rim drive "world's lightest" e-bike drive

[Rollodo]

This seems to be a year old - perhaps their first iteration? - but here goes:

http://www.bentrideronline.com/messageboard/showpost.php?p=1090008&postcount=17

 

[BlackStridaAustria]

This seems to be a year old - perhaps their first iteration? - but here goes:

http://www.bentrideronline.com/messageboard/showpost.php?p=1090008&postcount=17

Hi Rollodo,

that's not the drive but their rim dynamo.
http://www.velogical-engineering.com/rim-dynamo-en
Just to avoid misunderstandings

 

[Modbikemax]

Both seem pretty stupid to me. The clue is in the title "Friction".
If friction drives were any good the Chinese would be making millions of those instead of hub motors.

 

[parajared]

Cool; I want to strap a couple of $10 Hobbyking motors to a bicyle and see what happens now.

 

[Modbikemax]

Cool; I want to strap a couple of $10 Hobbyking motors to a bicyle and see what happens now.

Probably a waste of $10 and most likely a rim and tyre. :?

 

[parajared]

Probably a waste of $10 and most likely a rim and tyre

Ok, I tried it and no damage to motor, rim or tire, but it didn't work either. I attempted to propel my wheel forward using a 750kv 300 watt rc motor and a 4s 5ah lipo. At first I was having a lot of slippage, but after I got the hang of things I could make firm contact with the rim without slipping but that tiny motor would bog down and wasn't enough to even keep the bike rolling forward on a level road.

Here's the video of the experiment:
[youtube]vvU-F5hS8KM[/youtube]

 

[tahustvedt]

Probably a waste of $10 and most likely a rim and tyre

Ok, I tried it and no damage to motor, rim or tire, but it didn't work either. I attempted to propel my wheel forward using a 750kv 300 watt rc motor and a 4s 5ah lipo. At first I was having a lot of slippage, but after I got the hang of things I could make firm contact with the rim without slipping but that tiny motor would bog down and wasn't enough to even keep the bike rolling forward on a level road.

Here's the video of the experiment:

Nice attempt. The motor is way to high kv though. You probably need a maximum 300 kv motor. Two would help as well. It's difficult to find a motor like that, so it probably needs to be custom wound.

 

[Modbikemax]

Well done. True mythbusters spirit in doing the test. Most friction drives are just trying to avoid using a gearbox to match motor speed and wheel speed. If you get a suitable motor I am sure you can get it to work.

 

[parajared]

Nice attempt. The motor is way to high kv though. You probably need a maximum 300 kv motor. Two would help as well. It's difficult to find a motor like that, so it probably needs to be custom wound.

Maybe my math was wrong:
I came up with 4s lipo is 14.8 volts so calculating in the standard 70% load rpm of 7770 I would have a 1 1/2 inch wheel spinning at 34.6 mph at full throttle. My assumption was that if I spin my 1 1/2 in wheel at half throttle (15mph ish), my big wheel would spin at 15mph too, is that correct, or did I do my math wrong?

I am actually not sure exactly why it didn't work, but one hypothesis is that energy was lost from mashing the friction surface to the rim. I noticed during the test the harder I mashed down the more draggy the motor got. I had to squish the motor pretty hard to get it to maintain traction without slipping.

 

[tahustvedt]

The problem with running at half RPM is that the motor is not able to produce more torque. A motor with half the kv would have twice the kt (torque per amp), minus losses due to thinner and longer wire to fit double the windings of course.

Is that a 406 mm rim? Not sure what the total tire diameter would be, but if you were to drive it at the rim the rpm at 70% of unloaded speed would be 727.2 rpm. I get 39,5 mph with a 1450 mm circumference, so you're probably correct with your calculations.

 

[Adried]

http://www.velogical-engineering.com/velogical-velospeeder.en

 

[Timelord]

Hardly new. It was announced over a year ago and discussed here.

https://endless-sphere.com/forums/viewtopic.php?f=28&t=59867

That they still don't have any pricing or ordering information 15 months later basically says it's vaporware.

 

[LockH]

From June last year...
[youtube]JcxajpI94TM[/youtube]

 

[LewTwo]

Hardly new. It was announced over a year ago and discussed here.

https://endless-sphere.com/forums/viewtopic.php?f=28&t=59867

That they still don't have any pricing or ordering information 15 months later basically says it's vaporware.

Look on ebay. Search for "VELOGICAL Dynamo".
The video has no audio. I suspect that there is a very good reason for that.