Wanting to build my 5 year old an ebike. Where to start?

brumbrum · Jul 14, 2018

Hi guys, i have built many ebikes over the past 8 years for myself, family, friends, but i now want a new project building a small motored bike for my daughter who is not quite 6 years old. She's been a fully fledged bicycle rider since before she was four, and rides daily up front on my LMX 161 dirt bike and loves the buzz!

My main concern is how to get a hub motor in a small wheel on a small bike. Would i be better off thinking outside of the normal convential ebike type build and instead look at something more like a small dirt bike shell?
Any ideas or photos much appreciated,, i dont know where to start.
Andrew.

John in CR · Jul 14, 2018

2 words. Scooter hubmotor. I have several that take a 16" bicycle tire. DD hubbies perform so much better in smaller wheels and the lighter load to push makes real potential for an indestructible setup.

brumbrum · Jul 14, 2018

John in CR said:
2 words. Scooter hubmotor. I have several that take a 16" bicycle tire. DD hubbies perform so much better in smaller wheels and the lighter load to push makes real potential for an indestructible setup.

Excellent, 16" would be perfect. I Will have a gander at whats out there. Tar. Will this likely be a purchase of generic motor from china?

John in CR · Jul 14, 2018

brumbrum said:
John in CR said:

2 words. Scooter hubmotor. I have several that take a 16" bicycle tire. DD hubbies perform so much better in smaller wheels and the lighter load to push makes real potential for an indestructible setup.

Click to expand...

Excellent, 16" would be perfect. I Will have a gander at whats out there. Tar. Will this likely be a purchase of generic motor from china?

Check for used stuff for sale locally. Almost any cheapy low power scooter or scooter moped thing is likely to be perfect, and give you a number of parts for the build. Hubbies with a 10" scooter rim could be even better and something she can grow into with a programmable controller. More selection of fatter tires in a 10" scooter tire that end up a 16-19" OD wheel.

Once you see what's possible running small wheels you'll want one yourself too. Every hubbie you've run deserved a 20" or smaller OD wheel, so you could experience their true potential.

brumbrum · Jul 15, 2018

Haha, thanks for the advice!
My wife is not too keen on the idea as she feels it will stop my daughter from wanting to ride her push bike. So i might have to do it on the sly :twisted:

lionman · Jul 15, 2018

brumbrum said:
Haha, thanks for the advice!
My wife is not too keen on the idea as she feels it will stop my daughter from wanting to ride her push bike. So i might have to do it on the sly

I think you should build one for your daughter too!

John in CR · Jul 15, 2018

brumbrum said:
Haha, thanks for the advice!
My wife is not too keen on the idea as she feels it will stop my daughter from wanting to ride her push bike. So i might have to do it on the sly

She's right, but I sure wish I had an electric motorcycle when I was a kid. You can always make it pedal activated.

A kids ebike has none of the problems we face. Their far lighter load means low system stress. They don't need to go as fast or as far, so it's a smaller, lighter battery to fit. Once you accept the unsprung mass, hubmotors are the perfect solution for a super fun kids EV. You'll get tons of Dad points.

brumbrum · Jul 17, 2018

I may try and get a 250w 14" hub/wheel which 14" bike tyre will fit, and a get a small 25amp controller which i can program limits to. Donor bike will be a steel frame n fork and go from there. I may keep it simple and go for front wheel hub as long as forks are 100mm dropout. Least expensive and see how my daughter gets on.

Here's a 14" motor wheel.... https://www.aliexpress.com/item/32797584302/32797584302.html

Will front motor create too much weight to steer?

devo1223 · Jul 17, 2018

I've been thinking of the same project for my 5yr old too. He almost fits a 20in wheel bike so I was thinking a 250w hub motor in a 24in wheel full suspension frame with 20in wheels so he can grow into the 24in wheels.

brumbrum · Jul 17, 2018

devo1223 said:
I've been thinking of the same project for my 5yr old too. He almost fits a 20in wheel bike so I was thinking a 250w hub motor in a 24in wheel full suspension frame with 20in wheels so he can grow into the 24in wheels.

Consider how far the reach will be between seat and handle bar on a larger frame, it could be an issue.
My daughter is small for her age, so anything over 14" wheel will be too big. Its a good idea to future proof for sure, but finding a short frame could be tricky, otherwise get some crazy handle bars that bend in towards the seat

brumbrum · Jul 27, 2018

John in CR said:
2 words. Scooter hubmotor. I have several that take a 16" bicycle tire. DD hubbies perform so much better in smaller wheels and the lighter load to push makes real potential for an indestructible setup.

Found a donor bike on the street being thrown away....

Its a steel frame and forks, 100mm fork dropout, and its even got a pressed fit sealed cartridge bearing headset :lol:

Also found a geared 12" wheel... http://s.aliexpress.com/eaEneUFb
The rims currently on the bike are roughly 13" diameter. I should have room for a cheap kids motocross tyre with the 12" motor.

I will be buting a 17amp controller from Greentime which a 3 speed switch and on/off switch can be plugged into, along with ebrake.

John in CR · Jul 27, 2018

I'd spring for a programmable controller to be able to set it just right leaving room to grow. If you do go with the greentime, make sure it's one with the 3 wire 3 speed switch. The ones with 2 wires where you use a momentary switch generally boot up at high speed when you turn it on.

brumbrum · Jul 28, 2018

John in CR said:
I'd spring for a programmable controller to be able to set it just right leaving room to grow. If you do go with the greentime, make sure it's one with the 3 wire 3 speed switch. The ones with 2 wires where you use a momentary switch generally boot up at high speed when you turn it on.

Maybe i will stump up the extra cash for a small kelly unit i can program, its probably safer tbh, and i already have the programming cable n software experience. I will see whats oit there.

Wanting to build my 5 year old an ebike. Where to start?

brumbrum

100 kW

John in CR

100 TW

brumbrum

100 kW

John in CR

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brumbrum

100 kW

lionman

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John in CR

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brumbrum

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devo1223

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brumbrum

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brumbrum

100 kW

John in CR

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brumbrum

100 kW

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