Buerste wrote:
"Larry Jaques" wrote in message
...
On Thu, 4 Mar 2010 14:31:33 -0500, the infamous "Buerste"
scrawled the following:

Damn inertia!

I have an air cylinder, 1.5" x 4" stroke, that pushes a crank on a
shaft to
rotate the shaft about 90 deg. On the shaft is a gear with a
one-way clutch. The 4" x 1/2" gear turns about 3" at the perimeter
per stroke of the cylinder. By moving the link to the air cylinder
up or down on the crank the gear will rotate more or less per
stroke. A second gear is meshed
into the first gear with pressure from another air cylinder. Wire
is fed between the gears in a grove cut in the face of each gear. The
idea is to feed wire 3" per stroke.

What kind? Mangrove? Orange grove?


Is works perfectly and fast! By varying the pressure in the
cylinder that presses the gears together, the wire is gripped very
well at 60 lbs air pressure and will slip through the gears easily
at no pressure. The only problem I have is that the gears over-run and
feed too
much wire.

That doesn't sound quite like "perfectly" to me. g


I've considered lightening the gears by drilling a bunch of holes. Also,
a
drag brake on one or both gears with screws pressing brass pucks
against it.
Another idea is an air limit switch that is struck at the end of the
stroke
by the crank. This switch would unload the pressure on the clamping
cylinder and let the wire slip between the gears when they over-run.

Would the air limit switch work fast enough to unclamp the wire in
time? Would I be better off with an electric switch and valve? I
might have to lighten the gears, brake them and switch off the air
clamp The feed has to
take place in 300ms.

Why not feed 'em with stepper motors turning the gears, Tawm? That
would be much more precise than having to maintain exact feed tension
and maintain split-second air timing unless you're actually
ratcheting the gears. That design would make for a high-maintenance
situ, tho. --
An author spends months writing a book, and maybe puts his
heart's blood into it, and then it lies about unread till
the reader has nothing else in the world to do.
-- W. Somerset Maugham, The Razor's Edge, 1943


You're always so MEAN to me!

Steppers don't have the speed or oomph and I'm a "MECHANICAL"
engineer! Get it...mechanical??? Anybody can just stick in
electronics but it takes a mechanical guy to do a "Rube Goldberg".

could you stop it with electromagnets?