Okay time for a major update
. I took the bike on the ride to work this morning for it's first major shake down.Good news:
- it worked
- ~50kph on the flat
- ~40 kph up hill, with pedalling
- totaly disengages when not in use, and feels like a normal bike
- able to tune engagement to avoid slippingBad news:
- I think I cooked the motor Here is the summary
First ride with anti-slip tape on motor.
15km ride to work, through usual mix of rolling hills, and gentle slops.
Needed to adjust the drive engagement, as slipped first time I tried to go up a decent hill.
Strangely this actually twisted around the seat post slightly, which I hadn't expected.
Using the servo controller as a throttle was .. hmmm.... lets say, less than ideal.
So what did I learn from the first shake down:1) Throttle
- feel like I want a torque control rather than speed control.
- issue is that if you go faster than the set motor speed, the drive disengages. Then when speed drops the motor doesn't re-engage.
- with a torque based throttle, it would keep increasing the motor speed to keep drive in contact.
- so this implies some current sensing control loop2) Softer Deadstops
- both limit stops need to be softer.
- full engage stop can hit hard if you increase throttle quickly, soft start may help. Currenlty this is a hard stop
- full disengage stop can hit hard if you suddenly release the throttle, as the wheel spits the motor back out. Current stop is a rubber tube with ~2mm wall thickness over the head of an M4 scap head screw. 3) Drive Engagement / Pick-Up
- slowly increasing the throttle may not engage the drive properly
- could improve the spring balance, and reduce main pivot friction with non-journal bearing, to imporve pickup
- could uControl initial throttle to ensure enough torque to lift motor in to tyre
- could nominally have light contact with tyre 4) Power Limiting
- I cooked the motor
- need some way to protect the motor from over temperature events.
Here is what happened.
- I was about 10kms into the ride, only occasionally using the drive.
- Was starting to get a feel for when/how to use the drive, so started want to find out what it could do.
- First test was flat road/no pedaling speed. ~48kph
- then sat at the lights for a bit 1minute or so.
- Up hill test, pedalling @ 40kph, ~1km
- Round corner, another up hill, engage drive, little bit later suddenly drive kicks itself out, no power.
- pull over to side of road, lift wheel, apply throttle, motor stuttering back and forward
- ESC warm not hot
- motor hot to touch, IR temp sensor says 75C on pivot arm that has good face contact with stator.
- I did have a temperature/LVC alarm hooked up, but it wasn't getting an accurate measurement of the motor, as the sensor had lifted off the aluminium swing arm that mounts the stator.
- Looked at the watt meter stats. ~ 100wh, ~ 125 Amp Peak, ~ 2600 Watts peak. Ouch that's a bit more than I was expecting.
- no time to trouble shoot so, just rode to work.
- joined up with a couple of cyclist from work at the final hill climb to work, and easily kept up with them as the drive is totally disengaged. I would have really struggled with my Giant dual suspension hub motor ebike.
Just had a look at the motor and it looks like the windings might be toatsted, and shorting.
It is difficult to turn over by hand now, in a walking through mud type of way.
ESC looks fine.
Well that was fun.