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 doubt if you'd bid on an RFP as vague as this.

A hydraulic or pneumatic damper is comprised of a cylinder, a valve
that restricts flow, and perhaps a checkvalve that bypasses the
restriction in one direction. All of these components are readily
available.