The limits to friction drive
- Thread starter specialtreva
- Start date
Erogo
100 W
Nnyeah? They both look a bit doofy dont they? I'm used to seeing the elegance of solutions like Adrian's and Kepler's. Can't something equally as beautiful be done with an outrunner pressed against the rim?
Erogo
100 W
Perfect! Although, engaging thost sprockets in the spokes would no longer really count as a friction drive :wink:
spinningmagnets
100 TW
If you want to make a system that drives the rim,...aint nothin to it but to do it! So, get a vice and a cordless drill and get started!
Using a fat tire that has a relatively flat tread (beach cruiser style) provides a lot of tire/roller contact with very little tire wear. I hope I didn't sound as though I was disparaging of friction drives. I am SATISFIED with maintaining roller traction while having 1500W at my disposal.
When discussing LiFePO4, there is a big price difference between a 36V and a 48V pack of the same aH size. However, when contemplating a small and lightweight LiPo battery pack (one the biggest benefits of an FD is it is small and light), there is only a small price increase when going from 37V to 44V. I agree with Todd that at 44V, a friction drive would be an even better climber. For a shell drive (Kepler/Adrian) the issue would be finding an off-the-shelf motor with the target kV.
The cell_man kit and LiPo set-up I described before is fairly light and only $500 for an 8aH system,...but it is not easily removable.
Using a fat tire that has a relatively flat tread (beach cruiser style) provides a lot of tire/roller contact with very little tire wear. I hope I didn't sound as though I was disparaging of friction drives. I am SATISFIED with maintaining roller traction while having 1500W at my disposal.
When discussing LiFePO4, there is a big price difference between a 36V and a 48V pack of the same aH size. However, when contemplating a small and lightweight LiPo battery pack (one the biggest benefits of an FD is it is small and light), there is only a small price increase when going from 37V to 44V. I agree with Todd that at 44V, a friction drive would be an even better climber. For a shell drive (Kepler/Adrian) the issue would be finding an off-the-shelf motor with the target kV.
The cell_man kit and LiPo set-up I described before is fairly light and only $500 for an 8aH system,...but it is not easily removable.
Erogo
100 W
What - you mean I don't need to apply for a license or permission?
Actually are there advantages to getting a bit of slip in the system? I'm hoping for a bit of slip between wheel and road, to prevent stall and maybe save the controller. Poor-man's current limiting!
Oh, and yeah I've got a vice and a driller. Here's me half way through a shaft transplant on the turnigy:
Get the driller spinning the shaft at top speed, then attack it with the dremel spinning the other way. Perfect.
Hillhater
100 TW
Erogo said:
Rims are not designed for one sided loading, unless balanced as with those drives pictured. so any drive you build would effectively mean double the components compared to a peripheral contact drive.
Simplicity is one of the main advantages of FD's
Erogo
100 W
Sure is. Adrian's drive is what led me into the sphere, looking for a simple lightweight retro fit to a racingbike.
But, Adrian's done that. Just before we pack up and go home, we might have a bit of a laugh about other ways things might have been done.
Agreed rims aren't for single-sided loading. So either you could have a pair or motors pinching the rim, or you could have a motor balanced with a dummy roller, like an inline skate wheel or something. Maybe you could get them pivoting in such a way as that they pivoted forward into the rim as they engaged, coupled to each other via an overly complicated system of interconnected pulleys and levers, continuously sensing and adjusting.
Erogo said:
I like talking about different ways of doing friction drives as much as anyone else but we've discussed various ways (some being very cool and creative) to build one ad nauseum. I think there are at least a couple of people on here that would like to add a friction drive post filter to their web browser :lol: .
Erogo
100 W
Gosh, I'm sorry. It's not OK to talk about friction drive concepts, it'll annoy the oldtimers.
I searched "friction rim pinch", and found one relevant post, from 2009. "friction rim squeeze" = zero relevant posts. Apologies for going over old ground!
Sorry Trev, for clogging your thread.
LFP suggested some FAQs as homework for the entrance exam. Perhaps a list of topics it's still OK to discuss on ES?
It's not OK to talk about friction drive concepts, it'll annoy the oldtimers.I searched "friction rim pinch", and found one relevant post, from 2009. "friction rim squeeze" = zero relevant posts. Apologies for going over old ground!
Sorry Trev, for clogging your thread.
LFP suggested some FAQs as homework for the entrance exam. Perhaps a list of topics it's still OK to discuss on ES?
I think I came across the wrong way in my last post and I apologize if I did. I personally like seeing all the different friction drive ideas.
Like I said though, I think there are a couple of people on here that are starting to dislike all the friction drive posts. Maybe I'm wrong about that too. I dunno....
Actually, I do wish we would see more of the ideas built. I think that's what's great about friction drive. It can be simple and lots of people can build one if they just get a bit creative with it.
Like I said though, I think there are a couple of people on here that are starting to dislike all the friction drive posts. Maybe I'm wrong about that too. I dunno....
Actually, I do wish we would see more of the ideas built. I think that's what's great about friction drive. It can be simple and lots of people can build one if they just get a bit creative with it.
Erogo
100 W
Yeah sorry EVT, it's not just you - there's been a strange tone on ES recently of "what are these bloody newbs doing asking the same newb questions we asked years ago". Entrance exams etc to stop people "asking the same old questions". Then there's also a plea (in general discussion?) to post all questions on-forum, rather than by PM!
So, this was the wrong thread for me to vent, and you're not a specific target for that vent.
Lucky there's no requirement to read every post on ES eh! :wink:
Happy happy happy
So, this was the wrong thread for me to vent, and you're not a specific target for that vent.
Lucky there's no requirement to read every post on ES eh! :wink:
Happy happy happy
gtadmin
10 kW
I like friction drives, though I probably will never build oneEVTodd said:
and I read them all 8) What we need are separate sub-forums for: Hub drives; Friction Drives; Built from Scratch (for frame builders) in addition to a "Non-hub Motor Drives"
adrian_sm
1 MW
Just make one, you could knock one up in a arvo with your skills.
You know you want to
You know you want to
specialtreva
10 µW
I started this topic to learn more about the hill performance of friction drives.
My semi-informed hunch right now is to stick with friction drive but to go roller rather than motor drive. the amount of power reqd to carry me up a 15 % grade looks like a challenge for the motor on wheel type drives.
A little disappointed cos the elegance and simplicity of motor on wheel approach is what got me interested in this site as well.
Hey, even if it's geared down to say 20 kmh max and used just for the steep hills it'll make my riding much more enjoyable and that's what it's about for me. Thanx to all contributors for the shared info.
I'LL BE BACK.... with my story on how I got a friction drive to climb walls.
trev
My semi-informed hunch right now is to stick with friction drive but to go roller rather than motor drive. the amount of power reqd to carry me up a 15 % grade looks like a challenge for the motor on wheel type drives.
A little disappointed cos the elegance and simplicity of motor on wheel approach is what got me interested in this site as well.
Hey, even if it's geared down to say 20 kmh max and used just for the steep hills it'll make my riding much more enjoyable and that's what it's about for me. Thanx to all contributors for the shared info.
I'LL BE BACK.... with my story on how I got a friction drive to climb walls.
trev
spinningmagnets
100 TW
This is the April 2009 FD build-link from the sig at the bottom of EVtodds postings:
http://endless-sphere.com/forums/viewtopic.php?f=28&t=9652&start=0
It is 23 pages of FD discussion. It is the seed from which my drive, Keplers, and Adrians grew. There was very little discussion about friction drives before this thread. Todd Posted some better-than-expected performance data...and his enthusiasm was somewhat contagious!
I'm glad I built one. There isn't very much to discuss about a 9C and a 48V Ping. You buy it, install it, and enjoy the EV grin. What gets builders talking is suggesting whats missing from the Ebike world, and what might be some of the ways to fill the niches that the mainstream kits don't address.
I expect there will be some longtail-bike builds after a recent thread by Dogman, I also built a longtail that I like very much. John-in-CR posted about using a de-spoked hubmotor as a non-hub build, (along with rassy and some others), and I expect that there will be some interesting builds in that category too.
Hillhater
100 TW
specialtreva said:
That depends on the choice of motor !
IE: if you choose a high KV motor , you will have no chance !..
but if you happened to chose a low kv ( < 100) with reasonable power ( > 1kW) then you will be OK probably.
The secret is in finding the best motor to suit your circumstances.
For instance, a direct motor friction drive using a re purposed hub motor ( geared hub ?) would climb any hill you could find...but it would lose out badly on top speed
Bluefang
10 kW
The only really limiting thing with the friction drives talked about most on this forum is the controllers used. You add sensors and use a Lyen controller with a 63mm can motor and have no fear, you will make it over almost any hill . The sensor less controllers are just so simple cheap and easy to use they fit the idea of low power commuter friction drives very well. Personally i built a friction drive with a sensored 50mm can motor driving a roller on the wheel, could easily start from a stop and more then enough power to hit 35km/h. Could also flip the bike when i pulled the throttle without sitting on the bike It was my first ebike and i would have kept it but i frocked up the batteries and thought it was the drive that was shit......my bad 
To keep it simple, you could get a 12fet controller, a Turnigy 130(Has slots big enough to fit sensors into, low enough KV to run a high voltage without having to run a roller on the tyre, bigger roller on the wider tire = better contact for driving) and with that you could pump 7kw into the wheel, you would probably need to go for the fattest rear tyre you can get, even a motorcycle tire.
http://www.motorcycleforums.net/forum/paddock/11354-friction-drive.html
Talking about a 300+kg motorbike with a friction drive, google is your friend
. The sensor less controllers are just so simple cheap and easy to use they fit the idea of low power commuter friction drives very well. Personally i built a friction drive with a sensored 50mm can motor driving a roller on the wheel, could easily start from a stop and more then enough power to hit 35km/h. Could also flip the bike when i pulled the throttle without sitting on the bike It was my first ebike and i would have kept it but i frocked up the batteries and thought it was the drive that was shit......my bad To keep it simple, you could get a 12fet controller, a Turnigy 130(Has slots big enough to fit sensors into, low enough KV to run a high voltage without having to run a roller on the tyre, bigger roller on the wider tire = better contact for driving) and with that you could pump 7kw into the wheel, you would probably need to go for the fattest rear tyre you can get, even a motorcycle tire.
http://www.motorcycleforums.net/forum/paddock/11354-friction-drive.html
Talking about a 300+kg motorbike with a friction drive, google is your friend
adrian_sm
1 MW
Your right. A sensored friction drive is definitely a solid solution, and one I may revert to. I just like the small size of the RC ESCs, and not having to bother with sensors. But it means I compromise on not being able to start from a stand still.
The issue for me in going for high power friction drive is the efficiency losses that increase with higher contact pressure with the tire. You would end up having a chain/belt drive being more efficient.
But I do love the idea of using the 80100-130kV. Now that would be a beast of a bike.
I am sure there would be enough room on my hardtail mountain bike to fit it with my current friciton drive design too.
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=5142
Lucky they are out of stock, otherwise I may have just hit the purchase button, just for the sake of RnD. To hell with efficiency.
The issue for me in going for high power friction drive is the efficiency losses that increase with higher contact pressure with the tire. You would end up having a chain/belt drive being more efficient.
But I do love the idea of using the 80100-130kV. Now that would be a beast of a bike.
I am sure there would be enough room on my hardtail mountain bike to fit it with my current friciton drive design too.
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=5142
Lucky they are out of stock, otherwise I may have just hit the purchase button, just for the sake of RnD. To hell with efficiency.
Hillhater
100 TW
The big Turnigy would certainly provide an entertaining ride but i am not convinced you would be able to get all of its power to the wheel.
didnt one of you guys conclude that beyond 2-3 kW , drive slippage became too common ?
..and obviously with higher levels of power, range is reduced accordingly and /or battery and controller size increases .
so the whole package becomes something more conspicuous and weighty.
Also, there are still issues surrounding sensored Turnigy outrunners and Lyen controllers !!
didnt one of you guys conclude that beyond 2-3 kW , drive slippage became too common ?
..and obviously with higher levels of power, range is reduced accordingly and /or battery and controller size increases .
so the whole package becomes something more conspicuous and weighty.
Also, there are still issues surrounding sensored Turnigy outrunners and Lyen controllers !!
Erogo
100 W
OK how about this.
You have a disc like a brake disc, but with better clearance on either side. You have rollers made of something real hard and real grippy, like disc brake pads. The rollers are on either side of the disc, and pinch it under the control of a squeezer. With such low deformation you'd have good efficiency, and you'd be able to transfer buckets of power through it, because you could apply monster force. disc brakes can hold real hard, think of the torque they can counter, when a load is perched on a steep slope. They don't slip until your spokes are breaking. (not sure about that bit).
But here's the killer bit: the rollers can move radially, to determine the drive ratio.
You have a disc like a brake disc, but with better clearance on either side. You have rollers made of something real hard and real grippy, like disc brake pads. The rollers are on either side of the disc, and pinch it under the control of a squeezer. With such low deformation you'd have good efficiency, and you'd be able to transfer buckets of power through it, because you could apply monster force. disc brakes can hold real hard, think of the torque they can counter, when a load is perched on a steep slope. They don't slip until your spokes are breaking. (not sure about that bit).
But here's the killer bit: the rollers can move radially, to determine the drive ratio.
adrian_sm
1 MW
Hillhater said:
No guts. No glory.
I would do it just to shut people up about friction drives being piss weak.
A video of me doing burnouts and wheelies on a monster friction drive should do the trick.
full-throttle
1 MW
DO IT!adrian_sm said:A video of me doing burnouts and wheelies on a monster friction drive should do the trick.
You're welcome to borrow my C80-100 with sensors and delta-wye
Need a Schwalbe BigApple 2.35" to go with it :wink: after 20,000km I'm about to replace them and would love to see them go with a BANG!
