Smalest friction drive ever? Assist experiment

[bzhwindtalker]

22-sphing motor, 40a esc and 3s 1ah
I does not seems to work well rigth now on the road (unnoticable when on exept for the noise!) buit this gave me an awesome idea, more on that later

[def215]

interesting. this reminds me of the one guy on youtube, slofly.

i like the friction drive systems.

are you gonna experiment with other smaller outrunner motors also to see if you get good results? keep us posted, im interested to see if these smaller motors can be used.

[adrian_sm]

Cute. Looks like the motor needs to push into the tire more if you want to transfer power.

I find the 50mm motors to be a good light weight compromise that can still handle ~500w.

[nechaus]

Id like to see a friction drive with like 20 out runners around the wheel lol

[DeaninMilwaukee]

I tried to search that motor and came up with nothing, however, unless its around 500kv its not going to work well at all on 3s and will probably overheat since its being lugged down to way below its best rpm.

In brief: Motors run at their best at around 75% of no load rpm. Since that motor is probally limited to around a 100 watts, and 100 watts will push a good bike at perhaps 15 mph. This means you want the motor, at full throttle with the wheel off the ground turn the wheel at around 20mph. ( use a bike speedo on the back wheel to confirm this)

I'm guessing from the photo that the motor is around 1" diameter and is likely to be at least 1000kv if not more. That would put the wheels no load rpm at around 35mph and its most efficient rpm at 26 mph. Obviously thats not going to happen on only 100 watts, so in motion at only 15 mph or so the motors running at maybe 42% of no load rpm, making very little usable power along with winding-burning levels of heat. Most of the wattage isn't making the bike go, its just getting the motor hot.

In this case, going to a 2 cell lipo would actually make more usable power, reducing no load rpm to around 23 mph and best loaded rpm to around 17 mph, a speed that might be possible with pedaling.

I am actually considering trying a very similar project just to see how it would work, but would be using a 3000kv motor in a 6.3:1 gearbox into a 1" roller on 3s. With my motor this should give me around 50 net output watts and an effective kv of around 500. I am hoping this will allow a no pedal speed of around 10mph.

Dean in Milwaukee

[Dauntless]

Where did you get that clamp on the downtube?

[bzhwindtalker]

You guys are rigth about it being geared too high, but as an assist it does not need to propel me from 0kph; anyway this was just an experiment, my first go at friction drives and I tried it with this small motor rather than the 63-74 I had laying because wiring this controller was easier than setting up a ss190-200 setup. The clamp I used is from an old good quality front derailleur, I don't remember the brand or the model but those make really nice clamps, and they are made to be easy to put on and remove !