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Publication Title | Electro- Biking

Organic Rankine Cycle

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Homebrew

Homebrew

Electro- Biking

Bill Gerosa, Jr.

©1996 Bill Gerosa, Jr. The northeastern portion of the

United States is not particularly

kind to avid cyclists, especially those who work during prime daylight hours. The electro-bike, herein referred to as E.B., was designed to keep the user aerobically fit while creating some extra power to charge batteries.

Any bicycle will do. However, bicycles with wheels of larger diameters, such as 27 inches as opposed to 16 inches, create more mechanical advantage as will be shown. Both street bikes, with very narrow, smooth tires, and mountain bikes, with wide, knobby tires, have been used with equal success. The bicycle is placed upon the stand, which is an Advent Mag-Trainer. It comes assembled and folds up easily for transport— even after the generator is added.

Construction

First, we removed the roller and flywheel mechanism from the Advent Mag-Trainer’s frame. Two nuts and bolts hold the roller in place. Then, a metal plate, with two holes drilled in it, was placed upon the bike stand’s swivel mount, right under the rear wheel of the bike. This plate was 11 inches by 7 inches and stiff enough to allow slight flexing. Two nuts and bolts were used to secure the plate to the swivel mount. The generator was mounted upon this plate using four, two inch L brackets. There are two long bolts that run through the generator, horizontally when the generator is on its side. The L brackets can simply be fastened to these.

It is not feasible to have the axle of the generator pressed up against the bike’s rear wheel because massive slippage occurs. A small wheel needs to be fastened to the generator’s axle. Anything with a circumference between 2 and 10 inches should do. The smaller the wheel, the greater the mechanical advantage, but the more likely slippage is. I simply used the flywheel that came with the stand. Since the generator’s axle was too large to be fastened to the flywheel, I had to grind the axle down. Hooking the

generator to a 12 Volt battery and running it as a motor allowed the use of a file to whittle down the axle to the proper size. Once this was accomplished, we put the flywheel on the generator and drilled a hole through the flywheel mount and generator’s axle to get a secure fit. A bolt was passed through this hole and fastened with a lock washer and nut.

Operation

The bicycle is secured upon the stand by placing the E.B.’s back wheel between the Advent stand’s two cup holders. A cycle’s rear wheel has an axle with a lug nut at each end. These lug nuts are to be placed in each one of the cup holders. Then the cup holders are to be tightened down on the lug nuts until the bicycle is held firmly. This also allows perfect alignment (left to right) of the rear wheel directly above the generator’s wheel. Now the tension of the generator mount needs to be set. The knob under the metal plate changes the inclination of this plate upon which the generator is mounted. The adjustment knob should be tightened so that you can hold the generator’s wheel with one hand while trying to spin the bike’s rear wheel with the other and get no slippage. Do not overtighten. This will put undue stress on the components. It does not take much tension to eliminate slippage.

Since the rear wheel of the bike is about one inch off the ground while in the stand, place a piece of wood under the front wheel. This will make the bike level and prevent the rider from sliding forward on the seat while pedaling. Keep in mind that the folks at Advent constructed this stand so that you may easily remove a fully functional road bike and take it out for a spin on a sunny day. Simply unscrew the holder cups from the lug nuts of the E.B. and the bike easily comes away from the stand.

Math and Mechanics

The Univega Mountain Bike we used for most of the testing has 26 inch wheels. The circumference is approximately 82 inches (Circ. = PI * Dia. or 3.14 * 26 =

Home Power #56 • December 1996 / January 1997 75

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electro--biking
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