Electric Bikes - Which Unit to Power Wife's Bike?

We got this bike for the wife because that's the one she wanted.

http://www.trekbikes.com/women/wsd_products/bikes/bike_path/navigator20wsd/

Now she's got a knee issue caused by nothing regarding the bike.

But now she can't peddle much at all due to pain. I want to buy an

electric power unit/system to install on this bike so she can do a

couple of consecutive hours of riding with me. Which units/systems

do you all recommend? I think I saw one that involves the motor be-

ing installed where the front axel is now and the spokes get connect-

ed to this motor. I guess 25 miles would surely be enough range. So

please make your recomendations and cite web sites too.

The fork on the bike may be aluminum, in which case you'll need to look at rear wheel kits or consider replacing the fork with a steel one. (The drop outs on aluminum forks are cast and may fail if you place a hub motor on the front wheel. Clearly such failures can cause significant damage and injure the rider. Here's a photo showing how the cast drop offs on aluminum forks can fail.)

http://www.lucidscience.com/temp/crash2.jpg

There are a number of good kits. Decide what her requirements are (does she need lots of torque for steep hills, etc.) If she's not going to be able to pedal at all, you may have to spend a fair amount of money for a powerful battery (may influence your decision on the controller as well). For example, I installed the Currie conversion kit on my mountain bike; I pedal but needed power assist on the steep mountain roads where I live now. I have traveled 25 miles easily and still had battery power, but I pedal as much as I can. Without pedaling, I might deplete the battery within 8 miles, given the terrain of the area I live.

Once you know what your requirements are and what your budget is, start your online window shopping. Come back and post any questions you might have about particular kits.

Good luck.

For a quality front hub application check out eZee at www.ebikes.ca
So long as everything is mounted, seated and secured properly an eZee front hub on an aluminum fork should be fine. Mine has been failure free since day one (and going strong for almost a year now).
http://ebikes.ca/store/store_ezee.php
Optional torque arm:
http://ebikes.ca/store/photos/TorqArmRev2.jpg

B.

I have the same bike, a Trek Navigator. I installed a kit from EBikeKit (rear Hub) and it works great. a very smooth ride. By going with the rear hub you can keep the front fork, shocks,etc. Here is the Link

http://www.e-bikekit.com/

The E-BikeKit Conversion (http://www.eco-wheelz.com/catalog/ebike-kit-tm-electric-bike-kit-p-5.php) is our favorite kit as well. It's fairly priced and includes a popular 9 Continents motor. Distributed by several different companies (ie: Amped, E-BikeKit, eBike.ca) this motor is well-known in the e-biking community and has been through lots of "real-world" testing. We like E-BikeKit best because the setup is safe and easy-to-install. Fronts and rears are available...

AvenJack,

Here's a link to a website that compares different e-bike kits. http://www.electric-bikes.com/bikes/kits.html

El Duderino,

You may really want to consider investing in a steel replacement fork. The photo I linked is posted on an e-bike builder's site. He included that photo and a couple of others in his 3 July 2009 blog after his fork failed. He now clearly warns that you absolutely should not use a front hub motor on an aluminum fork. He knew about the risks of putting a hub motor on an aluminum fork but ignored them and put one on one of his personal bikes that had an aluminum fork. Torque arms didn't help him. When his drop offs failed, the bike rolled over twice, he was thrown onto concrete and injured his ankle. The bike's frame and fork were bent, the front rim warped and spokes broken.

Here' what he posted after his accident. "DO NOT consider using any aluminum frame or forks with a hubmotor. Aluminum fails instantly without warning and becomes brittle over time due to vibration." Here's a link to his blog about the accident--go to the 3 July entry. http://www.atomiczombie.com/june-sept09.htm

Thank you all very much. Good data to pour over.

Bicycles were not built to handle motors at the drop-outs.

No matter what type of metal is used for your fork, or your rear drop-outs, you must install torque arms.
It is not a matter of "IF" your hub motor will rip out the drop-outs, but WHEN. It WILL happen at some point, and you will risk harm to your wife. You MUST install torque arms.

Besides, they are a fraction of the cost of your ebike.

Snowsurfer,

I haven't read about anyone with a hub motor on a steel fork having the drop outs fail. I agree one should have a torque arm. I think they should be standard with all kits; unfortunately, I suspect some who purchase kits where the torque arm is sold separately may skip that important safety feature.

Common sense dictates that all of us with bikes, including e-bikes, should be inspecting them periodically to make sure everything is functioning and operating safely. I'm a bit compulsive and check my wheels, especially the back wheel where the non-hub motor is, after every day. I tend to check the entire bike out weekly, especially the brakes. You can't be too safe.

TORQUE ARMS! Rest assured folks, I'll take that advice for sure!

TORQUE ARMS! Rest assured folks, I'll take that advice for sure!

For sure. It will protect your wife. Doesn't matter if the drop-outs are made of steel. Steel has a property called malleability. This means that it may not break, but it will certainly bend. It has a point when it will fail, and you will be prepared by having torque arms. Two of them.

A guy from Australia makes a sick set. He uses them for his electric dirtbike. Highly recommended. They are made of a high grade steel. Ultra-resistant, and stronger than anything your hub motor can dish out. Even at 100V and 50A, I don't think you can wreck his torque arms. But if you are running that much juice, you really ought to have 4 torque arms.

He builds powerful set-ups in Australia:

http://www.stealthelectricbikes.com.au/

AdvenJack

Ebikes.ca also has a nice adjustable torque arm than many e-bike owners use, even if they got their conversion kit elsewhere.

http://endless-sphere.com/forums/download/file.php?id=26126

http://endless-sphere.com/forums/download/file.php?id=26133

One of the other advantages of a rear wheel hub motor is less risk of the rider being thrown if there's a controller failure that causes instant plug braking; such a failure on a front wheel hub can launch the rider over the handlebar. There's a long discussion of the risks of front wheel hub motors on another forum. Here's the link, if you're interested. http://endless-sphere.com/forums/viewtopic.php?f=3&t=12475

Seems to me a good, high powered Schottky diode in the controller to motor circuit should prevent plug brake lock up.

NEVER use a front wheel kit. Its hell on the frame. Its hell on any fork. NEVER use a front wheel kit on a suspension fork ever. It will fail its only a matter of time and place. I dont care if its steel or aluminium. Its going to break and destroy your front end along the way.

Rear wheel kits are the only way to go unless you want your wife sliding down the street on her face. There are a few yxm shops. You can buy the kit in a bundle. She should not need more then 36v/600w. A 10ah lifpod battery is all you need. Im sure its more then she will ever use. She can cruise at 15-22mp on a 26 inch rim for over 20 miles without a problem.

I would like to point out that nobody seams to notice what the forks mount on. Bearings are not meant for those forces. You will oval the headset over and over. Aluminium frames are not welded proper for those forces at the front end. Get a rear wheel kit and take advantage of the strongest parts of the frame for safety and longevity.