A very large Goto GEM built with DIY techniques.

[MarcusH]

Feeling the peer pressure already.😅

Nah, just kidding.😁

Let's see if I can't whip up some sort of preliminary sketch....

[JamesF]

15 minutes ago, MarcusH said:

Feeling the peer pressure already.😅

You sure that isn't pier pressure?

James

[Chriske]

Awesome project..!!

I'm drooling here...

 

[Rusted]

5 minutes ago, Chriske said:

Awesome project..!!

I'm drooling here...

 

Thanks.

Shall I get some paper towels?

Edited January 28, 2020 by Rusted
typo

[Rusted]

Episode 11. Correcting the most obvious Fullerscope MkIV design flaws: PA support fork:

In the last [rather wordy] episode I discussed the weak "ears" of the PA support fork of the MkIV
Also, how the short screws were very limited in their ability to tighten the fork tines firmly onto the Polar Axis casting.
So my big mounting went totally overboard in fixing these perceived design flaws.

 

Once again the scrap metal gods smiled on me and provided a strip of 20mm thick aluminium at precisely the time I needed it.
After making a rough, cardboard template, to check the dimensions needed, I miter sawed it into three pieces.

As in all, low budget projects the available materials define the build.
So I kept one rectangular piece for the base plate and made the fork tines as tall as possible.
This is important for matching the longest possible PA housing while allowing adequate clearance for the 11" RA drive wormwheel.

The 12" compound miter saw was actually bought for building the dome but I was advised that it would also cut aluminium.
It does! But makes one hell of a mess of the lawn! Paraffin [heating or odour free, lamp oil] makes an excellent cutting fluid.
I just brushed it generously along the marked cutting line each time and this really helped to avoid aluminium welding itself to the saw's teeth.

These heavy fork tines were then drilled and tapped on their lower edges and fixed to the base plate through recessed holes.

 

 

This heavy fork is to support the weight of the rest of the  mounting, telescopes and counterweights while allowing altitude adjustment.
The altitude pivot is a 16mm stud with pretty brass domed nuts for a bit of character. It is placed to just miss the Polar Axis shaft.
So the stud can be tightened to the breaking limit of  the nuts if so desired. Though it isn't remotely necessary, of course.

The very solid, Polar Axis, bearing housing is clamped very firmly between the support fork tines.
I actually used the PA bearing housing as a spacer for the fork tines as I fixed their exact position on the base plate.
The hope is that this heavy clamping effect will further reinforce the already massive fork against any chance of twisting.
 

A turnbuckle is hidden inside the support fork to allow fine adjustment of PA altitude. I'll show that in a later episode.
The northern plate of the fork [with the large hole for hand insertion] provides a further clamping surface.
I put my hand through the hole to adjust the turnbuckle for PA altitude.
This large hole was cut with a hardened tooth, hole saw in the bench drill with more lamp oil to aid cutting.

[Dr_Ju_ju]

Brilliant !!   now what monster OTA(s) are you planning to put on ?? 🤔 

[Rusted]

30 minutes ago, Dr_Ju_ju said:

Brilliant !!   now what monster OTA(s) are you planning to put on ?? 🤔 

Thanks.

Until last week the mounting held a 7" f/12 refractor, a 6" f/8, modified PST, H-alpha refactor and a 90mm f/11 Vixen. [With a 9x50 finder. Just in case.]
I am presently building a completely new 6" f/10 iStar, H-alpha, modified PST refractor. Which will join the 7" f/12 [for solar white light.] 
The Vixen will be rested as somewhat superfluous.

[Michele Scotti]

On 27/01/2020 at 07:56, Rusted said:

The more typical DIY habit of fixing pillow block bearings to a flat plate, or even plywood, is fraught with danger.
A flat plate, or even an inverted U-beam, are the weakest forms in twisting.

Can you elaborate on this?

I understand that the flanged bearing and "boxed" approach holds the inherent value of offering solid sides for the fork on the RA axis.

[Rusted]

I was basing my statement about pillow block bearings on half a century of examining mostly amateur, equatorial, mounting designs.
The wide spread of the "ears" on the pillow block, bearing housing usually suggests a flat plate approach to fixing the axes bearings.

Having handled strips of many different materials over a very long period, I have become aware of their natural characteristics.
Pillow block bearings on the tops of fork tines make more sense. Though flange bearings will better spread the loads into the sides of the tines.

Handling a wide variety of beam shapes, I, U and T, and the typical, double-U "girder," it is obvious where real stiffness lies. They all lack stiffness in rotation.
Torsion loads will twist each of them far more easily than round tubes or tubular box sections of similar proportions and materials.
One only has to handle the same cross sections in plastic to become acutely aware of how much larger sections in steel will behave.

Depth of a section is vital to beam stiffness but the width of the section must also match the likely torsion loads.
Deep floor joists are typically braced against rotation. Using any "steel girder" section as a telescope pier will be an exercise in frustration!
Too heavy to lift unaided, but still twists like a plastic roof gutter! Gutters are one of the weakest sections in torsion you could possibly imagine.

[windjammer]

Hi 

Great thread, can't wait for the next installment. I finished my own monster bearing block GEM about 18mths ago and have been enjoying it since.  Its carrying about 30kg now as bits have gone on.  But starting to collect parts, materials and ideas for a mark2!

I used 2inch pillow blocks, and as you say, ended up fixing them to flat plates.  I looked at the flanged bearings and couldn't see a way to make them work without welding up a bearing box (not in my skill set unfortunately!).  I am amazed that your bolted up boxes are strong enough - they are very elegant solution.  A problem I came across in previous models is that if the scope is unbalanced and heavy then the slow motion drive ends up winding up the metalwork and bracketry rather than turn the shaft.  When the tension in the metalwork gets high enough, the shaft lurches round and the winding up starts again.  So preventing twisting is key, as you say.

I looked at 2inch ground solid shafting - cost alone put me off that, never mind the weight of it!  It speaks well of your design that the bearing boxes can carry this.  I went for 48mm scaffolding pipe with 5mm wall and shims to fit into the 50mm bearings.  My research seemed to indicate that tube was actually more rigid than solid bar?  Being hollow one can fit barrel nuts into the tube to attach gears and plates to the ends.  Your shaft clamps look huge - did you look at taper bushes with bolt on hubs ? I thought I might experiment with these in Mk2.

Very interested to hear about the drive arrangements you have used.  Those worm wheels look very handsome - did you hob them yourself on the lathe?  I did not find wormwheels and worms at a reasonable price (for what might not workout) so went for straight cut MOD1 spur gears. Two problems with these: unbalanced loads get transmitted back through the gear train in a way that the worms don't, and the very devil of backlash - which means having a friction brake on each shaft to control slop is mandatory.  As it happens, I wanted a design where the gearing could be uncoupled so that the axes rotate freely - so having friction brakes was needed anyway.

I found it difficult to get motors to respond over the speed range for tracking and slewing. If,say, you want an axis to slew at 1 turn in 2 minutes and track as well (1 turn/24hrs), that is almost 1000:1 speed range.  So I ended up with 2 motors per axis - one for slew (DC motor) and one for track (stepper) and a remote controlled gearbox to swap motors.  Making 4 motor controllers got very boring! - but in the end what sounds OTT has ended up as very reliable.  How did you manage this aaspect ?

The wedge has ended up being the weakest point of my effort - rigidity, and its size and shape have given rise to collision issues when pointing south at higher elevations.  The way you have angled the yoke arms is clever. It is impossible to imagine every position the OTA can take and arrange the metalwork accordingly!  Your huge refractors must make this an issue ?

I pivoted the wedge around an M16 stud like yours.  I think perhaps it is not beefy enough.  I was toying with the idea of using a short length of 2inch pipe rotating on V blocks as the pivot.  A high end mount I saw at a show made intriguing use of a dividing wheel to adjust the wedge angle.

Thinking about this brings back hilarious memories of weekends trying to machine stupidly large chunks of metal in a  small drill press.  Drilling and tapping M16 into steel and aluminium is quite something - watching huge curls of swarf come off the drill while frantically squirting cutting fluid onto it. Great stuff.

Looking forward to your next episodes

Simon
 

[JamesF]

Are there pictures of your mount, Simon?  I'd love to see them.

As regards the comparative rigidity of tube and solid bar, I don't think there's really very much in it as long as the wall of the tube is sufficiently thick (clearly a tube of tin foil is never going to be very strong).  As I recall, stiffness varies with the square of the diameter, so that's what really makes the difference.

James

[Rusted]

Thank you for your very thorough post Simon. It all sounds fascinating.
We really do need to see some pictures of the results of all your great ideas and all that effort!

I was able to access 50mm stainless steel bar at cost, locally. So maximized all the consequences of that choice.

It is a difficult to pin down what will work with particular telescopes. A lengthy, f/12 refractor is not remotely a compact f/12 SCT.
So I used the D&G optical website for shaft size suggestions against refractor size.
They have been at it for decades so know what works. An AP Titan was just outside my "scrap metal builder's "budget.

Rather than respond directly to all your points I will post another episode on the drives today.
That will share the information more widely in case it aids other's build projects.

I have been rather busy building a new 6" H-a telescope. This will be a foot [30cm] longer and a bit heavier than the last one.
I shall be mounting the 180/12 and 150/10 side by side again but no 90mm/11 this time.

Plans to make the scopes easily removed and replaced individually did not work out.
Not even with my 3x4 overhead, pulley system. The scopes were actually quite manageable.
Adding and removing 5kg weights from a stepladder was just too difficult and too dangerous for me! 

[Rusted]

Episode 12. Drives: Wormwheels & worms:

I waited months for the wormwheels and worms from Beacon Hill. I had ordered an  11" and an 8" with 50mm bores and matching stainless steel worms.
After endless excuses they admitted they could not supply them. So out of desperation I accepted a pair of wormwheels with the wrong bores.
60mm instead of 50mm. That meant turning bushes [in my lathe] to match the difference in diameter. Which is a serious "No-No" in mechanical terms.

Concentricity of the insides and outsides of the bushes must be maintained or the wormwheels will be eccentric.
So I turned and bored [brass] bushes without removing them from the 3-jaw chuck. It seems to have worked.

On arrival, the 11" wormwheel proved to have some serious "issues" apart from the "bad teeth."
The single nylon pad "clutch" soon proved to be totally inadequate to the task. So I radial drilled the wheel hubs and the new bushes to make three clutch pads each.

Then the worms would immediately wind themselves out of their bearing housings during slews. So I added screws and oversized washers to restrain them inside and out.
The drive belt timing pulleys couldn't possibly grip the worm shafts well enough with only one grub screw. So I had to drill the hubs of those for extra grub screws.
[Much shorter than shown here.] Then I had to drill the edges of the worm supports so I could use a long series, hex key down the hole to reach the invisible grub screws.
The worm bearing housings are just a short slice of channel profile. It really isn't up to the task without further reinforcement. More on this later.

All this extra work was vital to making these commercial products into useful drives for a large mounting carrying long and heavy telescopes.
Without a lathe and bench drill it would have been impossible. Note that I used stainless steel hardware throughout. I hate rust!

I have no idea if Beacon Hill is still offering wormwheels.  At the time they blamed an elderly machinist giving up his role in their production.

In the next episode I shall show the worm bearing supports in more detail.

[Rusted]

Episode 13: Saddle and Declination attachment:

There is a lot of strain on the saddle to Dec shaft connection. So I used another Tollok bush embedded in a hefty brass sleeve turned in my lathe from a piece of scrap.
Only the short, flange section has quite a thin tube encasing it. The rest of the Tollok bush is encased in the full thickness of the massive bush.
Ensuring great resistance to expansion and flexure. The top, inner section of the Declination flange bearing fits tightly into the brass sleeve. Providing extra stiffness and a tidy appearance.

The saddle consists of two heavy 4" wide, channel sections of aluminium bonded and then bolted together at the flange and tube rings.

I shaped the two channel sections for maximum strength at the center while allowing the tube 8" rings to clear the channel at the tips. 

The ring of washers under the 10 x M10 screws helps to spread the loads from the saddle into the end of the Declination shaft.
I deliberately drilled and countersunk an inspection hole in in the center of the saddle. So I could easily confirm the shaft was pushed right up to the underside of the saddle.
The entire length of the Tollok bush carries the loads from its flange, through the heavy brass sleeve into the Declination shaft.

The Tollok bushes are easily removed from their respective shafts by removing the ten clamping screws.
Then the same sized screws are inserted into separate holes to push the two tapers apart.
I used stainless steel fasteners but was careful to lubricate all the threads to avoid galling during removal.
 

[windjammer]

Very interesting !  I had thought that Beacon Hill had gone - as of a few years ago I was searching for parts and they had disappeared.  I googled their web site now and they still have a catalogue with worm gear sets listed.  Sounds a bit hit and miss though.  Nice looking worms.

What gear ratio are the worms and belt drives ?  Is the stepper motor microstepped ?

The Tollok bushes look absolutely enormous !  I was able to bolt my gears directly to the DEC bearing plate (RA gear) and the saddle (DEC gear).  Here are some older pics of my gem during construction for comparison:

https://www.flickr.com/photos/31131978@N00/albums/72157683523839235

More stuff has been added since those pics - the GEM now carries an 150mm F5 refractor and a 90mm F10 guidescope, plus 3 video viewfinders at different FoVs.

I have put up some more detailed stuff as contact sheets here: If you fiddle with the full screen mode and + icon you should be able to see the individual pics at a reasonable size (I hope the links work...).

https://www.flickr.com/photos/31131978@N00/albums/72157712988317928

These two pics show how an M16 threaded rod is mounted inside the 2inch axis shafts:

https://www.flickr.com/photos/31131978@N00/49493473818/in/album-72157712988317928/lightbox/
https://www.flickr.com/photos/31131978@N00/49493472653/in/album-72157712988317928/lightbox/

These two pics show the RA axis attached to the DEC bearing plate through the drive gear:

https://www.flickr.com/photos/31131978@N00/49494189772/in/album-72157712988317928/lightbox/
https://www.flickr.com/photos/31131978@N00/49494188827/in/album-72157712988317928/lightbox/

That was not quite strong enough,so I fitted a key - first version:

https://www.flickr.com/photos/31131978@N00/49493975151/in/album-72157712988317928/lightbox/

But the screws sheared off, so stronger pins added:
https://www.flickr.com/photos/31131978@N00/49494183267/in/album-72157712988317928/lightbox/

These three pics show the attachment of the saddle to the DEC axis through the drive gear:

https://www.flickr.com/photos/31131978@N00/49494186572/in/album-72157712988317928/lightbox/
https://www.flickr.com/photos/31131978@N00/49493471228/in/album-72157712988317928/lightbox/
https://www.flickr.com/photos/31131978@N00/49493470093/in/album-72157712988317928/lightbox/

Looking forward to your next installment

Simon

[Rusted]

Hi Simon,

Absolutely incredible work! You are astonishingly inventive and creative!

I went for minimalism and simplicity. The Tollok bushes were a wonderful discovery for so heavy a mounting.
Encasing them in serious cross sections maximized their stiffness on top of incredible shaft grip.
They are normally used for seriously heavy chain sprockets and multi-V belt drives on heavy machinery.

My stepper motors are micro-step driven by AWR[Tech] with Intelligent Handset 2, simple handset and ASCOM[AWR] driver.
Not without endless problems but the latest ASCOM[AWR] driver is a vast improvement.
I was absolutely hopeless before that!

Beacon Hill is/was still going when I bought my wheels and worms 3-4 years ago.
The owner is aging and strictly pre-computer.
The website hasn't changed in years and can probably be ignored.
A telephone call will discover what can still be managed. Or [rather] promised. Eventually...
There was talk of finding a new wormwheel maker at the time I was involved.

Both wormwheels are 287T.  11" RA and 8.75" Dec. I asked for the 14" but they couldn't supply by then.
287 is far better than finer toothed IMO for DIY mountings. They are more "forgiving."

The BH worm housings are terribly flimsy and poorly designed. 
Needing lots of mods even to make them work as intended.
Very poor bearing retention and no real stiffness to the skinny, channel profile.

The worms moved sideways out of their housings almost on the first slew! Unbelievable!
The worm shafts are almost worthlessly short for timing belt drive sprockets.
I shall make some massive worm housings with far better and bigger bearings... one day.

A new episode is due. Probably about worm housings, their mounting and driving.

[MarcusH]

Wow, Simon, simply WOW ! 👍

That mount would be very unproductive in my hands, though. I would just stare at it the whole night, mesmerized, and forgetting all about imaging. 😄

[Michele Scotti]

3 hours ago, Rusted said:

The BH worm housings are terribly flimsy and poorly designed. 
Needing lots of mods even to make them work as intended.
Very poor bearing retention and no real stiffness to the skinny, channel profile.

The worms moved sideways out of their housings almost on the first slew! Unbelievable!
The worm shafts are almost worthlessly short for timing belt drive sprockets.
I shall make some massive worm housings with far better and bigger bearings... one day

my 2 cents - from previous picture the housing and bearing general dimension doens't look bad - I'd suggest to switch to tapered bearings with a (simple) system to pre-load one of the bearing. That will kill any lateral movement. 

Is the BH fixed or does it have a system to cope witht he inevitalbe run-out of the wormgear? 

[Rusted]

25 minutes ago, Michele Scotti said:

my 2 cents - from previous picture the housing and bearing general dimension doesn't look bad - I'd suggest to switch to tapered bearings with a (simple) system to pre-load one of the bearing. That will kill any lateral movement. 

Is the BH fixed or does it have a system to cope with the inevitable run-out of the worm gear? 

Thanks.

The 50mm bore, flange bearings are very large, self-centering in spherical housings and have a load capacity well beyond the needs of a humble telescope mounting.
I considered end loading the PA bearings [from below] but it never seemed necessary. I merely push the hefty bottom clamping collar upwards as hard as I can while tightening the three, large collar screws. I have considered using a strong coil spring to achieve the same end loading but finding a suitable example to slide over a 50mm shaft is difficult. 

I have a simple test of any equatorial mounting: Point it at the pole and then rattle the OTA up and down while holding the focuser body or locked barrel. Any flexure, or bearing play, is instantly sensed through the fingers. Particularly with such long and heavy refractors like mine providing plenty of leverage. 

I still plan to spring load the worms on sturdy hinges.  Presently I am using a pin to provide spring loaded rotation into the worm wheel. I believe a suitably tight, brass door hinge would be far superior. The worm bearing, profile housings are weak and need considerable reinforcement over and above my present arrangements. I need to add considerable cross sections to properly support the bearings against end loading.

Taper roller, thrust bearings, or even axial thrust, ball bearings, on the worm shafts would be better. Sadly, the worm shaft extensions are miserably mean. I am trying to avoid couplers just to hang the belt drive pulleys onto something more solid. The shoulders on the worm shafts cannot be brought inwards, to make room for better bearings, because of clearance problems on the large, wormwheel rims.

 

[windjammer]

>>Taper roller, thrust bearings, or even axial thrust, ball bearings, on the worm shafts would be better. Sadly, the worm shaft extensions are miserably mean

Maybe a small live centre pushing into a dimple on the end of the worm shaft would do the trick, either fixed or sprung - something like this:

https://www.arceurotrade.co.uk/Catalogue/Centres/Mini-Live-Centres

The one on the 10mm plain shank looks suitable.  No extra length on the worm shaft required.

Simon

[Rusted]

1 hour ago, windjammer said:

>>Taper roller, thrust bearings, or even axial thrust, ball bearings, on the worm shafts would be better. Sadly, the worm shaft extensions are miserably mean

Maybe a small live centre pushing into a dimple on the end of the worm shaft would do the trick, either fixed or sprung - something like this:

https://www.arceurotrade.co.uk/Catalogue/Centres/Mini-Live-Centres

The one on the 10mm plain shank looks suitable.  No extra length on the worm shaft required.

Simon

That's a fascinating idea Simon! Affordable too these days. Not sure how I'd cope with the extra width.
Though, as you say, the plain shank 10mm model would avoid the need for an angle grinder on an MT.
Cantilever the outer supports on a solid bar, or angle profile, without needing to replace the existing worm bearing housings.
Nor even disturb the belt drives. A nice and easy, bolt on-solution. Quite literally, lateral thinking.

Thanks for sharing your inspiration!

EDIT: Your link has awakened my interest in the bearings used in the BH worm housings.
I shall have to see if I can find a serial number to confirm angular contact type.

Edited February 6, 2020 by Rusted

[Michele Scotti]

7 hours ago, Rusted said:

I still plan to spring load the worms on sturdy hinges.  Presently I am using a pin to provide spring loaded rotation into the worm wheel. I believe a suitably tight, brass door hinge would be far superior. The worm bearing, profile housings are weak and need considerable reinforcement over and above my present arrangements. I need to add considerable cross sections to properly support the bearings against end loading.

I’d suggest a different approach: fixed bearing housing after lapping. The way I see it, is that you have a run-out from the shaft to tollok, tollok to sleeve, sleeve to worm gear I and finally ID to the generated teeth. Actually it’s not all –  your shaft has a nice press-fit brass thread. All of the mentioed interfaces might be very precise but they all come with few hundreths mm of run-out or clearance.

Lapping will take care of all of them. I have to be honest – never did it myself  just because I’ve recently stayed away from worm gears in my telescopes. Also I reckon it is only mandatory for Dec axis. It’s maybe a lengthy process (and messy?) but not that complicated. Let me know what you think about.

7 hours ago, Rusted said:

Taper roller, thrust bearings, or even axial thrust, ball bearings, on the worm shafts would be better. Sadly, the worm shaft extensions are miserably mean. I am trying to avoid couplers just to hang the belt drive pulleys onto something more solid. The shoulders on the worm shafts cannot be brought inwards, to make room for better bearings, because of clearance problems on the large, wormwheel rims.

I suppose the shaft material is not treated/hardened. You could tap an M5 and add an extension – belt&pulleys are pretty forgiving to run-out errors. I would never suggest that for a gear coupling. What is the ID/OD of the bearing and the width of housing? 12x30x8?

[Rusted]

6 minutes ago, Michele Scotti said:

I’d suggest a different approach: fixed bearing housing after lapping. The way I see it, is that you have a run-out from the shaft to Tollok, Tollok to sleeve, sleeve to worm gear I and finally ID to the generated teeth. Actually it’s not all –  your shaft has a nice press-fit brass thread. All of the mentioned interfaces might be very precise but they all come with few hundredths mm of run-out or clearance.

Lapping will take care of all of them. I have to be honest – never did it myself  just because I’ve recently stayed away from worm gears in my telescopes. Also I reckon it is only mandatory for Dec axis. It’s maybe a lengthy process (and messy?) but not that complicated. Let me know what you think about.

I suppose the shaft material is not treated/hardened. You could tap an M5 and add an extension – belt&pulleys are pretty forgiving to run-out errors. I would never suggest that for a gear coupling. What is the ID/OD of the bearing and the width of housing? 12x30x8?

Thanks. Re: Bearings: I'll get back to you on that. Easier in daylight when I'm not needed at dinner.
BTW: I have tried lapping the worms/wheels with assorted materials but is incredibly slow going even when the worms are motor driven.

[MarcusH]

47 minutes ago, Michele Scotti said:

Lapping will take care of all of them. I have to be honest – never did it myself  just because I’ve recently stayed away from worm gears in my telescopes. Also I reckon it is only mandatory for Dec axis. It’s maybe a lengthy process (and messy?) but not that complicated. Let me know what you think about.

 

36 minutes ago, Rusted said:

BTW: I have tried lapping the worms/wheels with assorted materials but is incredibly slow going even when the worms are motor driven.

Also lapping should only be done as a finishing touch to polish out the very last imperfections of the wheel, not correcting a run-out. And when lapping make sure that your worm is made of a much harder material (e.g. steel) that your wheel (e.g. brass) as you really do not want to deform your worm - at all. Lapping a brass worm against an aluminum wheel is a no-no as the two materials might be too similar in hardness. 

[Rusted]

13 hours ago, MarcusH said:

 

Also lapping should only be done as a finishing touch to polish out the very last imperfections of the wheel, not correcting a run-out. And when lapping make sure that your worm is made of a much harder material (e.g. steel) that your wheel (e.g. brass) as you really do not want to deform your worm - at all. Lapping a brass worm against an aluminum wheel is a no-no as the two materials might be too similar in hardness. 

All true, if the quality of machining supported the theory. I was even advised against lubrication by BH!
Note that I was expecting the "stainless steel worms" advertised on the Beacon Hill website to this day.
"The finest wormwheel sets available to astronomers in this country!"

Then, when I assembled the drives for the first time I could hear a nasty "graunching" on every worm rotation.
Slews became a constant reminder of the poor workmanship of both worms and wheels.
The worms were actually eccentric!

So I resorted to metal polish paste. A fine abrasive for cleaning chrome on old cars.
It didn't want to be a liquid or it might have found its way into the bearings.

I spun the RA worm using an electric drill and applied the paste.
It helped to polish the worm and the roughness of the machining improved.
Sufficient to end the horrible noises during slews.

Though there was no sign of any change on the wormwheel teeth.
Which were very rough and black with grime on receipt.
I had cleaned them thoroughly with a toothbrush and washing up liquid.

Copy and Paste from the Beacon Hill website this very morning: 7.02.2020

"Worm and Wheel Sets

 The matching stainless steel worms are held in sealed roller bearings in substantial brackets and are fully adjustable to eliminate any developing end float.
  They are the most accurate worm and wheel sets available to astronomers in this country."

£400 GBP + £60 delivery charges. Higher than the advertised prices [even today] and not to the ordered specification of 50mm bore.

In fact the worms are clearly of brass and the bearings are plain ball journal bearings.
With no obvious adjustment for end float and held in place by a thin film of shellac! [sic]
The solitary grub screw locked the races solid in the flimsy off-cut of aluminum channel profile, if over-tightened in the slightest.

Edited February 7, 2020 by Rusted
typo