One-off eCortina bicycle powered by motor, pedaling, or both


July 13, 2011

The eCortina v2 is a one-off hybrid bicycle designed to be motor-driven, pedal-assisted, or pedaled like a regular bike (Photo: Roy Prince)

The eCortina v2 is a one-off hybrid bicycle designed to be motor-driven, pedal-assisted, or pedaled like a regular bike (Photo: Roy Prince)

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Electric bicycles, with some exceptions, generally fall into one of two categories: those that can be powered solely by their motor, and those in which the motor is only used to augment the rider's pedaling power (commonly known as "pedelecs," or pedal-electrics). In both cases, they can also simply be pedaled, without any contribution from the motor. California electric vehicle designer Roy Prince, however, decided that he wanted all three - a bike that could be motor-driven, pedal-assisted, or just plain pedaled. The result is his intriguing creation, the eCortina v2 hybrid.

Prince's bike started life as a standard off-the-rack Cortina Triton DS hardtail downhill mountain bike, and was transformed within a three-month period early this year. Among other things, it now features a motor and controllers originally designed for use in radio-controlled models. Those motors are powered by two packs of lithium-polymer batteries, which are electronically monitored while the motor is in use, to extent their lifespan by avoiding over-charging and over-depletion. Running in parallel, the battery packs have a combined output of 48V-10Ah.

The dual drive system mostly uses standard bicycle parts, including two BMX-style freewheels - these are what allow the eCortina to be pedaled without motor assistance, or to be motor-driven without the pedals being engaged. Beefy BMX chains are used throughout, while a 3-speed Shimano Nexus rear hub is also incorporated.

Although Roy is still working out the performance and range parameters, he estimates that the bicycle should be able to travel about 15 miles (24 km) on one charge, given mild riding demands and some pedaling. With the addition of two more battery packs, he hopes to boost that distance to 23 miles (37 km). Using the motor alone, it is geared for an invigorating top speed of 45 mph (72 kph).

Tipping the scales at just under 60 pounds (27 kg), however, it's certainly no lightweight. Considering Prince's design intention, however, that's OK - "Realistically the eCortina must be considered a motor bike with human assist," he states on his website.

Source: Bicycle Design

About the Author
Ben Coxworth An experienced freelance writer, videographer and television producer, Ben's interest in all forms of innovation is particularly fanatical when it comes to human-powered transportation, film-making gear, environmentally-friendly technologies and anything that's designed to go underwater. He lives in Edmonton, Alberta, where he spends a lot of time going over the handlebars of his mountain bike, hanging out in off-leash parks, and wishing the Pacific Ocean wasn't so far away. All articles by Ben Coxworth

Why? Why a dual drive?

You either have to have a fixed gear (for the motor) or triple internal hub (for pedaling), neither of which is satisfactory on its own.

I really find an additional motor that drives the SAME chain (and uses the same pedaling derailer gearing) a simpler and more effective solution.


I think any hybrid solution like this the bike has to be lite. If not, the extra weight is extra pedaling work. Also, having two chains is not elegant (I agree with Nehopsa). But since they are made up of ready-made parts, I guess it is a boon for hobbyists. There are many mountain bikes out there. If someone can come up with an easy to install DIY kit to turn a m-bike into an e-bike. I think many people will be interested if it saves them $$$. Of course, it has to comply with most e-bike onroad regulations!


I wouldn\'t like to hit a pot hole at 45mph! Ouch! This bike sure looks complicated.


The 60 lbs does not bother me if I stay on the flat land and use the power for acceleration. But using a nexus hub for a powered bike seems wrong since shimano says it\'s not to be used for even mountainbiking. And I think it looks col with the double chain.


Found another article that says it weighs 60lbs - 10lbs heavier than a fully kitted DH bike, so you wouldn\'t for instance be able to just use that motor to get you up to speed and continue on leg power only at 25/30mph or so, you\'ll need that motor running all the time to maintain any decent speed. Probably a blast to ride though, and a 15 mile range is long enough for a short commute, then how long to recharge?


How is this concept any different than an ordinary moped (at least the ones with pedals)?


At GLOBIKE llc. we have a finished GLOBIKE drivetrain that allows any mountain bike to be converted to a legal electric-bicycle. It is crazy to push beyond US legal limits because the cycle becomes a motor-vehicle and cannot be used for inter-modal tranport. It must be licensed as a mo-ped or other type of motor vehicle depending on state. It requires insurance and a special class drivers license.

If that isn\'t enough the payload of this bicycle is not close to the 400 pounds our GLOBIKE drive-train equipped mountain bicycle currently enjoys and our range is from 50-80 miles with dual LiFePO4 15aH [tested in real world condition] can carry. Also kindly remember that cycle life of LiFePO4 is 2000 cycles. We estimate that a fully loaded GLOBIKE e-cycle can run for 1 penny per mile.

We are currently building a complete GLOBIKE Mustang bicycle that should be ready for release in 2nd Quarter 2012. Drive-trains will be available sooner for conversions.

Bob Kiger

Thank you for your interest in my work - I want to remind everybody that this is a work in progress, not a \"for production\" effort - it is my exploration of the potentialities, possibilities and limitations of electric two wheeled vehicles using mainly bicycle components.

Any and all constructive criticism is greatly appreciated, since it is my desire to move this technology forward.


Nice prototype, but it has a way to go before being useful except to the experimenter. My own eZee Titanium with 14Ah LiPoly is street-legal (fed law allows up to 20mph) and gives me a range of 30 mi with mild pedaling. The controller system allows full motor drive force merely if the pedals are moving, even if near zero pedal force being applied. A 2nd parallel 14Ah gives me potential of 60 miles (which is in excess of my butt\'s ability to tolerate a bike seat!). When i attach the trailer (100 lb carrying capacity) and put two more 14Ah \'s in there, well, we\'re starting to talk \'trans-continental!\' .. all without the added weight of a dual drive train. True, it costs some $$\'s .. but at my age, what is money anyway??? Is the goal to fill one\'s coffin with it?? haha.


Yep, legally in the US, an electric assist bicycle is limited to 20mph under assist, so this bike would be considered a moped. In terms of using the same method on a soft-tail bike, it would complicate things without a shared motor/pedal bottom bracket pivot point. It is a much better solution than a hub motor though. I like.


I have been considering powering my old hardtail Merlin with a hub motor, but I want to have the motor on the front wheel & leave the chain drive completely stock. I am told the torque of the motor would exceeds the strength of the telescopic forks, but that doesn\'t make sense to me because the forks withstand much more (negative) torque whenever one applies the brakes!


I\'ve used an e-Zip Currie drive bike which does both pedal assist and electric power alone. It is fairly heavily built in the \"hybrid\" trail/comfort style, with less expensive sealed lead acid batteries. I am quite pleased with it, for senior\'s town use. These bikes are inexpensive (about US$400 at Walmart at one time). E-Zip also makes more sophisticated and expensive e-bikes. Adding the wider \"comfort\" sprung-post saddle available at Walmart and many stores also extends the comfortable range of use.

This e-zip has I believe a 450 watt motor. Bikes with lower motor power are a bit weak. Some jurisdictions restrict the power to less than 750 watts (1 horsepower) for classification as an e-bike, as well as the top speed restrictions already noted in other comments.

re: Grunchy, front wheel e-drive. As you know, there are various front hub electric motors for bicycles. One occassional problem to be alert to is that if the front axle nuts loosen in the fork, the e-hub\'s torque can pull the front wheel out of the forks when power is applied. I know personally of two occassions when this has happened on custom well-made e-bikes.


Interesting concept, though E conversion kits also allow one to use either the motor, or the pedals, or both, as I\'ve found from personal experience ( Mr. Prince\'s bike is lighter than mine though, by nearly 20 lbs, and faster too, by about 10 mph, though as others have mentioned, e-bikes aren\'t allowed to go faster than 20 mph - I have to watch out for cops when I go faster than about 23 mph (I sometimes see them pacing me to clock my speed - maybe I need to install a doughnut ejector).

Always good to see people experimenting and hopefully pushing the boundaries of what\'s possible.

Suman Subramanian

Front shocks are diametrically opposed to the torgue of a front hub motor. It is almost impossible in the US today to buy a mountain bike that does not have a front shock so GLOBIKE drive-train includes fork, wheel, motor, brake, front rack and dashboard for mountain bike conversions. BTW we will also accommodate the 29\" [700c] diameter. See: for preliminaries.

Bob Kiger

This bike would be legal in TX provided that the only way to exceed 20 MPH is with the pedals turning. TX laws allow e-assist bikes to travel any speed between the 20 MPH federal cut-off and the posted limit provided the pedals have to be turning.

John Clary
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