Leroy's Power Steering Dump Bed

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The 14-1/2" X 76" tailgate follows the same construction pattern and is hinged at both top and bottom for dumping or oversize hauling. Sliding 1/2" X 8" hinge pins, mated to angle and channel iron brackets, allow the gate to be removed completely if desired. And to support especially heavy tail loads, the lower hinge arms are fabricated from 3/8" X 1-1/4" X 4-1/2" stock.

Critical to the success of any dump-bed design is the rear hinge setup, which, in this case, is made from 3" channel iron, 1" steel pipe, and some cold-rolled rod. Two 3" X 10" channel iron posts, boxed at the top end for extra strength, are bolted and welded to the truck's chassis rails at the rear. Two-inch lengths of 1" Schedule 40 pipe, welded through the posts, serve as bushings for the 1" X 40" hinge pin, which is locked to the bed through similar pipe mounts that are boxed and welded to the bed's main rails.

SIMPLE GEOMETRY

With the bed, tailgate, and hinges finished, Leroy was faced with an important decision: where to mount the hydraulic cylinders. The 2-1/2 "-bore units (which were salvaged from an industrial press) have a stroke of 24" and an overall length of 56". Given a pressure of 1,200 pounds per square inch (psi), the pair has a straight load-lifting capability of 11,780 pounds... but since they had to be mounted at an angle (to push upward as well as rearward), some of that capacity was sacrificed to geometry.

So, the final placement of these components represents a compromise between the cylinders' physical limitations and the available structural mounting points on the truck and bed frames (see diagram). One cross member on the latter component was just forward of the bed's halfway point, so Mr. R chose that as the upper mount. Then, by chaining the nose of the bed to a tree limb and driving forward a little, he was able to trial-fit the extended cylinder and mark a spot on the chassis rails that'd allow a bed tilt of 32° but would still permit the cylinders to tuck away nicely with the bed lowered. (Actually, Leroy admits that he would have preferred a clean 45° lift angle, but he'd gotten a good price on the cylinders and decided to work with them the best he could, rather than look for a more suitable—and more expensive—pair.)

The cylinders' upper clevis eyes are locked with 3/4" cold-rolled pins to 3/4" X 2-1/2" X 4" brackets on the bed crossbar. Leroy fashioned the same type of brackets for the lower eyes, but in that case welded them to a 3/8" X 3" X 33-1/2" section of angle iron, capped its ends, and mounted it between the frame rails at the spot he'd previously marked. (Since truck chassis are tempered, he purposely did not make a weld joint at this high-stress point, relying instead on hardened 1/2" bolts.)

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