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6" refractor mount refurbish after 20yrs

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#1 dave brock

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Posted 10 January 2021 - 05:14 AM

About 20yrs ago I bought a brass 6" Watson refractor. It came with a non-Watson equatorial mount that I'm

pretty sure is home made. It's been stored in the factory where I work for most of those 20yrs. 

 I recently realised that some of it's parts are actually brass that is coated with nickel or zinc or similar and got to

thinking it would look a lot better taken back to brass to match the tube.

 

It was missing the tube rings so I initially contemplated having them made from brass but decided I didn't want to spent

a lot on this as I really don't know what I'm going to end up doing with it. Decided to make them myself out of aluminium

so I could use woodworking tools grin.gif.

 

Bought an offcut of 1" aluminium, blocked it up, made a template and routed out the inside circle 1mm deep at a time. 

 

rings a.jpg

 

rings b.jpg

 

Drilled holes around the outside of the rings.

 

rings c.jpg

 

rings d.jpg

 

Cut around with a bandsaw, re-blocked and routered the outside with another template. This time I could

go deeper with each cut, about 3-4mm.

 

rings e.jpg

 

rings f.jpg

 

rings g.jpg  

 

To be continued soon....


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#2 dave brock

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Posted 10 January 2021 - 06:02 AM

Moved the template around to finish the outside.

 

rings h.jpg

 

rings i.jpg

 

Blocked up again so I could drill down for the swivel joining bolt (or whatever it's called crazy.gif ).

 

rings j.jpg

 

rings o.jpg

 

rings p.jpg

 

Then used a trimmer to square out the hole.

 

rings k.jpg

 

I then cut the rings in half, rounded the ends that hinge together and sanded flat the two mating faces

at the other end.

 

Next I made the swivel joining bolts.

I cut the head off two partially threaded bolts and drilled through the side of the smooth shank close to the end.

A small brass bolt was tapped into the ring to act as a pivot.

 

The hinges were made using metal from a brass hinge smile.gif

 

rings l.jpg

 

They were cut and sanded to shape, holes drilled and brass screws tapped into the rings. Care was taken to drill

and tap to such a depth so the screws don't hold the plates tightly but allow them to move but the screws are tight.

There are small brass washers under the plates so they don't scrape the rings when opening and closing.

 

rings m.jpg

 

Holes drilled and tapped for the bolts to attach the rings to the saddle plate.

 

rings n.jpg

 

I'm undecided yet how I'll finish the rings. When I made them I intended to paint them black to match the mount but

I am now thinking I might get them black anodised. The felt at this stage is applied with double sided tape so can

easily be removed.

The nuts on the swivel joining bolts are temporary at this point. I ended up using my drill press and a drill bit as a 

lathe to turn brass door knobs into thumb nuts.

 

Midnight here now so to be continued...


Edited by dave brock, 10 January 2021 - 06:12 AM.

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#3 dave brock

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Posted 10 January 2021 - 06:17 AM

Oh just quickly, I forgot to post pics of the mount as bought.

 

6inch mount 005 sm.JPG

 

6inch mount 001 sm.JPG

 

6inch mount 006 sm.JPG

 

 


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#4 retroman2

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Posted 10 January 2021 - 06:28 AM

Very nice.



#5 dave brock

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Posted 10 January 2021 - 06:30 AM

Incidentally, I always assumed the pier is an old truck axel housing but looking at google images they

all seem to have a ring of bolts, not just four. Any thoughts?

 

6inch mount 010sm.jpg


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#6 JOhio

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Posted 10 January 2021 - 10:13 AM

Nice work.

Could the base be a 4 bolt trailer hub?

Example of a modern hub.

https://www.autozone...wE&gclsrc=aw.ds



#7 ccwemyss

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Posted 10 January 2021 - 10:14 AM

Maybe a lamp post base? It looks like there is a cutout for a wire to come out of the base and go into the ground, with some sort of cover bolted over it. 

 

The rings turned out very nicely!

 

I'm curious about the router bit(s) you were using to mill the aluminum. I'd be afraid to ruin any of my good woodworking bits. Was it a carbide bit, or just steel? What size?

 

Also, what grade of aluminum? 6061? 5052? Did you have to do anything special to cool the bit? Change the speed of the router?

 

Chip W. 


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#8 starman876

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Posted 10 January 2021 - 10:28 AM

Nice work.



#9 ShutterAce

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Posted 10 January 2021 - 10:50 AM

Well done!



#10 Terra Nova

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Posted 10 January 2021 - 12:02 PM

Great work. Ingenious using a router to get around a mill! Very nice end result.



#11 Astrogarage

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Posted 10 January 2021 - 02:11 PM

Very inspiring work.

 

Finish the rings with heavy brass plating ?



#12 dave brock

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Posted 10 January 2021 - 04:19 PM

Nice work.

Could the base be a 4 bolt trailer hub?

 

 

 

Maybe a lamp post base? It looks like there is a cutout for a wire to come out of the base and go into the ground, with some sort of cover bolted over it. 

 

Thanks for the suggestions. Could be a lamp post base. Could be something off an industrial piece of machinery.

Everything I've searched has not really looked similar.

 

Thanks also for the other comments everyone.



#13 dave brock

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Posted 10 January 2021 - 04:23 PM

 

The rings turned out very nicely!

 

I'm curious about the router bit(s) you were using to mill the aluminum. I'd be afraid to ruin any of my good woodworking bits. Was it a carbide bit, or just steel? What size?

 

Also, what grade of aluminum? 6061? 5052? Did you have to do anything special to cool the bit? Change the speed of the router?

 

Chip W. 

Just used an ordinary router bit from work, 1/2" I think but yes carbide tipped. It is 6061 aluminium .



#14 dave brock

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Posted 10 January 2021 - 04:51 PM

Started sanding and polishing the brass pieces

Here's the declination  setting circle.

 

circle before.jpg

 

Put it on my drill press and sanded the coating off. Smoothed with various grades of paper then polished. Luckily the edge with the engraving was not coated so that needed a very fine sand and polish. Didn't want to eat into the engraving.

 

circle during.jpg

 

The centre hole and shaft are tapered and when the holding nut is tightened it locks tight. Somebody in the past has belted it to get it off so I had to sand quite a bit to remove those marks.

 

circle after a.jpg

 

The three tapped holes are actually there so bolts can be used as a gear puller to remove the circle without damage. I don't know if the maker made those as an after thought or the guy with the hammer didn't realise what they are for.

 

Anyway it come up pretty well. R.A. circle was done the same. Hammer marks were even worse.

 

circle after b.jpg

 

Incidentally, the counterweight shaft must have been threaded on a lathe and not perfectly. The brass nuts will thread on easily one way but if you turn them over they jam up. I guess the lathe threading tool wasn't angled correctly? I have lots of taps and dies but none of the correct thread. I think this is 7/8 UNC. All mine are UNF in that size. I'll run a die nut over it if I can find one that doesn't cost too much or to borrow.


Edited by dave brock, 10 January 2021 - 05:08 PM.

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#15 dave brock

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Posted 10 January 2021 - 05:30 PM

The declination tangent arm. 

 

tangent 1.jpg

 

After polishing.

 

tangent 2.jpg

 

The tangent pivot is particularly interesting. It is made up of three pieces, each stamped ( not sure why 7. Maybe 7 or more mounts were made or randomly grabbed a punch? ).  Very labour intensive to make this, assumedly to help stop binding?

 

tangent 3.jpg

 

tangent 4.jpg

 

After using the scope I've found that the nut at the end of the drive shaft will tighten itself and bind the action. It maybe needs a pin or a lock nut. Might be better with a Teflon washer as well. I didn't notice this before possibly because it was tighter on the threads before cleaning.

The chromed shaft is of course temporary. Will replace with a longer brass shaft and knob.

 

 

Attached Thumbnails

  • tangent 5.jpg

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#16 dave brock

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Posted 10 January 2021 - 05:54 PM

The R.A. gear and worm were polished in the same manner. I made mdf circles to mount the gear onto the drill press as it has a larger central hole than the setting circles.

 

20201214_182602a.jpg

 


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#17 dave brock

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Posted 10 January 2021 - 06:58 PM

Re-assembly of the R.A. shaft.

 

ra shaft 1.jpg

 

Clutch plate.

 

ra shaft 2.jpg

 

R.A. gear. The teeth were left with the ( nickel? ) plating on to keep their hardness.

 

ra shaft 3.jpg

 

Pressure plate.

 

ra shaft 4.jpg

 

Pressure adjustment collar. It is threaded onto the shaft, not easily seen in the pics.

 I've just realised I didn't photograph the other side of this. It has three strong springs sitting in

holes that push the pressure plate against the R.A. gear. Tightening the collar determines how freely the R.A. turns by hand.

It has a grub screw on the edge that locks it in position

 

ra shaft 5.jpg


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#18 dave brock

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Posted 10 January 2021 - 07:17 PM

Stripped down the mount, Sanded and repainted matt black to help hide the casting imperfections.

If I were to do this again I would use satin black. Matt shows fingerprints too much. Live and learn.

 I could have spent a lot more time filling all the imperfections but where do you stop? Also the mount was spread about my work space and today is the last day of my Christmas holidays so I needed to get it back together.

 

assembly 1.jpg

 

assembly 2.jpg

 

assembly 3.jpg

 

assembly 4.jpg

 

assembly 5.jpg

 

assembly 6.jpg

 

assembly 7.jpg

 

assembly 8 .jpg

 

assembly 9.jpg


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#19 dave brock

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Posted 10 January 2021 - 07:46 PM

Mounted it on lockable swivel casters. Used four. Three is more stable in use but is more prone to tip when wheeling

unless they are a lot wider spaced. I may make three wind down bolts for it to sit on in use. As I've said, I'm really not sure

what I'm going to do with it. I don't have room at home and I have three bigger reflectors that get more use.

Still a few things to do. Coat the tube rings and make proper slow motion controls.

Anyway a couple of pics.

 

20210109_170036s.jpg

 

 

20210109_170334s.jpg

 

 


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#20 dave brock

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Posted 10 January 2021 - 07:57 PM

A couple with the scope.

 

watson mount a.jpg

 

watson mount b.jpg

 

 


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#21 Jim Curry

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Posted 11 January 2021 - 01:13 PM

Now that is a serious labor and effort of love.  Nicely done!


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#22 Bob Myler

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Posted 11 January 2021 - 02:01 PM

Simply beautiful.



#23 dave brock

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Posted 11 January 2021 - 02:41 PM

Thanks Jim and Bob.

#24 Paul Hyndman

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Posted 11 January 2021 - 02:55 PM

Beautiful work, Dave... I am in awe!



#25 charlieb123

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Posted 11 January 2021 - 03:08 PM

Amazing work. Thanks for sharing the shine with us.

 

Reminds me of a lamp post from a long gone era.




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