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orlyandico
Postmaster
*****

Reged: 08/10/09

Loc: Singapore
Re: Open Source Equatorial Mount new [Re: skywolf856]
      #5631565 - 01/19/13 01:21 PM

you can get the gears from Aeroquest:

http://www.aeroquest-machining.com/pricing.php

smaller one for the DEC. or, if goto is not necessary, use a tangent-arm DEC. it would be simpler, cheaper, and suffer less from backlash and stiction.

i would vote for a Raspberry Pi (or Chipkit32 Arduino) for the Goto controller, if Goto is desired.

the 10 Micron mounts use an embedded Linux SBC, not the cheesy low-RAM microcontrollers that are generally used in mounts.


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BoriSpider
Carpal Tunnel


Reged: 08/10/04

Loc: S.W.FLA
Re: Open Source Equatorial Mount new [Re: orlyandico]
      #5633021 - 01/20/13 11:25 AM

I should know a little about the OpenSource licensing since I
follow alot of OS projects, but I don't. Adam can join the G+
community "Makers, hackers, artists, engineers" community run
by adafruit.com and get the answers there.

I like this open source astro equipment trend. I have(just got)
a 3d printer. If the cad files are in a Blender friendly format
I can get them to my printer and print them to see how they fit together.
If the files can be exported to a '.stl' file, even better. If proto-typing in plastic will help I can be of
service.


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hectar
member


Reged: 12/24/12

Loc: Ontario, Canada
Re: Open Source Equatorial Mount new [Re: BoriSpider]
      #5633072 - 01/20/13 12:09 PM

Quote:

I should know a little about the OpenSource licensing since I
follow alot of OS projects, but I don't. Adam can join the G+
community "Makers, hackers, artists, engineers" community run
by adafruit.com and get the answers there.

I like this open source astro equipment trend. I have(just got)
a 3d printer. If the cad files are in a Blender friendly format
I can get them to my printer and print them to see how they fit together.
If the files can be exported to a '.stl' file, even better. If proto-typing in plastic will help I can be of
service.




Me too!. "3d printer" which is kinda misleading term, is actullay a full manufacturing device; I dont have yet, but I am planning to get one. They are great for building proto-type parts.


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ccaissie
professor emeritus


Reged: 09/13/10

Loc: Whitefield, Maine
Re: Open Source Equatorial Mount new [Re: hectar]
      #5633319 - 01/20/13 02:19 PM Attachment (40 downloads)

A lot of nice looking work can be done using pipe fittings bored to suit bearing inserts etc. Clearly you want to get past the "sawmill" look on your mount.

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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]
      #5634425 - 01/21/13 07:21 AM

Tony,
I've actually got 2 trailers underway. One is a stock 16ft beavertail twin axle car trailer that I got for moving my tractor with. The other is a purpose built 9ftx16ft dual axle trailer for a 14.5f30 Shiefspeigler Bino obs. I just got the plans approved by MD Motor Vehicle Administration (after 4 yrs of design work!) & the construction/welding jig built. I haven't done much more than gather steel & axles yet. & I'm still guessing that the Opticcraft 8-9 will hold the scope. The scope & mirrors haven't been built yet.

Clear Dark Skies
Startraffic
39.138274 -77.168898

Edited by Startraffic (01/21/13 11:32 AM)


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Adam Brunette
member


Reged: 01/13/13

Loc: Charlton, Massachusetts
Re: Open Source Equatorial Mount new [Re: ccaissie]
      #5634773 - 01/21/13 11:41 AM

Quote:

you can get the gears from Aeroquest:

http://www.aeroquest-machining.com/pricing.php

smaller one for the DEC. or, if goto is not necessary, use a tangent-arm DEC. it would be simpler, cheaper, and suffer less from backlash and stiction.

i would vote for a Raspberry Pi (or Chipkit32 Arduino) for the Goto controller, if Goto is desired.

the 10 Micron mounts use an embedded Linux SBC, not the cheesy low-RAM microcontrollers that are generally used in mounts.




Hello orlyandico,

Those are some nice gears!! Looks like top quality machining. I will keep them in mind, but they are super expensive.

This will be a GOTO mount.

The electronics will be AVR based which will make it Arduino compatible. My actual passion and schooling is electronic design. Machining and engineering is just a hobby.

This little guy I built a few months ago for work is a hand held network tester and cable checker complete with 2.4" color touchscreen: https://lh4.googleusercontent.com/-RIAzV510C8Q/ULts6l3hUJI/AAAAAAAAF3s/nhOLF8...
https://lh4.googleusercontent.com/-QVrQ1Gw6FI8/ULtsVaUQEEI/AAAAAAAAF28/nwWoxE...

Quote:

I should know a little about the OpenSource licensing since I
follow alot of OS projects, but I don't. Adam can join the G+
community "Makers, hackers, artists, engineers" community run
by adafruit.com and get the answers there.

I like this open source astro equipment trend. I have(just got)
a 3d printer. If the cad files are in a Blender friendly format
I can get them to my printer and print them to see how they fit together.
If the files can be exported to a '.stl' file, even better. If proto-typing in plastic will help I can be of
service.




BoriSpider,

YES!! all the files can be exported in numerous 3D formats. When the time comes, this might be an excellent way of building prototype pieces instead of aluminum!

Quote:

A lot of nice looking work can be done using pipe fittings bored to suit bearing inserts etc. Clearly you want to get past the "sawmill" look on your mount.




ccaissie,

That is a great idea! I will keep it in mind for a smaller project. This one Im sticking with pieces designed for the mount specifically and easy machining on a lathe.

-Adam


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Adam Brunette
member


Reged: 01/13/13

Loc: Charlton, Massachusetts
Re: Open Source Equatorial Mount new [Re: Adam Brunette]
      #5634847 - 01/21/13 12:22 PM

Alright, Sorry for the delay on the cutaway and dimensions.

First, the cutaway:
https://lh6.googleusercontent.com/-75FhZ3YBJAY/UP1waxVB8qI/AAAAAAAAHa0/JjdttC...

As you can see, The gear end of the 2 axes are supported by 6218-2rs deep groove bearings. At the far end of the housing, there is another bearing with a bearing pre-load nut. This is tightened down to take all the backlash out of the bearings and provide a fluid axis. The RA axis will be set up the same way.

You can see at the top of the DEC that I have been playing with a clutch design. This is based on the clutch in the Losmandy G11. The tan layer is a piece of cork used as a slip/friction surface for the clutch pad. This would have a secondary shaft through the center of the main shaft and a hand wheel on the end to adjust clutch tension. The thing that worries me is if the end plate and shaft are not rigid enough, they could flex when the clutch is loose and cause inaccuracy. I think bushings would be sufficient for holding the clutch shaft concentric with the axis shaft.

If this is acceptable, I will replicate it on the RA axis.

Here is a rough dimensional drawing. The ones marked "True" are radiuses.

All measurements are in Inch's.

https://lh5.googleusercontent.com/-Vo9XJry7Sek/UP1wbI-xfNI/AAAAAAAAHa4/EaOkyF...


Im still looking for suggestions on the range of latitude the mount should be capable of.

-Adam


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ahopp
sage


Reged: 05/24/12

Re: Open Source Equatorial Mount new [Re: Startraffic]
      #5635039 - 01/21/13 02:04 PM

Mine has an 8.5' by 10' observing room, retractible fabric roof. The front has an 8.5'x10' plus v-nose, for computer room and living quarters. I use a 3K Honda generator with a 200 AH battery for power. Custom 12vDC control panel to power all the gear. A/C plus baseboard and gas heat.

Tony


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BoriSpider
Carpal Tunnel


Reged: 08/10/04

Loc: S.W.FLA
Re: Open Source Equatorial Mount new [Re: ahopp]
      #5635439 - 01/21/13 05:48 PM

Looking good so far Adam. I love the 'lil tester/checker thing.

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neo
Carpal Tunnel
*****

Reged: 02/12/08

Loc: Iasi, Romania
Re: Open Source Equatorial Mount new [Re: BoriSpider]
      #5636279 - 01/22/13 06:20 AM

Nice design Adam!
How do you plan to mount the worm gears on the shafts( if that is what you are going to use)?
It would be a good idea though to use roller bearings instead of ball bearings for a better precision and as a sophistication you could use taper roller bearings on the back end of the shaft, especially if you want to go with the preloading idea. Also it would be a more efficient way to deal with the axial and radial forces when the mount points in different positions. I believe Takahashi uses this set up in their mounts.
If you want to go Losmandy way then you should consider mounting the worm wheel on a bearing on the Ra (or DEC) housing itself making it independent to the shaft and avoid the small errors due to flexing or bearing runout. The most important thing I see with this set up is that the worm and worm wheel keep the same contact which will help accuracy. In this way the shaft is driven only by the friction between the worm wheel and the flange of the shaft.
http://www.astro.uni-bonn.de/~mischa/mounts/g11_experiences.html

http://www.astromaster.org/esperienze_file/G11maintenance_e.htm

Here's also a new ukrainian series of mounts using pretty much the same design with very good accuracy, not very hard to build on a lathe.
http://www.youtube.com/user/WhiteSwan180/videos?flow=grid&view=0


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m. allan noah
scholastic sledgehammer


Reged: 08/14/09

Loc: Virginia, USA
Re: Open Source Equatorial Mount new [Re: neo]
      #5636379 - 01/22/13 08:24 AM

You need to add a flange or washer that covers the seals on the exposed side of the bearings. Eventually during transport, one of those will get hit and damaged.

allan


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Adam Brunette
member


Reged: 01/13/13

Loc: Charlton, Massachusetts
Re: Open Source Equatorial Mount new [Re: neo]
      #5636608 - 01/22/13 10:34 AM

Quote:

Nice design Adam!
How do you plan to mount the worm gears on the shafts( if that is what you are going to use)?
It would be a good idea though to use roller bearings instead of ball bearings for a better precision and as a sophistication you could use taper roller bearings on the back end of the shaft, especially if you want to go with the preloading idea. Also it would be a more efficient way to deal with the axial and radial forces when the mount points in different positions. I believe Takahashi uses this set up in their mounts.
If you want to go Losmandy way then you should consider mounting the worm wheel on a bearing on the Ra (or DEC) housing itself making it independent to the shaft and avoid the small errors due to flexing or bearing runout. The most important thing I see with this set up is that the worm and worm wheel keep the same contact which will help accuracy. In this way the shaft is driven only by the friction between the worm wheel and the flange of the shaft.
http://www.astro.uni-bonn.de/~mischa/mounts/g11_experiences.html

http://www.astromaster.org/esperienze_file/G11maintenance_e.htm

Here's also a new ukrainian series of mounts using pretty much the same design with very good accuracy, not very hard to build on a lathe.
http://www.youtube.com/user/WhiteSwan180/videos?flow=grid&view=0




The large cylinder that mounts on the large bearing is to be the worm gear.

Taper bearings are better for preloading, but with every advantage comes drawbacks. Taper bearings are never sealed units (that I have seen). This means measures have to be taken to hold the grease in the bearings.

One major issue to overcome in the homemade/diy category is in order to use needle and direct roller bearings is the shafts need to be hardened and ground as they serve as the inner race. Without this, you will have very poor results. From my past research, it is perfectly acceptable to preload deep groove bearings. A common preload for these is about 4 percent. 5% is 300lbs of preload.

Thanks for the links. Lots of good breakdown pictures to look at.

The Ukrainian mounts are really nice! They look very well built. I cant understand anything they are saying, but I can tell they have has the shafts of the axes hardened and ground. In the 240 mount I made out what I think is cork for the friction pad between the RA gear and end mount.

Quote:

You need to add a flange or washer that covers the seals on the exposed side of the bearings. Eventually during transport, one of those will get hit and damaged.

allan




Allan,

The small end of each axis will be covered by the knob that tightens the clutch. The large bearing will need some kind of cover, but this will also serve as a gear cover.

-Adam


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Adam Brunette
member


Reged: 01/13/13

Loc: Charlton, Massachusetts
Re: Open Source Equatorial Mount new [Re: Adam Brunette]
      #5637096 - 01/22/13 02:58 PM

Does anybody know if the diameter and thread of polar scopes for aligning a mount are a common size? I was looking at some of the Celestron ones, but they don't have any measurement, They just say that they fit X mount.

-Adam


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hectar
member


Reged: 12/24/12

Loc: Ontario, Canada
Re: Open Source Equatorial Mount new [Re: Adam Brunette]
      #5637483 - 01/22/13 06:14 PM

Quote:

Alright, Sorry for the delay on the cutaway and dimensions.

First, the cutaway:
https://lh6.googleusercontent.com/-75FhZ3YBJAY/UP1waxVB8qI/AAAAAAAAHa0/JjdttC...

As you can see, The gear end of the 2 axes are supported by 6218-2rs deep groove bearings. At the far end of the housing, there is another bearing with a bearing pre-load nut. This is tightened down to take all the backlash out of the bearings and provide a fluid axis. The RA axis will be set up the same way.

You can see at the top of the DEC that I have been playing with a clutch design. This is based on the clutch in the Losmandy G11. The tan layer is a piece of cork used as a slip/friction surface for the clutch pad. This would have a secondary shaft through the center of the main shaft and a hand wheel on the end to adjust clutch tension. The thing that worries me is if the end plate and shaft are not rigid enough, they could flex when the clutch is loose and cause inaccuracy. I think bushings would be sufficient for holding the clutch shaft concentric with the axis shaft.

If this is acceptable, I will replicate it on the RA axis.

Here is a rough dimensional drawing. The ones marked "True" are radiuses.

All measurements are in Inch's.

https://lh5.googleusercontent.com/-Vo9XJry7Sek/UP1wbI-xfNI/AAAAAAAAHa4/EaOkyF...


Im still looking for suggestions on the range of latitude the mount should be capable of.

-Adam




Adam,
I am trying to figure out your design. when designing with two bearings, one end is always "locked". ie one bearing should be: #1. locked on the shaft (ie it's inner race locked with a nut) , and, #2. Locked with in the casing. i.e. Its' outer race locked "with in the casing/housing" by means of a cap, leaving only 0.001-0.003" clearance for the thermal expansion of the bearing race itself.
Now, the other (2nd) end/bearing would be be still in the casing and bearing cap should be there but it will not be locked. it would have rather 0.032 to 0.125 or more gap between the outer race and cap.(Gap is necessary for the thermal expansion of the shaft in the axial direction)

Your design has lock nut in the bottom (so inner race is locked up against the shaft shoulder but outer race is not locked (no bearing cap there), what will stop it from falling? which way it expand due to heat or cold?? it also raises the question how/which order you will install those two 6218-2RS bearings.

In my opinion, 6218-2RS is not a thrust bearing. It is rather just a radial bearing. ( single row deep groove ball bearing with two seals )(suffix RS ). (Although, it can be used as a hobby project, but it wont be a perfect design).
Also, are you suggesting preloading it by the nut to somehow eliminate the bearing's own internal clearance?
I am thinking about posting a sketch here, but I would wait: what you and others think about this?
Btw, lattitude could be 0-90 degrees. if you end up with 70-80, it's ok

Hectar


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hectar
member


Reged: 12/24/12

Loc: Ontario, Canada
Re: Open Source Equatorial Mount new [Re: neo]
      #5637498 - 01/22/13 06:23 PM

Quote:

Nice design Adam!
How do you plan to mount the worm gears on the shafts( if that is what you are going to use)?
It would be a good idea though to use roller bearings instead of ball bearings for a better precision and as a sophistication you could use taper roller bearings on the back end of the shaft, especially if you want to go with the preloading idea. Also it would be a more efficient way to deal with the axial and radial forces when the mount points in different positions. I believe Takahashi uses this set up in their mounts.
If you want to go Losmandy way then you should consider mounting the worm wheel on a bearing on the Ra (or DEC) housing itself making it independent to the shaft and avoid the small errors due to flexing or bearing runout. The most important thing I see with this set up is that the worm and worm wheel keep the same contact which will help accuracy. In this way the shaft is driven only by the friction between the worm wheel and the flange of the shaft.
http://www.astro.uni-bonn.de/~mischa/mounts/g11_experiences.html

http://www.astromaster.org/esperienze_file/G11maintenance_e.htm

Here's also a new ukrainian series of mounts using pretty much the same design with very good accuracy, not very hard to build on a lathe.
http://www.youtube.com/user/WhiteSwan180/videos?flow=grid&view=0



I like your idea better. If someone can translate video, it would be great.


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Adam Brunette
member


Reged: 01/13/13

Loc: Charlton, Massachusetts
Re: Open Source Equatorial Mount new [Re: hectar]
      #5637652 - 01/22/13 08:14 PM

Hectar,

Some gaps and reliefs need to be updated. I have done extensive work on the design today, and hope to post a new picture some time tonight. I think it will clear up some questions.

I understand about the bearing concern. The 7218 angular contact ball bearing is a direct fit for the deep groove bearing, but the cost is alot higher. It is a good fit for the task though. There is also the 30218 which is a taper roller bearing.

There are options for the far end bearing as well. The part I don't like still is these type bearings need lubrication.

-Adam


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m. allan noah
scholastic sledgehammer


Reged: 08/14/09

Loc: Virginia, USA
Re: Open Source Equatorial Mount new [Re: hectar]
      #5637665 - 01/22/13 08:21 PM

Quote:


In my opinion, 6218-2RS is not a thrust bearing. It is rather just a radial bearing. ( single row deep groove ball bearing with two seals )(suffix RS ). (Although, it can be used as a hobby project, but it wont be a perfect design).
Also, are you suggesting preloading it by the nut to somehow eliminate the bearing's own internal clearance?





Don't get caught up in the name 'thrust' vs 'radial' a deep groove ball bearing is not all that far removed from an angular contact bearing. I routinely use them in this type of service with a bit of preload.

However, I would say that the 6218 is really much bigger than needed. In fact, I would be inclined to forgo the rolling bearing entirely on the big end of each axis. I am partial to something more like the Discmount uses, either a disk or a cone of plane bearing.

allan

Edited by m. allan noah (01/22/13 08:23 PM)


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m. allan noah
scholastic sledgehammer


Reged: 08/14/09

Loc: Virginia, USA
Re: Open Source Equatorial Mount new [Re: m. allan noah]
      #5637738 - 01/22/13 08:55 PM

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

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


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hectar
member


Reged: 12/24/12

Loc: Ontario, Canada
Re: Open Source Equatorial Mount new [Re: m. allan noah]
      #5637812 - 01/22/13 09:29 PM

Re: 6218-2RS, I almost forgot the cost. since they can take some axial load in both directions, they may be ok.
Adam, you could use/accomodate a cheap automotive lip seal at either one/both bearing caps, which would contain the grease, thus allowing you to use roller/taper/cone bearing at one end. They do come with both races (as suggested above as well). You have to search for a cheaper one though.

Thanks for posting link Allan.


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Adam Brunette
member


Reged: 01/13/13

Loc: Charlton, Massachusetts
Re: Open Source Equatorial Mount new [Re: hectar]
      #5637870 - 01/22/13 10:15 PM

Allan,

Do you have an example of this Diskmount method?

I still think the 6218-2rs is be best low cost solution. It will never spin more then 1 RPM. They can be had new on ebay for $30 each. Im thinking I will start with these bearings and if they are not up to the job, there are 2 other options that are a direct fit.

Thanks for the link to that! Im looking through it now.

Hectar,

That's a good idea about the lip seals. I never thought of those.

-Adam


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