> what do you guys think would be the best to buy ??? It has to let the
> gate
> down easy and raise it easily... I know I can adjust it by moving the
> attach
> point of the cable to the gate and also I guess I could move the
> spring in
> the housing tube .... but what # spring to buy ??
Well, you want the force from the spring to be zero with the ramp closed, so
the spring needs to be fully relaxed/retracted at that point. And the force
should be just slightly less than what it takes to lift the ramp off the
ground at full extension. So figure out how far it can stretch between
those two extremes, and choose a spring that supplies that much force at
that much extension.
But unless I'm missing something, I think you will be unhappy with the
result. The force from the spring is more or less linear with displacement,
while the force to lift the door depends on the cosine of the angle between
the door & the ground. If your spring is strong enough to nearly lift the
door off the ground, I suspect it's going to slam into the trailer plenty
hard enough to smash fingers, tear up the trailer and so on. Swinging
garage doors actually have multiple cam actions built into the hinges, to
deal with this problem.
-- Randall
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