Wheelbarrows might have been with humanity almost as long as the dirt they carry. The common wheelbarrow provides about a 5:1 mechanical advantage by placing most of the weight over a front mounted wheel, allowing a single person to transport several times his own weight. One thing it cannot do, however, is flatten hills. There may be no more difficult task than trying to push a heavily loaded wheelbarrow up a grade. This homemade powered wheelbarrow comes to the rescue, and it is fun to use.
Compound power strategy
The unit uses a 2 1/2 horsepower petrol engine driving a small hydraulic pump, which in turn powers two hydraulic motors through a reversible four-way toggle valve on the handle. The heavily cogged drive wheels on each side are mounted directly on the hydraulic motors. As well as being self-propelled, the wheelbarrow has rotating casters on the rear. The user releases a safety-stop squeeze-bar on the handle like a self-propelled mower.
Fill and dump strategy
Except for the tray being pivoted from the sides and the tray lifting independently of the wheels and engine, it works like a regular wheel barrow. Nearly all the weight is concentrated on the two independent drive wheels on the sides. A small hydraulic valve loads a hydraulic cylinder and the tray slowly lifts to unload approximately 0.28 cubic metres (10 cubic feet) of contents.
The polythene plastic dump tray is a replacement for a 0.28 cubic metre (10 cubic foot) wheelbarrow. The tires and hubs are 40 cm (16 inches) high by 16.2 cm (6.50 inches) wide by 20 cm (8 inches) rim diameter tractor turf tyres. The hubs should be 2.5 cm (1 inch) diameter shaft size with 10 cm (4 inch), 4-bolt circle configuration, allowing them to mount directly on the hydraulic motors. The frame should be all-welded 5 cm (2 inch) square steel tubing. Engines and many components are available on the Internet. Pick a very small hydraulic pump in the 4 to 8 cubic centimetre (1/4 to 1/2 cubic inch) range. Motors should be in the 147 cubic centimetre (9 cubic inch) range. Adjust the pulley size to achieve approximately 4.8 kph (3 mph) forward speed at full throttle. Hydraulic valves should include a four-way reversing spool valve as well as a bypass valve for the dead man's control. Use all corrosion-resistant hardware.
Two sets of two longitudinal 5 cm (2 inch) square steel tubes should run the length of the unit, about 1.65 m (60 inches). They will be 75 cm (30 inches) apart, and they are joined by crosspieces of 5 cm (2 inch) square tubing welded fully around. Use 8-gauge steel plate welded to the steel frame to support the engine, pump and hydraulic motors. Mount a frame of 5 cm (2 inch) square steel tubing around the bottom of the dump tray. The hydraulic cylinder needs to lift directly to the bottom rear of the tray for dumping. The tray's pivot pins should be right at about the centre of gravity of a full tray, about one-third of the way back. Component alignment is important, especially between the engine and the hydraulics. Mount the valves to the handles for easy access. Test all hydraulics for leaks. Test the speed by walking with a hand-held GPS.
The sheer power of this unit makes heavy excavations and hauling a pleasure. If you can convince your neighbours to build their own, power wheelbarrow races with full loads provide plenty of excitement.