Roller bearings on a Dob

If you have a basic Dob that has been modified with roller bearings, sure,
grease is a simple way to add some drag.

Given the location of the bearing and the propensity of grease to attract dust
and dirt, I think its a good way to end up with a bearing full of yuck.

jon

Chris L Peterson wrote in message ...
On Tue, 21 Dec 2004 00:58:17 -0600, Bondo wrote:

I beg to differ. It depends on the grease. Light lithium is just fine in
fact I wouldnt use anything else on mine. But the right smooth (pure)
grease can add
just the amount of "drag" you were talking about -

The problem is that you don't have good control over the drag this way. I
was
speaking of what I consider the ideal design, with frictionless bearings
and a
tensioner system to set the drag. With such a design, you don't want drag
from
using a viscous grease in the bearings.

If you have a basic Dob that has been modified with roller bearings, sure,
grease is a simple way to add some drag.

_______________________________________________ __

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

I fully agree, it would be best to have the 2 functions completely and
reliably separated . Frictionless bearings (or as low friction as possible)
and a separate way to adjust friction . Also, important to have *friction*
and make the device less sensitive to stiction .

best regards,
matt tudor

In that location dirt is almost inevitable unless you have a trully
closed system. I do agree that a drag control is nice. I was just
talking bare-bones.



Jon Isaacs wrote:

If you have a basic Dob that has been modified with roller bearings, sure,
grease is a simple way to add some drag.

Given the location of the bearing and the propensity of grease to attract dust
and dirt, I think its a good way to end up with a bearing full of yuck.

jon

Nothing is perfect. Symbios always applies in any practical realisation.
I sound like Greenspan!

jerry




wrote:

The mind boggles at the concept of reducing friction via a roller
bearing and then adding extra friction via a seperate component to
increase the reduced friction of the roller bearing! ;-)

Larger & heavier dobs might well benefit from reduced friction in the
base bearing. But using roller bearings on smaller ones just smacks of
salesmanship.

The silky movement of Formica ( or Ebony Star) on Teflon is no
accident. The static and dynamic friction are closely matched. Start
pushing and the friction doesn't increase or reduce as it starts to
move and keeps on moving. See Dennis Woos' post above. :-)

Chris.B

My 22" has roller bearings for both altitude and azimuth, with slip
clutches on both axes. They are very smooth, and can be as loose or
tight as you might want.

Clear skies,
Shneor Sherman

I wish I'd said that. ;^)

Chris.B

wrote:

The mind boggles at the concept of reducing friction via a roller
bearing and then adding extra friction via a seperate component to
increase the reduced friction of the roller bearing! ;-)

Larger & heavier dobs might well benefit from reduced friction in the
base bearing. But using roller bearings on smaller ones just smacks of
salesmanship.

The silky movement of Formica ( or Ebony Star) on Teflon is no
accident. The static and dynamic friction are closely matched. Start
pushing and the friction doesn't increase or reduce as it starts to
move and keeps on moving. See Dennis Woos' post above. :-)

Chris.B

Does it have to be the Formica 'Ebony Star' brand or is there a generic
substitute? How about the Teflon?


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Does it have to be the Formica 'Ebony Star' brand or is there a generic
substitute? How about the Teflon?

The Kriege & Berry book "The Dobsonian Telescope" recommends:

1) Virgin teflon. The lower grade "mechanical" teflon is recycled, and not
as slippery. I have used both thin, etched teflon and glued it down, and
thicker teflon with small screws.

2) Wilsonart "Touchstone" or Formica "Quarry Finish" laminates. Ebony Star
is an example of the former, and Stardust is an example of the latter, and I
think the book is saying that any laminates within these two lines are
equally good. Some time ago I bought a 4'x8' sheet of Ebony Star, and have
been using it up over the years. I have never tried the other flavours.

This book also recommends loading the teflon/laminate bearings at 15psi, and
applying silicone car wax to the laminate. Works great for me.

Dennis

My 22" has roller bearings for both altitude and azimuth, with slip
clutches on both axes. They are very smooth, and can be as loose or
tight as you might want.

I recently read a thread about roller blade wheels as bearings. Now that
sounded intriguing.
john

jerry wrote:
In that location dirt is almost inevitable unless you have a trully
closed system. I do agree that a drag control is nice. I was just
talking bare-bones.



Jon Isaacs wrote:


If you have a basic Dob that has been modified with roller bearings, sure,
grease is a simple way to add some drag.

Given the location of the bearing and the propensity of grease to attract dust
and dirt, I think its a good way to end up with a bearing full of yuck.

jon



Sealed bearings are available in all popular sizes. No grease required,
and no contamination under most circumstances.

Uncle Bob