On Tue, 24 Nov 2009 18:18:55 -0600, Tim Wescott
wrote:

I asked this question once before moths ago, but didn't get the answer I
wanted -- so now I'll try again and see if anything has changed.

I have a scissor-action gate, a great big heavy thing. It's nicely
counterbalanced with springs, but when it comes down it does so with a
BANG! The shock is bad enough that the gate is currently in my shop
getting all the broken bits welded so that it doesn't fall on a child or
a UPS guy or something.

I don't want to put it back into service without fixing the root cause.
What I really need to fix this is one or more really heavy duty motion
dampers. Ideally these things will have check valves that will let them
move in one direction easily but not the other, and they'll damp in
extension (although I can probably get around that problem).

A really heavy duty screen door damper that worked in reverse (i.e. damps
on the way out instead of the way in) would be absolutely perfect.

Oh -- and it's gotta work outside in the rainy part of Oregon without
rusting up.

So: Anyone worked with something like this? Know anywhere to look
(McMaster doesn't have what I need)? The current keywords that seem
pertinent are "Hydraulic dampers", "gas springs", and "air springs", but
the signal to noise ratio with those keywords isn't high, and I haven't
figured out how to refine it yet.

I built something similar to damp the slam of a heavy swinging-gate. I
used the cylinder from a surplus foot-operated tire pump. It was fussy
to tune, but it did the job for years. You could mount something like
that on the end of the gate where it would have the most leverage.

Wayne