wdwrkr51
100 mW
Hey guys,
If an MTB conversion is the F150, and a beach cruiser conversion is the Cadillac, then the good BMX 20-inch "Urban Bike" conversion is the Mazda Miata of E-Bikes. We might not want to take a thousand mile cross-country trip on one, but our day-to-day driving will be very enjoyable. My experience bears this out! I'd like to persuade you to consider this format for your next e-bike project.
In general, the stronger frame and wheels are part of the appeal, especially if we choose the "freestyle" type frame over a lighter "race" type frame. Precise handling is a great benefit. Stronger thrust from any motor, as compared to a 26" or 700c bike is also a real plus. It is also nice for us older riders to be able to place both feet on the ground at a stop, making mounting and dismounting easier.
There are also certain real drawbacks inherent to the concept; limited space overall for battery placement being one. The narrow rear dropout width (110mm) makes a rear drive motor problematic. Still, with good planning and execution, a really outstanding urban bike is possible.
FYI: my BMX conversion features: a Trek TR10 steel frame(20" top bar and 14mm dropouts), a GT steel front fork (3/8" dropouts), a stock Trek 48-spoke rear wheel, and Maxxis "Miracle" ribbed 20" x 2.1" tires (85 to 110 lbs. pressure rating) at about 90 lbs. pressure. I have a two-speed derailleur on my front sprockets (40/48 teeth) and a 15-tooth rear sprocket. I use standard V-brakes. (A big, wide, coil spring suspension saddle from cloud nine takes care of the bumps for my old back.)
I have an AMPEDBIKES/9c (2807?) front-mount direct-drive motor, with stock 35-amp (max) 36-60volt controller, stock thumb throttle, etc. as supplied by AmpedBikes and Doug Daut at Electric Bike Kit Solutions (gocarlite.com.), and a hand assembled Turnigy RC 10 amp-hour (5S2P x 6) - 55.5 volt nominal LiPo battery (high of 63 volts, low of 48 volts).
My battery pack weighs a tiny bit more than ten pounds when wired and bagged for riding, and is mounted on a TopPeak rear touring rack capable of 50 pounds load. My controller is mounted underneath the rack. The extremely heavy rear dropouts made it simple to drill and tap holes for mounting the rack support legs.
I also operate two LED battery operated headlights, two ebike.ca halogen 10 watt headlights that run off the main battery, and a Planet Bike LED battery operated taillight.
This complete package weighs in at slightly less than 69 pounds on the bathroom scale. Measured range when ridden for conservative use of available power is 30+ miles. Top speed is about 28 mph on the flats @ 63 volts right off the charger. That doesn't last long! More realistically, top speed is a nominal 25 mph. AVERAGE speed in my subdivision, up hill and down, maxes out at a measured 21 mph.
This bike tackles the hills with verve, yet has plenty of speed for the flats, and I only pedal when I want to. Rarely is the hill so steep that I feel like I HAVE to pedal. (That was not the case with my old 36-volt 26" lead-acid MTB.)
There seems to be enough rake and trail with the GT fork that the steering is not at all twitchy. Potholes are handled with aplomb due to the strong small wheels.
Interestingly enough, the "magnetic drag" issue is less of a factor on this bike with 20 inch wheels than it was on the MTB with 26 inch wheels. I don't know why, but it is not nearly so apparent when coasting down steep hills. I would have thought the opposite would prove true.
For the future: I am strongly considering conversion to rear drive. I'm about at the limit of front-wheel drive traction at this voltage, on wet pavement, so I believe I'd need rear wheel drive before making any further upgrades. I have ordered a "spare 9c side cover, threaded for freewheel" from ebikes.ca just to see if it is possible to adapt one to the other using the front drive motor with the short axle. If I can, I want to fit the motor between the rear drop outs with a single speed freewheel. I'm willing to spread the rear "fork" a tiny bit if need be. 110mm does not leave a lot of room to play.
Then I will consider ordering an Edward Lyen 72 volt 45-amp controller, and adding one battery pack assembly to my power pack, just to see what a difference that makes. (high of 84 volts right off the charger, low of 64 volts - this is higher than my HIGH voltage now)
IF I can successfully adapt the front mount DD motor to rear drive, complete with single-speed freewheel, I will post the results here. I will also strongly consider adding an RST Capa T10 Suspension front fork to the bike, and front disc brakes to boot.
Hopefully, this narrative will encourage more of you to take on the BMX-20-inch build for your next e-bike. I'D like to read about your BMX frame build experiences.
wdwrkr51 - Greater Atlanta area, State of Georgia
If an MTB conversion is the F150, and a beach cruiser conversion is the Cadillac, then the good BMX 20-inch "Urban Bike" conversion is the Mazda Miata of E-Bikes. We might not want to take a thousand mile cross-country trip on one, but our day-to-day driving will be very enjoyable. My experience bears this out! I'd like to persuade you to consider this format for your next e-bike project.
In general, the stronger frame and wheels are part of the appeal, especially if we choose the "freestyle" type frame over a lighter "race" type frame. Precise handling is a great benefit. Stronger thrust from any motor, as compared to a 26" or 700c bike is also a real plus. It is also nice for us older riders to be able to place both feet on the ground at a stop, making mounting and dismounting easier.
There are also certain real drawbacks inherent to the concept; limited space overall for battery placement being one. The narrow rear dropout width (110mm) makes a rear drive motor problematic. Still, with good planning and execution, a really outstanding urban bike is possible.
FYI: my BMX conversion features: a Trek TR10 steel frame(20" top bar and 14mm dropouts), a GT steel front fork (3/8" dropouts), a stock Trek 48-spoke rear wheel, and Maxxis "Miracle" ribbed 20" x 2.1" tires (85 to 110 lbs. pressure rating) at about 90 lbs. pressure. I have a two-speed derailleur on my front sprockets (40/48 teeth) and a 15-tooth rear sprocket. I use standard V-brakes. (A big, wide, coil spring suspension saddle from cloud nine takes care of the bumps for my old back.)
I have an AMPEDBIKES/9c (2807?) front-mount direct-drive motor, with stock 35-amp (max) 36-60volt controller, stock thumb throttle, etc. as supplied by AmpedBikes and Doug Daut at Electric Bike Kit Solutions (gocarlite.com.), and a hand assembled Turnigy RC 10 amp-hour (5S2P x 6) - 55.5 volt nominal LiPo battery (high of 63 volts, low of 48 volts).
My battery pack weighs a tiny bit more than ten pounds when wired and bagged for riding, and is mounted on a TopPeak rear touring rack capable of 50 pounds load. My controller is mounted underneath the rack. The extremely heavy rear dropouts made it simple to drill and tap holes for mounting the rack support legs.
I also operate two LED battery operated headlights, two ebike.ca halogen 10 watt headlights that run off the main battery, and a Planet Bike LED battery operated taillight.
This complete package weighs in at slightly less than 69 pounds on the bathroom scale. Measured range when ridden for conservative use of available power is 30+ miles. Top speed is about 28 mph on the flats @ 63 volts right off the charger. That doesn't last long! More realistically, top speed is a nominal 25 mph. AVERAGE speed in my subdivision, up hill and down, maxes out at a measured 21 mph.
This bike tackles the hills with verve, yet has plenty of speed for the flats, and I only pedal when I want to. Rarely is the hill so steep that I feel like I HAVE to pedal. (That was not the case with my old 36-volt 26" lead-acid MTB.)
There seems to be enough rake and trail with the GT fork that the steering is not at all twitchy. Potholes are handled with aplomb due to the strong small wheels.
Interestingly enough, the "magnetic drag" issue is less of a factor on this bike with 20 inch wheels than it was on the MTB with 26 inch wheels. I don't know why, but it is not nearly so apparent when coasting down steep hills. I would have thought the opposite would prove true.
For the future: I am strongly considering conversion to rear drive. I'm about at the limit of front-wheel drive traction at this voltage, on wet pavement, so I believe I'd need rear wheel drive before making any further upgrades. I have ordered a "spare 9c side cover, threaded for freewheel" from ebikes.ca just to see if it is possible to adapt one to the other using the front drive motor with the short axle. If I can, I want to fit the motor between the rear drop outs with a single speed freewheel. I'm willing to spread the rear "fork" a tiny bit if need be. 110mm does not leave a lot of room to play.
Then I will consider ordering an Edward Lyen 72 volt 45-amp controller, and adding one battery pack assembly to my power pack, just to see what a difference that makes. (high of 84 volts right off the charger, low of 64 volts - this is higher than my HIGH voltage now)
IF I can successfully adapt the front mount DD motor to rear drive, complete with single-speed freewheel, I will post the results here. I will also strongly consider adding an RST Capa T10 Suspension front fork to the bike, and front disc brakes to boot.
Hopefully, this narrative will encourage more of you to take on the BMX-20-inch build for your next e-bike. I'D like to read about your BMX frame build experiences.
wdwrkr51 - Greater Atlanta area, State of Georgia