Pedal-Electric Hybrid Bike – Status and Photos

electric bike - left side

[More pics below, showing details of the throttle, drive chain tensioner, motor, and battery mounts.  I’ve also started a page on the sidebar with technical details, in case other folks want to build a similar rig.]

I rode the electric-assisted bike to work 3 days this week.  This evening I made it home in 34:40 rolling minutes; with stoplights etc the elapsed time was 36 minutes.  This is effectively the same amount of time that it takes to drive, unless there is bad traffic in which case it is at least 45 minutes to drive. There are still a handful of refinements to be made, but overall I think it is a success.

Comfortable cruising speed with little or no pedal effort is 25 mph on the flat; battery life with moderate pedal input seems to be around 20 miles; I have not run the batteries flat but there is a noticeable drop-off in power; this AM I completed a round trip I started the previous afternoon without recharge, and the voltage on arrival was around 23.5.  Top speed at full sprint (human+electric) is around 31mph on the flat.  Acceleration and top speed are sufficient to comfortably keep pace with cars in traffic.

At first I had some issues with the chain coming off the electric drive side; I’ve corrected this for now by adding a chain tensioner sprocket to the return side of the drive, but it’s a bit of a kludge so more refinements will probably be called for.  The chain drive makes a noticeable sound at moderate speeds; at cruising speed it’s not very noticeable over the sound of the wind rushing in your ears.  I haven’t had someone else zoom past me at cruising speed so I don’t know how annoying it is to be buzzed by the thing.  I think a toothed belt drive might be superior in terms of sound; if it could be made a bit quieter the aesthetics would be that much better.  Given the noise I’ve been letting off the throttle when passing other cyclists and sprinting past with muscle power; recreational cyclists don’t seem surprised (I guess they’re used to folks on road bikes whizzing past) but a couple of spandex-clad road warriors have sprinted up behind me to see what I’m about; of the two I’ve interacted with both were intrigued rather than offended to be waxed by a scruffy looking guy on an old steel electrictrified bike.

electric bike - handlebar

electric bike - drive side detail

electric bike - motor side detail

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