Best lightweight geared hub for a bmx bike?

[EvoBikeShop]

I'm possibly thinking of going with a rear hub motor on a bmx style bike for my next project. It needs to be extremely durable/reliable, lightweight, simple plug and play, 24v, 15amp max, single speed freewheel, and with a top speed of 20mph. Any ideas or recomendations?


EBS

 

[motomech]

If you want to order a complete kit from one of the big suppliers in China, then there is really only two choices, the small Bafangs and the "Cute" Q100.
We have been discussing their relative merits for a couple of weeks now and the easiest way for you to review them is to click on my username, then search using, Q100, bafang or mini-motor as key words.

 

[chisixer6]

I am currently building a small wheel bike , light weight, about 20mph and compact size with single speed. I ordered this motor, due here tommorrow, so I will measure for spoke size and cut and thread them by this weekend.

http://www.greenbikekit.com/index.php/electric-motor/rear-bldc-1/gbk-100r-36v.html

I just finished another small wheel bike with a longtail, hopefully to prevent wheelies, a 9c 5 wind will go into this one, picture below.

 

[izeman]

If you want to order a complete kit from one of the big suppliers in China, then there is really only two choices, the small Bafangs and the "Cute" Q100.

i would have suggested Q100 as well. a Q100 with 24v in a 20" rim could do around 20mph. the fast wound Q100 @24v gives you 328rpm. 328*1,55m*60/1000=30km/h=18mph no load speed. i doubt 15a (15*24=360w) will be enough for that. better go to 36v and 20a.

you could try though

 

[motomech]

Also, this thread at the top of this page has some mini-motor info;

Brushless Geared hubmotors: BIG list & details

 

[richmpdx]

chisixer6,
Did you build the frame on the yellow bike? Or is that a commercially available frame? If so, what source?
Thanks,
Rich

 

[chisixer6]

richmpdx;

frame is homebuilt, was suppose to be a Cannondale Hooligan copy, but my memory got confused and couple of tubes didn't go where they were supose to go.

Jerry

 

[EvoBikeShop]

I am currently building a small wheel bike , light weight, about 20mph and compact size with single speed. I ordered this motor, due here tommorrow, so I will measure for spoke size and cut and thread them by this weekend.

http://www.greenbikekit.com/index.php/electric-motor/rear-bldc-1/gbk-100r-36v.html

I just finished another small wheel bike with a longtail, hopefully to prevent wheelies, a 9c 5 wind will go into this one, picture below.

Thanks for the info. Let me know how that goes.


EBS

 

[neptronix]

No such thing as an extremely durable geared motor. Geared motors are great, but they are the least reliable.
If you buy a geared motor, it's important to get one that you can find replacement parts for down the line when it dies.

If that's a priority, a MAC, BMC, or Bafang BPM would be what you're looking for.

 

[neptronix]

By the way, you can't hit 20mph on 24v/15A. That's only 360 watts. you need about 500 watts or above to hit 20mph on flat ground with no headwind, a perfect road, and no incline. The power requirements to maintain that speed when you are going up a small hill, going against wind etc can jump to 800-1500W continuous.

24v/15A would be OK for a very anemic ( to the point where you can barely tell the motor is doing any work ) 15mph ride. But you'd still lose a lot of speed on hills, with inclines, etc.

 

[EvoBikeShop]

Ok so what about 36v 30a (max)? Or is the smart pie any good?

EBS

 

[maydaverave]

Another thing to consider is the larger 14mm bmx dropouts. Unless you get a cheap kids bike you will have to modify the dropouts.