Old version
After building and riding my front wheel drive motorized Raleigh 20 I found that it became a bit unsteady at about 27 mph. Most people who rode it thought the extra weight on the front wheel was "weird". Sooooo, out with the sawzall and torches, and a couple of parts bikes later, voila (see pics below). I nabbed some decent bikes at the Bainbridge Island Rotary auction for about $2 each for this project. Got a nice 24" wheeled Trek mountain bike for my son Evan, another good chrome-moly mountain bike for its rear triangle, and an old Schwinn with a freewheeling crankset! A generator light came on the Schwinn. Those things sell for $50 these days! This plus some parts for only $12! Love that Rotary auction.
The concept here was to convert to rear wheel drive while maintaining the ability to carry items such as groceries. I'd been pondering locating a jackshaft behind the seatpost of a standard upright bike to facility a geared engine for some time and decided to take the plunge. The tricky parts were building the asymetric lower stays that allowed space for the chain to move out and back when shifting and making a sturdy engine mount. One significant change was rotating the Staton-Inc 18.5:1 gear reducer 90 degrees from its original orientation to the engine. This actually brought the center of gravity lower.
Old version
Just before our friend (and talented singer/songwriter) Valerie Markell rode it in it's rough, pre-paint condition, she asked if her pants would get grease on them from the chain. I realized then that I'd have to make some chain guards. I made a wood mold from a 2x6, waxed it with a candle, and laid polyester resin and fiberglass cloth over it. They came out pretty well, certainly functional.
In a nutshell, it's a MUCH better bike than before. Very fun to ride, way more stable. Quieter since the engine's behind the rider. In fact, at speed you can hear the sound of the front tire hitting the pavement. I think this one's a winner.
Right side view.
And left.
Left side, showing shrouded jackshaft.
Right side, showing bigger chain guard, orientation of chains, and front chain tensioner.
Jackshaft detail from behind.
Jackshaft detail from front.
View from the front. Generator light is mounted below front cargo basket.
View from the rear, showing motor mount.
The asymetric rear triangle. A conduit tube bender was used to bend the right-side lower stay out, then a chunk of a front fork was spliced on. Thus the ovalized, increasing diameter of the tube as it goes rearward.
Left side, showing how another chunk of a front fork was used to meed the upward-oriented rear triangle.
Moi, with subject bicycle for scale.