Power
There are many kinds of forklifts that are operated by propane gas. Forklifts which use propane are really easy to refill. The gas is stored in a pressurized tank on the rear of the truck. The propane is pushed into the engine, where it is converted into vapor and the vapor combines with air. The throttle of the forklift is utilized to control the vapor flow. A spark plug ignites the vapor and air mixture producing pressure which makes the pistons move. The pistons run the hydraulic pump and turn the wheels.
Propane powered forklifts are recommended for use within other buildings and warehouses since they are clean burning with low emissions.
Hydraulics
What enables a forklift to lift and move heavy stuff from one place to another is the hydraulic system. A pump, tubes and cylinders make up the hydraulic system. The pump forces dense fluid through the tubing and into the cylinders. The build up of pressure pushes a piston, which raises the forks. When the forks are lowered by the operator, the hydraulic fluid flows out of the cylinders and back in the pump.
Steering
Propane forklifts work well where maneuverability is necessary. Not like a car, a forklift uses its back wheels to pivot, that allows the forklift to rapidly pivot on a tight radius.