Building a fixed post mirror grinding machine

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Kanadalainen
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Building a fixed post mirror grinding machine

#1

Post by Kanadalainen »


Hello all,

I'm fascinated by those who can grind and figure their own mirrors for reflecting telescopes. With the availability of kits to finish beautiful ATM dobs from companies like dobstuff, the lure of building one's own scope to high tolerances and good performance is clearly doable.

So...

I've decided to build my own fixed-post glass grinding and polishing machine. Gordon Waite is probably one of the better mirror makers using this machine and have incorporated some of his ideas into my plan. I like the fixed-post plan vs others with eccentric drives, because it gets the heavy grinding done in an automated manner, but still give you the chance to hand-figure.

Things I have (mostly purchased through closing sales at labs at the university):

- a German-made IKA DC mixing motor with electronic speed control (pulse-width modulated) with internal belt drive - rated for continuous use (free)
- an old homemade desk - serve as the platform (free)
- a surplus 2000 lb trailer wheel bearing and steel stub axle (given to me by a neighbour)
- tools but no router.
- plans for the mirror-o-matic machines which I will use for gear reduction.

Things I need
- belts, pulleys, pillow block bearings, a nice turntable (not wood, but either aluminum or corian), hardware.

Stay tuned!

Ian
Last edited by Kanadalainen on Thu Aug 15, 2019 1:13 pm, edited 1 time in total.
Ian

Fracs: Stellarvue 70T f6; SW 120mm Esprit f7; "Mark Mk. II" - 60 mm Tasco f6; C80 frac f 11.4
SCT: C8 Edge f10 or f7 with reducer
Dob: 14.5" homebuilt strut dob (f4.5 ZOC mirror), Nexus II, Moonlite focuser
Mounts - Ioptron Skyguider pro, Astro Physics GTO900
Cameras and lenses - ZWO 2600 mc, 290 mm mini, Canon 60D modded with Rokinon 10mm 2.8; Rokinon 135mm f2

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Kanadalainen
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Re: Building a fixed post mirror grinding machine

#2

Post by Kanadalainen »


Update: I bought a 14" v-pulley (Princess Auto) and am welding it to the axle stub and bearing.

This will form the base of the main drive for the turntable which will use the stub of the axle, set into the desk top. That will be driven by the reduced gear drive tied to the variable DC motor.

Below is the welding job.. please forgive my garage, I promise I will clean it. :lol:
Attachments
IMG_9999.JPG
IMG_9813.JPG
IMG_5051.JPG
Ian

Fracs: Stellarvue 70T f6; SW 120mm Esprit f7; "Mark Mk. II" - 60 mm Tasco f6; C80 frac f 11.4
SCT: C8 Edge f10 or f7 with reducer
Dob: 14.5" homebuilt strut dob (f4.5 ZOC mirror), Nexus II, Moonlite focuser
Mounts - Ioptron Skyguider pro, Astro Physics GTO900
Cameras and lenses - ZWO 2600 mc, 290 mm mini, Canon 60D modded with Rokinon 10mm 2.8; Rokinon 135mm f2

Skysafari 6 Pro, Astro Pixel Processor, Pixinsight - using Mac tablet and ASIair pro to run the AP rig.

"Mothers! It is there!" - Rafael Gonzales-Acuna, 2018.
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Kanadalainen
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Re: Building a fixed post mirror grinding machine

#3

Post by Kanadalainen »


Here is a mock-up of the welded drive pulley/trailer axle drive. It looks spindly (no pun intended :)) but the final drive will be locked down with pillow blocks etc. This test is just to make sure the drive spins freely, which it does.

Oops, I ran into a glitch posting this .mov file. Mods, please let me know if this is doable?

/Users/idixon/Desktop/58579884405__05188D89-36A0-4530-AB10-2AC3361FB429.MOV

In the meantime, here is a loose idea of what the final product might look like:
Attachments
049f9820b46c588cb9695fa81f0bfc61.jpg
Ian

Fracs: Stellarvue 70T f6; SW 120mm Esprit f7; "Mark Mk. II" - 60 mm Tasco f6; C80 frac f 11.4
SCT: C8 Edge f10 or f7 with reducer
Dob: 14.5" homebuilt strut dob (f4.5 ZOC mirror), Nexus II, Moonlite focuser
Mounts - Ioptron Skyguider pro, Astro Physics GTO900
Cameras and lenses - ZWO 2600 mc, 290 mm mini, Canon 60D modded with Rokinon 10mm 2.8; Rokinon 135mm f2

Skysafari 6 Pro, Astro Pixel Processor, Pixinsight - using Mac tablet and ASIair pro to run the AP rig.

"Mothers! It is there!" - Rafael Gonzales-Acuna, 2018.
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Re: Building a fixed post mirror grinding machine

#4

Post by Kanadalainen »


Lets try this link of the mock-up of the main drive:



Much better! I posted the video to youtube and pasted the link. It looks fragile, but its simply free-standing. I was checking the welded pulley for any distortion, I think we are good to go.
Ian

Fracs: Stellarvue 70T f6; SW 120mm Esprit f7; "Mark Mk. II" - 60 mm Tasco f6; C80 frac f 11.4
SCT: C8 Edge f10 or f7 with reducer
Dob: 14.5" homebuilt strut dob (f4.5 ZOC mirror), Nexus II, Moonlite focuser
Mounts - Ioptron Skyguider pro, Astro Physics GTO900
Cameras and lenses - ZWO 2600 mc, 290 mm mini, Canon 60D modded with Rokinon 10mm 2.8; Rokinon 135mm f2

Skysafari 6 Pro, Astro Pixel Processor, Pixinsight - using Mac tablet and ASIair pro to run the AP rig.

"Mothers! It is there!" - Rafael Gonzales-Acuna, 2018.
Don Quixote
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Re: Building a fixed post mirror grinding machine

#5

Post by Don Quixote »


Wow !
This is going to be a great pleasure to follow your progress, Ian.
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Re: Building a fixed post mirror grinding machine

#6

Post by Kanadalainen »


Thanks Mark!

I'm pondering the finer points of this design and most importantly finding ways to keep the turntable flat during rotation. It'll be a sandwiched turntable I think with one or two layers of 3/4" baltic birch plywood (varnished with urethane) and an aluminum cap. 6061 aluminum may be ok... and for stiffness I should shoot for .5" thickness.

Anyway I rough cut an 18" circle of plywood drilled it and fit to the hub. The 1/2" bolts underneath will make it adjustable.
Attachments
IMG_5988.JPG
Ian

Fracs: Stellarvue 70T f6; SW 120mm Esprit f7; "Mark Mk. II" - 60 mm Tasco f6; C80 frac f 11.4
SCT: C8 Edge f10 or f7 with reducer
Dob: 14.5" homebuilt strut dob (f4.5 ZOC mirror), Nexus II, Moonlite focuser
Mounts - Ioptron Skyguider pro, Astro Physics GTO900
Cameras and lenses - ZWO 2600 mc, 290 mm mini, Canon 60D modded with Rokinon 10mm 2.8; Rokinon 135mm f2

Skysafari 6 Pro, Astro Pixel Processor, Pixinsight - using Mac tablet and ASIair pro to run the AP rig.

"Mothers! It is there!" - Rafael Gonzales-Acuna, 2018.
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Juno16 United States of America
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Re: Building a fixed post mirror grinding machine

#7

Post by Juno16 »


Wow, Ian, that is awesome!

Like Mark, I am anxious watching your progress. Looks like you will be working on a mirror soon. Best of luck!

A few years ago, I was thinking about hand grinding a mirror. I watched a YouTube video of John Dobson hand grinding a mirror. I don’t really remember how big it was, but it was big. Maybe 14”. Maybe larger.
John was no youngster in this video and even though he is a master, he sure put a hellova lot of labor into that mirror.

I don’t have that much patience.

I hope that you get this going without too many bumps in the road.

Please post your progress!

Thanks,
Jim
Jim

Scopes: Explore Scientific ED102 APO, Sharpstar 61 EDPH II APO, Samyang 135 F2 (still on the Nikon).
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Don Quixote
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Re: Building a fixed post mirror grinding machine

#8

Post by Don Quixote »


I wonder if using a salvaged cast iron deck from a scroll saw as the top plate would give a suitable flat unflexing mounting deck. ?
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Re: Building a fixed post mirror grinding machine

#9

Post by Kanadalainen »


Juno16 wrote: Fri Aug 16, 2019 12:21 am Wow, Ian, that is awesome!

Like Mark, I am anxious watching your progress. Looks like you will be working on a mirror soon. Best of luck!

A few years ago, I was thinking about hand grinding a mirror. I watched a YouTube video of John Dobson hand grinding a mirror. I don’t really remember how big it was, but it was big. Maybe 14”. Maybe larger.
John was no youngster in this video and even though he is a master, he sure put a hellova lot of labor into that mirror.

I don’t have that much patience.

I hope that you get this going without too many bumps in the road.

Please post your progress!

Thanks,
Jim
Thank you Jim, I recall a nice video of Dobson's self-proclaimed "cave-man" work doing the rough grinding. In that video he made a 16" mirror. Fearless!

After hogging my mirror(s) out I would like to be able to test by generating

-ronchigram
-interferograms (bath interferometer)
-Foucault -style analysis
-Ross null test
http://www.ceravolo.com/ross_null.pdf

I'm reading up on Foucault at present.

Lots of work to build this, but it'll save a ton of manual labour in hogging out to the proper saggita.

Ian
Last edited by Kanadalainen on Fri Aug 16, 2019 3:40 am, edited 1 time in total.
Ian

Fracs: Stellarvue 70T f6; SW 120mm Esprit f7; "Mark Mk. II" - 60 mm Tasco f6; C80 frac f 11.4
SCT: C8 Edge f10 or f7 with reducer
Dob: 14.5" homebuilt strut dob (f4.5 ZOC mirror), Nexus II, Moonlite focuser
Mounts - Ioptron Skyguider pro, Astro Physics GTO900
Cameras and lenses - ZWO 2600 mc, 290 mm mini, Canon 60D modded with Rokinon 10mm 2.8; Rokinon 135mm f2

Skysafari 6 Pro, Astro Pixel Processor, Pixinsight - using Mac tablet and ASIair pro to run the AP rig.

"Mothers! It is there!" - Rafael Gonzales-Acuna, 2018.
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Kanadalainen
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Re: Building a fixed post mirror grinding machine

#10

Post by Kanadalainen »


Don Quixote wrote: Fri Aug 16, 2019 1:22 am I wonder if using a salvaged cast iron deck from a scroll saw as the top plate would give a suitable flat unflexing mounting deck. ?
Yes! That's a good idea. I think any old free-standing scroll saw skeleton would make a nice starting point, sometimes you can find a good single phase 1800 rpm motor in those, too!

You could easily gear them down for glass grinding. :).

I have a buddy that can CNC water-jet cut aluminum plate and so will be paying him a visit tomorrow.
Ian

Fracs: Stellarvue 70T f6; SW 120mm Esprit f7; "Mark Mk. II" - 60 mm Tasco f6; C80 frac f 11.4
SCT: C8 Edge f10 or f7 with reducer
Dob: 14.5" homebuilt strut dob (f4.5 ZOC mirror), Nexus II, Moonlite focuser
Mounts - Ioptron Skyguider pro, Astro Physics GTO900
Cameras and lenses - ZWO 2600 mc, 290 mm mini, Canon 60D modded with Rokinon 10mm 2.8; Rokinon 135mm f2

Skysafari 6 Pro, Astro Pixel Processor, Pixinsight - using Mac tablet and ASIair pro to run the AP rig.

"Mothers! It is there!" - Rafael Gonzales-Acuna, 2018.
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Re: Building a fixed post mirror grinding machine

#11

Post by Kanadalainen »


I found my old desk in the basement. Sturdy with 3/4" plywood construction.

I strengthened the top by adding a layer of 3/4" pressure treated plywood, cut from a half sheet I had lying around. I countersunk 6 x 2" stainless Phillips head screws to button it up.

Last night I also test fitted the DC motor and its stand. The placement of the turntable base is approximate. I'm not sure whether the reduction (5.6:1) will be enough for this little 1/8 hp DC motor, but that's why we have prototype development. :)

If it doesn't work I'll figure out an alternative. :lol:
Attachments
IMG_1854.JPG
IMG_3774.JPG
IMG_4919.JPG
Ian

Fracs: Stellarvue 70T f6; SW 120mm Esprit f7; "Mark Mk. II" - 60 mm Tasco f6; C80 frac f 11.4
SCT: C8 Edge f10 or f7 with reducer
Dob: 14.5" homebuilt strut dob (f4.5 ZOC mirror), Nexus II, Moonlite focuser
Mounts - Ioptron Skyguider pro, Astro Physics GTO900
Cameras and lenses - ZWO 2600 mc, 290 mm mini, Canon 60D modded with Rokinon 10mm 2.8; Rokinon 135mm f2

Skysafari 6 Pro, Astro Pixel Processor, Pixinsight - using Mac tablet and ASIair pro to run the AP rig.

"Mothers! It is there!" - Rafael Gonzales-Acuna, 2018.
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Re: Building a fixed post mirror grinding machine

#12

Post by Kanadalainen »


Of course I had to gain access to place the drive shaft through the table top.

Which means hacking through the desk, thereby demanding the use of one of my favourite tools, the garden-variety hole saw!! :)

Sobering thought du jour: Because I have the bearing housing literally welded to my drive pulley, I am forced to go with a final drive system that is above the surface of the desk. This is not optimal because of the glass mud and grinding slurry that I will generate, but I have no choice.

Lets see what pans out... I think it will work fine.
Attachments
IMG_1345.JPG
Ian

Fracs: Stellarvue 70T f6; SW 120mm Esprit f7; "Mark Mk. II" - 60 mm Tasco f6; C80 frac f 11.4
SCT: C8 Edge f10 or f7 with reducer
Dob: 14.5" homebuilt strut dob (f4.5 ZOC mirror), Nexus II, Moonlite focuser
Mounts - Ioptron Skyguider pro, Astro Physics GTO900
Cameras and lenses - ZWO 2600 mc, 290 mm mini, Canon 60D modded with Rokinon 10mm 2.8; Rokinon 135mm f2

Skysafari 6 Pro, Astro Pixel Processor, Pixinsight - using Mac tablet and ASIair pro to run the AP rig.

"Mothers! It is there!" - Rafael Gonzales-Acuna, 2018.
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Re: Building a fixed post mirror grinding machine

#13

Post by Kanadalainen »


Et voila, the prototypical final drive. :). I use a 52" kevlar v belt purchased at a local shop (Princess Auto). This belt may be too stiff, but they *are* strong.

I stayed up late to do all of this, but its worth it, now I'm checking the run out and trying to figure out how to anchor the spindle properly (tight clearance with no wobble) into the desk.

Next I'll adjust the bearing and spindle for orthogonality. Also, I will paint the plywood base with urethane, fit a much larger piece over that, urethane coat that and finally lay the hypothetical aluminum base over all of that to make a reasonably strong and water proof base.

My spouse asked me what all the hammering and sawing noises were all about. Inquisitive spouse: "Whats going on? Are you working on another telescope?" Me: "Not this time, this is a glass grinding machine". Spouse: "OK, Have fun with that, be sure you vacuum up the mess, and throw out all the sundry flotsam."

Its going to take a huge vacuum.
Attachments
IMG_9672.JPG
Ian

Fracs: Stellarvue 70T f6; SW 120mm Esprit f7; "Mark Mk. II" - 60 mm Tasco f6; C80 frac f 11.4
SCT: C8 Edge f10 or f7 with reducer
Dob: 14.5" homebuilt strut dob (f4.5 ZOC mirror), Nexus II, Moonlite focuser
Mounts - Ioptron Skyguider pro, Astro Physics GTO900
Cameras and lenses - ZWO 2600 mc, 290 mm mini, Canon 60D modded with Rokinon 10mm 2.8; Rokinon 135mm f2

Skysafari 6 Pro, Astro Pixel Processor, Pixinsight - using Mac tablet and ASIair pro to run the AP rig.

"Mothers! It is there!" - Rafael Gonzales-Acuna, 2018.
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Re: Building a fixed post mirror grinding machine

#14

Post by Kanadalainen »


Update: I have my 22" full size piece of 3/4" baltic birch, cut for me by the local shop who sells building supplies.

I need to find its centre, and then saw matching cutouts for the bearing bolt pattern.

Then I will screw it down to the base cap and level the entire laminated top with the supporting nuts on the main spindle.

The images below show the full size birch ply base, finding centre (using Gordon Waite's method -really slick) then the rest show the small cap bolted to the wheel bearing, and then a shot of the main 22" cap, cut to fit over the smaller wood cap. (I will varnish them today).

Centre of a circle:
Attachments
IMG_2499.JPG
IMG_1733.JPG
IMG_0513.JPG
IMG_7440.JPG
Last edited by Kanadalainen on Fri Aug 16, 2019 4:43 pm, edited 1 time in total.
Ian

Fracs: Stellarvue 70T f6; SW 120mm Esprit f7; "Mark Mk. II" - 60 mm Tasco f6; C80 frac f 11.4
SCT: C8 Edge f10 or f7 with reducer
Dob: 14.5" homebuilt strut dob (f4.5 ZOC mirror), Nexus II, Moonlite focuser
Mounts - Ioptron Skyguider pro, Astro Physics GTO900
Cameras and lenses - ZWO 2600 mc, 290 mm mini, Canon 60D modded with Rokinon 10mm 2.8; Rokinon 135mm f2

Skysafari 6 Pro, Astro Pixel Processor, Pixinsight - using Mac tablet and ASIair pro to run the AP rig.

"Mothers! It is there!" - Rafael Gonzales-Acuna, 2018.
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Re: Building a fixed post mirror grinding machine

#15

Post by Kanadalainen »


Update: Rough levelling of the supporting laminate for the turntable:

I quickly painted the wooden ply discs, and then put everything back together using a level to rough it into shape, but found the best way is to bolt it top and bottom (1/2" bolts with washers) and check run out on the vertical axis, slowly adjusting tension of each bolt.

Simple but gives good results. :). My next problem is to be sure the spindle sockets into the desk top squarely.

Later, if needed, I will run caster wheels under the turntable, each at 120* from each other. The table might be stiff enough that this step may not be needed.
Attachments
IMG_6727.JPG
IMG_0667.JPG
Ian

Fracs: Stellarvue 70T f6; SW 120mm Esprit f7; "Mark Mk. II" - 60 mm Tasco f6; C80 frac f 11.4
SCT: C8 Edge f10 or f7 with reducer
Dob: 14.5" homebuilt strut dob (f4.5 ZOC mirror), Nexus II, Moonlite focuser
Mounts - Ioptron Skyguider pro, Astro Physics GTO900
Cameras and lenses - ZWO 2600 mc, 290 mm mini, Canon 60D modded with Rokinon 10mm 2.8; Rokinon 135mm f2

Skysafari 6 Pro, Astro Pixel Processor, Pixinsight - using Mac tablet and ASIair pro to run the AP rig.

"Mothers! It is there!" - Rafael Gonzales-Acuna, 2018.
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Re: Building a fixed post mirror grinding machine

#16

Post by Kanadalainen »


Update: I had intended to weld up an overarm. However I found a main support for the overarm, which is probably better because its adjustable. Its part of an old binocular optic used for gross dissection. A square steel support is held by a heavy bracket to support the binos, which peer down at the subject on the desk. Given to me by my buddy at work who is retiring and clearing out his lab. :)

I can use 1.25" steel tubing, cut to size and weld together something that fits the bracket.
Attachments
IMG_9603.JPG
Ian

Fracs: Stellarvue 70T f6; SW 120mm Esprit f7; "Mark Mk. II" - 60 mm Tasco f6; C80 frac f 11.4
SCT: C8 Edge f10 or f7 with reducer
Dob: 14.5" homebuilt strut dob (f4.5 ZOC mirror), Nexus II, Moonlite focuser
Mounts - Ioptron Skyguider pro, Astro Physics GTO900
Cameras and lenses - ZWO 2600 mc, 290 mm mini, Canon 60D modded with Rokinon 10mm 2.8; Rokinon 135mm f2

Skysafari 6 Pro, Astro Pixel Processor, Pixinsight - using Mac tablet and ASIair pro to run the AP rig.

"Mothers! It is there!" - Rafael Gonzales-Acuna, 2018.
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Re: Building a fixed post mirror grinding machine

#17

Post by Kanadalainen »


Update: The 6061 aluminum turntable top was ready this morning and I went to pick it up from the shop.

Still plastic wrapped, but temporarily fitted to the base.

Ian

Fracs: Stellarvue 70T f6; SW 120mm Esprit f7; "Mark Mk. II" - 60 mm Tasco f6; C80 frac f 11.4
SCT: C8 Edge f10 or f7 with reducer
Dob: 14.5" homebuilt strut dob (f4.5 ZOC mirror), Nexus II, Moonlite focuser
Mounts - Ioptron Skyguider pro, Astro Physics GTO900
Cameras and lenses - ZWO 2600 mc, 290 mm mini, Canon 60D modded with Rokinon 10mm 2.8; Rokinon 135mm f2

Skysafari 6 Pro, Astro Pixel Processor, Pixinsight - using Mac tablet and ASIair pro to run the AP rig.

"Mothers! It is there!" - Rafael Gonzales-Acuna, 2018.
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Re: Building a fixed post mirror grinding machine

#18

Post by Kanadalainen »


Update: I had some time today so I focused on the overarm. I made the overarm from 1.25" steel tube, cut and fitted to size. Butt-welded, cleaned up with a grinder, painted and trial fit.

It seems too low, but I will build sandwiched plywood layers, glued together and put everything up on that.
Attachments
IMG_6086.JPG
IMG_6924.JPG
IMG_8879.JPG
Ian

Fracs: Stellarvue 70T f6; SW 120mm Esprit f7; "Mark Mk. II" - 60 mm Tasco f6; C80 frac f 11.4
SCT: C8 Edge f10 or f7 with reducer
Dob: 14.5" homebuilt strut dob (f4.5 ZOC mirror), Nexus II, Moonlite focuser
Mounts - Ioptron Skyguider pro, Astro Physics GTO900
Cameras and lenses - ZWO 2600 mc, 290 mm mini, Canon 60D modded with Rokinon 10mm 2.8; Rokinon 135mm f2

Skysafari 6 Pro, Astro Pixel Processor, Pixinsight - using Mac tablet and ASIair pro to run the AP rig.

"Mothers! It is there!" - Rafael Gonzales-Acuna, 2018.
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Re: Building a fixed post mirror grinding machine

#19

Post by Kanadalainen »


This is turning into a blog... maybe too much detail?

This past weekend I had a few hours to build the base for the overarm and work on the bracket to mount the shaft which will locate the grinding tools.

The plan is all of my grinding and polishing functions in the TOT configuration.

Glueing the bases for each side, after clamping, I put a few screws in each to keep everything solid:
Attachments
IMG_5756 2.JPG
IMG_4554 2.JPG
IMG_1854 2.JPG
IMG_7819 2.JPG
Ian

Fracs: Stellarvue 70T f6; SW 120mm Esprit f7; "Mark Mk. II" - 60 mm Tasco f6; C80 frac f 11.4
SCT: C8 Edge f10 or f7 with reducer
Dob: 14.5" homebuilt strut dob (f4.5 ZOC mirror), Nexus II, Moonlite focuser
Mounts - Ioptron Skyguider pro, Astro Physics GTO900
Cameras and lenses - ZWO 2600 mc, 290 mm mini, Canon 60D modded with Rokinon 10mm 2.8; Rokinon 135mm f2

Skysafari 6 Pro, Astro Pixel Processor, Pixinsight - using Mac tablet and ASIair pro to run the AP rig.

"Mothers! It is there!" - Rafael Gonzales-Acuna, 2018.
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Kanadalainen
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Re: Building a fixed post mirror grinding machine

#20

Post by Kanadalainen »


I I had a nice piece of 3/4" stainless dowel that was begging to be used. So I bought a cheap pillow block to provide the locator for the metal dowel, and then drilled the overarm to fit. These pillow blocks are $8 and come complete with a locking collar - great deal. :)

I then needed to build another locator for the dowel to keep it from shifting under load and have a bar of 6061 aluminum, repurposed from another project that I worked on about 10 years ago. Sometimes, keeping old stuff works out well.
Attachments
IMG_7843.JPG
New base sides for overarm with the placement of dowel
New base sides for overarm with the placement of dowel
IMG_8527.JPG
IMG_9822.JPG
Ian

Fracs: Stellarvue 70T f6; SW 120mm Esprit f7; "Mark Mk. II" - 60 mm Tasco f6; C80 frac f 11.4
SCT: C8 Edge f10 or f7 with reducer
Dob: 14.5" homebuilt strut dob (f4.5 ZOC mirror), Nexus II, Moonlite focuser
Mounts - Ioptron Skyguider pro, Astro Physics GTO900
Cameras and lenses - ZWO 2600 mc, 290 mm mini, Canon 60D modded with Rokinon 10mm 2.8; Rokinon 135mm f2

Skysafari 6 Pro, Astro Pixel Processor, Pixinsight - using Mac tablet and ASIair pro to run the AP rig.

"Mothers! It is there!" - Rafael Gonzales-Acuna, 2018.
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