Trying to figure which outrunner motor to go with here, looking at the SK3 - 6374-149KV if my math is right that motor with a 36v battery would be spinning at 59km/hour and the 192kv would be 76km/hour. Add 200lbs to that motor to propel and the speeds gets cut how much?
Friction drive motor top speeds?
- Thread starter forcefed
- Start date
spinningmagnets
100 TW
I understand the appeal of using the can of an outrunner as the drive-roller. Its quite an elegant and sleek solution. However, when you give the controller a full throttle signal, it will provide a rising-rate of amps until the drive begins approaching its top RPM. This has led to quite a few overheated motors in the past. There have been extensive experiments by Adrian and Kepler about this. The 63mm diameter outrunners seem to be the best option, and when you select the lowest possible Kv.
Power application is limited by the traction between the tread and the roller. If your set-up has quite a bit of traction, then the next concern is volts and amp selection (why pay for a high watt system when the roller is limited to low watts?). Feel free to experiment, experiments can be fun. However, under the best of conditions...53/kmh (33 mph) when unloaded would be the max I would attempt. After adding a rider and wind resistance, it would be around 45/kmh (28 mph).
The ESCs that operate these outrunners usually allow a range of voltages, and I'd recommend starting with 6S / 22V, using high-amp batteries. If you were to take the extra time and effort to make the roller a separate component, the diameter of the roller and the rest of the system can be selected individually, which provides a much wider range of options for you.
It is vital to add several $2 low-ESR capacitors to the power inputs of the ESC, or the ESC will blow. Pay the extra and get the ESC model that can run up to 44V / 12S, even if you run a lower voltage. That gives you a safety margin for voltage ripple damage.
Here's an index of past examples...
https://endless-sphere.com/forums/viewtopic.php?f=28&t=14403
Power application is limited by the traction between the tread and the roller. If your set-up has quite a bit of traction, then the next concern is volts and amp selection (why pay for a high watt system when the roller is limited to low watts?). Feel free to experiment, experiments can be fun. However, under the best of conditions...53/kmh (33 mph) when unloaded would be the max I would attempt. After adding a rider and wind resistance, it would be around 45/kmh (28 mph).
The ESCs that operate these outrunners usually allow a range of voltages, and I'd recommend starting with 6S / 22V, using high-amp batteries. If you were to take the extra time and effort to make the roller a separate component, the diameter of the roller and the rest of the system can be selected individually, which provides a much wider range of options for you.
It is vital to add several $2 low-ESR capacitors to the power inputs of the ESC, or the ESC will blow. Pay the extra and get the ESC model that can run up to 44V / 12S, even if you run a lower voltage. That gives you a safety margin for voltage ripple damage.
Here's an index of past examples...
https://endless-sphere.com/forums/viewtopic.php?f=28&t=14403
Thanks for the info, 45km/hour is more than fast enough... for now 
I'm a bit of a newb when it comes to esc's, i've narrowed it down to these 3, i'll be running a 36v li-ion in possibly a 9ah or most likely 18ah config. Now for some reason all those esc's say lipo lipo lipo in the specs, does that mean that 36v li-ion won't work. I mean its just a battery, what difference can it make... right? Any suggestions on an esc would be great.
Hopefully i'll find some more answers in the threads you posted, this might take a while.
https://hobbyking.com/en_us/hobbywing-platinum-100a-v3-brushless-esc-w-10a-bec.html
https://hobbyking.com/en_us/hobbykingr-tm-x-car-beast-series-esc-1-8-scale-150a.html
https://hobbyking.com/en_us/hobbywing-ezrun-max10-sct.html
I'm a bit of a newb when it comes to esc's, i've narrowed it down to these 3, i'll be running a 36v li-ion in possibly a 9ah or most likely 18ah config. Now for some reason all those esc's say lipo lipo lipo in the specs, does that mean that 36v li-ion won't work. I mean its just a battery, what difference can it make... right? Any suggestions on an esc would be great.
Hopefully i'll find some more answers in the threads you posted, this might take a while.
https://hobbyking.com/en_us/hobbywing-platinum-100a-v3-brushless-esc-w-10a-bec.html
https://hobbyking.com/en_us/hobbykingr-tm-x-car-beast-series-esc-1-8-scale-150a.html
https://hobbyking.com/en_us/hobbywing-ezrun-max10-sct.html
spinningmagnets
100 TW
One odd thing about friction-drives is that the road-speed will be at the speed of the roller, regardless of the tire diameter. It sounds odd, but its been verified many times. Just calculate the circumference of the roller times the motor RPM's to get the road-speed. For a 63mm diameter motor-shell, its (63 X 3.1416 =) 198mm per 1-revolution.
Another thing that is the opposite from the common electric drives that propel the axle of a wheel is that...a larger diameter wheel will help the motor run cooler than a smaller wheel. For a hubmotor it is the opposite.
If you imagine the roller driving on top of the rear wheel, then look at the wheel as a lever...the ground is the fulcrum, and the axle is the load that is being pushed forward.
Another thing that is the opposite from the common electric drives that propel the axle of a wheel is that...a larger diameter wheel will help the motor run cooler than a smaller wheel. For a hubmotor it is the opposite.
If you imagine the roller driving on top of the rear wheel, then look at the wheel as a lever...the ground is the fulcrum, and the axle is the load that is being pushed forward.
Kepler
10 MW
forcefed said:Thanks for the info, 45km/hour is more than fast enough... for now
I'm a bit of a newb when it comes to esc's, i've narrowed it down to these 3, i'll be running a 36v li-ion in possibly a 9ah or most likely 18ah config. Now for some reason all those esc's say lipo lipo lipo in the specs, does that mean that 36v li-ion won't work. I mean its just a battery, what difference can it make... right? Any suggestions on an esc would be great.
Hopefully i'll find some more answers in the threads you posted, this might take a while.
https://hobbyking.com/en_us/hobbywing-platinum-100a-v3-brushless-esc-w-10a-bec.html
https://hobbyking.com/en_us/hobbykingr-tm-x-car-beast-series-esc-1-8-scale-150a.html
https://hobbyking.com/en_us/hobbywing-ezrun-max10-sct.html
I would not recommend any of those for a friction drive. The choice is simple get a Vesc. A little more expensive but worth every penny.
Best version is the FOCBOX. http://www.enertionboards.com/elect...CBOX-programmable-brushless-motor-controller/
Best price version is the Maytech https://www.ebay.com/p/Maytech-Benj...troller-Vesc-for-Electric-Longboard/853254976
Hobbyking are even getting into the act. On backorder at the moment though. https://hobbyking.com/en_us/turnigy-sk8-esc-for-electric-skateboard-conversion.html
I am currently using both the FOCBOX and Maytech. Both have been great.
For some reason the diameter was listed as 59mm on hobby king, if it is 63mm then the new numbers are 63/72/82km/h for the 149/168/192kv motors.spinningmagnets said:
Is the maytech and the hobbyking turnigy sk8-esc the same vesc? They look identical.Kepler said:
So it seems that maytech vesc has regenerative braking, so if i have the friction motor constantly on the tire it'll charge the battery back up if i coast down a hill? Is the motor hard to spin when its in this mode, is it basically slowing you down more compared to if it wasn't touching the tire?
Kepler
10 MW
Any of those motors will work fine. I would go with the lowest KV on 36V though.
Not sure if the Maytech and Turnigy are built by the same company. I wouldn't be surprised if it was though.
If you kept the roller engaged all the time you could use it for regen. Little gain though on a light weight build. You are better off going with a design that decouples from the tire.
Not sure if the Maytech and Turnigy are built by the same company. I wouldn't be surprised if it was though.
If you kept the roller engaged all the time you could use it for regen. Little gain though on a light weight build. You are better off going with a design that decouples from the tire.
