Carl Chatfield home page | Getting from A to B | Electric Bicycles | Electric Wedgie

Carl's Electric Wedgie

Here I am in my normal commute-to-work mode: laptop computer and change of clothes tucked away in the panniers, and power-assist electric motor mounted on my bike. I regularly commute about seven miles per day between home and work, and with various errands usually average around 10 miles per day. I know that is not far, but I have the good fortune of living close to where I work. And believe me, on the roads between my home and work, one less car on the road does help. Mainly it helps me maintain my sanity, and sneak a bit of exercise into my otherwise sedentary life.

The Bike

The bicycle itself is an REI Novara Viaggio touring bike. The power assist component is the Currie Technologies ProDrive system. This was installed on the bike by Eric and friends at Electric Vehicles Northwest. If you are an adept bike mechanic and know something about electricity (though I've always heard these two attributes are mutually exclusive!), you could probably install the kit yourself. In my case though, I was quite happy to leave the installation in the very capable hands of my friends at  EVNW.

The initial bike price was around $600, and the ProDrive kit was around $550. So my total cost for the e-bike is around $1,150.

Click the thumbnails below to see larger images.

With big 12-amp battery (more on batteries below)

With small 7-amp battery

Thumb throttle mounted on the handlebar

Here's what the bike and batteries weigh:

Yes, this is a heavy setup! You will not see me on it at the local velodrome.

The Motor

This is an Eco-Torque Drive, 24-volt brushless motor with electronic pulse-width modulated (PWM) controller. 

The main distinctions I've noticed between different e-bike motors is how they drive the wheel:

• There's friction drive, like the Zap motor, which rubs against the tire. While mechanically simple, I found when test-riding such bikes that the friction drive can slip against the tire, especially on wet roads (e.g. Redmond 9 months of the year). I suspect there's quite a bit of power lost in the transfer between the battery, motor, tire and road with such motors.
• Hub motors, such as the Heinzmann, mount right on the front or rear wheel hub. The only hub-motor bike I've test ridden is the EVGlobal e-bike, which I believe uses a Heinzmann hub motor on the back wheel. Overall I really like the look and feel of the hub motor, though everything I've read suggests they do not yet have the power of the Currie motor. BTW I did test ride the EVGlobal bike twice, and here's my quick summary: very nice ride overall. EVGlobal did a great job of incorporating head and tail lights and an on-board battery charger right into the main power system. I was disappointed with the 5-gear bike; I'd prefer a larger gear range. If they could find a somewhat more powerful motor and lighter, next-generation batteries, they'd have a sure winner. EVGlobal seems to be targeting car dealerships to sell the bikes, and I must say it seemed a little strange to me when I took up about a 1/2 hour of a car salesman's time to go over the bike. 

Recently I attended a transportation fair where my e-bike was on display next to the EVGlobal e-bike. Here's a side-by-side comparison of the two:

• Chain drive motors, of which the Currie ProDrive is the only example I'm familiar with. This motor hangs off the left side of the rear wheel hub, and directly powers the rear wheel via a pair of chain drives. For a great technical explanation of why chain drive motors work so well, see this page on Ed Benjamin's great e-bikes site. Initially I thought the motor looked a little ungainly, but I've never found that it gets in my way. In fact I usually have a pannier mounted right above it, and you have to look carefully to even see it. 

The Battery

This functional but somewhat ungainly box contains Dual 12-volt, 12-amp hour sealed recyclable lead acid batteries. This is by far where most of the weight of the system resides. I've fully exhausted the batteries only once. I blew the fuse once too, and carry a few spares with me at all times now. Here are some photos of both the larger 24-volt/12-amp and smaller 24-volt/7-amp batteries.

The frame-mounted 12-amp battery is probably the most visible part of the power system. (The smaller battery you see mounted ahead of the USPD battery is for my headlights.) I've found that it's well-placed in the frame, however, and has not interfered with my riding at all. I've noticed that the more current Currie batteries are in a slightly smaller, gray box--a nice improvement. EVNW has come up with a smart way of mounting the big battery horizontally on a pannier rack, though my specific rack didn't accommodate it very well so my battery remains mounted in the frame.

Normally I ride with the 7-amp battery pack mounted on my pannier rack. This battery substantially shortens my powered range, but it still works well within my round trip commute to work and back. It is  substantially lighter. Theoretically I could mount both batteries on my bike, and on an exceptionally long trip, switch from one battery to the other. The normal refrain one hears is "but doesn't the extra weight of the battery negate its value?" My reply is, No! More on the quality of the bike ride below.

But How Is The Ride?

Overall it's excellent! I definitely feel the additional weight of the power system when starting off and when going up hills, but it's exactly at these times when the benefit of the power system is most strongly felt. The thumb-activated throttle is theoretically a variable speed throttle, but I've found it to be basically an on/off toggle in most cases. On flat roads running on electric power alone (which I normally don't do), I can achieve about 18 MPH fully loaded with gear.

I am an enthusiastic commuter cyclist, but not a roadie. I never had the urge to don lycra head-to-toe and cover one hundred miles in a day. I've never gone bike camping. I cannot true a wheel. But I do enjoy the smart and elegant personal transportation solution the e-bike affords.

The main benefit I notice in my specific riding pattern is that I can generally keep up with vehicle traffic on my regular commute to work. I subscribe to John Forrester's Effective Cycling philosophy that bicyclists are safest when they ride like a vehicle with traffic, rather than on sidewalks or bike trails. I come much closer to maintaining traffic speeds with electric assist than I otherwise could. I especially enjoy taking left turns at controlled intersections right along with moving traffic; I think it surprises the drivers behind me how quickly I can get up to vehicle speed.

I have no scientific measurements to back this up, but I'd guestimate that the motor approximately matches my maximum energy input into the bike at 50%. The motor's torque is immediate and quite strong. In fact I've found that it's a good idea not to engage the motor when taking off from a standing start, as the jolt on the bike and rider can be surprisingly strong.  I also frequently "top out" the motor at maximum speed from time to time. I can tell this more by ear than anything else. Despite what you often hear about electric motors, they are in fact somewhat loud and high-pitched. When the motor is "topped out," it makes a distinctly different sound and that's my queue to disengage it.

Compared to the other e-bikes I've ridden, my Currie-equipped e-bike is (to me) noticeably better. I think this is a combination of the superior power of the Currie motor, and the better gearing of my bike. For whatever reason e-bike manufacturers like EVGlobal are limiting themselves to 5- and 7-speed bikes, and are geared too low for my taste. I prefer the full 21-gear range of my bike, and like having the flexibility of relying on the full gear range when I don't want to engage the electric motor.

 Updated 07/09/06