On Feb 5, 10:03*am, 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've seen cantilevered scissor gates with a supporting swivel caster
at the opening edge. Maybe adding a caster would provide enough drag
to prevent damage from slamming the gate. It would also lessen the
load on the pivot hinges.