I just recently finished my first bike conversion. It's not something fancy or high speed, but it gets the job done. I bike to work and the distance is around 0.5 miles to my work I think. I decided to make the trip a little easier and looked around for a e-bike kit. Now I could get a kit with a hub motor like the modern kits out there now, but they all fall out side my price range and I needed to get this built relatively quickly so I didn't have time to save up for one. So I searched eBay and found one that has an old school motor on bracket type design.
(click to enlarge)
I bought a cheap tool box and used a Drimmel to drill out holes and stuff. There is some hooks on bottom (not visible in image though) that I use to anchor it to the seat rack. It's got a pad lock on the tool box and on one of the mounts I put for it on the bottom. It probably won't deter a determined thief, but then again, he's going to have trouble lugging around the 50Ib+ tool box away as it's got 3 12Ib 12v 12ah SLA batteries in there.
I don't really leave it outside for very long anyway as I designed the whole thing to be removed from the bike relatively easily. I just unplug the motor and throttle cables, and then detach it from the seat rack and I bring it inside to charge. (the throttle cable is wired up to a modified USB cable and the wire from the box is from the the other end of a USB extension cable so I can unplug it easily) The above images were when I had the bike inside. I built the thing inside and doing it outside in the middle of winter is not really a good idea for me.
The motor drives a small BMX chain that is currently using the 16 tooth gear on my freewheel. It tops out at 17mph and averages 15-16mph if I'm fighting some wind or a small incline. (it's relatively flat where I live and I only weight only around 125Ibs so the bike doesn't have to work very hard to lug me around town.
) My bike has a speedometer on it so I know how fast it's going at all times. I might be able to improve it's speed a little by using a slightly larger freewheel as the motor might not be hitting it's top RPM yet. This is s 36v system by the way and the motor is a 36v 350watt brushed motor....I think. I don't know if it's brushed or not. I do know it's geared down in a manner similar to the motor on some of the older Currie e-bikes which also have a motor design similar to mine.
Currently I'm planning on getting a new rear rim with a longer axle with two BMX freewheels attached via an adapter. (My kit came with one but it's rather crappy and the threading on it doesn't seem to fit it's own freewheel very well....aka it's a bit loose and I can actually pull the freewheel off the adapter without unscrewing it!) Right now it works with my 6 speed freewheel, but it's having trouble keeping the chain tight as the chain seems to be getting loose after 2 or more days of riding it on average. The first time this happened the chain tried to jump to a higher gear and the chain snapped off as a result. I now make sure to keep it nice and tight and it prevents that. (not too tight though. I'm aware the chain needs a bit of slack in it. I try and make sure the chain isn't loose enough to reach a tooth on the next gear and I should then be fine)
The chain issues will be solved once I get the double BMX freewheel on there. The increased spacing and freewheel adapter should then allow me to reattach a chain to the pedals since currently I can't pedal it as the motor is using the same freewheel that my pedals would have been using.
I removed the derailler and shifter as this bike won't be set up as a multispeed anymore. It will eventually have the one speed freewheel with the second freewheel drivin by the motor.
The batteries I bought from a local store and they are made in Taiwan. Not much else I know about them other then their specs which is 12v 12ah capacity. They were a bit expensive, but they are pretty good quality. A bit heavy though so I will be saving up to get a LifePO4 pack as the bike is kinda top heavy right now. I don't have the e-brake handles attached (though I have prepared wiring for it inside the battery box where the speed controller lives as well) as I don't have problems braking since I end up letting go of the throttle anytime I brake anyway. I plan on getting a thumb throttle though and once that happens, the e-brakes will be installed then.
I've read up a little on Texas law and as far as I can tell my e-bike is road legal. (Texas doesn't have a pedal assist requirement that I know of and my bike doesn't go faster then 20mph)
Not that I would have legal issues anyway. My bike looks like a normal bike from a distance aside from the tool box on back which I already had someone mistake for a "lunch box" at my work place. I work at a local Wal-Mart and bring it to the back during work to keep it out of the weather and one customer thought the tool box on back was my lunch box...lol
Well I discovered something interesting. It appears I was only running the bike at maybe 75% of it's actual peak power. There are two small black wires with connectors on them that fit each other. I assumed they had to be connected for it to power on. But before I left for lunch from work, I decided to run the bike with those two wired disconnected. Now it seems the bike has more kick to it and I've seen it push 18mph+ in the short test run I gave it. (the torque was starting to work the right side nut lose on the rear wheel causing issues with the chain alignment so I couldn't go for too long). I've retightend the right side nut and will work on getting more tension on the chain as I think it's a bit too loose right now. When I was hitting the 18mph mark the motor was sort of making a hopping noise with a noticeable jittering of the speed of the bike but only when hitting a speed past 18mph. It's hard to describe but it sounds like the chain might be the cause. I may try and record a sound clip of it when I get the time to see if any of you more experienced bikers might know what it might be.