Another possibility, I have a garage door that is attached
to a link on what looks like a long bicycle chain. Two
sprockets and a motor, shutoff at the ends is done by flags
attached to links which open mechanical switches.

Allen

> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-
> bounces@mit.edu] On Behalf Of Joe McCauley
> Sent: Wednesday, July 22, 2015 6:48 AM
> To: Microcontroller discussion list - Public.
> Subject: RE: [OT]: Mechanism for moving a trolley on 3
meter
> rails?
>=20
> Had not thought of that Alan, thanks. I was fixated on a
steel
> cable or maybe timing belt solution. I'll investigate the
gate
> systems.
>=20
> Thanks,
>=20
> Joe
>=20
> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-
> bounces@mit.edu] On Behalf Of alan.b.pearce@stfc.ac.uk
> Sent: 22 July 2015 10:58
> To: piclist@mit.edu
> Subject: RE: [OT]: Mechanism for moving a trolley on 3
meter
> rails?
>=20
> > I'm looking for a cheap reliable motorised mechanism for
> moving a
> > trolley back & forth over a 3 meter rail system. It is
for use
> outdoors.
> >
> > I'm sure something like this exists & I'd rather buy off
the
> shelf if
> > possible. I'd like something compact as well as I'm a
little
> limited in terms of space.
> >
> > I've done some searching, but am likely using poor
search
> terms. I
> > thought to put a motor driven pulley on one side of the
rails
> with a
> > tensioned steel cable (the small diameter kind used on
boats
> etc.
> > about 2-3mm diameter) looped twice around it. One end of
> said cable
> > would be connected to the trolley on the same side as
the
> motor, the
> > other would loop through a pulley to the opposite end of
the
> rails
> > from the motor going back to the trolley. This might
work,
> but there
> > is potential for slippage in wet weather. There is also
> potential for entanglement of the cable on the driven
pulley.
> >
> > Hope the explanation above is clear. I'll be grateful
for any
> pointers
> > to commercial products. Failing that any clever ideas
will also
> be appreciated.
>=20
> How about a linear gate opener, like used for sliding
security
> gates at industrial sites? Those would move a gate around
3
> meters to make an opening wide enough for a truck.
>=20
>=20
>=20
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