Tim Wescott wrote:

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

I didn't read the previous thread, but if you are looking at those kind
of loads, I'd think you should be looking at a standard hydraulic
cylinder, tank and needle flow control valve.