On Feb 5, 8:03*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

Tim, there is a place NW of Redmond that has a heavy steel gate with a
similar pivoting scheme. He has a chain drive an an electric motor to
raise and lower the thing. It is not 18 ft long, but is still pretty
heavy.

Could you construct a similar mechanism for your gate?

Paul