Help - Sticky Dob

[Lyinxz]

Hi All,

I have a ARGO NAVIS connected to my 10" SW Dob, it’s doing great but one major drawback for me seems to be that the mounts ALT and AZ are sticky. Which makes it hard to fine tune the accuracy of the OTA's movement. Which in turn affects the Argo.

I’ve done my research and spoken to some of the older guys in my astro-club and have had a couple of suggestions given to me.

I’ve decided to fix the ALT by replacing the nylon stubs with shielded bearings of the same diameter.
As per this post below:
http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/2841780/page/2/view/collapsed/sb/5/o/all/fpart/1' (http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/2841780/page/2/view/collapsed/sb/5/o/all/fpart/1')


However I would love some suggestions on fixing the AZ motion.
I have read that "Felt Pads" are good?
Has anyone had any experience with these? I would love to hear your thoughts on this..

Someone also suggested a Lazy Susan to be installed, but I don’t know where to start with installing or even getting the parts for it.

Any other ideas guys?

Really appreciate your advice..:)

Cheers,
Ash

[erick]

First thing is to try and get it working better as it is, before you start changing things. Hard to do without seeing it. You need to have a good look at the bearings. The altitude can be easily examined. The azimuth - you have to pull the ground board off the base.

Can you take some photos and describe the current bearings for us. There have been many changes in design over some years.

It might be as simple as a good clean and the application of some good silicone car polish to the surfaces that the high density PTFE bearings are contacting.

[Rod]

Hi Ash,

I had sticky bearings once on a home made dob. The simplest fix is to try virgin teflon instead of the plastic that it sounds like is supplied on your scope.

I did what you are proposing with the bearings on both the altitude and azimuth bearings, except that I kept one teflon bearing on each surface. This added back a little friction and gave a very nice motion in both axes. The bearing solution works best against a metal surface although I have found it works OK on smooth laminate too.

Good Luck!

Rod.

[Lyinxz]

Hi Erick, Rod
Thanks for your response and interest to assist.
The link below shows the current white nylon bearings that are currently in use for the ALT motion and also the replacement shielded bearings.
http://www.spacealberta.com/equipment/dob12/bearing3.jpg

As for the AZ motion, I’m pretty sure as Rod has mentioned they are cheap Teflon pads.
Rod: by “Virgin Teflon” are you referring to “new” Teflon pads or is “virgin” a type of Teflon pad?
Erick, I did read that car polish or wax can help with resolving the stickiness of movement, however I really want to find a permanent fix..

[Rod]

Hi Ash,

Virgin Teflon is "pure" Teflon, that is, it has no fillers (impurities) added.

I have used cheaper teflon mainly but did try virgin teflon once and it was significantly better.

Rod.

[erick]

I'm not clear on the nature of the bearings in the SW - I'm not sure how the bearings in the photo work, so I cannot say much else.

I suggest that you keep searching IIS and wider for "improving dob movement" and "dob stiction" "dob bearings" etc. You will find a thread with me installing ebony star laminate on alt and azi bearing surfaces and installing better teflon. You will find threads with discussion of cleaning and lubricating (silicone polish, even Mr Sheen!) of the surfaces. You'll find mention of providing better support at the azi pivot point to reduce friction. You'll find where people have installed "lazy susan" bearings for the azi movement. Big hardware stores sell them and there are specialist suppliers with a bigger range. I've forgotten what they are called - it's not "lazy susan"!

[Batfink]

Hi Ash,
I have the 8" version and am having the same trouble, where did you get those bearings, is there a part no.
Thanks
Peter.

[nightstalker]

I tried a felt and a few differant ways of improving movement when I finished my dob, felt was always a little sticky I found .. In the end I went with a wipe of metho to clean the surfaces .. and when dry a wipe with mr sheen.. alt every trip out as it only takes a minute and az every couple of trips as it dosn't seem to gather as much crud.

I find it works great.. that little nudge that sends your argo target
out of view all the time just dosn't happen when I keep both clean and sheened :)

[hickny]

Here is a web address for a lazy susan bearing
http://www.carbatec.com.au/lazy-susan-bearings_c15410

As Rod says virgin teflon should also do the trick.

[Lyinxz]

Thanks for the input guys, I'l keep on it.

Cheers for the website hickny, thats exactly what I was after! :)

Batfink: I am going to follow the post below:
http://www.iceinspace.com.au/forum/showthread.php?p=417436#post417436

I orderd the bearings from a company as recommended by the post called VXB in California.
These are the ones I orded: http://www.vxb.com/page/bearings/PROD/R4AZZ

They deliver international, so I am patentiley waiting! :)

[Lyinxz]

Erick, :question:

I did some research into "Ebony Star" and user comments and results seem to praise this concept very much. In fact it is mentioned that this is what is used on Obession telescopes?

My understanding is that it some side of material that you stick to the top base of the az base. Then this material glides really well with the teflon pads that are on the bottom base..

Could you be kind enough to explain why this works so well? And also If i am understanding the concept correctley?


:thanx:

[erick]

Ebony Star - read up here:-

http://astro.umsystem.edu/atm/ARCHIVES/SEP96/msg00425.html

http://www.meridiantelescopes.com/ebonystar.htm

Read up on fitting Ebony Star to a 12" dob here:-

http://www.iceinspace.com.au/41-451-0-0-1-0.html

Here is a thread where I installed Ebony Star on an 8" dob:-

http://www.iceinspace.com.au/forum/showthread.php?t=20612

and another discussing it:-

http://www.iceinspace.com.au/forum/showthread.php?t=19132

Some more info here:-

http://www.iceinspace.com.au/forum/showthread.php?t=40796

Hope this helps. :)

[Batfink]

Thanks for that, make sure you let us all know how it goes, I'm thinking of doing the same.

[Lyinxz]

Erick, thanks for finding those links for me! :thumbsup:

Batfink; will do mate

[Batfink]

I did this mod, replacing the teflon bearings with the shielded bearings, and what a difference it made, but, one small issue that others should be aware of, the shielded bearings are a slightly smaller diameter than the teflon ones, so when you have screwed in the tension handles they take up the difference in height and are actually supporting the weight of the scope rather than the bearings. You can actually see a small gap between the scope and bearings, so you may have to remove the plastic sleeves on the base that the handles slide through which makes the holes slightly wider so the scope can sit on the bearings.

Peter.

[mozzie]

hi ash i had the same prob with my 8" dob the teflon pads are stappled there and are cheap.
i went to my local plastics factory,they sell teflon,they cut me 3 pieces 25x50x5mm and 1 50x50x5mm.counter sunk the 3 smaller pieces so the stainless steel screws didnt pretude screwed them to the outside edge of the base and the 50x50 drilled the centre to allow base bolt to go through,this takes most of the weight of the scope.bolted base back together and the az movement is smooth and a pleasure to use without any sticking.
when buying the teflon its bloody expensive and they had a couple of different thicknesses,i choose the 5mm one to work with and was able to counter sink screw heads,also bevelled all the edges about 1.5mm to have nothing catch on the base
hope this helps you or other iis members

[norm]

I think Ash has parted ways with Astronomy and may have sold all his gear:shrug:.

Norm