Hi,
I have two e-bikes and I'll quickly describe how I got to the NuVinci hub.
My first e-bike was a 26" norco frame with a Golden Motor 500W front hub. I started with 36V 7Ah lead batteries, added another GM 500W wheel at the rear and moved to 36V 18AH lead batteries. The bike was extremely heavy. Adding a front suspension made handling a little less stiff and I bought a 36V 13AH NimH batterie to improve performance and weight. I liked the set-up but wanted improvement. Replacing the NiMh with a LifePo4 at 36V 20AH gave me reliable power and good acceleration. I called it 'my tractor', rear and front wheel-drive.
I've since removed the rear wheel mostly because I keep bending rims. Along with switching back to a normal wheel, I trashed the deraillors and added a 53T chainring in the front and a 16T freewheel in the back. I can pedal until I reach 27-28km/h and then the motor gets the bike up till about 34km/h. The lighter rear end stills needs a suspension set-up but the bike is fun and definitively as light as can be.
My second e-bike project started with a nice Jamis 26" frame. Once completed with parts from all over the world, it made a very, very nice fully-suspended ride. I installed a Super BMC 750W motor from EV Deals in front of the pedals and double-chained it using a ratcheted pedal set from Australia. It took a while to adjust the gearing since the motors runs real quick. I ended up with 10T on the motor, 48T attached to a 22T at the middle and a 53T sprocket on the rear wheel. I had good acceleration and a top speed of 42/44 km/h. The problem was that the pedals were absolutely useless. So I got a little more creative.
I found the widest BB I could buy and went back to normal pedals with one 53T sprocket. Behind that sprocket, I inserted a bearing that supports two other sprockets. Those link the motor to the wheel independantly from the pedals. The next miracle was to grind a normal 16T freewheel to fit over the existing freewheel found on the rear hub. One works on top of the other. When the motor runs, the wheel moves but the pedals don't. When I pedal, all three chains move but the motor also has a freewheel so I'm not fighting it. Sounds complicated but it works and I could then pedal a bit more effectively, to about 25 km/h and then it's useless. That set-up was usefull for steep hills, hills that I would never be able to go up with the other e-bike, pedal or not.
When I first spotted a NuVinci hub on E-Bay, I bought it right away out of curiosity and potential designs. It turned out easier than I thought. The hub is certainly heavy but it does incorporate a freewheel. In fact they give you a freewheel that screws on top of that freewheel. A simple clip retains an adaptor on which I welded a much bigger sprocket. I actually got a 60T and I don't think that I can go any bigger. The reason behing the bigger sprocket is that the NuVinci gives me underdrive and overdrive. I wanted to emphasize underdrive since I had already reached my top ratio in term of the motor. I thought I would only use half of the NuVinci potential.
Upon using the bike, I can report the following. Well. it takes a while for the hub to break-in. I was a little discouraged at first, I felt like I was dragging a caravan + I had problems figuring out the ratios. I was constantly overdoing the shifts. In fact, I initially thought that I could just switch the motor on full and slide those NuVinci balls up the ratio scale. It doesn't shift that well under power. Back to my motorcycle day: first gear, second gear, third gear with a slight pause in between. It's absolutely marvelous to come up to another biker with the little motor screaming, looking him in the eye, shifting and pulling away with that low growl that motors made in their low rpm. Priceless... And although it would be nice to be able to go to the max overdrive on motor alone, having that extra-overdrive actually permits me to pedal to excesses of 50Km/h. It's like going back to a pedal-assist motor. At those speeds, I actually help the motor help me. Cool!
I still have to figure out whether all of this is worth it. Electric motors do not have snappy reactions like a two stroke. They build up their rpm slowly and pull equally. What I mean to say is that it's not because I'm in a lower ratio that the bike jump-starts ahead faster. And I still have to evaluate it's climbing ability. I'm very happy that I can pedal through-out the speed range.
More tests and videos on Youtube will follow.
I have two e-bikes and I'll quickly describe how I got to the NuVinci hub.
My first e-bike was a 26" norco frame with a Golden Motor 500W front hub. I started with 36V 7Ah lead batteries, added another GM 500W wheel at the rear and moved to 36V 18AH lead batteries. The bike was extremely heavy. Adding a front suspension made handling a little less stiff and I bought a 36V 13AH NimH batterie to improve performance and weight. I liked the set-up but wanted improvement. Replacing the NiMh with a LifePo4 at 36V 20AH gave me reliable power and good acceleration. I called it 'my tractor', rear and front wheel-drive.
I've since removed the rear wheel mostly because I keep bending rims. Along with switching back to a normal wheel, I trashed the deraillors and added a 53T chainring in the front and a 16T freewheel in the back. I can pedal until I reach 27-28km/h and then the motor gets the bike up till about 34km/h. The lighter rear end stills needs a suspension set-up but the bike is fun and definitively as light as can be.
My second e-bike project started with a nice Jamis 26" frame. Once completed with parts from all over the world, it made a very, very nice fully-suspended ride. I installed a Super BMC 750W motor from EV Deals in front of the pedals and double-chained it using a ratcheted pedal set from Australia. It took a while to adjust the gearing since the motors runs real quick. I ended up with 10T on the motor, 48T attached to a 22T at the middle and a 53T sprocket on the rear wheel. I had good acceleration and a top speed of 42/44 km/h. The problem was that the pedals were absolutely useless. So I got a little more creative.
I found the widest BB I could buy and went back to normal pedals with one 53T sprocket. Behind that sprocket, I inserted a bearing that supports two other sprockets. Those link the motor to the wheel independantly from the pedals. The next miracle was to grind a normal 16T freewheel to fit over the existing freewheel found on the rear hub. One works on top of the other. When the motor runs, the wheel moves but the pedals don't. When I pedal, all three chains move but the motor also has a freewheel so I'm not fighting it. Sounds complicated but it works and I could then pedal a bit more effectively, to about 25 km/h and then it's useless. That set-up was usefull for steep hills, hills that I would never be able to go up with the other e-bike, pedal or not.
When I first spotted a NuVinci hub on E-Bay, I bought it right away out of curiosity and potential designs. It turned out easier than I thought. The hub is certainly heavy but it does incorporate a freewheel. In fact they give you a freewheel that screws on top of that freewheel. A simple clip retains an adaptor on which I welded a much bigger sprocket. I actually got a 60T and I don't think that I can go any bigger. The reason behing the bigger sprocket is that the NuVinci gives me underdrive and overdrive. I wanted to emphasize underdrive since I had already reached my top ratio in term of the motor. I thought I would only use half of the NuVinci potential.
Upon using the bike, I can report the following. Well. it takes a while for the hub to break-in. I was a little discouraged at first, I felt like I was dragging a caravan + I had problems figuring out the ratios. I was constantly overdoing the shifts. In fact, I initially thought that I could just switch the motor on full and slide those NuVinci balls up the ratio scale. It doesn't shift that well under power. Back to my motorcycle day: first gear, second gear, third gear with a slight pause in between. It's absolutely marvelous to come up to another biker with the little motor screaming, looking him in the eye, shifting and pulling away with that low growl that motors made in their low rpm. Priceless... And although it would be nice to be able to go to the max overdrive on motor alone, having that extra-overdrive actually permits me to pedal to excesses of 50Km/h. It's like going back to a pedal-assist motor. At those speeds, I actually help the motor help me. Cool!
I still have to figure out whether all of this is worth it. Electric motors do not have snappy reactions like a two stroke. They build up their rpm slowly and pull equally. What I mean to say is that it's not because I'm in a lower ratio that the bike jump-starts ahead faster. And I still have to evaluate it's climbing ability. I'm very happy that I can pedal through-out the speed range.
More tests and videos on Youtube will follow.
, tapholov
