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Adam Brunette
member


Reged: 01/13/13

Loc: Charlton, Massachusetts
Re: Open Source Equatorial Mount new [Re: Adam Brunette]
      #5638032 - 01/22/13 11:42 PM

Alright, As I promised, here is an updated cut away view. This is incorporating the cork friction disks I mentioned earlier on. RA shaft is hollow to accept a polar scope. Counterweight shaft screws into the DEC shaft for modular approach.

Next part I plan to work on is the fork mount and base.

Enjoy!



Link for full rez version. https://docs.google.com/file/d/0B_sezR3BZVeIYXUtS0Z4Ykhpdjg/edit

-Adam

Edited by Adam Brunette (01/22/13 11:47 PM)


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orlyandico
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Reged: 08/10/09

Loc: Singapore
Re: Open Source Equatorial Mount new [Re: Adam Brunette]
      #5638155 - 01/23/13 01:15 AM

sounds like it will need a lathe to build...

this is the cheapest source of gears I've seen...
http://www.gototelescopes.com/gears.htm

although Edward Byers (seller ID erbyers on ebay) sometimes sells his fabulous gears on ebay. They are more expensive than the Aeroquest gears though.. but are a known good quantity. The earliest Paramount GT mounts used Byers gears.


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Startraffic
professor emeritus
*****

Reged: 02/12/06

Loc: Lat. 39.143345, Long. -77.1748...
Re: Open Source Equatorial Mount new [Re: ahopp]
      #5638311 - 01/23/13 06:56 AM

Ahopp,
Mine will be a 8'x16' bumper pull Obs with a 1kw gen, solar & batteries. The mount will be lowered through the floor to sit in the ground & isolated from the trailer which will be raised on jacks to level. It'll make for a nice stable portable obs. The 8' dome will be either a Skyshed POD or an automated 8' Home dome & will be towards the front of the trailer for balance & ease of mount operation. The electrical will be towards the back to counterbalance the dome, mount & scope. I hope to have a small warm room on the back but I haven't figured that out yet. I don't want to hijack this thread any further though.

Clear Dark Skies
Startraffic
39.138274 -77.168898


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neo
Carpal Tunnel
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Reged: 02/12/08

Loc: Iasi, Romania
Re: Open Source Equatorial Mount new [Re: m. allan noah]
      #5638348 - 01/23/13 07:46 AM

Quote:

Oh, and perhaps this will be of some use to you:

http://translate.googleusercontent.com/translate_c?client=firefox-a&depth...




I like that for a home made mount!
That's basically the same setup used in the WS mounts in the Youtube videos, and what I was on about although the author used only needle bearings.

Adam you are right about the needle bearings but you can get ones which already have the inner and outer racers. Check the Timken catalog. I can't find the link right now

By the way very ingenious design, now that I see it more complete! But you have to admit it's not going to be easy to build without proper tooling. Al the shafts would need high precision machining to get good coaxiality.
Also, I'm not sure I might be wrong, but it looks like the worm wheels will take quite a bit of load, the outer/inner axles resting directly on them. Probably this could be much better judjed with a 'live' prototype and see how it tracks.
All in all a very good effort and quite different design from what most of us are used to, so can't wait for further refinements


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m. allan noah
scholastic sledgehammer


Reged: 08/14/09

Loc: Virginia, USA
Re: Open Source Equatorial Mount new [Re: neo]
      #5638399 - 01/23/13 08:30 AM

It appears that you want to use the worm wheel as the container for the outer race. In use, there will be some outward force from the bearing. I think your thin-walled gear will be harder to make, and more likely to distort in that situation. I think you need to consider making the design more adaptable to gears from different sources, since that is the most likely highest cost component. Builders might want to scrounge a little, or might already own a gearset from another mount.

allan


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Adam Brunette
member


Reged: 01/13/13

Loc: Charlton, Massachusetts
Re: Open Source Equatorial Mount new [Re: m. allan noah]
      #6023290 - 08/13/13 03:48 PM

Hello Everyone,

It has been awhile since I have posted anything related to this. However, This does not mean progress has stopped on it!

Allen's last post got me thinking and I decided to change a few things.

I have redesigned how the gears mount to the upper bearings. Instead of being cut with the axis hub, they will be separate gears, loc-tight'ed to the bearing. The hub will also be loc-tight'ed to the bearing. This allows anybody with a large enough gear to bore to 160mm (6.299") can fit them to the mount.

In the past few months, I have been sourcing parts to build the mount. I happened to get the chance to get a set of 9" Byers gears and worms directly from Ed Byers. I talked to him on the phone a few times and he said he retired 2 years ago and was just selling off his left over inventory. He does not have much left now and what is left is on his Ebay page.

Anyways, I was able to get 2 sets of 9" gears with worms mounted on 2 bearing blocks with custom bore for $650. While this is more then I wanted to spend on gears, I could not pass up the opportunity of using Byers gears in my mount.

I have mostly made refinements to the design I posted a few months ago. Shafts the main shafts of each axis is a standard diameter for linear bearing rails. These are very accurate in roundness and also are usually chrome plated. This is perfect for needle roller bearings. The RA clutch shaft is 40mm OD with a 22mm ID. This allows some amount of cables to pass through the RA. Its better then nothing I guess.

The azimuth adjustment is done with 2 precision set screws. These are 2" long and have 80 threads per inch. The push against a block in the base to twist the mount. When your in position, there is 6 locking levers that clamp the base plate with the azimuth plate. These levers are re-position-able so once locked, you can release them and rotate them out of the way. There is +/- 7.5 degrees of azimuth adjustment.

The altitude has been modified a good bit from the original design. The adjustment screw is also a 80 thread setscrew allowing for super accurate adjustments. The block that mounts the set screw is adjustable to 4 positions. The altitude ranges are 10-25, 25 - 40, 40-55, 55-70. I'm in the middle at 42 degrees. The main pivot of the RA axis is on 2 - 3/8" shoulder bolts, and is locked in place with 2.25" 5 lobe knobs.

The biggest changes are the gear box's / gear covers. The lower half of the gear cover is actually the structural mount of the worm gear and servo mount. These are probably some of the most expensive pieces of aluminum. Its about $360 for all the material for both of the gear box's. The lower part of the gear box is 1.5" thick milled to a shell with a 1/2" bottom. Its alot of material to remove, but no real better way to accomplish a tight cover that looks good. The lower cover is bored to fit nicely around the main tube of the axis and is secured to a mounting ring with 5 - 5/16 stainless steel bolts in a circle pattern. The mounting ring is also machined to fit the main tube snugly and is secured to the tube with 5 more 5/16 bolts. Both axes are set up this way.

The upper gear cover is also milled from solid aluminum with a whole bored to fit the hub of the axis. The hub rids on the main bearing. The worm wheel is loc-tighted to the bearing and secured to the hub with 5 screws.

Half of the upper cover is removable to allow easy access to the worm gear and servo components.

The worm gear and servo are mounted on a common pivot point and are held down with shoulder screws. This allows the whole worm/servo block to pivot to maintain constant pressure of engagement between the worm gear and wheel. This pressure is applied with 2 set screws with springs. These are accessible from outside of the gear casing.

The counter weight shaft is an off the shelf piece from Astro Phsyics. It is a 1.875" shaft. I liked the look of the shaft and counter weights and wanted to use these. The shaft can be re sized easily as long as it can thread into the DEC tube.

The mount can be taken apart at the intersection of the RA and DEC for easier transport. If wanted, the RA tube can be removed from the support arms by removing the 2 hand knobs and the 2 shoulder bolts. This would break it into 3 sections roughly about 30lbs each.

Here is a few older renders of the mount with a model of my Meade LX200 12" EMC on it as well as 2 - 18lb counter weights.

I have begun building this now and will post what I have done.

-Adam

Mount minus counter weight shaft:
https://lh3.googleusercontent.com/-x5xFO0elZE0/Ugp9WF4snCI/AAAAAAAAM-M/2f1rPc...

Base of mount:
https://lh4.googleusercontent.com/-AZRvAbH85FU/Ugp9W6s2H3I/AAAAAAAAM-U/7EoGVD...

Meade 12" Tracking:
https://lh3.googleusercontent.com/-zh23pPszEpA/UdQRc163ZWI/AAAAAAAALuc/1YRRsl...

Meade 12" almost home:
https://lh4.googleusercontent.com/-xkH3oCzbzII/UdQRedbCG7I/AAAAAAAALuo/r6nr9Z...


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Adam Brunette
member


Reged: 01/13/13

Loc: Charlton, Massachusetts
Re: Open Source Equatorial Mount new [Re: Adam Brunette]
      #6023324 - 08/13/13 04:04 PM

Here is a link to the latest render that just finished. You can see the servo/worm gear mount on the DEC axis.

https://lh5.googleusercontent.com/-38KHu1Rt1hY/UgqQetect7I/AAAAAAAAM-w/duSZZN...


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Pinbout
Postmaster
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Reged: 02/22/10

Loc: nj
Re: Open Source Equatorial Mount new [Re: Adam Brunette]
      #6023695 - 08/13/13 06:33 PM

again this is open source atm'ing

I see your very nice renderings, but I haven't seen access to your model.

and strock puts up a pdf of the cut parts and hand drawings for open source


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BoriSpider
Carpal Tunnel


Reged: 08/10/04

Loc: S.W.FLA
Re: Open Source Equatorial Mount new [Re: Pinbout]
      #6024833 - 08/14/13 10:44 AM

Yes, access to the models would be nice. That way others can contribute.
You can always put them up on thingiverse.com or Thingtracker which is a github.com based deal(since MakerBot is no longer open-source-ish).


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Adam Brunette
member


Reged: 01/13/13

Loc: Charlton, Massachusetts
Re: Open Source Equatorial Mount new [Re: BoriSpider]
      #6024853 - 08/14/13 10:55 AM

Can do! I will look into it. Currently it is in Solidworks.

-Adam


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Pinbout
Postmaster
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Reged: 02/22/10

Loc: nj
Re: Open Source Equatorial Mount new [Re: Adam Brunette]
      #6024903 - 08/14/13 11:31 AM

put it in sketchup

http://www.javelin-tech.com/blog/2011/03/export-sw-to-sketchup/


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jhayes_tucson
professor emeritus
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Reged: 08/26/12

Loc: Bend, OR
Re: Open Source Equatorial Mount new [Re: Adam Brunette]
      #6025141 - 08/14/13 01:30 PM

After taking a quick look at your design, I'll give you a few things to think about: You can get better load capability (both radial and axial) and zero out backlash by using tapered roller bearings. They need a preload, which can be done with a threaded nut bearing on the inner race along the axis. Shaft stiffness becomes a little more important but you want to pay attention to that anyway so you should look at the effect of hollow shafts on bending moments and torsional rigidity. In any case, you are wise to incorporate some way to add and control friction for each axis. With any kind of roller bearing, the motion will be way too smooth to balance without friction control. I believe that you are better off putting a mounting boss on the RA axis for a small alignment scope. Mount it with alignment pins and a quick release so that it can be easily removed. Putting a hole through the Dec axis to accommodate an alignment system isn't that good for rigidity; though it helps with weight. Finally, where do you put drives on this design?

John


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m. allan noah
scholastic sledgehammer


Reged: 08/14/09

Loc: Virginia, USA
Re: Open Source Equatorial Mount new [Re: jhayes_tucson]
      #6033178 - 08/18/13 04:39 PM

All these renderings just show us the same info over and over again. We all know what the outside of a black GEM looks like

We need a cutaway view to help you develop the idea further.

allan


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Adam Brunette
member


Reged: 01/13/13

Loc: Charlton, Massachusetts
Re: Open Source Equatorial Mount new [Re: m. allan noah]
      #6035555 - 08/19/13 10:57 PM

Hello Allan,

I generated this one a few days ago, but didnt get a chance to post it yet.


And a high rez iso sectional:
https://lh3.googleusercontent.com/-iOrZhxi8dLE/UhLYnA5htQI/AAAAAAAANIo/RL8upk...

The yellow rectangle with the notch is the worm wheel and the gold block with circle touching the worm wheel is the worm gear and mounting block. The grey block next to the worm block is the worm /servo mount.

The needle roller bearings are not shown on either axis so use your imagination where the cutouts are on the axis bearing preload shaft. The shaft inside the axis shaft is the clutch shaft for tightening the clutch.

-Adam


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