Why not friction drive?

Discussions related to motors other than hub motors.
This includes R/C motors, botttom bracket, roller and geared drives.

Re: Why not friction drive?

Postby Drunkskunk » Sun Oct 12, 2008 10:26 am

Don't get me wrong, I'm not knocking all friction rollers. Just the application of this one. Friction rollers are fine for use when its flat and dry, and reasonably clean road conditions. For wet, dirty conditions, and hill climbing, friction rollers are the wrong tool for the job.

you wouldn't take a Porche 911 turbo to go rock cralling in Moab, and you wouldn't take a lifted rock crawler Jeep to race in La Mons.
Buy the ticket, take the ride.
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Re: Why not friction drive?

Postby EVTodd » Sun Oct 12, 2008 11:11 am

Drunkskunk wrote:Don't get me wrong, I'm not knocking all friction rollers. Just the application of this one. Friction rollers are fine for use when its flat and dry, and reasonably clean road conditions. For wet, dirty conditions, and hill climbing, friction rollers are the wrong tool for the job.

you wouldn't take a Porche 911 turbo to go rock cralling in Moab, and you wouldn't take a lifted rock crawler Jeep to race in La Mons.


Like I said, I ride some pretty big hills around here and it works great. I also don't see why you would think you need clean road conditions. I ride on dirt, gravel, pretty much all conditions except wet (It really, really does suck in wet). I will say though, if I intended it to be a true off road bike I would choose a different drive system just because of the wet issue.

I just wish I could get some people on here to try my bike. I think they would be surprised. A local guy with a WE kit that tried it and was shocked. He now wants me to help him build a second bike. Some of you guys with super high power wouldn't be impressed but I only have around $125 in my motor, batteries, and controller. And for me, cheap is kind of the point of having an electric bike.

And actually, Porsche made some pretty good rallye cars. :wink: http://www.autoblog.com/media/2006/07/porsche-959-rally-dakar-dusty-resized.jpg

The issue in the past has been with really cheesy friction systems. It's a low cost way to make an e-bike so companies that made them used crap motors and cheap parts. From what I've seen on the internet, people that make their own friction system tend to go the cheesy route too. It' usually a non-freewheeling roller just hanging off a junk motor.

And don't get me wrong either. I'm just enjoying the conversation, I don't want to get in a big debate over it. I do totally understand why people don't think it would work. It just seems too easy and 'ghetto'. That's ok though, I like being different and most important, cheap. lol
New Tidalforce friction drive build: viewtopic.php?f=28&t=28029

My Friction Drive Outrunner Setup: viewtopic.php?f=28&t=9652&start=330
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Re: Why not friction drive?

Postby etard » Sun Oct 12, 2008 2:37 pm

Great discussion guys! Now, Fechter mentioned a setup that increased the pressure of the roller as torque permitted, that seems like it would solve tire slippage on steep inclines. Does anybody have a pic or patent link that I could see to understand how this works?
Drunkskunk, can you explain further the problem with a matching tread to roller design? I cant wrap my mind around the physics of going over a log or rock, and that shifting the tire to the roller.
That Whizzer setup is out of the question. :shock: Is there a place I can go to see the different roller setups already in use? EVtodd do you have a picture of your setup, and how would you do it different if you had chance with more money ($500 without battery)?
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Re: Why not friction drive?

Postby EVTodd » Sun Oct 12, 2008 2:58 pm

This thread shows a picture of my little setup:

http://endless-sphere.com/forums/viewtopic.php?f=2&t=6822

I'll try to get an updated picture of my bike today. I basically mount that motor setup to a rear seatpost rack. I also have supports that go to the frame that stop it from moving side to side. One of my fears has always been hitting a big bump and having the whole assembly shift to the side resulting in the motor getting stuffed into the wheel.

As far as improving it with more money. I guess the only thing I would change at this point is using an rc motor and controller. I'd rather save the rest of the money for batteries. I'm not sure I could even think of a way to spend $500 on the friction drive part of it. But I also have a couple of small cnc machines in my garage that save me $$$ instead having someone else making the parts.
New Tidalforce friction drive build: viewtopic.php?f=28&t=28029

My Friction Drive Outrunner Setup: viewtopic.php?f=28&t=9652&start=330
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Re: Why not friction drive?

Postby recumpence » Sun Oct 12, 2008 3:27 pm

My buddy with the RC motor friction drive setup has his motor carriage setup in a leading link fasion. With his arrangement, the more torque you pull, the harder the wheel presses into the tire. That increases his efficiency.

Now, think of this, with an RC setup, all you need to do is mount a high torque servo in parrallel with the ESC input and you have a way for the roller to be pushed onto the tire when the throttle is on and it will retract as the throttle is reduced. Heck, it will also increase roller pressure by amount of throttle. :mrgreen:

I think friction drive is a good idea, especially for those who do not have a ton of time for fabrication (or machines to do it).

My buddie's friction drive setup runs 48 mph (big RC motor on 48 volts) and was all made with had tools and Ace Hardware materials.

Oh, he did fight with tire wear untill he "Discovered" simple knurled aluminum as a drive wheel. Problem solved.

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Re: Why not friction drive?

Postby EVTodd » Mon Oct 13, 2008 6:11 pm

Matt,

What are your thoughts on running 2 smaller outrunner motors? I'm thinking about making a dual roller setup just for kicks and giggles. You can get some of the 80 amp or so motors/controllers on ebay dirt cheap. My theory is that with 2 motors it would take a lot of the strain off of the cheap esc's.

I'm wondering if I could get around the same power as my single kollmorgen setup with something like this. Maybe run 2 small rc type batteries to power the motors. Would be a cool, lightweight short range bike (5 or so miles) for running errands close to the house and my short trip to work (yes, I know, I could just pedal that far, but that's no fun). Maybe use a motorcycle throttle running to two slide potentiometers wired to 2 servo testers.

I know you've been warning me about the cheap esc's but it's tempting to try it. I also found a thread on an rc forum about the mystery controllers lasting a lot longer if you pop the heat sinks off and reinstall them making sure they touch all the fets. I guess they don't contact all of them stock.
New Tidalforce friction drive build: viewtopic.php?f=28&t=28029

My Friction Drive Outrunner Setup: viewtopic.php?f=28&t=9652&start=330
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Re: Why not friction drive?

Postby recumpence » Mon Oct 13, 2008 8:47 pm

I would say use two motors into one roller (one motor on the left and one on the right).

It should work fine. I like the logic on easing the controller load!

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Re: Why not friction drive?

Postby etard » Tue Oct 14, 2008 6:04 pm

Those Frenchmen are using some huge motors :shock: ! I think that a clip in mount on my rear triangle(full suspension), with a servo like Recumpence says that will squeeze the motors' rollers together when more throttle is applied would work perfect. Now, if you could just incorporate an anti-slip circuit similar to the ABS system used on even cheap chinese scooters (my 150cc claimed to have abs) you could do away with all the haters :wink: .

The dual motor setup could have several advantages:
1. You could have two different motors that phase in or out, one with high torque, and the other hi rpm efficiency.
2. If one goes out you still have one to get home
3. You could run two smaller battery packs

I am about to take the plunge, but I want to take advantage of the 30% off live.com is doing on ebay. I know castle creations are the best controllers, but what about the Rc Smart combo on ebay Would two of these work?
http://cgi.ebay.com/RC-Model-560-KV-Outrunner-Brushless-Motor-80A-ESC_W0QQitemZ300265958408QQihZ020QQcategoryZ34055QQtcZphotoQQcmdZViewItemQQ_trksidZp1742.m153.l1262

Or one of these
http://cgi.ebay.com/RC-Model-833-KV-Outrunner-Brushless-Motor-80A-ESC_W0QQitemZ270286448116QQihZ017QQcategoryZ34055QQtcZphotoQQcmdZViewItemQQ_trksidZp1742.m153.l1262

Or one of each?
Also, The input voltage is only for 30 volts, what if I tried to put 36, or 48 volts into one of these? the milwaukee 28 volts might work though, huh.
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Re: Why not friction drive?

Postby EVTodd » Tue Oct 14, 2008 6:25 pm

I still say you don't really need the adjustable friction pressure but if you can figure out an easy way to do it it would be cool to have. Traction control on the roller would be fun though. Actually, that might not be that hard to do with a simple encoder setup.

I think I'm going to go ahead and take the plunge too. It's getting cold here and I need a new project anyway. I'll probably use 2 of the same motor as I'm not sure how you would time two different types to work together.

And I'm still going for cheap cheap cheap. I can always upgrade to a castle creations esc later.
New Tidalforce friction drive build: viewtopic.php?f=28&t=28029

My Friction Drive Outrunner Setup: viewtopic.php?f=28&t=9652&start=330
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Re: Why not friction drive?

Postby etard » Tue Oct 14, 2008 7:23 pm

Would you recommend the lower rpm/v motor like the 560 or would you go a little higher? I did some visual measurements, and it seems that I will want a motor with minimal length if I go 2 motors on 1 roller cuz a wide setup will interfere with my heel on the upward stroke while pedalling. Unless, I put the roller underneath the bottom bracket, then I might need to add an extra roller for the chain to go around the right side motor.
I wonder if you gain or lose efficiency with 2 motor, 1 roller as opposed to 2 roller, 2 motor.
Is there any way to amplify the throttle signal and just split it to the 2 controllers. Or can you program the controllers to except different input parameters? I just got my magura throttle, and I love the build quality. Maybe I could use another servo (controlled by the throttle) to two pots. By the time I'm done this thing will have a trigger and a steering wheel, maybe some joysticks, HAHA!!
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Re: Why not friction drive?

Postby John in CR » Tue Oct 14, 2008 8:03 pm

I have a dual motor friction drive that I've yet to mount as it's too wide and heavy with a pair of wheelchair motors. I took 2 of the EV Warrior rollers and inserted them into one larger roller, so the clutch bearings in the EVW roller allow either, both, or neither motor to be in use. I want to swap the motors out for a lighter smaller unit, by using either 2 Kollmorgens with voltage boosted to 48V, or a pair of RC motors. I really appreciate the input in the thread, because now I know over 40mph is ok with friction, and I need to do some homework regarding a rig for variable pressure on the tire.

Going with dual RC motors, it might make more sense to use 2 of those EV Warrior rollers instead of the route I took, since their 1.3" diameter would put you at 38mph at 10rpms. The rollers themselves are some type of hard metal and have a diamond pattern I could never equal.

Regarding wet conditions, I remember 1 member who swears by friction drives and has used a friction drive wet and dry for years and still has the same tire. I think all that's needed is the right roller, though muddy conditions would obviously be a problem.

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Re: Why not friction drive?

Postby recumpence » Tue Oct 14, 2008 8:21 pm

You can just parallel both controllers into a single servo tester/pulse width modulator and they will drive fine. No amplification needed. :)

You will definately want to run one roller with two motors for best efficiency.

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Re: Why not friction drive?

Postby EVTodd » Tue Oct 14, 2008 8:42 pm

John in CR wrote:2 Kollmorgens with voltage boosted to 48V, or a pair of RC motors.


John, I've talked to a couple of people about dual Kollmorgens but I would personally just go with higher and higher voltages until I was happy with the power. 2 Kollmorgens both with external controllers would start to get expensive. I will say though, Kollmorgens do have a nice amount of torque and 2 would really be a kick.

Matt, good to hear that you can drive 2 controllers off of one servo tester. In that case I'll probably go with another cheap hall throttle with a voltage regulator to power it.
New Tidalforce friction drive build: viewtopic.php?f=28&t=28029

My Friction Drive Outrunner Setup: viewtopic.php?f=28&t=9652&start=330
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Re: Why not friction drive?

Postby etard » Tue Oct 14, 2008 9:07 pm

OK, I'm pulling the trigger.
I'm getting two of these: http://www.castlecreations.com/products/phoenix_hv_series.html

Two of these:http://cgi.ebay.com/RC-Airplane-Model-560-RPM-V-Outrunner-Brushless-Motor_W0QQitemZ300258577217QQihZ020QQcategoryZ34055QQtcZphotoQQcmdZViewItemQQ_trksidZp1742.m153.l1262

Now, Do I need two seperate batteries, or will one split to both controllers?

I think I will try the single roller, should I mount those motors directly to the roller, or use a freewheel setup between motor and roller in case the motors are not in sync? Should I be concerned about this?
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Re: Why not friction drive?

Postby John in CR » Tue Oct 14, 2008 10:25 pm

EVTodd wrote:
John in CR wrote:2 Kollmorgens with voltage boosted to 48V, or a pair of RC motors.


John, I've talked to a couple of people about dual Kollmorgens but I would personally just go with higher and higher voltages until I was happy with the power. 2 Kollmorgens both with external controllers would start to get expensive. I will say though, Kollmorgens do have a nice amount of torque and 2 would really be a kick.

Matt, good to hear that you can drive 2 controllers off of one servo tester. In that case I'll probably go with another cheap hall throttle with a voltage regulator to power it.


Todd

I already have 3 Koll's doing nothing, so it's just a matter of two 48V controllers that can handle the commutation rate, so for me it's about the cheapest thing I could do, especially since I already have the drive roller and housing that I made easily adaptable to accept most any motor pair.

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Re: Why not friction drive?

Postby EVTodd » Tue Oct 14, 2008 10:29 pm

Etard, I have to admit, you've lost me now.

The real reason I want to try two motors and controllers is because I'm cheap and I'm hoping to spread the amp load to avoid blowing one up. If you're going to get the castle creations controller (or two of them for big $$$) why not just use one motor? I'm sure that controller can handle the power from what Matt has said.

John, I hear ya. I tend to use whatever I have sitting around the garage too. If you do ever try the dual koll setup please let me know how it works.
New Tidalforce friction drive build: viewtopic.php?f=28&t=28029

My Friction Drive Outrunner Setup: viewtopic.php?f=28&t=9652&start=330
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Re: Why not friction drive?

Postby etard » Wed Oct 15, 2008 5:10 pm

For me the money isnt so much the issue, and all I hear is castle creations, nothing else works right. I want dependability.

Anywayz, I am having problems with mounting the roller setup because of pedal clearance. My remedy:

Attach the motor assembly to 2 carbon fiber rods that run to a mount at the rear dropout. The system will free float on top of the tire. I will use a conical roller (fat at edges, skinny in the middle) to keep it from walking side to side. I can set the axis where ever I want, but if I put it outside the axis it will act as Matts leading link idea and draw the motor into the tire for more traction. If you have ever seen a Softride bicycle you know that carbon fiber is torsionally stiff, light and strong. And the best part is that I will be able to remove the whole system (besides the mounts) with four screws in 1 minute.

Now, will someone send me a link for carbon fiber?
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Re: Why not friction drive?

Postby EVTodd » Wed Oct 15, 2008 5:27 pm

etard wrote:I will use a conical roller (fat at edges, skinny in the middle) to keep it from walking side to side.


I like that idea a lot actually, You could even machine it to kind of match the shape of the tire. The only problem I can see is that it would be impossible to knurl a shape like that (at least I don't know how to do it).

You might be able to find some carbon fiber stuff at http://www.mcmaster.com. I get sheets of it there from time to time.

etard wrote:For me the money isnt so much the issue, and all I hear is castle creations, nothing else works right. I want dependability.


Gotcha. But I still don't see the reason for two motors if money is no object. Some single outrunners can put out crazy power by themselves.
New Tidalforce friction drive build: viewtopic.php?f=28&t=28029

My Friction Drive Outrunner Setup: viewtopic.php?f=28&t=9652&start=330
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Re: Why not friction drive?

Postby recumpence » Wed Oct 15, 2008 6:59 pm

The only problem with a conical roller is friction. If it too closely matches the tire shape, you will have huge friction. I would make it flat with side dams (large washers) as flanges to keep it on the tire.

For CF tube, go with McLean Quality Composites. For flat panels, go with DA Graphite.

I have been working with carbon fiber for years. I have gone through tens of thousands of dollars worth. Those are the best suppliers I have ever found.

Oh, pulltruded CF tube is not torsionally strong. It twists alot. I use it for helicopter tail booms. You really need woven CF tube for torsional rigidity. However, it is very difficult to find woven CF tube in small diameters.

If you have any specific CF questions, PM me and we can talk. I know how to wet layup (without vacuum bag), I do CNC CF cutting, and I know alot about joining CF with various materials.

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Re: Why not friction drive?

Postby etard » Wed Oct 15, 2008 7:29 pm

Evtodd,
See thats what I was thinking too, just piggyback a single motor with either a belt drive (ha, I get another free reduction in gearing!), or with direct gears (noisy?).

Then I thought about the loss of efficiency of any drive......
Will the extra reduction make up for it in torque?
Or is a dual motor system already in theory less efficient because of syncing issues?

But now I think about how the contour of one of the AXI outrunners between those of the roller I could make it look like a shark fin. Beware, a Landshark!! Haha!

Matt,
Thats good news, I want to do simple flat bar, that operates like the leaf spring in a car. Will you recommend a thickness and width for use on 26 inch wheel?
Remember my setup is detachable, so I am not worried about freewheel friction. With that in mind, does your previous statement concerning friction still stand?
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Re: Why not friction drive?

Postby EVTodd » Wed Oct 15, 2008 7:30 pm

recumpence wrote:The only problem with a conical roller is friction. If it too closely matches the tire shape, you will have huge friction. I would make it flat with side dams (large washers) as flanges to keep it on the tire.


That is a good point about additional friction. I will also say that I've never had a roller even try to come off of a tire yet. I have braces from my mount to my frame but like I said before, that's just to make sure it won't move over a large bump or pot hole. My first try at friction drive was mounted to a cheap seatpost rack with no extra support and it never moved.

If you use an EV Warrior roller and leave a little room for movement it shouldn't be an issue since it floats on a roller bearing it pretty much self centers.

I say start with something simple and see how it works for you. I think you'll be surprised (yes, I know I keep saying that) at how good it works without getting overly complicated with the setup.
New Tidalforce friction drive build: viewtopic.php?f=28&t=28029

My Friction Drive Outrunner Setup: viewtopic.php?f=28&t=9652&start=330
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Re: Why not friction drive?

Postby recumpence » Wed Oct 15, 2008 8:01 pm

I would say 4mm would be a good thickness. Maybe even 5mm. But, anything less than 4mm thick would be wet noodle at a foot long unless you made the leaf really wide.

I love the friction drive idea. I think you may find lot of things that work well and a few that won't. Just keep working at it.

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Re: Why not friction drive?

Postby etard » Thu Oct 16, 2008 5:50 pm

So I have one RC SMART 560 KV motor, 80amp ESC, and I've contacted DA Graphite about what I need strengthwise (carbon fiber is relatively cheap). I have some gnarled bmx pegs coming, not sure of the diameter. I went ahead and also ordered some Goped drive spindles which come in sizes .600 inch to .800 inch. Those are available with grit, but I just got normal (on sale for $5). I also got a Maxxis training tire(for stationary training rollers) that is supposed to be long lasting.

My friend that works for a titanium medical instrument manufacturer says he can CAD and waterjet both the axle mounts and the motor housing (I wonder how much that would cost in titanium). The beta will be aluminium, but its wide open after I get good results.

I dont know how to calculate the belt drive because I dont know what roller will work in which diameter it will be available in. I was wondering how a belt drive acts above 10,000 RPM, does anybody know if this is too fast or noisy for belts? Also, I'm not sure this motor will put out enough power for what I am looking for. Since that controller only accepts >30 volts, I am thinking about ordering two Milwaukee (28 volt) batteries, with 2 chargers that would give me an hour long recharge, with a total system weight of under 10 pounds. It should be one of the first entries into the bantum weight class some are talking about.
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Re: Why not friction drive?

Postby recumpence » Thu Oct 16, 2008 6:25 pm

Most toothed belts run fine up to 20,000 RPM. I run mine at 6,000 RPM. Typical rule of thumb is 20,000 rpm for fine pitch, 10,000 rpm for course pitch.

Belts are generally silent unless they are really wide.

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Re: Why not friction drive?

Postby EVTodd » Thu Oct 16, 2008 6:32 pm

Etard,

If you get a chance check out the EV Warrior roller. It's by far the easiest way to get a freewheeling setup (and you really have to have a freewheeling roller imo). You can pick them up on Ebay 2 at a time for very little money.
New Tidalforce friction drive build: viewtopic.php?f=28&t=28029

My Friction Drive Outrunner Setup: viewtopic.php?f=28&t=9652&start=330
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