# How much pressure needed for pneumatic cylinders to lift?

## Main Question or Discussion Point

Hello,

I work for a company specialized in building van bodies. The problem is our engineer left and I know nothing about pneumatics.

The customer's requirement is to be able to raise and lower the roof by up to 1 m. The box bodies are 7-8 meters long, so I think 6-8 pneumatic cylinders will be required (3-4 for each side) just for the sake of even force distribution. The estimated lifting weight is 400-500 kg because the rear door frame has to be lifted too. This number could increase with snow.

I need to determine how much pressure is needed in the system for the cylinders to be able to lift in order to determine if it's even doable.

Can you point me in the right direction?

Many thanks!

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Baluncore
2019 Award
Welcome to PF.
Force = Pressure * Area of piston.

Distribute your cylinders so that each carries the same load per area of piston. That way they will all lift at the same pressure. You could also use different diameter cylinders to balance the load. You will probably need some form of mechanical balancing so all cylinders advance at the same rate and the body remains level during the lift.

Is it possible?
An acceptable maximum air pressure is say 100 psi = 690 kPa.
The total 500kg is about 1100 pounds.
So total piston area needed will be a minimum of 11 square inches.
12 square inches would be 6 cylinders of 2 square inches each.
Area = πr2 therefore piston diameter would be 2 * √ ( area / π )
Diameter = 2 * √ ( 2.0 / π ) = 1.6 inches diameter.

That is available without problems.