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Laminate on Dob Alt Bearing?

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#1 Namestaken

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Posted 11 July 2020 - 02:55 PM

I have an Orion XT10 Classic that has been sitting in my garage for a couple years and the bearings - which were never very good - are now awful. I replaced the azimuth with a Lazy Susan and absolutely love it, it's perfect. My problem now is the altitude bearing. I replaced the "Teflon" pads that came with it but it's still very sticky when moving up and down. The Teflon pads I have on it now were pretty cheap and I don't have a lot of confidence they are even Teflon because it actually got worse. So I ordered some virgin PTFE from a reliable astronomy vendor to take that variable out of the equation.

 

With all that said, do people put laminate (such as Formica 909-42) on the alt bearing or is that just an azimuth thing? If yes to putting it on the alt, does the laminate come with an adhesive back that I just stick right onto the circular altitude bearing? If all that's correct, will I need to add some weights to balance out the scope with the reduced stiction?

 

Dobsonian.gifThanks in advance!



#2 Pinbout

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Posted 11 July 2020 - 03:11 PM

 

With all that said, do people put laminate (such as Formica 909-42) on the alt bearing...

Si


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#3 tjschultz2011

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Posted 11 July 2020 - 03:17 PM

Yeah laminate is used on the alt bearings also. It will either come with adhesive on the back or you will have to buy a can of it to spread or spray on first


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#4 kfiscus

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Posted 11 July 2020 - 04:38 PM

You might find that real Teflon does the trick.  You should play around with different spacing to get the feel right (2-sided tape, carpet tape).  Farther apart increases drag.  When you are happy with the locations, you can mount the Teflon pads with 2 small wire brads (nails) each.  Be sure to use a nail set to get the heads below the surface of the pads.

 

I'd hold off on adding laminate until you do the Teflon upgrade.  Even though laminate is thin, adding it will make the altitude trunnions larger (maybe too large) without countersinking the Teflon.


Edited by kfiscus, 11 July 2020 - 04:40 PM.

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#5 Pinbout

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Posted 11 July 2020 - 05:00 PM

 

Does the laminate come with an adhesive back that I just stick right onto the circular altitude bearing? I

Contact cement the laminate. Laminate comes in two thicknesses - get the thinner one. Vertical grade.


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#6 lphilpot

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Posted 11 July 2020 - 05:28 PM

I put laminate on altitude bearings of my Hardin Deep Space Hunter (i.e., GSO) Dob several years ago. I used contact cement and a couple of small screws on each end of the laminate strip to keep it from pulling up. Be careful that the ends are positioned so they won't cross the Teflon pads during normal movement, though. As I recall, the joint was about 45 degrees to the left of vertical with the OTA straight up on mine.

 

hardin-dsh8_altbearing.jpg


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#7 Namestaken

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Posted 11 July 2020 - 05:58 PM

Thanks all, I've gotten great advice! I was feeling confused and now I have some confidence grin.gif


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#8 lphilpot

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Posted 11 July 2020 - 06:11 PM

You can see other equally-applicable tweaks I made here:  http://pages.suddenl...ilpot/dsh8.html



#9 kfiscus

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Posted 11 July 2020 - 07:33 PM

Let us know how you do, even when you're done and happy.  Good luck.


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#10 Namestaken

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Posted 11 July 2020 - 08:57 PM

You can see other equally-applicable tweaks I made here:  http://pages.suddenl...ilpot/dsh8.html

Nice, thanks for this! I love looking at what other people have done with their Dobs smile.gif

 

Added a few things from your list to my to-do list. Magnetic counterweights and secondary mirror thumbscrews are genius. The only thing that didn't make sense to me was the primary mirror plate being removed. What does that help with?


Edited by Namestaken, 11 July 2020 - 10:08 PM.


#11 kfiscus

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Posted 11 July 2020 - 10:13 PM

If you like mods, check out the HUGE "Mega-Mods for Zhumell Dobs" thread in the Reflectors Forum (most of the modifications will work on any make of dob).  I'll bump the thread to make sure it is on page one.


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#12 Namestaken

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Posted 14 July 2020 - 08:39 PM

You might find that real Teflon does the trick.  You should play around with different spacing to get the feel right (2-sided tape, carpet tape).  Farther apart increases drag.  When you are happy with the locations, you can mount the Teflon pads with 2 small wire brads (nails) each.  Be sure to use a nail set to get the heads below the surface of the pads.

 

I'd hold off on adding laminate until you do the Teflon upgrade.  Even though laminate is thin, adding it will make the altitude trunnions larger (maybe too large) without countersinking the Teflon.

I'm so glad you said this. I just put the Teflon pads on and it is an amazing difference. With the tension springs fully tightened, it doesn't hold it's place when close to 90 or 180 degrees. I'm a little concerned about the 90 but the 180 doesn't bother me since the light dome blots out most of the stars close to the horizon. It's nothing a magnetic counterweight won't easily solve. I couldn't be happier with the performance, it's so smooth dancey.gif

 

Turns out the cheap "Teflon" I got on Amazon probably wasn't real Teflon...no surprise. I was getting so frustrated with it that I nearly stopped going out even though we've had a ton of clear, beautiful nights.




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