SW Dob mod, new Alt bearings

[michaeldurban]

SkyWatcher 10" Altitude bearings modification

Ever since I first carried my SW 10" dob outside to look at the

marvels of the cosmos I was instantly put off by the creaky squeeky

and downright jerky action of the altitude adjusters.

Everybody who owns a SW dob knows the sticky and jumpy action

emanating from those pesky red rings.

The SW dob uses a (apparently patented) friction bearing system.

The problem is that the main circles on either side of the OTA rest on rollers

(which...don't roll..)

So, with the help of CN (see link below) I set out what I should have done

ages ago...

Get rid of those pesky rollers !

First...the ingredients..

I used four 8mm x 50mm bolts (0.25" x 2") and purchased 8 little roller bearings

(ID = 0.25", OD = 22mm or about 0.8" ?? )

Also bought some washers and locknuts.

Next I removed the old white rollers, and gently drilled out the holes to accomodate

for the larger 8mm bolts.

I know...it looks messy and painful..as you can see I tried sticking on milk jug cut-outs..

With the original rollers removed you slide in the new bolts.

Make sure the threaded part sticks outwards...

Then insert the bearings with washers.

Now, the bearings might be larger in diameter in relation to the original rollers. Which can cause

a problem when assembling the scope and trying to insert the handles.

Luckily there is about 3mm of play in the 'handle hole'...so there is no need to adjust anything.

And there it is...just need to cut down the bolts sticking out..

My scope is whole again..!!!

The result???

about a thousand times more smoother action...

This whole project took me about 20 minutes...and is rock solid...

(many thanks to CN and Iceinspace) click here for the CN link and more photo's http://www.cloudynights.com/ubbarchive/showflat.php/Cat/0/Number/2841780/page/96/view/collapsed/sb/5/o/all/fpart/1

[weareborg]

I've just done this mod on my 8" Skywatcher after reading this post a few weeks ago. It sure does make a difference. The only problem I had was the space between the bolt head and OTA bearing. Using 2 bearings resulted in the bolt head rubbing against it.

[Peter Drew]

I use a similar system on my 30" where the weight would be too much for the traditional arrangement. Adjustable PTFE pressure pads control the degree of effort to move in altitude. 

[DrNeb]

Old thread... I know.

However I'm in desperate need of this mod. I've pretty much stopped using my skywatcher because I had how jerky it is on both alt and az. This looks like a great fix for alt! 

What do you think of these? http://www.bearings-direct.com/Miniature-Metric-Series/Standard-Edge/Stainless-Steel/W607-2Z-SKF-Deep-Groove-Miniature-Metric-Ball-Bearing/flypage.tpl.html

they are slightly smaller in OD and ID, maybe it would help with assembly? or would you recommend I stick with 22mm?

[weareborg]

I don't see why not.  They are bit pricy though.  Think I only paid a couple of quid for a pack of 10 from China