RE: [CAD_CAM_EDM_DRO] hexapod universals - 1/2" socket universal joints

Doug,
if you're interested in universal joints that are smaller than those of the
drive train, you could look at those for steering shafts... they still have
needle bearings etc, and are quite a bit smaller...

Another option (if the angular range of movement was great enough) would be
spherical bearings (fish eyes or rod ends)

Bryan

-----Original Message-----
From: doug [mailto:doug]On Behalf Of Doug Fortune
Sent: Saturday, 01 September, 2001 5:35 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] hexapod universals - 1/2" socket universal
joints



Regarding the hexapod universal attachment points
(six at the spindle platform, six at the frame),
for quite a while I held off building one because
I had the mindset that, for the universal joint,
I'd be using a small car driveshaft universal.

But those are quite big, (resulting in a big machine)
and the costs add up rapidly when you need 12 of
them (a few hundred bucks).

I had the idea instead to try using 1/2" socket
universal joints (used with socket ratchet wrenches).
They are pretty small, and don't cost a lot, are
available at any hardware store, but are quite robust and
obviously meant to handle a lot of torque. Smaller
hexapods could use 3/8" and 1/4", and I suppose a bigger
machine could use 1" drive universals.

For those thinking about designing a hexapod, I thought
I might mention the idea.

For those who haven't heard about hexapods, they
are experimental positioning (and machining)
mechanisms, with six variable length legs. These
universals go on each end of the six legs. The
requirement for the swivel joints is that they
swivel in both directions (90 degrees to each other),
but do not rotate (so a swivel ball joint is no good).

Can anyone else out there report progress on their
own hexapod project?

Doug Fortune
http://www.cncKITS.com

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