20" BMX Front Hub Build

My other half recently got an ebike, and as much as I love riding with her, there's no keeping up for long going 15mph on a BMX. Only logical solution was to get a 20" Hub kit and get to work.

Ended up buying a Yosepower 250W front hub. Doesn't take much to get up to speed on this bike so don't need much torque, rather something to keep me going once I reach 10 / 15MPH.

Not a fan of wires going allover the frame so I'm planning to keep things simple with an console in the handlebar's centre which has wheel / brakes / throttle / lcd wires directly feeding in as well as holding controller and separate battery space to swap out easily. Should make for a slick solution.

Got a 10S4P battery on order which will fit nicely in the centre console. Currently working on a CAD which I'll 3D print and reinforce with Carbon Fibre cloth. Recently built an enclosure for an electric skateboard this way with 6 layers of CF cloth and turned out rock solid.

More to come

EDIT: Final build



[youtube]UITHNYopETg[/youtube]

Continue with the build below;

Great first post dude, seems like a really cool and different idea. I'm looking forward to seeing how it goes. The one possible downside is battery weight increasing the amount of steering effort and changing the center of gravity enough to really change handling. You won't know until you try it though and you can always do a frame mount later. Thanks for posting.

FWIW, this guy put together a really clean build with a BBSHD.

https://youtu.be/VQ96XPoMiMI

Great idea!
I first saw a front ghm eBike & it was a pretty step thru cruiser being driven fast and hard by a dude.
What I saw, your bike may handle like a wild wheelbarrow, OK ?,
With front wheel slideouts, and the rear skidding, rider had some skills.
Mike

Wolfeman said:

Great first post dude, seems like a really cool and different idea. I'm looking forward to seeing how it goes. The one possible downside is battery weight increasing the amount of steering effort and changing the center of gravity enough to really change handling. You won't know until you try it though and you can always do a frame mount later. Thanks for posting.

FWIW, this guy put together a really clean build with a BBSHD.

https://youtu.be/VQ96XPoMiMI

Click to expand...

Thanks, yeah the additional weight is something to take in account when getting up to speed. I've got a basket on my 700C bike which is often filled to the max so have some idea of what to expect.

That's a very clean built, if the centre console turns out to be a failure I'll likely end up making some kind of enclosure and mount it much like that guys' done.

Stealth_Chopper said:

Great idea!
I first saw a front ghm eBike & it was a pretty step thru cruiser being driven fast and hard by a dude.
What I saw, your bike may handle like a wild wheelbarrow, OK ?,
With front wheel slideouts, and the rear skidding, rider had some skills.
Mike

Click to expand...

Haha I am none too keen on front wheel sliding out so gonna take it slow. I have some experience with my regular bike, got a basket up front often filled to the brim and fast turns get... tricky. Can only imagine what this will be like on a BMX.

Some more progress below. Will mount this to the handlebars with some kevlar straps. Needs some screw holes and a lid and rev. 1 is near enough ready to print.

giek2000 said:

Haha I am none too keen on front wheel sliding out so gonna take it slow. I have some experience with my regular bike, got a basket up front often filled to the brim and fast turns get... tricky. Can only imagine what this will be like on a BMX.

Click to expand...

Standing on the pedals, I doubt you'll have much problem maintaining front traction. Seated, it will likely spin some. It's not a big deal, because the wheel still pulls where you're pointing it. Unpowered front wheel skids usually want to go sideways, but not so much with a front hub motor.

The closer you put the battery to the steering axis, the less it will affect steering qualities. So behind the bar, directly over the stem is probably as good as it gets.

IMHO, the steering will be terrible with all that weight on the handlebars and a front motor. Why don't you put the battery in the triangle, which will give much better handling?

d8veh said:

IMHO, the steering will be terrible with all that weight on the handlebars and a front motor. Why don't you put the battery in the triangle, which will give much better handling?

Click to expand...

Trying to eliminate as much loose cabling as possible. Tbf I don't mind a bit of tinkering so if this doesn't work out I'll have to live with some cabling and a mid mounted enclosure.

Printed the enclosure, took 41h at 0.3mm and 600g of filament or so. Still need to print 2 lids for it. Next on the schedule is to clean it up a bit and cover it with carbon fibre cloth for reinforcement.

Received the battery, 10S4P Samsung 29E's, need to solder the BMS to it and some charging cables etc.

Job for a rainy afternoon which luckily we have plenty of here in the UK

Ended up going a different route than planned. Started playing with a 12.5ah YosePower battery from my commuter bike which just about fit in the BMXs frame. Found this a much cleaner solution as the controller is built into the battery tray so ordered a new battery + mount / controller and started working on a custom mounting solution.

Carbon wrapped the 3D printed box before moving onto the 2nd idea.





Designed, 3D printed, and carbon wrapped a flat mount that would support the original battery tray. Used a Dremel to make channels for the hose clamps to the best of my ability. Turned into a hot plastic mess.



Battery + mount and a piece of inner tube so the whole thing doesn't slide about once attached.



Next problem the chain just about hit the battery. Opened up the battery to confirm there's no electronics near that corner and proceeded to cut away a piece and generously hot glued the gap. Might do a carbon wrap on the corner but reckon this will hold up just fine for the limited use it will see (dry days, summer only).





Mounting the battery.





Not shown, but clamps are resting on flexible printed straps and are shrink tubed so no chance to scratch the frame.



Next was mounting the PAS sensor. Rather than modify the original magnet ring I ordered some magnets and printed the below. This is currently where the project is at as its curing in a carbon wrap to hold the magnets in securely.



About 1mm clearance









More parts are incoming. Next piece is to fix a disc brake up front, mount PAS, route cabling and charge up

Completed this build now. Unfortunately the custom PAS disc did not work as the sensor appears to only read when disc spins in 1 direction. Flipped the magnets to no avail. Hey ho, printed a 2 part spacer which holds the PAS disc on the crank on the lefthand side and job done.

Cables are wrapped around the bottom of the battery and wrapped in velcro cable management 'wrapping' which nicely hides everything. Installed a suspension seat post and comfortable seat which makes it a dream to ride. Takes me up to 20 mph in no time with controller set at only 13amp. Excellent urban cruiser.



Modified the standard Wuxing throttle with my own handle. Had to print a little extra bit to extend the throttle with.