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cheap alt az mount

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15 replies to this topic

#1 Pinbout

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Posted 03 March 2013 - 10:23 AM

I made this with the strategy of a dob az bearing.

Posted Image

I only put a couple of teflon tabs to help pivot.

Posted Image

when I made this vid the stepup ring 38-t2 was stripped so the camera was not tight against the eyepiece.

http://www.youtube.c...h?v=agf9YsftLKA

this is my model

http://sketchup.goog...b616d61f0299...

visually it works well enough for me to sell my desertsky... :grin:

#2 kfrederick

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Posted 03 March 2013 - 10:41 AM

cool

#3 nirvanix

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Posted 03 March 2013 - 11:18 AM

Very nice. :waytogo:

#4 anrran

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Posted 04 March 2013 - 10:24 PM

Nice! Do the teflon pads slide against the wood, or is there something in between the two?

#5 Pinbout

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Posted 04 March 2013 - 10:32 PM

for this test I cut small pads to run against formica 909-42 crystal finish laminate and carpet taped them to the wood.

I have uhmw discs but haven't installed them yet. I have found the uhmw will be a lot stiffer, but I have a lot laying around. :grin:

Posted Image

I used the same hardware as what I do for a dob az bearing but I tighten it a lot more. it hold position very well.

#6 anrran

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Posted 04 March 2013 - 11:18 PM

Thanks for the info...I was debating between getting a desert sky dsv-1 or trying to make my own friction type mount for a small refractor I have. Since I'm on a budget and have some spare wood lying around I think make one now!

#7 Jerry-rigged

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Posted 05 March 2013 - 09:01 AM

Neat idea. I've been needing a mount for my ETX80. Something like that should work nice.

#8 Pinbout

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Posted 05 March 2013 - 09:53 AM

if you make discs of teflon, which would spread the forces out over the entire bearing surface, keep the teflon thin, like 1/32.

#9 Pinbout

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Posted 14 March 2013 - 05:06 PM

got it painted, need a logo and a dovetail. but last night I was tracking jupiter easily at 260 mag visual.

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#10 careysub

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Posted 15 March 2013 - 09:49 AM

You can't beat the KISS principle!

I notice that you are using a threaded hole for the pivot bolt, not an unthreaded one and a thrust bearing on the opposite side like the StarBlast system.

Any comment on your experience with this arrangement?

#11 Pinbout

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Posted 15 March 2013 - 10:42 AM

Any comment on your experience with this arrangement?



never saw how they do it. I'm doing it kind-of-sort-of like astrosystems az pivot, and how I do my dobs. [oops I forgot to label the bronze bearing the bolt goes thru.]


not an unthreaded one and a thrust bearing on the opposite side like the StarBlast system.


so with that system you have two plates that can spin? I only need one plate to spin. My milk jug washer/steel washer acts like a thrust bearing keeping the bolt from loosening.


Right now I'm using uhmw as a slip clutch material but with the teflon it would be buttery smooth. Last night I over tightened the az bearing too much so that was very stiff to try to hand track a vid of jupiter in the eyepiece.

For regular visual viewing its no problem but to keep jupiter at high mag onto the little vid chip is very painful even if I was using teflon.

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#12 Pinbout

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Posted 15 March 2013 - 10:37 PM

here's a really bad vid shootin jupiter, remember I had the azimuth too tight, and I can't keep my hands off the focuser or the zoom of the vid camera screwed to the eyepiece.

blackbox mount tracking jupiter

its a lot easier to track with the eyepiece then the vid.

#13 Gordon Rayner

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Posted 16 March 2013 - 11:06 PM

I accidentally saw some relevant bearing construction information from RichV. He used a small roller thrust bearing where you have a milk jug washer and a steel washer.

http://www.cloudynig...Number/5708871/

That post, and its vicinity, look to be useful.

Also see the following post, and its vicinity:

http://www.cloudynig...Number/5147471/

I have not tried the small roller thrust bearing method shown, but may do so soon for a bearing about to be constructed . 3-wave spring washers from McMaster-Carr have solved similar problems for me. Sandwiched between two ordinary steel washers, a 3-wave spring washer provides a range of stable preloads on some small teflon washers for p-mount joints

Some combination of Teflon (or milk jug PE, if you must) and/or the cited roller bearing and/or a 3-wave washer
should be a satisfactory way to load the large main Teflon disc thrust bearing.

#14 Pinbout

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Posted 16 March 2013 - 11:47 PM

thanks for the links, yes these are great. I like the wavey washer also. I'm more of a needle roller thrust bearing guy myself.

but yes I must use the milk jug, its simple.

but when I do this for my dob az bearings I only use a bronze bearing with a shoulder and a metal washer, I don't put a lot of "load" onto the system.

#15 Mirzam

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Posted 17 March 2013 - 11:02 AM

Another option would be to get a 6" length of 6" aluminum square tubing from online metals. This would make a nice stiff support.

Aluminum mount structure

JimC

#16 Pinbout

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Posted 17 March 2013 - 11:31 AM

that would be cool. and get 1/2" thk discs waterjetted for around $40. but the b.b. would does hold its own.


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