From: MitchAlsup{at}aol.com
To: atm{at}shore.net
Reply-To: MitchAlsup{at}aol.com



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Tom:

There is a varient of the rod bearings Bruce Sayer used known as Spherical
Bearings. These
are the bearing part of a rod-end without the rod. I used 1/4" ID SB
in my cell to good effect.

To attach the threaded rod to the spherical bearing, I turned down a length
of 3/8 brass
threaded rod so that it exactly matched the ID of the spherical bearing. The threaded
rod is attached to the spherical bearing by a 4-40 bolt axially holding a
small washer just
bigger than the ID of the SB.

I controlled friction in the colimation bolts by using a coupling bolt as
the threads in the square tube.
The two sets of nicely machined surfaces deliver low controlled friction.
This resulted in a very light
smooth action in my 20" DOB. I found there was on the order of 3
thousandths slop out of the threads
and another 1 thou or so from the spherical bearings.

Mitch

In a message dated 12/11/2002 1:25:05 PM Central Standard Time,
tkrajci{at}san.osd.mil writes:


> I've posted a discussion of the problem I am facing with main mirror cell
> design.  I need to eliminate 'slop'.  See:
> http://overton.tamu.edu/aset/krajci/scope-design.htm )very bottom of page)
> and specifically:
> http://overton.tamu.edu/aset/krajci/cell-bearing.htm
>
> I am trying to find ways to use rolling element bearings to solve two
> different problems:
>
> 1.  Tilting of the pivot/balance member in the main mirror cell.
>
> 2.  Movement of the 'lead screw' collimation bolt.
>
> All comments and feedback are welcome!  (Once I get some good ideas
> together
> on how to approach these design problems, I'll add them to the website.)
>
> Tom Krajci
> Tashkent, Uzbekistan
>


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Tom:

There is a varient of the rod bearings Bruce Sayer used known as Spherical
Bearings. These
are the bearing part of a rod-end without the rod. I used 1/4" ID SB
in my cell to good effect.

To attach the threaded rod to the spherical bearing, I turned down a length
of 3/8 brass 
threaded rod so that it exactly matched the ID of the spherical bearing.
The threaded
rod is attached to the spherical bearing by a 4-40 bolt axially holding a
small washer just 
bigger than the ID of the SB.

I controlled friction in the colimation bolts by using a coupling bolt as
the threads in the square tube.
The two sets of nicely machined surfaces deliver low controlled friction.
This resulted in a very light 
smooth action in my 20" DOB. I found there was on the order of 3
thousandths slop out of the threads
and another 1 thou or so from the spherical bearings. 

Mitch

In a message dated 12/11/2002 1:25:05 PM Central Standard Time,
tkrajci{at}san.osd.mil writes:


I've posted a discussion of
the problem I am facing with main mirror cell  design. 
I need to eliminate 'slop'.  See:
http://overton.tamu.edu/aset/krajci/scope-design.htm )very bottom of
page) and specifically:
http://overton.tamu.edu/aset/krajci/cell-bearing.htm;

I am trying to find ways to use rolling element bearings to solve two
 different problems:

1.  Tilting of the pivot/balance member in the main mirror cell.

2.  Movement of the 'lead screw' collimation bolt.

All comments and feedback are welcome!  (Once I get some good
ideas together 
on how to approach these design problems, I'll add them to the website.)

Tom Krajci
Tashkent, Uzbekistan



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