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Compact Powertrain Boosts Bicycles

Compact Powertrain Boosts Bicycles

Denver-If the world's streets are teeming with motorized bicycles a decade from now, then engineer Stephen Katsaros believes the internal combustion (IC) engine will have played a key role in that revolution.

The Denver-based patent agent is convinced that battery-powered bicycles are not the answer to the world's traffic dilemmas, and his gasoline-based Revolution Motor serves as proof of that belief. "There's a real move toward electric (bikes) right now, but those bikes all weigh around 80 lbs and only have a range of 10 to 15 miles," Katsaros points out. "The problem is that it takes about 377 lbs of lead-acid batteries to equal the energy stored in a pound of gasoline."

His Revolution Motor provides a lightweight, energy-efficient alternative to the electric bike by employing a 27 cm3, two-stroke engine and a gear train that neatly fits within the 3-inch-wide confines of a conventional bike frame fork.

The powertrain's design is critical, he says, because it offers a 100:1 speed reduction ratio between the engine and drive wheel, and yet enables the Revolution Motor to easily adapt to a conventional bicycle without modifications. The gear reduction is especially important, he says, because small engines tend to run at high revolutions, thus necessitating greater speed reduction.

To make the unit so compact, Katsaros used six spur gears to achieve three reduction steps. He said he tried dozens of configurations before settling on the final design, rejecting most of them simply because they didn't fit . "If I had used a planetary gear assembly, it would have been too wide," he says.

Equally important, Katsaros designed a starter motor that enables users to start the engine when they are ready to accept the engine's power assist. To accomplish that, he used a set of ball bearings in conjunction with a tapered axle, which imparts a force on brake pads that act on the gears. As a result, the starter allows users to work up to a couple of miles an hour before the engine kicks on. "If you had to start the engine and then get on the bike, you wouldn't be able to get your balance," Katsaros says. "This gives users an easy way to get started."



Want to change the world? The Revolution Motor fits within the frame of a conventional bicycle and requires no modifications to the original equipment.

Katsaros also endowed the unit with an overrunning clutch that allows the engine to continue to run when the bike is stopped, or when riders are speeding downhill faster than the engine can turn the drive wheel. For that, he used a series of tapered slots with needle bearings located between the shaft and gear set, which enable power to be disengaged from the wheel. "With the overrunning clutch, the engine isn't directly attached to the axle," Katsaros says. "It allows you to ride the bike, even when the motor is turned off."

Using the 10-lb. Revolution Motor, Katsaros estimates OEMs can cut the total weight of a motorized bike to about 30 lbs. With a quarter of a gallon of fuel, he says most bikes will have a driving range of about 20 miles. Moreover, refueling is far simpler than the six- to eight-hour recharge process required for battery-powered bikes, he says.

"The goal is an elegant solution to convert any of the world's 1.4 billion bikes into motorized vehicles," Katsaros concludes. "This is simple to install and adaptable to any bike."

The gear train, which installs on the wheel hub, uses six spur gears to achieve 100:1 speed reduction.

"This is simple to install and adaptable to any bike."

Contact Steve Katsaros, Patent Engineering, 2610 Dexter, Denver, CO 80207; Tel: (303) 514-1991; E-mail: kats@ecentral.com; or Enter 552.

Stephen Katsaros
Katsaros, holds a BSME from Purdue, passed the patent bar exam, and is registered as an agent with the U.S. Patent and Trademark Office. Previously, he worked for eight years in product development in various industries. His products include a ski boot licensed to a major ski equipment manufacturer. He has earned one patent and has five more pending. On the Revolution Motor, Katsaros machined the prototypes in his own workshop.
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