Commuter bike planning/build thread

[motomech]

A couple of observations;
First off, the notch in the end of the axle should be facing down. The idea is, in wet conditions, the water running down the cable will not enter. After it is repositioned, fill the opening with silicone.
Also, technically, the torque arm would be positioned in the opposite direction, pushing against the fork tube rather than pulling away from it. But, the Cute really doesn't generate enough force to cause the hose clamp to fail, so I'm sure it's fine that way.
Be sure to ck. the axle nuts, they tend to work loose, especially at the high current you are running. I Loctite them.

I decided to replace the DC bullet connectors with some locking MC4 PV connectors. I would like to do something similar for the motor phase connectors, as I don't require anywhere near the 1m of (rather inadequate looking) cable that it came with.

The OEM 9-pin wire is used on larger motors than the Cute, no need to be concerned about the current capacity. I use 4 mm bullets on the power wires, 3.5 mm bullet connectors on the phase wires and a 5-wire JXT connector for the Halls when shortening the cables.

The wheel is also somewhat out of true. Perhaps I would have been better off building my own wheel.

All the BMS Battery wheels come that way. It really shouldn't be out of true, as it hasn't had the spokes tensioned. It's a simple matter to bring the spokes in tension.

The thumb throttle is installed on the outside of the grip. I can operate it with the edge of my hand. No room for it with the bulky combo brake/shifter. Putting it on top of the shifter might work.

I mount thumb throttles on the left side since the frt. chainring is never shifted with a motor. The action of pushing down the lever is very natural.

The motor was only a little warm after this kind of riding, and the controller was cold. I had set what I thought was a 25A/1.25 current limit according to the parameters, but that may be operating on the $CONTROLLER_MAX-0.5*n schedule instead.

Current limiting only works in PAS.

Pulls over 1150W. I will have to watch the torque on the nylon gears more than anything, I would love to see what it could do with some steel gears.

Steel gears would whine like a dentist's drill, besides, the clutch failure limit is close to the limit of the nylon gears. The S12S has enough of a "soft start" that they should be ok. When the gears are strained, you can feel it and be more easy with the throttle.

Even with an external speed sensor, it isn't currently reading the speed when freewheeling. I also had to guess at the motor pole count, which is set to 12.6 * 16 poles = 208 (no spec I could find anywhere), does anyone here know?

I never solved that problem before I switched back to a square wave controller. It could be that your speed reading is from the motor only. You may need to reposition the sensor closer to the magnet. It's a finicky thing.There is a thread I started dealing with the SLCD-3 display. A search should turn it up. Most Cute models have the pole # listed in the product info @ BMS Battery.

Haven't tried the PAS yet, it may yet make the throttle redundant.

Possibly, but with my bikes, pedal strikes in the corners are common. It's then when the throttle is useful.

 

[jmz]

So the setup is:

Q100H, 201rpm
S12S controller, 25A nominal
48V 8AH BMSbattery bottle pack

High voltage + slow wind is definitely the way to go. Lower DC currents is a bonus. I wanted to oversize the controller for thermal margin and reliability. Even if the parameter-based current limiting does not have any effect, the graduations in the 0-5 assist level seem to accomplish that just fine. The torque control of the S12S is very good, it seems to have some internal rate-limiting, giving a linear torque ramp when you open the throttle.

I mounted the battery upside-down so I would be able to mount the controller above it, while still being able to remove the battery. It also gives a low DC cable length, with the business end the same side as the controller. Some work to do in the future on cable management and waterproofing.

Good catch on the axle notch, I may just leave it oriented how it is and seal it. I have also sealed the DC cable outlet grommets.

 

[d8veh]

I've been thinking about your battery. All the weight of the battery and impact forces are now supported by only the pin on the battery lock. I don't yhink that it's strong enough. It's not designed to support any weight.

 

[jmz]

It seems reasonably sturdy. Not only is it quite a sizable locking pin, there is quite a lot of friction from the mounting plate interface, which is apparent when removing the battery for charging. If it started to smoothen with wear, I think some kind of surface roughness could easily be applied.

I could go 'right side up', but it would mean relocating the controller to the rear. I could do that as part of the planned weatherising/cable tidying. Any good options for controller bags etc?

 

[chas58]

nice looking bike.

That is a big controller you have there. You are runnning 25amps through that motor????

Keep an eye on those spokes. Those wheels are loosely built (as noted above).
(that and the shipping cost of the wheel is why I sometimes buy and build the wheel local)
Unfortunately for me I had to by an extra large spoke wrench to fit those nipples (Park tool black I believe).

 

[jmz]

nice looking bike.

That is a big controller you have there. You are runnning 25amps through that motor????

Keep an eye on those spokes. Those wheels are loosely built (as noted above).
(that and the shipping cost of the wheel is why I sometimes buy and build the wheel local)
Unfortunately for me I had to by an extra large spoke wrench to fit those nipples (Park tool black I believe).

Thanks! I've got it limited to 20A through the controller limiting. Turns out it does work with the S-LCD3 and the S12S.

Thermally, it's been great, I've never noticed the motor more than slightly warm to the touch, and the controller is likewise doing fairly light duty.

I get about 38 km/h no-pedal cruise at 400-600 W (verified on GPS). The limiting factor definitely seems to be the bus voltage / battery internal resistance. I would like to try it with a high-discharge 25R pack. It pulls wonderfully, though I haven't yet had the chance to try it on any hills.