"Tim Wescott" wrote in message
...
A 120 pound gate, 18 feet long and 3 feet high, hinged at one of the
lower corners and supported by a damper that is pivoted to the top corner
and working at a 45 degree angle, puts a 510 pound load on the damper
_just_ to keep the gate still -- decelerating the gate takes even more
load, to the tune of 1700 pounds if you want to close the gate in one
second (that's assuming constant deceleration over 45 degrees in 1/2
second).

(I decided I didn't want to close it that fast).

Anyone who suggested a fire-door damper -- where can I find one that'll
support a ton?

--
www.wescottdesign.com



Years ago I saw a hydraulic cylinder with a cushion at the end of the
stroke. Instead of the cylinder bottoming out harshly the last bit of oil
would flow through a smaller orifice. One could use a flow control on both
stages to make the gate close at a slower rate near the end of the motion.

http://www.hydraulic-equipment-manuf...articles2.html

Steve