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Look, a wheelie! Oh wait... it's not, lol

Started by Altema, August 27, 2022, 01:58:40 PM

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It technically was a wheelie, but only for a second, then the bike left me behind. This happened when I sped up to jump off of a speed bump, and gave it a bit too much throttle. I thought it was a whiskey throttle, but after looking at the video frame by frame, the power level did not change and it wasn't even full throttle. I'd stood up on the pedals a bit which raised the center of gravity, and the front wheel came up on it's own and kept going. Another factor is that this was the first group ride with a new motor, which appears to have an unexpected amount of torque at lower power levels.

The bike sustained some damage this time, as it went airborne and came down hard on the right side. The right pedal is ground down, the crank arm and chainring are bent enough so the chain won't stay on, and the spindle itself is bent. Both hand grips are torn, and I have to check my bar end mirrors to see if they are just loose or broken. Oh well, time to order more parts! A frame grab from the video is below.


The Radmini is back on the road! I figured since the spindle AND crank were bent, I'd remove the crank, rotate it 180 degrees, and the bends would cancel each other out. They did come pretty close, and with a few adjustments to the chainring, I got it almost as true as before the flip. I'll still replace the parts when the new ones arrive, but this lets me ride the bike again in the meantime. Yes, I changed the position of the other crank as well 😉. While this made the bike ridable again, the crank alignment is not perfect and the pedal alignment is off, so the pedal does not remain true in the course of rotation. This gives it that weird left-right-left-right squirming movement, but it's only for a few more days.

Additional Damage
I found more damage in the process of working on the bike. Adding to the list are a bent derailleur support, a broken aftermarket headlight mounting screw, and a broken bottle cage.
The bottle cage I'll just have to replace, and I can probably glue the headlight mount. The derailleur support drove home the logic in using a support instead of mounting the derailleur directly to the frame, as the removable support was bent instead of the bike frame. Fortunately I happen to have a 12 ton hydraulic press in the basement, so I took the support off and used some shims with the press to make it straight again. It's a weirdly shaped piece that sort of looks like a duck looking over his shoulder, and one portion is thinner than the other, so it was a bit of a challenge. I also had to re-index the shifter so I could hit all 7 gears again after reassembly. I went for a nice 15 mile ride this morning, and it went well.

Additional cause factor
This morning's ride made me realize something. I've done bunny hops off of speed bumps dozens of times and at many speeds, and I'm consistent in the method. Heck... I've jumped a good portion of a bridge (a good ten feet before I landed), and had no issues with control. So what was different this time?
A new motor.
It's the same model, Bafang G62, but this particular unit definitely has more torque. I've turned it down, reducing the peak power by 400 watts, but it still pulls harder than the two previous motors. It also requires less power to maintain the same speed, and I had to drop my PAS down one step from my normal setting. Perhaps they made a mistake at the factory, and I wound up with a 7 strand motor instead of a 6? I'm just guessing at this point, but perhaps JTK77 would care to chime in...