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Need some help building a friction drive.

Old 07-03-19, 03:45 AM
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evbkzzzz
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Need some help building a friction drive.

Hey all!
I am new to this forum and ebikes as well. I would like to build a ebike myself.
This is going to be my first build and I have few questions ahead. Hope you guys help me with it.

Here is what I am trying to achieve:
  1. control engagement and disengagement using the front derailleurs
  2. Keep the motor power at or below 250W still being able to achieve 25Km/hr without pedal assist.
  3. Climbs hill with a incline of 15deg
  4. Be able to use on wet and muddy weathers
What motors should I be using on my build? I researched online and get the idea that 200kv is the right choice. But have no understanding why. Am I correct? Should I stick to a 200kv motor?
I also read that the speed depends on the diameter of the drive wheel and for a 2.5in drive wheel 2000rpm is required for speed of 25km/hr.
Should I drive the motor shell directly or should I use a coating of sandpaper or rubber? Sandpaper provides best cof but wears out the tires pretty soon... Couldn't get much info on rubber.... is there something that can hit a number between?
Coming to the tires, what kinda tires should I use? flat centre region?
If I want to be able to accelerate the cycle from rest, should I stick to using smaller rollers? I read large rollers have terrible low end power.. How does the diameter of the roller affect the power delivery? speed? torque?

Thanks!
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Old 07-03-19, 09:07 AM
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Hope you get some help here, but I haven't seen friction-drive discussed except commercial systems. Check "Kepler" on endless sphere; he's the expert on DIY systems.
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Old 07-03-19, 09:23 AM
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Yeah, endless sphere has tons of threads on friction drives and how to make 'em. There's one really long one where Kepler goes through his development and all his iterations. Also, he used to sell a sort of mini-kit, if he still does that might work out for you. It was all too complicated for me so I went with a commercial system. Good luck!!!
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Old 07-03-19, 10:47 AM
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VéloSoleX .. a French company making a friction drive front wheel powered Moped..

They apparently produced an electric version (as the Wikipedia item suggests)





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Old 07-08-19, 02:13 PM
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I don't know if you are going to post more than one post, but yeah, what they said.

Friction drives are rather noisy and haven't really gotten much "traction" in the ebike world...
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Old 07-08-19, 10:16 PM
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Why********************??? Friction
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Old 07-08-19, 11:09 PM
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If you build it right, there's nothing lighter that can supply the same amount of power. My 1Motor pushes 750w and weighs 4.5lbs including
battery. Not everyone wants or needs a big heavy powerful e-bike motor.
I wouldn't have bought a super light 19lb Bike Friday if I had just planned on adding 10 (likely more) pounds to motorize it. I've got a 23.5lb e bike =). So that's why a friction drive! And it works great. They're ideal for light road bikes, too.
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Old 07-09-19, 05:10 AM
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Originally Posted by 2old
Hope you get some help here, but I haven't seen friction-drive discussed except commercial systems. Check "Kepler" on endless sphere; he's the expert on DIY systems.
Originally Posted by linberl
Yeah, endless sphere has tons of threads on friction drives and how to make 'em. There's one really long one where Kepler goes through his development and all his iterations. Also, he used to sell a sort of mini-kit, if he still does that might work out for you. It was all too complicated for me so I went with a commercial system. Good luck!!!
Originally Posted by chas58
I don't know if you are going to post more than one post, but yeah, what they said.

Friction drives are rather noisy and haven't really gotten much "traction" in the ebike world...
Originally Posted by linberl
If you build it right, there's nothing lighter that can supply the same amount of power. My 1Motor pushes 750w and weighs 4.5lbs including
battery. Not everyone wants or needs a big heavy powerful e-bike motor.
I wouldn't have bought a super light 19lb Bike Friday if I had just planned on adding 10 (likely more) pounds to motorize it. I've got a 23.5lb e bike =). So that's why a friction drive! And it works great. They're ideal for light road bikes, too.
Thank you everyone, I just got busy. I have understood that the friction drive doesn't offer much benefits to consider it. I am now planning to build a mid-drive.
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Old 07-09-19, 07:30 AM
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Two positive considerations for a friction drive AFAICT: light weight and stealth (maybe almost imperceptible with a seat bag battery). Kepler on ES has gone so far as to adapt one for a full suspension off road bike. Hope to try one someday.
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Old 07-09-19, 09:41 AM
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Good luck with your mid-drive build. I'm always impressed by folks who can build their own!
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Old 07-09-19, 11:08 AM
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Originally Posted by evbkzzzz
Thank you everyone, I just got busy. I have understood that the friction drive doesn't offer much benefits to consider it. I am now planning to build a mid-drive.
Curious, why Mid drive? You can go lighter and more stealth with a hub, but if you are doing hills, mid drive is the way to go. Just wondering what your decision process is...
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Old 07-09-19, 11:38 AM
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Originally Posted by linberl
If you build it right, there's nothing lighter that can supply the same amount of power. My 1Motor pushes 750w and weighs 4.5lbs including
battery. Not everyone wants or needs a big heavy powerful e-bike motor.
I wouldn't have bought a super light 19lb Bike Friday if I had just planned on adding 10 (likely more) pounds to motorize it. I've got a 23.5lb e bike =). So that's why a friction drive! And it works great. They're ideal for light road bikes, too.
Maybe you can teach me something. Got some examples of some well built friction drives? I've done some research on them, but they always seem to disappoint - like 750w just doesn't pull like a 750 watt hub or mid drive. Maybe you know something I don't?

I guess I'm different then you, because I did what you wouldn't do, lol. I put a 2.1kg hub motor on my 19lb bike. If I found an alternative that could save me 1.1kg with similar performance, I would be interested...
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Old 07-09-19, 01:20 PM
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Originally Posted by chas58
Maybe you can teach me something. Got some examples of some well built friction drives? I've done some research on them, but they always seem to disappoint - like 750w just doesn't pull like a 750 watt hub or mid drive. Maybe you know something I don't?

I guess I'm different then you, because I did what you wouldn't do, lol. I put a 2.1kg hub motor on my 19lb bike. If I found an alternative that could save me 1.1kg with similar performance, I would be interested...
You can read up on what I ended up buying, ymmv. also I'm 135lbs so even with the bike pretty light. I guess it depends on what you're looking for - I am not interested in a fulltime electric bike. I choose to ride leg powered whenever I can and power up for hills and inclines that would hurt my knee, and in nasty ocean headwinds. I've had zero problem climbing 25 degree grades with my drive at a pretty good speed. You can read up on what I have if you want (or not): https://electricbikereview.com/forum...eroller.28504/
If you have any other questions I'd be happy to try to answer. For reference, I previously owned a dedicated electric bike with a hub front motor, had it about a year, maybe a little more, when I first returned to riding after a 20 year absence.
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Old 07-10-19, 12:20 AM
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Originally Posted by linberl
Good luck with your mid-drive build. I'm always impressed by folks who can build their own!
Thank you for the wishes. Hope to learn many things in the process.

Originally Posted by chas58
Curious, why Mid drive? You can go lighter and more stealth with a hub, but if you are doing hills, mid drive is the way to go. Just wondering what your decision process is...
Umm. Mid drives because there isn't much I can do myself in hub motor except for designing the motor itself. And yeah, I quite frequently drive uphills.

Originally Posted by linberl
You can read up on what I ended up buying, ymmv. also I'm 135lbs so even with the bike pretty light. I guess it depends on what you're looking for - I am not interested in a fulltime electric bike. I choose to ride leg powered whenever I can and power up for hills and inclines that would hurt my knee, and in nasty ocean headwinds. I've had zero problem climbing 25 degree grades with my drive at a pretty good speed. You can read up on what I have if you want (or not): electricbikereview.com/forum/threads/review-onemotor-the-device-formerly-known-as-shareroller.28504/
If you have any other questions I'd be happy to try to answer. For reference, I previously owned a dedicated electric bike with a hub front motor, had it about a year, maybe a little more, when I first returned to riding after a 20 year absence.
This is interesting, I would love to build something like that.
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Old 07-10-19, 09:15 AM
  #15  
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Mid drives because there isn't much I can do myself in hub motor except for designing the motor itself.
I'm lost. What can you do yourself with a mid drive that you can't do with a hub?

Sounds like you will enjoy the process. Just let us know if you have any more questions!
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Old 07-10-19, 09:28 AM
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Originally Posted by linberl
You can read up on what I ended up buying, ymmv. also I'm 135lbs so even with the bike pretty light. I guess it depends on what you're looking for - I am not interested in a fulltime electric bike. I choose to ride leg powered whenever I can and power up for hills and inclines that would hurt my knee, and in nasty ocean headwinds. I've had zero problem climbing 25 degree grades with my drive at a pretty good speed. You can read up on what I have if you want (or not): https://electricbikereview.com/forum...eroller.28504/
If you have any other questions I'd be happy to try to answer. For reference, I previously owned a dedicated electric bike with a hub front motor, had it about a year, maybe a little more, when I first returned to riding after a 20 year absence.
That is a great write-up. I appreciate it. I love hearing of experiences with a light weight build. You have a great setup there!

good to hear they have minimized that RC motor whine. The PAS sounds great. Probably the best Friction Drive example I have seen. Looks like a viable option to a small hub drive, one that works very well for your usage. Good to see bikes that are pedaled like a bike with e-assist (as opposed to converting a bike to an electric mini-bike).

I did a little research on the motor you listed. I agree, for your application, a small 200-350 watt motor can be useful for short ranges on a light bike. I always enjoy seeing light weight builds. Its my passion.

Your build looks like a 250 watt motor that saves 0.5 to 1.1 kg over a small hub motor. It works well on your setup.


I get frustrated with a company like OneMotor specs are a little opaque, and seem to me to be misleading. Maybe I missed something.
https://onemotor.co/indepth/

For instance, the <5lb package has a 130Whr battery, typically 10s1P. That is capable of continuously giving about 4 amps, which puts us at 130 watts continuous. Maybe it can do 8 amps if they are using the best chemistry available. Not exactly a 750 watt motor. It says the top speed is 20mph, which is about 150+ watts on an efficient drop bar bike or 340W on a typical mountain bike. That could be brutal on that little battery – and more practical on their larger battery.

The motor with the small battery would typically be labeled as a 250 watt set up (or whatever the continuous power is), not 750 peak power with a larger battery. With a larger battery, I would guess it as a 350 watt motor as you are not really going to want to pull more than 10 amps continuous on that battery.

Last edited by chas58; 07-10-19 at 09:31 AM.
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Old 07-10-19, 09:51 AM
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Originally Posted by chas58
That is a great write-up. I appreciate it. I love hearing of experiences with a light weight build. You have a great setup there!

good to hear they have minimized that RC motor whine. The PAS sounds great. Probably the best Friction Drive example I have seen. Looks like a viable option to a small hub drive, one that works very well for your usage. Good to see bikes that are pedaled like a bike with e-assist (as opposed to converting a bike to an electric mini-bike).

I did a little research on the motor you listed. I agree, for your application, a small 200-350 watt motor can be useful for short ranges on a light bike. I always enjoy seeing light weight builds. Its my passion.

Your build looks like a 250 watt motor that saves 0.5 to 1.1 kg over a small hub motor. It works well on your setup.


I get frustrated with a company like OneMotor specs are a little opaque, and seem to me to be misleading. Maybe I missed something.
https://onemotor.co/indepth/

For instance, the <5lb package has a 130Whr battery, typically 10s1P. That is capable of continuously giving about 4 amps, which puts us at 130 watts continuous. Maybe it can do 8 amps if they are using the best chemistry available. Not exactly a 750 watt motor. It says the top speed is 20mph, which is about 150+ watts on an efficient drop bar bike or 340W on a typical mountain bike. That could be brutal on that little battery – and more practical on their larger battery.

The motor with the small battery would typically be labeled as a 250 watt set up (or whatever the continuous power is), not 750 peak power with a larger battery. With a larger battery, I would guess it as a 350 watt motor as you are not really going to want to pull more than 10 amps continuous on that battery.
Well, you'd have to email Jeff at 1M about all that amp stuff, lol, way over my head. What I can tell you from actual use, with the small 130wh battery, is that on low PAS with a cadence of 80 I've gotten 24 miles on a charge. And using the throttle I have also pushed it up to 24 mph on flats (supposedly you can go 28 but I was already scared at 24, I'm a wuss). Having had a hub motor bike before, I assumed a rate of 20wh per mile but this friction drive doesn't seem to follow those same rules. And, wonder of wonders, Jeff's range estimates were actually on the low realistic side rather than the typical overstated b.s. I've seen on many e-bikes. If you're interested in the amp stuff, email Jeff - he's an engineer and would probably love to geek out on it with you =).
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Old 07-10-19, 11:41 AM
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you have a great build. That little battery is good for how you use it (not using it full out most of the time).
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Old 07-10-19, 12:50 PM
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Originally Posted by chas58
That is a great write-up. I appreciate it. I love hearing of experiences with a light weight build. You have a great setup there!

good to hear they have minimized that RC motor whine. The PAS sounds great. Probably the best Friction Drive example I have seen. Looks like a viable option to a small hub drive, one that works very well for your usage. Good to see bikes that are pedaled like a bike with e-assist (as opposed to converting a bike to an electric mini-bike).

I did a little research on the motor you listed. I agree, for your application, a small 200-350 watt motor can be useful for short ranges on a light bike. I always enjoy seeing light weight builds. Its my passion.

Your build looks like a 250 watt motor that saves 0.5 to 1.1 kg over a small hub motor. It works well on your setup.


I get frustrated with a company like OneMotor specs are a little opaque, and seem to me to be misleading. Maybe I missed something.
https://onemotor.co/indepth/

For instance, the <5lb package has a 130Whr battery, typically 10s1P. That is capable of continuously giving about 4 amps, which puts us at 130 watts continuous. Maybe it can do 8 amps if they are using the best chemistry available. Not exactly a 750 watt motor. It says the top speed is 20mph, which is about 150+ watts on an efficient drop bar bike or 340W on a typical mountain bike. That could be brutal on that little battery – and more practical on their larger battery.

The motor with the small battery would typically be labeled as a 250 watt set up (or whatever the continuous power is), not 750 peak power with a larger battery. With a larger battery, I would guess it as a 350 watt motor as you are not really going to want to pull more than 10 amps continuous on that battery.
So I emailed 1M about the amp stuff. Not sure I totally understand the answer but thought you might find it interesting:
Our Compact Battery Pack is 12S1P, and built with Sony VTC6 cells, which are capable of 20A continuous discharge. And 20A*43V (under load) = 860W We limit it slightly below that. As far as we know, these are the only cells in the world that can put out 20A for nearly an entire discharge cycle (and 30A for partial) and still have 3.0Ah capacity (other high discharge cells have less capacity), which is why they are multiples more expensive than the average 18650 Ebike cell… in keeping with every component of OneMotor I guess!



Here's a plot in case you’re interested.

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Old 07-10-19, 03:08 PM
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Originally Posted by linberl
So I emailed 1M about the amp stuff. Not sure I totally understand the answer but thought you might find it interesting:
Our Compact Battery Pack is 12S1P, and built with Sony VTC6 cells, which are capable of 20A continuous discharge. And 20A*43V (under load) = 860W We limit it slightly below that. As far as we know, these are the only cells in the world that can put out 20A for nearly an entire discharge cycle (and 30A for partial) and still have 3.0Ah capacity (other high discharge cells have less capacity), which is why they are multiples more expensive than the average 18650 Ebike cell… in keeping with every component of OneMotor I guess!


Here's a plot in case you’re interested.
Wow, that is an impressive battery!
Battery technology is changing fast, and he is using top shelf stuff. that is good to see. Best friction kit I have seen!

(There is a lot of junk out there, and batteries are an easy way to save money and make the price look good - until it craps out a year later).

I usually run at 10 amps (which is 350 watts) and your battery will last about 18 minutes under that load.
(at 20 amps, that specific battery lasts about 8 minutes - don't be doing that!).

Still, this is impressive performance which wasn't available a year or two ago.

Its interesting that he is not running the standard 36 or 48volt system, but actually 43 volts. Never seen that before (although some people like using a 52v battery on a 48v sytem).

Thanks for the info!

(if you want more of those geeky charts - here is his source: https://lygte-info.dk/review/batteri...een)%20UK.html
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Old 07-10-19, 03:45 PM
  #21  
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Originally Posted by chas58
Wow, that is an impressive battery!
Battery technology is changing fast, and he is using top shelf stuff. that is good to see. Best friction kit I have seen!

(There is a lot of junk out there, and batteries are an easy way to save money and make the price look good - until it craps out a year later).

I usually run at 10 amps (which is 350 watts) and your battery will last about 18 minutes under that load.
(at 20 amps, that specific battery lasts about 8 minutes - don't be doing that!).

Still, this is impressive performance which wasn't available a year or two ago.

Its interesting that he is not running the standard 36 or 48volt system, but actually 43 volts. Never seen that before (although some people like using a 52v battery on a 48v sytem).

Thanks for the info!

(if you want more of those geeky charts - here is his source: https://lygte-info.dk/review/batteri...een)%20UK.html
I'm not one of those people who just wants to go super fast all the time. I just want some assist. Basically, I use the 1M to put in the same effort as when I don't have a motor (by pushing a higher gear at same cadence) but I go a little faster. While I can pedal at 15mph with no motor, I can't sustain it for long rides, so 1M allows me to still work hard but keep up or ride in ocean headwinds without worrying being blown backwards, lol. I don't think I'll blow out my battery that way =)
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Old 07-10-19, 10:47 PM
  #22  
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Originally Posted by chas58
I'm lost. What can you do yourself with a mid drive that you can't do with a hub?

Sounds like you will enjoy the process. Just let us know if you have any more questions!
The PAS system, designing planetary gear to get the torque, choosing the motors,etc. in comparison a hub motor is just get a outrunner motor and fix it on the wheels. Correct me if I am wrong.

After reading @linberl posts, I am thinking if I should go back to a friction drive build.
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Old 07-10-19, 11:35 PM
  #23  
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I'm hardly an expert, but I think it depends on what you want and how you want to use it. I know mid-drives are great for folks who climbs lots of hills. Hub motors aren't as good on hills but are great on flatter terrain. Both are fine for someone who wants to run the motor all the time on their rides. I've never had a mid-drive but I had a 350w front hub bike at one time, and it suffered on really big hills (Bay Area) and got super hot. Friction drives are, I think, for someone who wants to just have some assist maybe on hills and in winds or to keep up with others on rides, but wants to preserve the human powered nature of their bike...especially if they have a lightweight bike. What do you want? Or are you just looking to build what seems interesting?
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Old 07-11-19, 03:46 AM
  #24  
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Friction drive on wet/muddy tyres and you're doing maths?! Lol

And the reason we use 54v on a 48v system is because of voltage drop. A half-full 54v battery is around 48v, and it's 42v by the time it needs charging.
Use a 48v battery on a 48v system and it'll cut out at the first steep hill.
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Old 07-11-19, 07:28 AM
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chas58
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Originally Posted by evbkzzzz
The PAS system, designing planetary gear to get the torque, choosing the motors,etc. in comparison a hub motor is just get a outrunner motor and fix it on the wheels. Correct me if I am wrong.
When engineering my build of a hub motor, I had to balance the motor windings, noload speed, human input, hill climbing, motor torque, motor speed, motor power. Its purpose built for me, rather unlike anything else, and does 25mph for 25 miles with 25lb weight (+3lb battery, lol).

Of course you can just build a 50+ lb bike that goes 15-20mph without any design effort.

yup, what linberl has is a good alternative too (if you want low torque, fair weather, light weight low powered build). So many Choices!
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