DIY Electric Tiller Conversion: Page 2 of 2

The Motor

The motor is a 1 hp, 120 VAC general-duty motor with a capacitor start and overheating protection, and has a cord with a switch. We found it on a surplus supply website for less than $100. There’s one feature of this motor that’s particularly important: It can be reversed with a simple change of wiring. Steer clear of a nonreversible motor, because most gasoline engines run in a counterclockwise direction (viewed from the output shaft end) and AC motors are set up to run in a clockwise direction. There’s no practical way to reverse the direction of a nonreversible AC motor.

These motors have a standard mounting base, which works well for our tiller, and a commonly found 5/8-inch output shaft, so pulleys are readily available. This motor runs at about 3,000 rpm, so it’s a good replacement for a 5 hp Briggs & Stratton gasoline engine running at full throttle. One hp—since it’s measured as continuous horsepower versus the “peak” rating of 5 hp for the gasoline engine—seems to be in the ballpark.

To align the pulleys, we had to move the motor a little off-center. This shifts the tiller balance a little to one side, but only a fraction of an inch. We offset the motor using a square channel, to allow bolting to the frame through the bottom, then bolted the motor (about a 3/4-inch offset) to the top. Completing the power train was a matter of getting the same size pulley for the 5/8-inch shaft.

At this point, the tiller was operable—but not yet safe. The power switch is at the far front of the machine, making an emergency cutoff switch necessary. We found one at an industrial supplier. It’s a simple wiring job—just put it inline with one power lead to the motor. Solidly mounted to the tiller’s handle with aluminum angle stock, you have a safe, big, red, push-button kill switch. Since it’s not rated for continuous use, the switch is only for emergencies. You could eliminate this by moving the main switch to the bars, but it’s nice to have that red kill button, much like other shop tools.

The tiller’s operation lived up to every expectation. The motor makes a quiet “whoosh,” and you hear an occasional clank of the tines or transmission bumping around. Because of its quiet operation, it can be run at virtually any time of day, regardless of the proximity to neighbors or your sleeping family. It produced one of the best-prepared beds we’ve seen —with no grease, oil, smoke, or noise.

Power Cord

Managing the extension cord is similar to working with a corded lawn mower, except with a tiller you’re covering less ground and moving slower. Lay the cord out from your starting point, and always turn the tool away from the cord source. This keeps the cord behind and to the side of the business end of the tool.

Pay attention to the gauge and length of the extension cord you use. Extension cords are rated to handle only a certain amount of amperage—for example, a 16 AWG cord is rated up to 13 A, while a 10 AWG cord is rated up to 30 A. Excessive voltage drop can damage motors, so the cord’s length must also be considered. Make sure you use an outdoor-rated cord of the appropriate gauge, and consult voltage drop tables to make sure you limit voltage drop to no more than 5%.

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Ted Dillard has been an avid gardener since childhood and is an evangelist for all things electric. He writes “The Electric Chronicles” (devoted to two-wheeled electric vehicles), and is the author of ...from Fossils to Flux, a basic guide to building an electric motorcycle. When he’s not in his garden or in his shop working on his next electric project, he can be found at evmc2.com.