D
Deleted member 4366
Guest
Some of you might remember this that I built about a year ago.
The drive chain kept jumping under power, so I shelved it. Yesterday, I decided to see if I could sort it, so I put a brand new Diamondback BMX chain and free-wheel on the motor, but the jumping was worse. So I had a long think about it and decided that the only possible cause was that the motor bracket twists under load, which sends the chain out of line even though it feels very stiff and you can't twist it with a lever. I therefore added a compression bar between the left-hand motor bracket and the bottom bracket. Presto! It works perfectly now. It climbs our steep test hill without pedalling, which puts it on a level (climbingwise) with a BPM motor at 25amps and my dual-drive Rocky Mountain.
It's not very refined: The motor's quite noisy, and when I change gear without pedalling under power, it goes with a bit of a bang. There's also no free-wheel between the motor and pedals, so your feet go round when the motor's on, although you can pedal without turning the motor because there's two free-wheels in that direction - one in the motor and one in the sprocket. Top speed depends on gearing. With the 14/44 setup at the moment, it's doing about 25mph with 12S lipos at 48v. With a 36v battery, it pedals at a nice cadance of about 75 (no-load), but a little to fast for me with the lipos; however, you can easily adjust the cadence with the throttle.
It's a bit weird with your feet off the pedals running up and down the gears like on a motorbike, but without using a clutch.
For those interested it's a front Bafang QSWXK with a free-wheel thread grafted on to the disk brake mount with KU62 controller at 15amps.
The drive chain kept jumping under power, so I shelved it. Yesterday, I decided to see if I could sort it, so I put a brand new Diamondback BMX chain and free-wheel on the motor, but the jumping was worse. So I had a long think about it and decided that the only possible cause was that the motor bracket twists under load, which sends the chain out of line even though it feels very stiff and you can't twist it with a lever. I therefore added a compression bar between the left-hand motor bracket and the bottom bracket. Presto! It works perfectly now. It climbs our steep test hill without pedalling, which puts it on a level (climbingwise) with a BPM motor at 25amps and my dual-drive Rocky Mountain.
It's not very refined: The motor's quite noisy, and when I change gear without pedalling under power, it goes with a bit of a bang. There's also no free-wheel between the motor and pedals, so your feet go round when the motor's on, although you can pedal without turning the motor because there's two free-wheels in that direction - one in the motor and one in the sprocket. Top speed depends on gearing. With the 14/44 setup at the moment, it's doing about 25mph with 12S lipos at 48v. With a 36v battery, it pedals at a nice cadance of about 75 (no-load), but a little to fast for me with the lipos; however, you can easily adjust the cadence with the throttle.
It's a bit weird with your feet off the pedals running up and down the gears like on a motorbike, but without using a clutch.
For those interested it's a front Bafang QSWXK with a free-wheel thread grafted on to the disk brake mount with KU62 controller at 15amps.
