First, I'd like to say thanks to everyone in these forums for all the information and great ideas. Until now I've just been a "taker" from this forum, but now I'd like to share my build so that perhaps others can learn from my mistakes and success. Perhaps you have similar goals to mine, and will find this post useful.
Goals
Create an electric bike that:
1. accomplishes my 16+ mile commute in 45 minutes or less without extreme effort (traffic is awful, but I find the un-assisted bike commute too physically draining to do every day). My initial goal was a top speed of 40 miles per hour.
2. assists me in pedaling...I still want to get exercise.
3. looks at least somewhat like an ordinary bike so that it doesn't stand out to much
4. utilizes my bicycle's 27 gears so that it has maximum efficiency and versatility
5. will last several years without replacing major components (i.e. motor, batteries)
6. cost me less than $1000
7. would allow me to experiment with gearing ratios and be very flexible in this regard
Specs
Motor: 36 volt, 600 watt gear-motor, with fan, ~7:1 planetary gear reduction ratio, output shaft max speed 550 RPM
Controller: 36 volt, 650 Watt, 25 amps max, hall effect thumb throttle, power-cut brake lever
Battery: 36 volt, 20 aH, LiFePo with BMS
Gearing: 10-tooth sprocket on motor output shaft to 52-tooth chain-ring on left side of bottom bracket. This means that if the motor is running at its max speed, it will force me to have a cadence of 105 RPM. I shoot for a cadence of 80-100 RPM.
Other features: custom chain tensioner, chain guide (to prevent it from falling of left chain-ring)
Vendors: TNC scooters, electricscooterparts, monsterscooterparts, robotmarketplace, Ebay (daoji666@126.com), numerous online bike part stores, Fry’s, McMaster-Carr
My favorite vendor was TNC scooters. They were the most helpful and had the best prices. I should have bought everything from them.
Final Results
Top Speed: 35 mph
Usual cruising speed: 28-30 mph
Total Cost: $916
Total Cost after mistakes: $1200
Overall a great commuter vehicle. I can consistently do my commute in 40-45 minutes and now I really look forward to it. The motor utilizes all 28 speeds on my bike so it can take hills just as easily at it takes the flats.
Mistakes/Learnings
The biggest difficulty was mounting the motor to the frame and dealing with frame/mount-bracket flex when under load. My first mounting schemes were woefully under-built and flexed so much that the chain would always fall off the chain-ring. I destroyed a chain and put lots of gouges in various components. Even now, with a better mounting scheme, the frame and everything flexes enough that a chain guide and active chain tensioner are necessary to keep the chain in place. One downside of this design is the length of the chain. It just requires a lot of chain management.
Another issue was figuring out how to mount a bunch of right-handed things on the left side of the bike. I had to buy two sets of clipless pedals since I needed two right-handed pedals. Also, the clipless pedals needed to be symmetric with respect to the cleat since I would in effect be using them backwards. The most cost effective option I found were the cheapest egg-beaters.
The controller got really warm when put inside the rack bag, so I have loosely strapped it on top of the rack bag so that it gets convective forced flow air cooling while I ride. The motor, controller, and BMS only get mildly warm after 45 minutes of full throttle. If it starts to rain, I have a rain cover that goes over everything…not the cleanest option, but it works.
The motor/power-system behind all the gearing can really do some damage. I broke chains, ruined derailleurs, and chewed up sprockets before I got it right.
Another downside of this design is that the back of the bike is very back and top-heavy.
Goals
Create an electric bike that:
1. accomplishes my 16+ mile commute in 45 minutes or less without extreme effort (traffic is awful, but I find the un-assisted bike commute too physically draining to do every day). My initial goal was a top speed of 40 miles per hour.
2. assists me in pedaling...I still want to get exercise.
3. looks at least somewhat like an ordinary bike so that it doesn't stand out to much
4. utilizes my bicycle's 27 gears so that it has maximum efficiency and versatility
5. will last several years without replacing major components (i.e. motor, batteries)
6. cost me less than $1000
7. would allow me to experiment with gearing ratios and be very flexible in this regard
Specs
Motor: 36 volt, 600 watt gear-motor, with fan, ~7:1 planetary gear reduction ratio, output shaft max speed 550 RPM
Controller: 36 volt, 650 Watt, 25 amps max, hall effect thumb throttle, power-cut brake lever
Battery: 36 volt, 20 aH, LiFePo with BMS
Gearing: 10-tooth sprocket on motor output shaft to 52-tooth chain-ring on left side of bottom bracket. This means that if the motor is running at its max speed, it will force me to have a cadence of 105 RPM. I shoot for a cadence of 80-100 RPM.
Other features: custom chain tensioner, chain guide (to prevent it from falling of left chain-ring)
Vendors: TNC scooters, electricscooterparts, monsterscooterparts, robotmarketplace, Ebay (daoji666@126.com), numerous online bike part stores, Fry’s, McMaster-Carr
My favorite vendor was TNC scooters. They were the most helpful and had the best prices. I should have bought everything from them.
Final Results
Top Speed: 35 mph
Usual cruising speed: 28-30 mph
Total Cost: $916
Total Cost after mistakes: $1200
Overall a great commuter vehicle. I can consistently do my commute in 40-45 minutes and now I really look forward to it. The motor utilizes all 28 speeds on my bike so it can take hills just as easily at it takes the flats.
Mistakes/Learnings
The biggest difficulty was mounting the motor to the frame and dealing with frame/mount-bracket flex when under load. My first mounting schemes were woefully under-built and flexed so much that the chain would always fall off the chain-ring. I destroyed a chain and put lots of gouges in various components. Even now, with a better mounting scheme, the frame and everything flexes enough that a chain guide and active chain tensioner are necessary to keep the chain in place. One downside of this design is the length of the chain. It just requires a lot of chain management.
Another issue was figuring out how to mount a bunch of right-handed things on the left side of the bike. I had to buy two sets of clipless pedals since I needed two right-handed pedals. Also, the clipless pedals needed to be symmetric with respect to the cleat since I would in effect be using them backwards. The most cost effective option I found were the cheapest egg-beaters.
The controller got really warm when put inside the rack bag, so I have loosely strapped it on top of the rack bag so that it gets convective forced flow air cooling while I ride. The motor, controller, and BMS only get mildly warm after 45 minutes of full throttle. If it starts to rain, I have a rain cover that goes over everything…not the cleanest option, but it works.
The motor/power-system behind all the gearing can really do some damage. I broke chains, ruined derailleurs, and chewed up sprockets before I got it right.
Another downside of this design is that the back of the bike is very back and top-heavy.