We have just finished attaching an electric motor to Mrs. True's bucket bike.
Here are a few pictures of the bike as it currently stands:
The process that we went through to get it all put together was as follows:
Mrs. True researched what type of motor she wanted. We found really good reviews for a few types of electric motor kits, so we went with the cheapest one that looked like it would do the job.
It is a mid drive kit from gng electric. Mid drive motors attach near the pedals and drive the chain, as opposed to hub drive motors, the other main affordable option, which replace a wheel with a battery-driven wheel. Mid drive motors allow different gears to have an effect while the motor is running and tend to be the more powerful option. For moving a heavily loaded cargo bike up hills, this seemed like a good idea. Also, with a front disc brakes and a bucket over the rear wheel, a hub motor would have been hard (and more expensive) to install.
The cheapest hub motor that Mrs. True found was $500 including the battery, so her goal was to get a mid drive and battery for that price. The name brand mid drives are at least $600 without the battery, but we found a cheap kit from China for $288 including shipping but not the battery.
Many people on the internet advise against the cheap Chinese kits. We will see in a year if we end up agreeing. There were certain penalties associated with it from the start, but they did not outweigh the price savings to us.
The main problem with the kit was the bottom bracket they sent. Despite the seller asking for the measurement of the bike's bottom bracket, the one they provided did not fit at all. We had to order a separate bottom bracket, and it had to be a very unusual shape to allow the motor to attach. We ended up finding one that would work at SickBikeParts.com. They have a variety of bottom brackets in odd sizes and fast shipping. This cost us another $23.
The plug the kit provided to attach the motor to your battery was very strange, so I bought new plugs from the Home Depot and wired them on. A more expensive kit may have used a more regular plug, and of course buying the battery and motor together would ensure that wiring was not a problem. It was worth the money to us to do it ourselves. We also had to buy longer bolts to hold the motor to the bike frame, but we can't really blame that on the cheap kit. The Madsen has a very large frame; the supplies they sent would have worked on any normal bike. Both of those together added another $5.
The last problem we ran into was the idler wheel in the motor. It's not in line with the path of the chain, so sometimes it derails. We have not yet resolved that issue, but we don't expect it to be an expensive fix; it will just take time.
We had to take the bike to the bike shop to get the bottom bracket removed and the new one put on, since we don't have the right wrench. Our local bike shop guys were very nice and did it for free. That was awesome. If you're near Salt Lake, check out Revolution Bicycles; we like them and will continue giving them our business.
The other major part was the battery. Mrs. True tried to argue that since we'd only paid $200 for the motor, we could afford $300 for the nice batteries. I argued that it would be easy to chain together three batteries made for power tools to get the correct specs (36V and 20 amp hours) and it would only cost $114. We went with the cheaper option, which will probably not surprised readers. Here are the batteries that we bought, as well as the charger.
Mrs. True had second thoughts on seeing the batteries, which were 3 times as big and 5 times as heavy as the expensive ones, but I was confident. And once they were attached to the bike, she agreed that the weight didn't make that much difference.
However, attaching them was an interesting problem. We engineered three different solutions before finding one that we think will work. The first try was too bulky to fit in the available space. The second looked like it worked, but pedaling became an art form to keep your shoes from hitting the box. This is our current solution:
We bought 4 L-shaped brackets and two mending plates and eight bolts and eight nuts and a slew of bungee cords, all at the Home Depot for about $20. First we formed shelves for two batteries with the mending plates and L brackets. It looks like this:
We then bolted the shelves together, straddling the bike frame behind the seat, as you can see above.
We drilled holes in the bucket and attached U-bolts as anchor points for the bungee cords and bungee corded the batteries in place. The third battery was laid on top of the other two and bungee corded to the mending plates below. The final arrangement looks like this:
The controller, a very small box, was zip tied to the frame in front of the batteries and all the wires were attached. We also had to cut off one handlebar grip to replace it with the twist controller for the motor. We still need to come up with a way to make it all waterproof, but in Utah that is less pressing.
All this took a couple of days of work, three trips to the Home Depot, and two trips to the bike shop. Most of the time was spent on the battery holder; the kit was simple to install with the exception of the bottom bracket. I enjoy this kind of project, so this was a good choice for us. We saved at least $200 over the cheapest simple install kit and got a more powerful motor.
It has worked on an unloaded test drive around the neighborhood and once we adjust the alignment of everything on the chain, we expect good results. Mrs.True plans to bike the kids to the library this week (3 miles with several hills). That will be the test. We'll report the results.
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