E-bike project, I think I want a lightweight system

[Captain slow]

I've been lurking for a while and wanted to say hi.

Former e-bike owner who sold it because I didn't like the extra weight and I got to the point where I was fit enough to make my 17 km ride each way on my own. But the e-bike was great for getting me back on the bike after a decade off the bike and helped me really improve my fitness.

I ride to work about 100 days a year. I take days off because my old legs get tired, so I'd like to get another e-bike in the future. Hence why I joined this forum. I hope to learn enough to select a more suitable e-bike for my needs the second go round. I have to admit the first time I didn't really do any research and ended up with an e-bike that probably wasn't the best suited to my needs and hence why I sold it after only a year.

I'll be posting in the e-bike forum for suggestions on what to get. Until then, just wanted to say hi to everyone.

 

[arkmundi]

Hi! You've go the right starting point, of deciding what your needs are, thence your power requirements.

 

[Captain slow]

As I said in another post, I've been lurking for a while as I want to get another e-bike. I had a Bionx 250 watt system that was great for getting me back on the bike and commuting after nearly a decade off the bike. What I didn't like about the bike, was the weight. I didn't like how the bike handled and it was a pain to lift and carry up a set of stairs. Anyhow, enough about the past, here are some of the factors affecting my decision.

Commute - I plan to ride a cross bike unassisted roughly half the time. I currently ride about 100 days a year and would like to double that. I figure an electric bike will get me riding on the days when I feel "tired". My commute has 140 metres of elevation gain each way and is just under 18 km's.

Light weight - as I said I didn't like the weight of the Bionx system. I love the idea of the Vivax assist, except that there are no Canadian distributors and the system seems pretty pricey. I love Kepler's bike that I saw on www.electricbike.com and that system seems great to me. I think I'd use an aluminum frame to save some money and put up with 2 more lbs.

Speed - With me supplying about 100 to 150 watts of pedaling power I'd like to go about 30 - 40 km/hr.

"normal bike" - I'd like the bike to seem like a regular bike as much as possible.

Is my best bet to simply copy Kepler's build? Is the best route to lightweight simply using a smaller battery since I'm willing to pedal a fair bit? I don't have any desire to have the power Kepler has in his build. I think 400 to 500 watts would be fine if I could get the total weight of the battery and motor to 10 lbs or less. Is that realistic? The battery Kepler used looks pretty small, so I'm guessing it doesn't weigh too much.

Unsure of what bike I'd put this on. I don't think I need a suspension fork, and I prefer drop bars to flat bars so I'm thinking a 700c cross or road bike. One thing I'm concerned about is the dropout spacing. Are most hub motors spaced for 135 mm? Can I get something with 130 mm spacing? I don't mind going with a hybrid bike if I have to have 135 mm spacing, but I prefer a road bike if possible.

Anyhow I'm interested in suggestions. I have a clean slate, so I could get a hub motor, or mid-drive, I'm flexible on the type of bike, etc ..... Just would like opinions and ideas.

Thanks

 

[dogman dan]

130mm spacing is possible, but you'd likely have to run less cogs on the back, like a 6 speed instead of 7. 5 mm of flex out is fine for steel or alloy frames. I don't know if you can flex out carbon that much safely. 5 mm is not much.

I'm not sure what the new bafang bottom bracket drive weighs, but if you never use the small gears on the front rings, that could work well for you.

7 pound motor is definitely common, but a 3 pound battery will not take you far. 15 pounds for the system is more realistic. an 8 pound battery can take you quite a ways.

The lightest motor setup I've seen is the kepler.

 

[Cephalotus]

My lightweight e-bike has an aluminium frame and a solid steel fork, 28"/2"tires, a Cute 85 motor (available with 328rpm @ 36V) and a KU63 controller with the shunt filed down that it is limited around 11A at 36V.

The weight is around 15kg incl. lights, rack, fenders, hydraulic rim brakes (HS11),...

Add a 10s2p or 10s3p battery with 18650 LiMn cells in a PET bottle adds another 1-1,5kg.

At 40km/h I need around 10Wh/km, at 30km/h around 3Wh/km (using the Cute 85 with 201 rpm, in reality more like 230rpm).

I would not recommend the Cute 85 for longer uphill riding and I would not recommend to use it with a 14A controller.

 

[d8veh]

Depending on your front drop-out width, either a 201 rpm Q85 or Q100 with a S06S controller. Standard speed in a 26" wheel is just over 25km/h, but you should use a 5aH 12S Hobbyking lipo pack which will increase that speed by 20%. The speed will be a bit faster still if you have a larger wheel than 26". The total weight of that kit will be about 4kg, and it'll take you 15 to 25 miles with pedalling.

The battery will be pretty small depending on which packs you buy, so can fit in a medium/large tool-bag

These motors run very freely, and with the S06S sinewave controller, they're very smooth and quiet too. You have to order the PAS, throttle, LCD and wheel-speed sensor separately.
http://www.bmsbattery.com/ebike-kits/600-250w350w-q-85100sx-motor-e-bike-kit.html