A Restoration

[dweller25]

Great thread this, I appreciate the effort you are putting in 👍

[Franklin]

I stripped down, cleaned up and re-greased an old CG5 head a few years back with the aid of some very helpful info/videos online, but THIS is something else! Thanks Alan, can't wait for the rebuild, as I definitely struggled to set up the worms properly and remove all that pesky backlash! 👍

[Alan64]

On 04/07/2021 at 00:32, Franklin said:

I stripped down, cleaned up and re-greased an old CG5 head a few years back with the aid of some very helpful info/videos online, but THIS is something else! Thanks Alan, can't wait for the rebuild, as I definitely struggled to set up the worms properly and remove all that pesky backlash! 👍

Oh dear, the worms, yes; those are going to give me trouble as well.

[Alan64]

The bronze sheets arrived a few days ago...

Both sets are 0.008" in thickness, but the smaller set on the right was advertised as being 0.006" thick.  Now that I think about it, those two smaller sheets are the same size as I have gotten in the past.  Well, no matter, as they'll come in handy nonetheless.

Edited July 5, 2021 by Alan64

[wookie1965]

Such an interesting thread cannot wait to see everything back together and working to see how it performs. 

[Alan64]

22 minutes ago, wookie1965 said:

Such an interesting thread cannot wait to see everything back together and working to see how it performs. 

I can't wait, either.  But it's going to be slow go.

[Alan64]

Scratch this...

This outside area(arrowed in green) is lower than the outer diameter of the RA-axis' sealed-bearing...

The RA worm-gear bears against that outermost surface, and not the bearing itself which is raised slightly.  Hence...

Now, that bronze washer that I just made is for the RA worm-gear to bear against.  It's similar to the original plastic washer, but it's more precise.  Behold...

  

It's not even greased, yet the gear spins ever so smoothly and easily, and the bronze washer does not oscillate in the very least, as the plastic washer glaringly did.

The raised area of this part of the axis is what, in theory, bears against the inner, rotating portion of the sealed bearing...

 

Now to make a washer for that union next...  

[Alan64]

I've never been particularly fond of crow, nor humble pie.  With that being said...

I never did get a chance to take my Vixen GPD apart, as I only had it for about two years, and long before I'd have a need to do so.

I've been using K&S Metals .008"/0.20mm phosphor-bronze sheets for a few years, and for my telescopes and mounts.  You get used to doing that, so that when the next project comes up, out comes the same thickness of bronze.  It had always been satisfactory, but not in this instance, admittedly.  It was this last washer I made...

...35mm i.d., 40mm o.d., that enabled me to finally see that the 0.020"/0.5mm thickness of the original plastic washers is correct, and necessary.  Else, the RA-worm gear will move up and down a bit, along the shaft, albeit slightly.  Given that, and with the mating of the worm and gear ever present in the back of my mind, I have placed an order for 0.020"/0.5mm thick phosphor-bronze, a 6"/152mm wide x 50"/127cm long roll.

In addition, I have always been leery, suspicious, regarding all manner of products manufactured in mainland China.  But then, I am reminded that the quality of their bicycles is world-renowned, although that born out of necessity.

Edited July 11, 2021 by Alan64

[Alan64]

Whilst waiting for the thicker bronze to arrive, I turned towards the latitude-axis, and removed the paint from the bearing surfaces of the mount's base.  Who paints bearing surfaces...

Next, I will need to remove the paint from the area circled in red, but only from the top surface, and for both sides...

Incidentally, I found no stray paint anywhere inside the mount-head's axes, none whatsoever.

I don't know if any of my fellow members have ever heard of Etsy...

https://www.etsy.com/

...but that's where I found sheets of 0.040"/1mm thick aluminum...

The seller listed the sheets only as being 18-gauge.  I was concerned that it might not be exactly the thickness needed, but my fears were allayed once I measured a sheet with calipers.

I will be making the two single washers for the latitude-axis from that, one for each side, and to replace the four 0.020"/0.5mm clear-plastic washers provided by the factory.

[Alan64]

The other half of the latitude-axis has been stripped of its paint...

I may have to touch up the white paint here and there, but no problem.  We will want it ship-shape, and in Bristol fashion.

[Alan64]

Two 58mm diameters have been described onto one of the aluminum sheets...

There are actually two circles for each, one slightly smaller than the other, and to help craft them more accurately.

[Alan64]

Just now, the thicker sheet of phosphor-bronze arrived...

I had ordered it Sunday night.  That was fast.

The roll came with a "pedigree" even...

The chemical analysis is most interesting, and may offer some insight as to how difficult it is to cut and fashion.

[Alan64]

Before the circles were described, a very tiny drill-bit was used to create a pilot-hole for the compass's leg.  Using increasingly larger bits, for accuracy, I enlarged the holes to their final diameter: 25/64", or 9.9mm...

The holes fit a little tightly over the latitude-axis's bolt, therefore the exact measurement must be metric, and at 10mm. 

This should be done before the washers are cut out from the sheet.

[dweller25]

Still following this excellent post 🙂👍

[Alan64]

In determining the extra thickness required for the latitude-axis, I used these four 0.0095"/0.24mm pieces cut from a sheet of aluminum-flashing, as test-shims, a pair for each side...

That's a total of 0.019"/0.48mm for each pair, and when combined with the thicker washers results in a total thickness of 0.059"/1.5mm for each side of the axis, for a snug union.

But I wasn't about to make four washers out of the flashing, so I went out yesterday to my big-box, hardware/lumber haunts.  The 0.019" sheets were out of stock at the first store, despite showing "3" online, but at the second store I found this sheet...

That sheet is ever so slightly thicker, and at 0.025"/0.64mm.  Now, take a look at this...

The other side is smooth, even, and level, however the side illustrated is not; a close-up...

The spokes are thickened, along their lengths from the hub to the rim.  After I level those, I may very well need the extra 0.006"/0.15mm thickness.  Stay tuned.

Edited July 15, 2021 by Alan64

[Alan64]

The spokes and part of the hub were levelled, more or less, with a Dremel tool and a diamond-bit...

Then, the areas were sanded, and polished with steel-wool and lemon-oil...

The other side, that I said was level, is satisfactorily.  The hub does rise above the spokes, but I don't dare to decrease its thickness...

The washers should easily conform to that side; or rather, it must.

Edited July 15, 2021 by Alan64

[Alan64]

Of the thinner aluminum, pilot-holes have been drilled, and the washers described...

For the latitude-axis, I realise that I'm going to a lot of trouble, "The plastic washers are fine", but I'm on a mission, and to rid this mount-head of every last bit of plastic as is possible.

[Alan64]

After the thinner washers were cut out, dressed and polished, it was no go.  They were simply too thick to combine with the thicker washers, so off to the sander they went...

After several hours, sanding and testing, over and over, I finally arrived at the magic numbers...

I didn't sand the thicker washers at all; dressed and polished only.  

The motion is solid, and smooth(bronze would be smoother still), but that's neither here nor there, given the range of movement, and the rarest of need to move it.  Rather, I have exchanged plastic and paint for metal, and in joining the two sections together...

 

Edited July 16, 2021 by Alan64

[SpookyKatt]

Love this thread, this is what I call a hypetune.

[Alan64]

I neglected to mention: since the thinner washers did not fit initially, I then decided to level the other hub with its spokes, thereby reducing the need to sand the washers further...

The total thickness of the washers per side is roughly 0.0575".  In future, I may re-do this with one washer per side, and of brass.

Incidentally, aluminum doesn't play well with copper, brass, or bronze, among others...

https://www.archtoolbox.com/materials-systems/metals/galvanicaction.html

However, it seems that if the dissimilar metals are saturated with grease, then there shouldn't be a problem. 

Food for thought, and when incorporating said metals within this aluminum mount-head.

[Alan64]

The time came to unfurl the roll of bronze sheet.  I began by cutting at its cardboard band within the house, but then decided to take it out to the shed.  Good thing that, as it violently exploded to its full length once the band gave way...

  

[Alan64]

Starting over from scratch, the following measurements for the RA-axis's washers were made with a relation's Mitutoyo digital-calipers, and leagues above my generic Chinese calipers...

The RA primary washer...

The RA secondary washer...

I suppose that the inner-diameters of both can be made at an even 62mm; but no narrower than 61.80mm for the primary.  

However, that for the secondary washer is most critical, given the rather narrow bearing surface onto which it will rest...

Then, the inner-diameter, at 61.95mm, is quite close to 62mm after all, but we do want that as snug-fitting as possible.  Why, you could even glue the washer into place if you wanted.  In so far as the outer-diameter, it can be the same as the bearing-surface itself, but I'd hate having to make a washer that narrow.

The washers will be born from this beautiful 152mm x 90mm x 0.020" sheet of phosphor-bronze...

[johninderby]

Yes you could buy a case full of cheap Chinese callipers for the price of a Mitutoyo caliper but once you used the Mitutoyo you just can’t go back. Had mine for years. 👍🏻👍🏻👍🏻🙂

Edited July 17, 2021 by johninderby

[Alan64]

6 hours ago, johninderby said:

Yes you could buy a case full of cheap Chinese callipers for the price of a Mitutoyo caliper but once you used the Mitutoyo you just can’t go back. Had mine for years. 👍🏻👍🏻👍🏻🙂

The relation saw what I was doing, whilst using the China-made, and introduced me to those.  What a wonderful introduction.

[johninderby]

Mitutoyo are a bit like Snap-On tools in a way in that they are what professionals that need tools they can depend on use. 👍🏻