Leroy's Power Steering Dump Bed
(Page 4 of 5)
January/February 1985
The Mother Earth News staff
The upper chambers of the double-acting cylinders are likewise joined through a T and plumbed to the control valve's other working port.
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To complete the fluid circuit, the valve's outlet port is tied back into the steering box (through a reverse-flared fitting), and the box is plumbed to the pump return port in the standard fashion. Of course, as he would with any hydraulic circuit, Leroy was careful that all the lines and both sides of the cylinders were filled with fluid, to assure that no air pockets were trapped in the system, before he made the final connections.
Under normal driving conditions, with the bed down, the three-position four-way valve's open-center design allows pressurized fluid to bypass the working ports and travel directly to the steering box, which is essentially what it did before Leroy's modifications. But once the valve lever is pulled to activate the lifting cycle, "live" fluid is directed to the cylinders' lower chambers... which lifts the bed, but also simultaneously forces fluid in the upper chambers to exhaust past the unused working port, through the open return circuit in the valve, and into the steering box, where it's returned to the pump reservoir.
Conversely, when the control valve lever is pushed to lower the bed, the cylinders' upper chambers are pressurized... and the evacuated fluid on the pistons' opposite sides is relieved through the valve as before. To compensate for the additional fluid required by the cylinders, fittings, and extra hoses, Leroy simply cut a hole in the side of a 1-gallon fuel tank, brazed a 1-1/2" collar over the opening, and joined the fender-well-mounted tank to the neck of the pump reservoir with a length of radiator hose. Though the neck cap fits the tank, he's had to work up a baffled vent that doesn't allow returning fluid to escape with the pressure.
PUT TO THE TEST
Though our Eco-Village director has been using his rig daily for about a year now, there are a few people around here who still say what he's done is impossible. Nonetheless, the unassuming little power-steering pump was designed to put out up to 1,500 psi at a rate of about 2 gallons per minute... and any way you cut it, that's enough to accomplish the job at hand.
The truck has, in fact, repeatedly hauled and dumped 6,000-pound payloads of 3/4" gravel with no mechanical difficulties. Leroy has enough faith in its ability to continue doing so that he recently took the time to build up a chassis-mounted angle iron framework that holds a set of homemade utility boxes for beneath-the-bed tool storage, and to add another cross member and a 3/4" X 2-1/2" X 18" tongue to support a large ball hitch.
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