16" Wheel / front hub motor

kitchenman

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I want to do this. Has anyone done this? I reckon the spokes will need to be 6-7 inches. Is that a problem? As a 16" wheel is smaller than say a 28" wheel doesn't that mean its lighter? Doesn't that mean that the hub motor is going to work better in a small wheel?
 
D

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Some motors are available in 16" versions like this one:
Bafang QSWXH 250W Rear Driving E-Bike Kit - BMSBATTERY
These motors have various windings that control the speed and the torque . As the speed goes up, the torque goes down (more or less), so you have to choose an appropriate one for the size of wheel you have. If you had a lot of hills in your area and weren't too interested in speed, you could choose a motor for a bigger wheel. The motor designed for a 16" wheel will probably do about 17mph on the flat.
 

flecc

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Oct 25, 2006
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The Nano-Brompton uses the Tongxin motor highest revs version but only manages 13/14 assist limit. Many feel that's enough in a small wheel folder.

Smaller wheels have a big mechanical advantage for hill climbing, so this will be much better at it than if the same motor was in a 26" or 28" wheel, even when rev adjusted for size.

On my 20" wheel legal SB rear-motored bike, take off from standstill is easy on a 1 in 4.5, apart from the huge wheelie. If it had 16" wheels I think it would turn turtle on take-off.
.
 

jerrysimon

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Aug 27, 2009
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Like this :p



Follow my full thread here

EBrompton complete and before wire tidy up.



Spokes are about 120mm (so nearer 5") long, you will only get a cross one pattern and the motor needs to have a higher RPM (260RPM) for the smaller wheel which gives me around 14-15mph unassisted. Spokes are readily available from SJC.

I would say the Tongxin is more an assist motor, than one for powering up steep hills though as Flecc indicates it climbs hills well.

Tongxin motors are quite hard to get hold of for DIY builds, so if you are not so fussed about it being silent you might like to look at one of the Cute motors on the BMS site already listed. Also check your fork spacing as again you might need a slimmer motor than the more standard 100mm width ones.

Regards

Jerry
 
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yes, lower rpm means higher torque, in simple words

but in a small wheel you dont need so much torque because the advance of the small 16" rim give you a lot more hillclimbing ability as an high torque motor in a 28"rim

Important is what you want on speed and noise,
speed and torque you receive from a Bafang SWXU-Motor for 16" with 275rpm but the motor is more noisy.
Low noise but lower assist you receive from a tongxin nano or cute , you must decide what is your main point

Weigth is on small motor around all the same, between 1,7kg to 2kg
but tongxin and cute you can buy with only 85mm wide and Bafang is always 100mm wide

regards
frank
 

kitchenman

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Jul 9, 2010
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Aberaeron, West Wales
Thanks. I'll have a proper read of this lot tomorrow!
Alan
 

kitchenman

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Jul 9, 2010
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Aberaeron, West Wales
So, I could de-install my CX700 which has a 175 rpm Tongxin motor and have a go at installing it on the Spirit that I have just bought.. I could ask Simon at Cytronex to build the wheel for me and then I can have a go messing about with routing the wires and finding a suitable place to hang the bottle battery ..
Thats going to be my cheapest option and something I can do now! ..
 

kitchenman

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Jul 9, 2010
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Thanks Jerry. I think I'll do the same as you but use the Tongxin I already have in my CX700, get someone to build the wheel for me, leaving me to work out what to do with the wires - that'll be enough of a challange for me! ...
:)
 

kitchenman

Esteemed Pedelecer
Jul 9, 2010
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Aberaeron, West Wales
Needed to do something!

Taken my front wheel off and I am looking at it! ..and have just put the kettle on ..

DSC00123_RESIZED.jpg
DSC00121_RESIZED.jpg
DSC00122_RESIZED.jpg

I'll put it back on in a while ..
 

jerrysimon

Esteemed Pedelecer
Aug 27, 2009
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Cambridge, UK
Can I see the whole bike ?

Is that a disk brake ?

If you do want to build a motor into the front wheel, I think its probably best to keep the old wheel and start afresh with a new rim. That way its easy to put it back to how it was.

Regards

Jerry
 

kitchenman

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Jul 9, 2010
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Aberaeron, West Wales
Thinking results!

As I'm already in bed with Cytronex ... Order a 16inch wheel with one their 180w 175 rpm motors. De-install the electrics from my CX700 and install in on the recumbent for Louise.
Meanwhile, I'll get an electric bike from Evans on my C2W scheme.
Job done?
 

daniel.weck

Esteemed Pedelecer
Aug 8, 2009
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I want to do this. Has anyone done this? I reckon the spokes will need to be 6-7 inches. Is that a problem? As a 16" wheel is smaller than say a 28" wheel doesn't that mean its lighter? Doesn't that mean that the hub motor is going to work better in a small wheel?
Just to add some material to the already-excellent responses:

http://www.pedelecs.co.uk/forum/electric-bicycles/4682-diy-stage-1-received-bafang-tongxin-kits-photos.html#post59183

(that's my e-Brompton self-build log)

Cheers, Dan
 

jerrysimon

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Aug 27, 2009
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Hey Dan how you keeping :)

Regards

Jerry
 

kitchenman

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Jul 9, 2010
1,309
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Aberaeron, West Wales

jerrysimon

Esteemed Pedelecer
Aug 27, 2009
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Cambridge, UK
... also I came across a bottle battery that looks similar to my current one ..
Enix Energies Rechargeable Bike Bottle Battery - Cell Pack Solutions
although it only weighs 750g! .. umm...
It is also only 13.2v, so too small :eek:

I am guessing it is for lights. Note it has a 6amp fuse.

If you want a small light battery why not go for a couple of 6s1p, A123 packs ? 39.6v nominal and 43.2v fully charged.

See here.

Just connect them both in series. You will need to balance them initially but after that they won't need a BMS and can be charged with a cheap charger. At 2.3Ah they are limited range though depending on motor and terrain.

Regards

Jerry
 
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jerrysimon

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Aug 27, 2009
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Cambridge, UK
This is always another option that I often forget about a Crystalyte 209.

A little heavy but silent.

Google Translate

Regards

Jerry
 
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kitchenman

Esteemed Pedelecer
Jul 9, 2010
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Aberaeron, West Wales