What type of bearing is required.

[Doc]

I need opinions guys....

Imagine a dobsonian scope, it only has one bearing on the altitude side of it. A shaft goes through the bearing, on one end of the shaft is a dovetail for the scope to be attached on the other end are threads and a handle.

What bearing is needed to adjust for tension and locking, the tension is produced by tightening and untightening a handle that in turn tightens/untightens against the bearing.

I hope I made this clear.

I'm thinking either taper roller bearing or thrust bearings.

Any ideas.

[FraserClarke]

cantilevered weight, or counter-balanced?

[barkis]

You want it as a clutch as well as a support bearing Mick?

I think the two will need to be separate entities, unless someone has a solution. A taper roller bearing can be tensioned to eliminate play, but some sort of fixed plate, faced with a tensionable clutch plate needs to be employed. The tension on the clutch can be applied by having a threaded shaft through the bearing, and fixed plate, then the clutch disc placed on the shaft, and a threaded wheel to apply the tensioning. The Dob. side supporting this weight, will by necessity, have to be robust.

A lot depends on weight of course.

Ron.

[Bizibilder]

Barkis is right - a bearing should be just that! Both taper roller and thrust bearings are critical in their set-up in order to function properly, so the "clutch" should be entirely seperate.

[Doc]

Any sites on the web guys that sell these clutches, or anymore info anywhere.

So just tightening a washer against a taper roller bearing isn't enough.

My thought was as long as the OTA is balanced correctly, a little tension applied to a taper roller bearing should be enough to stop it from moving.

I'll look up clutches.

[Doc]

The actual side support Ron is going to be made up of 40mm thick baltic pine, I know a friend who has some. Might even make the ground board from it.

The idea originally was to make it all from aluminium but the price is rather steep.

[Rusty Strings]

Just curious Mick, what scope is this to mount?

[Doc]

It's not my LB

Thinking about a 6" F11 dob from OO.

[barkis]

Mick, that scope is not going to be a heavyweight by a long chalk.

Using compression of the taper roller bearing will make a poor clutch in my opinion. If you applied a 1/4" thick felt pad disc to the side of the Dob. and got a disc of 1/4" Aluminium, machined to a polish finish, then place a compression spring between the polished ally, and the threaded wheel that will apply the tension, you will have a decent and smooth operating braking mechanism.

Felt, riding on Teflon is a smooth operator too.

I think something like 6" diameter will be OK. Keep the felt a lttle less diameter.

Just a suggestion Mick, you may get one that appeals more.

Ron.

[Doc]

I like this suggestion Ron, I'll do a few drawings and post them up so you can comment on them.