the gear.

When I repalced the final fourth section of the track - and before I have changed teh slider - I notice the track segment jammed in a few places - and needed a slight push or a slight change of height of the track neare the motor - a push up or down - to get it turning well.

It makes me believe the track height and distance from gear wheel to nylon slide has to be very finey adjust to get it to all works reliably agin - my job for this week!

At least the home position sensor I bought from Digikey in the USA (for $12 + shipping) worked perfectly!

[g__day (Matthew)]

So quite a bit of success!

I replaced the nylon spacer - bit of fiddly effort there - it is simply remove three bolt and the nylon spacer unit disconnects - you just have to make sure the bolts don't drop anywhere hard to get too as the motor housing flops down and feels rather loose and the bolts were just resting with friction and gravity...

The old nylon spacer unbolted easily - but the new spacer had one of its two attachment holes drilled in a slightly different location - about 4mm from the old unit holes. This wasn't too hard to re-drill and countersink with my drilling gear.


Reattaching the unit was challenging - as I found in my astro lab - custom built - the track sits about 4-5mm from the motor control unit - so I never knew this before and I guess I need to add packing pieces to the brackets - I had to apply a bit of strength omce teh slider was over the track to bend it 4 mm or so into position so the motor unit could attach to it!

So this means there is a lot of stress (and thus wear) on the outer edges of the nylon washer to pull the track into position this wears the outside corners of the slider badly over time!

I wonder if me mounting the dome on my own astro lab on the supplied ring means the motor unit sits differently to how it would sit in a full Sirius labs assembly.

To get around this I plan add 3-4mm packing pieces between each bracket and the track - so Astrolabs assembly will become dome -> bracket -> packing piece -> track to move it closer to the motor unit.

So question to folks with Sirius labs - for you does the track normally sit square in the middle of the nylon washer with no effort? If this is the case I guess I definitely need to simply add packing pieces.

So the track turns much better now - there is one pinch point in one direction where the track sticks - I think it needs to be either in 4 mm or down 1mm.

[g__day (Matthew)]

Could anyone with an Sirius Labs dome and a MaxdomeII motor share a picture of how close their track is to the control box on the left vs the right hand side of their motor unit please?

I notice on the left hand side the track is maybe 10 mm away from the edge of the motor box - but on the right hand side its about 20mm - it puzzle me very much why it is not sitting equidistant when the unit is fitting snug in the mounting ring all the way!

[g__day (Matthew)]

Well the dome rotates both ways now - success

I put a 60mm long strip section of new toothed rail over the old - set the the correct height - and not more stoppages or snare points.


But it goes to show for anything precision like this the fitting instructions I feel should have been all lot more detailed and cover how to fit on a ring as opposed to the normal Sirius labs vertial cylinder.


The main point it should have covered I feel would be to set the rail heigth at the point where your motors gear wheel will be - and rotate the dome setting all heights relative to that one fixed point in space. That way if the dome's surface was even slightly uneven - the rail would always be at the same height as it passes by the motor.

I would guess in my dome the rail height may vary by +/- 4 mm. The bigger issue I am pondering is what distance the motor gear should be from the side of the dome. I still feel mine is out about 5mm more that it should be - I have emailed Owen at Sirius labs about this to see what he reckons.

So a request to anyone with a motorised 2.3metre Sirius lab dome - could you provide me four measurements please:

1. How far your rail is from the side of the dome - mine is about 55mm
2. How far the centre of your nylon slide's groove for the track is from the side of the dome (reckon mine is closer to 60mm - hence the excess stress)
3. How far the left hand side of your motor control box is from the rail (mine is 15mm) and lastly
4. How far the right hand side of your motor control box is from the rail (mine is 25mm)

PS

Dome Auto calibrated again for new track (201 revolutions versus 227 to rotate the dome fully - as the new track spaces the teeth further apart and with broader peaks and valleys). Alignment between scopes and dome slit great on half a dozen dispersed targets

[g__day (Matthew)]

Guys can anyone with a Sirius Labs dome help please (I know a few folk here have these units) - it is really just the first two measurements I need most - if anyone could provide me with those two distances it would really help me out!

Thanks,

Matthew

[g__day (Matthew)]

So someone selling their dome (look it up - these are great value, reliability and convience - and they hold there resale value very well) - has shared their Dome <-> rail distance is the same as mine, the spacing on the side of the motor unity LHS and RHS is the same as mine - but there motor to dome distance is 40mm wheras mine is 60mm!

Waiting for Owen at Sirius Labs to come back to me (or anyone here, or on the Maxdome II forums or on Cloudy Nights Observatory forums) - hopefully a few more folk can share there data and I can then lock in the best mechanical solution!

[g__day (Matthew)]

Why tracks sometimes get their teeth sheared off - I think I have seen the problem and a very simple fix to avoid this ever occurring again.

I think I have discovered how my steel tracks lost a few teeth - and it all comes down to one design decision coupled to installation instructions that lack a warning about one use case that absolutely must be avoided - a non level track based at your motor position!

The original installation instructions for my Dome ring specified where to bolt the brackets that hold the track to the dome - using wooden L shaped blocked that you place on your dome cylinder or dome ring at set positions around a compass - basically at 8 compass bearings that are 45 degrees apart. The L shaped blocked are designed so you mount your steel track at the right height for the motor kit.

But this presumes the dome is perfectly level - if for any reason it is not then when a bracketed segment of your dome turns to the motor - well at that point - and really that point alone it needs to be at a very set height and distance from the motor. If your dome ring wasn't level then the L brackets spread around a non level dome will mean you are either slightly too high or low when that part of the dome ring passes by the motor!

This leads to the second and more serious problem - the bracket being too high or low means the motor gear and slider pushes the track either up or down - with some force as that segment of track approaches the motor. Now all the brackets are only mounted to the dome with a large washer and a 25mm long M6 stainless bolt - but with just one bolt. This means over time the track can be continually forced up and/or down as it passes around the motor location. This can cause it to loosen as it continually shift up and down over time. You would need two or more well spaced bolts to prevent the bracket ever turning over time.

There are 8 brackets supplied - four bolt at the mid point of your tracks with a single M5 bolt and four join two track segment together so they are bolted with two bolts. The segments held with just one bolt therefore are even more susceptible to working loose from these turning forces over time.

This sets up for a catastrophic failure over time - because if a bracket raises or lowers by too much then it will hit the nylon slide - and either gouge through it if you are lucky - as evidenced by mine (my nylon slider has these exact gouge marks where over time the bracket started hitting the slider until one day it hit too hard; if you are unlucky the the bracket attaching will hit the slide and jam - while the motor forces the track to try and turn.

It is this situation of jamming that can shear the tips of your track and then you are left with a damaged track that will stall when that segment of track is reached.

The way to avoid this is really simple - 1) really precisely set the vertical height of each bracket so the track is at the correct height when it passes the motor location and 2) all the brackets should be double bolted to the track and the brackets themselves should have been double or triple bolted to the dome.

With this design the track will never shift position and the motor won't get jammed by a bracket hitting the slider.

Owen from Sirius Domes mentioned a few folk had track segments that lost teeth - I believe this is the reason why - having watched it happen! I will pass these suggestions on to him!

[g__day (Matthew)]

Hi Leo,

Many thanks for really trying - and it points to part of the issue I raised - a lack of solid documentation. So a Dome rotation kit costs about $3,000 to $4,000 - not cheap but really worth it. You think it would be well documented - especially how to fit it correctly - but there you go!

Still waiting for Owen's latest update...

[g__day (Matthew)]

I found the original fitting instructions filed away (in a sealed astronomy box of old gear - in a mostly dis-used outside toilet ).

So I am a bit of a hoarder it seems!

So the instructions on the first two pages should have said rotate the dome so each bracket will be positioned to the exact same vertical height at your desired motor location - rather than just move along the dome when positioning brackets using the three wooden L shaped spacers; that one change in instructions could have saved so much pain!

[g__day (Matthew)]

Leo - well done!!!

BTW - Owen emailed me to say he should have stainless steel rails available shortly and nowadays the brackets are shipped with double bolt holes so they can't twist up.

I shared the original fitting instructions with him - and the suggested amendments so folk know what to do so the track doesn't lift up and cause the bracket to hit the slider and jam the track whilst the motor is still turning =- which causes it to chew the tips off a stalled track!!

Matt