The eCortina’s drive-side uses an ingenious two-chain setup
The eCortina could be considered an electric bike, but its builder — Roy Prince — prefers to call it an “eBike hot rod.” With a motor that can take the hard-tail downhill bike up to 45mph and “lift the front wheel almost at will,” it’s easy to see why.
Prince chose the Cortina Triton as a base bike as it is designed to go downhill at speed, and — more importantly — it’s made of steel. This let him weld and clamp the motor and other necessary parts. The motor, by the way, is an Astroflight 3220. It spins up to 10,000rpm, weighs four pounds and needs to be geared way down when used on a bike. If you want one, it’ll cost you $700.
What drew my eye, though, was the two chains on the drive side. One will be familiar: it connects the pedals to the rear wheel just like any other. The second runs from a tiny chainring to a giant rear sprocket. This gear reduction is required because of the high-revving motor.
The first of two gearing reductions sits out of the way on the bike’s left side
The motor itself drives the crank from the left (non-drive side) of the bike, where the gearing is further reduced.
Both the pedal power and electric power go into a three-speed Shimano Nexus hub.
This ingenious setup exploits the freewheel. Because the pedals can stay still while the wheel turns, neither drive mechanism interferes with the other. It also lets you use the electric motor as an assist for your legs. And just as well — at 60 pounds you won’t be riding this far on human power alone.
The eCortina is actually version two of the design, improving in v1.0’s 35mph. Lord knows how fast v3 will go.
eCortina project page [RPEV via Bicycle Design]
See Also:
- 'The Beast' Electric Bike: 50mph, $33500
- Awesome DIY Electric Bikes Defy Laws, Good Sense
- Amazing Electric 'Bike' Is a Junkyard On Wheels
- Minimal Electric Bike Contained In a Single Wheel
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