Enclosed Cargo Trailer Ramp Door Lifting Capacity Determination

Updated 05/19/2021 | Published 05/17/2021

Question:

I have a cargo trailer that originally had a roll up door like a box truck. It had the double head torsion spring system in it. The door was 3/4inch treated plywood with all steel hardware. I have removed this style and built ramp door as pictured. This door will weigh approximately 340lbs when complete with inner plywood. My question is what will be the required force spring to lift this door? The spring from the original door is old and would not have a rating on it, but I would imagine it will work for as little ar I will use it. I am a mechanic and have work some with repairing this type of system, I just dont know how to factor the required tension for the spring.

asked by: Shawn

Expert Reply:

The Conventional Ramp Door Spring # CB250D96SHD on your trailer is similar to that of a home garage. The best way to determine how much weight your current system is capable of lifting you can find calculators online or contact a garage door service company. The weight that the springs can lift are determined by the length of the springs, diameter of the coil, and thickness of the coil material.

The kit that I have referenced is capable of lifting 250lbs of door. This means if you were to use this on your door you would have to provide the other 90lbs of lifting force required.

expert reply by: Bud M