Need help picking a motor for first e-bike.

[Hep!]

I am looking to build a commuting bike. This bike will not be used off road at all, it will only be ridden in NYC and a little bit in rural NJ.
I do not need speeds exceeding 20mph. Even 15mph would be sufficient in most cases. I will be pedaling nearly all the time.

1. I have an aluminum frame but a steel fork that passes the magnet test. I was originally planning on using a front wheel mount hub motor because of the ease of installation. After reading the safety concerns involved with forks breaking even with torque arms installed I am now unsure. I would not be able to weld my own torque arms, I would have to use something that I could install myself. If I were to go rear hub, is it safe to use a rear hub motor on an aluminum frame? If I have a steel frame available, should I use that instead? I'm trying to be weight conscious, as I will be having to carry this up and down stairs to my apartment.

2. Direct drive hub motors don't freewheel and create extra friction. I've read "5-10%" and "15%" increased friction. I've read [in separate places] that it can be negligible or that it can be very noticeable.
I will be pedaling without any power often. When I do use electric, I will usually pedal. I do, however, want the ability to ride without needing to pedal if I so choose. I don't need to go very fast, though.
The longevity of a DD hub motor appeals to me over a geared motor. How much am I going to notice a hub motor? Is it really a huge drag?

I thought that as I read I would be more sure of what I wanted, but I've only become less sure!
I plan on building a pack from these cells in 12s: http://bmsbattery.com/lifepo4-cell/132-401600s-10c-c-rate-16ah--lifepo4-cylindrical-battery-cell.html .... or possibly these... http://bmsbattery.com/lifepo4-cell/89-38140s-10c-c-rate-12ah-lifepo4-cylindrical-battery-cell.html
Still undecided on that too.

 

[bigisland]

Hey fellow New yorker, well I moved out of the city a year ago after 45 years, now on the Big Island,

Well after reading your post the key thing for me in designing your build in what you wrote is:

as I will be having to carry this up and down stairs to my apartment.

You defiantly want to go as light as possible. Aluminum frame is fine. I would go with a geared motor for the weight reduction, don't worry about the durability issue if your not planning on jumping curbs and really stressing out the motor. If you got a steel fork with solid dropouts and you can fit some good torque arms it should work out. May be look at an good geared kit from e bikes CA or Amped although I find amped as a company a little not to my taste in appearance but I guess they shouldn't be judged by that. So where you going to ride?

 

[theRealFury]

Hello Hep,

For the kind of speed you are wanting and the fact that you want to pedal without power and minimal to no drag i would suggest a small geared hub, my 250w bafang was installed on ALUMINIUM SUSPENSION FORKS with no torque arms and i had even upped the power from 250w to 800 watts. MY suspension forks never flinshed in 750 miles and some off roading as well towards the end. I didnt know any better at the time so thought nothing of it but looking back now after all the posts on here saying that you should never do it and you will kill yourself... i find it a hard pill to swallow for a small powered kit. Fair enough if your wanting to run a 2kw high torque motor then yea, its not the best idea but for a road only bike with a small less than 1kw motor and speeds of 20mph or less i dont think it matters.

So for my money if i only wanted 20mph and on road use only then it would be a geared hub. Perhaps a small bafang geared hub like i had or one of the more expensive but better quality (from what i hear) BMC or MAC geared motors. Alternatively you might look at the ezee hubs sold by ebike.ca, they are said to be decent quality and the 36v kit will just about get to 20mph, the 48v kit should do 25+mph if you want that bit extra. They would all suit you fine no doubt. Only reason i ditched the bafang setup was because i wanted more speed and serious offroading ability.

I cant really give you any direction on the headway battery cells as i have never had any but i would advise reading forum posts on here as i seem to remember reading some posts that were less than positive about them. If you ask me though you either want a li-ion pack or a longer lasting but slightly more expensive 15-20AH LiFePo4 PING pack. These are both suitable for a small hub motor and are plug and play batteries with no real maintenance requirements and they will last several years of service if looked after.

Well what ever you do choose to get in the end i wish you all the best with your build.

 

[wdwrkr51]

Hey, HEP:

I've built two bikes using the AMPEDBIKES motor kits, and for a first-timer, they are hard to beat. Prices are good, too. I'd suggest you contact Doug Daut at Electric Bike Kit Solutions (http://www.gocarlite.com) and discuss your needs. He is an Amped dealer and was very helpful with my second purchase. I only have experience with the direct drive kits, but I believe Doug can give you good advice regarding the geared drive kits they also offer. He gave me excellent service.

You are trying to consider the advantages of light weight vs. ultimate durability. For me, the direct drive motor was worth the extra four pounds difference. You may decide differently. I would stay away from lead-acid batteries, based on my first project experiences. You would do well to consider LiPo batteries, even with the premium price attached. Doug can help you with a very user-friendly plug-and-play battery setup, and the price is still much better than many other sources.

They also offer a very good torque arm setup, and just about universal in application. I believe it comes included with the direct drive kit.

Hey, tell him Bill Lloyd recommended him to you! It won't hurt! !

Starting with this conversion kit and a good battery setup, it will be hard to go wrong. You will be one happy e-biker, I do believe.

wdwrkr51

 

[neptronix]

If you are looking for great freewheeling, the MAC/BMC are the best freewheelers that i know of.
I had a smaller geared motor and it was nowhere near as good, it did have perceptible drag, although barely..

All the hub motors i have ridden have tremendous drag and are not fun to pedal unpowered. ( which i also do a lot of )

Headways are great cells, but you need to take a measurement before using them. They are pretty stinkin' huge. However you should be able to get by on 36 volts ( 12 cells ) just fine.