Hello ES peeps,
I'm beginning my next ebike build. As reference, my first build is a FS Motobecane with a BBSHD and a plastic "shark" pack mounted on the downtube. It's a beast, both in looks and in power. I built it clean without any wires dangling around, but there's no fooling anyone that it's an ebike. This time I'm going in the completely opposite direction.
This time I'm using an ultralight aluminum single-speed track style frame, and I'm using a Q100H with a Phaserunner controller. I'm also building a 14s2p pack using LG MJ1 3500 mAh 18650 battery cells. So, I'll have 51.8V 7Ah with 20A discharge available to power this thing. I'll probably only put 11-15A out to the motor to start. I do have a couple hills that can be challenging, so I'll need to test the bike to see if I need to put a few more amps into the motor or not. The battery will be contained in a seat bag behind the seat and I'll be running the wires inside the seat tube to exit just above the bottom bracket shell in the rear.
I'm taking this build slow so there won't be a mad flood of updates to this thread all at once, but I'll post new images as I make progress.
Here's the bike I'm using as a base:
The bike in stock form comes in at about 18 lbs (8.16 Kg). I don't have a specific weight goal other than "as light as possible while meeting my needs".
I got the Q100H already, so I decided to do a test fit. This frame has only 120mm dropouts, so I decided to remove the nut and one of the spacers on the drive side of the shaft. I knew I could flex the dropouts to fit the motor with just the 2 spacers and no nut, but I wanted to get the drive side as close to the dropout as possible since I'm only using single-speed. This actually worked out really well, because shifting the motor over by removing the spacer ended up mostly centering the motor in the dropouts and is going to give me a nice straight chainline for the single-speed.
I took some measurements, and the motor is shifted towards the drive side by 4.5mm. This should be a very easy dish. Time to go plug the numbers in to the spoke calculator over on ebikes.ca
Here's what the motor looks like in the frame:
Here's the centering of the motor in the dropouts:
I think this photo makes it look a little more offset then it actually is. I need to take some measurements to know for sure. I'm OK with a little dishing as long as it's not too much.
Here's the chainline using a straightedge pressed against the inside of the chainring:
I need to pick up some washers to fill the gap between the remaining spacer and the drive-side dropout:
Over on the brake side of the motor, I'm thinking about removing this side of the shaft and drilling a hole to run the wire out between the case and the dropout. I'm using rim brakes so I don't need to worry about clearing a rotor or anything.
Here's the gap I have to work with if I decide to go this route:
Do you guys think this might weaken the axle too much? I could live with the shaft-end exit, but if it didn't risk integrity, I'd love to hide the wire even better (and protect it) by keeping the wire inside the dropout.
That's about all I have to show so far. I'll update the thread as I do more work.