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ATM [Fwd: Pipe Thread Mounts]

Sue&Alan French wrote:
> 
> >Mark Gilbert wrote on Sun, 01 Sep 1996 01:28:36
> 
> >I am a first-time telescope builder.  I checked out Richard Perry's
> >book, Build Your Own Telescope, from the library, and I am building his
> >4.25" reflector.  My concern is with the equatorial mount.  It is made
> >of 1 1/2" galvanized pipe, and turns by rotating on the pipe's threads.
> >I am afraid that the mount will not have enough friction to stay put
> >once I point the scope.  Does anyone know a way to add friction to the
> >pipe joints?
> 
> Mark,
>         As others have mentioned, lack of friction should not be a problem.  I
> have a German Equatorial made of 2.5" pipe fittings.  It has no clamps in either
> axis but stays very nicely where it is aimed.  It has been used with 6" f/8 and
> 8" f/8 Newts with no problem, but was a bit unsteady with a heavy 10" f/6.
>         You will probably find the mount works better if you lap the pipe threads
> well before final assembly.  I used a mix of oil and abrasive (120 grit, I
> think) and kept screwing and unscrewing the fittings until I gained some
> threads.  Make sure you have something VERY solid holding one piece if you want
> to make serious progress.
>         This won't apply to the design you are using, but I was nervous about the
> looseness of the thread bearing on the RA axis.  I lengthened it, ran a piece of
> sheet steel around the top end, and put two roller bearings under it. The weight
> keeps the axis against the bearings.
>                                                 Clear skies, Alan

-- BEGIN included message

>Mark Gilbert wrote on Sun, 01 Sep 1996 01:28:36

>I am a first-time telescope builder.  I checked out Richard Perry's
>book, Build Your Own Telescope, from the library, and I am building his
>4.25" reflector.  My concern is with the equatorial mount.  It is made
>of 1 1/2" galvanized pipe, and turns by rotating on the pipe's threads. 
>I am afraid that the mount will not have enough friction to stay put
>once I point the scope.  Does anyone know a way to add friction to the
>pipe joints?

Mark,
        As others have mentioned, lack of friction should not be a problem.  I
have a German Equatorial made of 2.5" pipe fittings.  It has no clamps in either
axis but stays very nicely where it is aimed.  It has been used with 6" f/8 and
8" f/8 Newts with no problem, but was a bit unsteady with a heavy 10" f/6.
        You will probably find the mount works better if you lap the pipe threads
well before final assembly.  I used a mix of oil and abrasive (120 grit, I
think) and kept screwing and unscrewing the fittings until I gained some
threads.  Make sure you have something VERY solid holding one piece if you want
to make serious progress.
        This won't apply to the design you are using, but I was nervous about the
looseness of the thread bearing on the RA axis.  I lengthened it, ran a piece of
sheet steel around the top end, and put two roller bearings under it. The weight
keeps the axis against the bearings.
                                                Clear skies, Alan

-- END included message