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Home made Binocular fork mount

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#1 tomb18

tomb18

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Posted 11 January 2020 - 07:32 PM

Hi

Recently I purchased an APM 100mm Apo Binocular with the APM center mount.  While the center mount is nice and compact and works well I found that as I increased the magnification to 60x and beyond, the vibration was just a bit too much.  Thus I started thinking about building my own fork mount.

The difficult part for this was coming up with decent bearings for altitude and azimuth. So I got to thinking and looking at the commercial APM fork mount, it seemed that the azimuth bearing is quite close in appearance  to the center mount bearing.  So I decided to use the existing az bearing and find ways for the Alt bearings.

 

Looking through the McMaster Carr catalog turned up the following 4 parts:

IMG 11012020 185423 (1080 X 1920 pixel)

I used a teflon bearing that fit a flange mount 3/4" shaft that had a 5/8" thread at the end. A thrust bearing made out of 1/8" teflon sheet provided the perfect spacing through the 1/4" aluminum arm.  On the other end, I added a 3/4" inside diameter roller bearing and then 3d printed a knob that held a 5/8" bolt.  The result, assembled looks like this:

IMG 11012020 185112 (1080 X 1920 pixel)
 
That took care of the azimuth.  I then purchased some 20x80 and 20x60 aluminum extrusions as well as a nice vixen dovetail mount from ebay.
 
IMG 11012020 185137 (1080 X 1920 pixel)
 
I wanted to have shaft encoders to use with a Nexus DSC so I drilled out and tapped one altitude axis and placed an AMT 101 encoder there with a 3d printed support. 
 
The azimuth axis turned out to be more challenging.  I first started to drill through the shaft for the azimuth thinking I would add a shaft through the existing bearing.  Well the main shaft was far to hardened for me to do anything with it.  So instead I 3D printed a GT2 pulley which was a press fit on the outer azimuth bearing casing and designed a support for a smaller pulley with a shaft through to the azimuth encoder.
IMG 11012020 185155 (1080 X 1920 pixel)
.
 
The resulting complete fork mount looks like this:
IMG 11012020 185359 (1080 X 1920 pixel)
IMG 11012020 185221 (1080 X 1920 pixel)

 

The black box under the mount is the Nexus II DSC which I use with an Android tablet and Sky Safari.
Total cost was around $320, a lot of which was postage ordering the things from all over the place. So here in Canada I saved a cool $1000 or so over the commercial cost. (Money's gone.  I bought a mini-lathe with the savings) The aluminum arms were done on a Shapeoko 3 CNC mill but you could do the same with hand tools if you have the patience.
Hope this helps some adventurous ATM's.
Tom

 

 


Edited by tomb18, 11 January 2020 - 07:39 PM.

  • Diego, PrestonE, psandelle and 7 others like this

#2 yukosteel

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Posted 13 January 2020 - 02:57 PM

This is extremely nice DIY guide, thanks for sharing! Very cool result!



#3 Ken Watts

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Posted 16 January 2020 - 11:04 AM

Nice build!



#4 John Miele

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Posted 17 January 2020 - 01:27 PM

Outstanding!!!


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