Hi,
I am a old fat geezer whom had just had a taste of motor-assisted bicycle and I want more.
A month + ago, I started an experiment on low power ebike by converting my Dahon Boardwalk into a front geared hub motor. The battery pack is 48V 12AH, ON/Off Throttle only with brake sensors. The battery and controller are stuffed in a waterproof handlebar bag, Something really straight and simple.
I use it to run errand around town and join spirited rides in the evening hitting 30~40km/h for 80km rides with young and strong Lycra laden cyclist along the highway, you can imagine how wide a grin is on my face
Now that I am out riding more, I am surprise that I actually got some decent workout and my breath and legs got stronger. I call the experiment a complete success. #except for heating problem with the controller and hub motor.
For my second build, I need something to cool the controller and the hub.
After weeks of endless-sphere I had come to this point.
My objective is to ride gentle 5% gradient for 30km continuously. 120kg rider, 15kg bike, 20" (406) wheels, front geared hub motor. speed doesn't matter but I do understand that the motor will be happy if I keep it 20+km/h.
Controller
The controller is the easy bit, water/weather proof (by applying nail polish on the PCB and silicone the controller case), mount it on the bike frame and let natural air do all the work. if it doesn't, I will add as many heat-sink on the casing to make it works.
Actually, I reckon waterproofing the wires are more challenging... Yes, a Sine wave FOC controller if I can find one for hub motor. 20A with 5 levels if I can find any.
Geared Hub Motor
I will stick to geared front hub. for convenient sake. If it works here, it will work elsewhere.
The hub will receive oil bath mod with ATF. I learnt that the coil varnish is rated to 150C, I also know wire rubber insulation for most high temperature electrical wires (for motor phase and halls) are 120C. so this leads to my design max. temp cut-off of 110C. Theoretically, any water ingestion should boil out at that temp given enough time, which is a bonus. Not forgetting to coat all wires and plug all holes with high temp RTV liquid gasket paste which usually has 250C temp rating. Use rubber seal bearing for the external hub bearing.
From many oil cooled hub projects I read on the forum, it seems that an air breather valve is missing from most projects. Breather valve is an old tested way to equalize internal pressure due to heat and expansion of the air and oil in the hub which could cause bleeding bearings and dripping wires, they are used everywhere, eg, transmission gearbox, engine block, differential gearbox, motor gearbox, gas tank, diesel tank, etc. The breather valve I found looks like a M6 bolt with holes drilled into it and built-in 0.07bar relief valve and oil filter, it should keep the oil in and water oil of the hub. not forgetting it can breath 300ml/min.
Thermometer
While I am at it, I will install dual BBQ probe to monitor the coil and controller temperature.
Heat sink
Solder/blaze on vertical air fin on the hub (unlike the Hubsink which is radial fin), at least double up hub surface area if possible.
While I am at it,
find a good looking battery case....
These are about everything that I could think off for the mod, what else other sensible stuff can I incorporate into this build?. I am open to all suggestions while I am at it....
You comments and suggestions are most appreciated.
I am a old fat geezer whom had just had a taste of motor-assisted bicycle and I want more.
A month + ago, I started an experiment on low power ebike by converting my Dahon Boardwalk into a front geared hub motor. The battery pack is 48V 12AH, ON/Off Throttle only with brake sensors. The battery and controller are stuffed in a waterproof handlebar bag, Something really straight and simple.
I use it to run errand around town and join spirited rides in the evening hitting 30~40km/h for 80km rides with young and strong Lycra laden cyclist along the highway, you can imagine how wide a grin is on my face
Now that I am out riding more, I am surprise that I actually got some decent workout and my breath and legs got stronger. I call the experiment a complete success. #except for heating problem with the controller and hub motor.
For my second build, I need something to cool the controller and the hub.
After weeks of endless-sphere I had come to this point.
My objective is to ride gentle 5% gradient for 30km continuously. 120kg rider, 15kg bike, 20" (406) wheels, front geared hub motor. speed doesn't matter but I do understand that the motor will be happy if I keep it 20+km/h.
Controller
The controller is the easy bit, water/weather proof (by applying nail polish on the PCB and silicone the controller case), mount it on the bike frame and let natural air do all the work. if it doesn't, I will add as many heat-sink on the casing to make it works.
Actually, I reckon waterproofing the wires are more challenging... Yes, a Sine wave FOC controller if I can find one for hub motor. 20A with 5 levels if I can find any.
Geared Hub Motor
I will stick to geared front hub. for convenient sake. If it works here, it will work elsewhere.
The hub will receive oil bath mod with ATF. I learnt that the coil varnish is rated to 150C, I also know wire rubber insulation for most high temperature electrical wires (for motor phase and halls) are 120C. so this leads to my design max. temp cut-off of 110C. Theoretically, any water ingestion should boil out at that temp given enough time, which is a bonus. Not forgetting to coat all wires and plug all holes with high temp RTV liquid gasket paste which usually has 250C temp rating. Use rubber seal bearing for the external hub bearing.
From many oil cooled hub projects I read on the forum, it seems that an air breather valve is missing from most projects. Breather valve is an old tested way to equalize internal pressure due to heat and expansion of the air and oil in the hub which could cause bleeding bearings and dripping wires, they are used everywhere, eg, transmission gearbox, engine block, differential gearbox, motor gearbox, gas tank, diesel tank, etc. The breather valve I found looks like a M6 bolt with holes drilled into it and built-in 0.07bar relief valve and oil filter, it should keep the oil in and water oil of the hub. not forgetting it can breath 300ml/min.
Thermometer
While I am at it, I will install dual BBQ probe to monitor the coil and controller temperature.
Heat sink
Solder/blaze on vertical air fin on the hub (unlike the Hubsink which is radial fin), at least double up hub surface area if possible.
While I am at it,
find a good looking battery case....
These are about everything that I could think off for the mod, what else other sensible stuff can I incorporate into this build?. I am open to all suggestions while I am at it....
You comments and suggestions are most appreciated.