Ebike week 5: Mech prototype

Not a huge amount of progress this week, as I'm (unusually) taking time to make things reasonably carefully, even though most of this is a prototype I know I'll end up remaking later on. I also didn't take a lot of photos while I was working so you'll have to use a little imagination.

gearbox iso

The first job for this week was mounting the belt pulley and freewheel bearing on the jackshaft. The freewheel was salvaged from a powered golf trolley, which had one in each wheel so it could power a solid axle and still act like a differential. The bearings were pressed into plastic hubs which then held the wheels, and I didn't want to destroy the plastic hub in case I couldn't make anything suitable as a replacement. I instead turned down the hub to a snug fit inside my aluminium pulley and cut flats on the side, which will hopefully work to transfer torque with some mods to the inside of the pulley bore.

The pulley itself was also turned down to reduce its width, as it originally had a big cone-shaped protrusion on one end intended to bolt to a skateboard wheel.


The freewheel bearing had a section with slots presumably intended for some kind of cotter pin, which meant I could drill straight through my jackshaft and put in a 3mm bolt for now. I'm hoping that at a lightly geared down 250W this will have enough shear strength.

top photo

The whole shebang then had to mount to the bike frame. I previously worked out it couldn't fit at the bottom of the seat tube because it interfered with the pedals, so I bolted the frame to a piece of 3x20mm steel flat bar and bolted that to the bike frame.


It's still got the problem of being tilted to the side slightly, so the bar will need a bit of twist to account for this, and it might need the position adjusted side-to-side to minimise getting in the way of my legs.

more machine than man, twisted and uneven

I'll hold off on finishing the mechanical side until it's mounted straight and centred, so the next job will be finding somewhere to mount the VESC and battery.