Re:[ATM] ATM- GEM declination clutch

[Thomas A Simmons <tasimmons@raytheon.com>]

Hi Dave,

  First off, what a beautiful scope! And great pictures detailing
your construction. While being able to copy what you did is beyond
my abilities, and beyond the capabilities of my humble wood lathe,
it is truly a work of art.

 Apparently you fabricated your clutch to be ~ 60MM dia, if I'm
scaling your pictures correctly, and your pressure plates are maybe
1-2 MM thick? You kindly offered to send .dwg files off line, and if
you don't mind, I would love to see the specific ones for this. My
home addy is dialup, but tasimmons@raytheon.com and then I can just
move them to a finger drive. Thanks in advance.

 Where I'm confused on this issue is how stiff I need to make the
pressure and backing plates. In the archives several mention that
Teflon makes great clutch material but the pressure needs to be high.
Greased cork, milk jugs, HDPE cutting boards and automotive gasket
material (among others) are also mentioned as suitable clutches.
And so my guess is that depending on what eventually is used as a
clutch is going to influence the choice of material and stiffness
of the plates.

 All that said, since this would be for a Dec axis, and therefore
loaded infrequently (except for slewing), in your opinion would I be
able to fabricate the pressure and backing plates out of, let's say,
1/8 inch thick 6061 T6 plate, and for the sake of simply mounting the
6 inch gear, a diameter of 5 1/2 inch? Let's also infer sandwiching two
0.032 teflon disks with a same guage steel plate between them. That would
leave some way of loading the clutch, which perhaps I could do with
pipe fittings-or perhaps have a local shop thread a delrin plug and nut?

Tom
Tucson, AZ


Date: Tue, 22 Mar 2005 17:56:52 -0800 (PST)
From: dave g <omegacent@yahoo.com>
Subject: [ATM] ATM- GEM declination clutch
To: atm list <atm@atmlist.net>
Message-ID: <20050323015652.71151.qmail@web41315.mail.yahoo.com>
Content-Type: text/plain; charset=us-ascii

G'day Thomas,

>I have a Byers 6 inch gear with the worm... the Dec axis of an old GEM.

My clutches are made by sandwiching 2 disks of 0.25mm teflon sheet between
the  4 aluminium faces of my clutch.  For photos ect see my website...
http://users.tpg.com.au/daveg/

The action is very smooth and ensures I won't strip the worm wheel is the
scope is pushed.

I can send .dwgs files if requested offline.

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