Electric Bike Build

[SHARKBITEATTACK]

Hello, I'm a new member here and I wanted to show off my ebike project.

I had two major when designing this bike. One was that I wanted a relatively low center of gravity which means the batteries would have to be located down low. My second goal was to design a system so that the pedals and motor could freewheel independently.

I found a burly all aluminum mountain bike frame to start my project. It's an elevated chainstay design which prevents the chain from whacking the chainstays when shifting gears. It's a nice feature but the reason I opted for this frame is because it doesn't have a down tube and makes a perfect location for a battery box.

The bike will use a BladeZ scooter motor running at 36v for a total of 675 watts. Batteries will be 12v 12ah leads. The bike won't have a controller, instead I'll have to pedal, build up some momentum and hit a solenoid. The motor runs at about 4500rpm which means I would need a reduction of about 15:1. So I am using a 90 degree gear reduction from an angle grinder to give me a more suitable speed. I'm going to experiment and see what a good speed would be, but I'm thinking 20-25mph.

The hardest part of this project will be trying to make a drive shaft that connects the motor to the gear reduction. Worse case scenario is I have a machine shop customly make me one. I'm simply just going to have 2 freewheeling sprockets on the rear hub, 1 for the motor and one for the pedals. However I will try and keep all three chainring sprockets up front so I can change gearing from commuting to hills and offroading.

 

[Lowell]

I have a very similar frame design, and speaking from experience, the bike will handle terrible with all the weight down there. Consider putting at least one of the batteries insdie the frame, just below the seat.

 

[TylerDurden]

Greetings,

Sound like a challenging (fun AND frustrating) project!

Motor couplings are very diverse... DIY units can benefit greatly from rubber hose and duct-tape. Keeping a stock of many sizes and colors could be very handy.

Closeup shots of all sides of the reduction gearing will be helpful.

I like the frame shape. Has loads of potential.

 

[CGameProgrammer]

Yeah, bikes are actually more stable with the weight higher up. A low center of gravity mainly just helps non-leaning vehicles from tipping over on turns.

 

[SHARKBITEATTACK]

I was under the impression that the higher center weigh of gravity only keeps a bike stable at high speeds, where as a low center weight of gravity helps with balance at low speeds and cornering. Maybe I will move the battery box right above the pedals and use it as part of the frame.

 

[fechter]

Welcome aboard Nice to see refugees from the old Voltage Forum.

We'll have to see about that gear reduction interface. Most of the units I've seen have the teeth ground right into the motor shaft. But there's always a way...

Yes, try to get a picutre of the gear unit guts.

 

[SHARKBITEATTACK]

gearbox pics, as you can see I will need a shaft that for the pinion gear and bearing.

the first pic is the sprocket after some weight reduction

theres nothing really done to the bike, I just had some mock-ups on it to give a general idea of what it would look like. So it's is more or less just a bunch of parts laying around.