Friction drive outrunner setup. New DJ bike.

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EVTodd   10 kW

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Re: Friction drive outrunner setup. New DJ bike.

Post by EVTodd » Jul 25 2010 6:52pm

I finally got the bearing and sleeves out of one of my ev warrior rollers. The bearing was a VERY tight press fit. The good news is that it is exactly the same clutch bearing VXB sells: http://www.vxb.com/page/bearings/PROD/Kit8658 same part number and everything.

Not a bad price. Still more expensive than what the whole ev warrior roller was when they were surplus.

That's actually one of the things holding me back from making these. I'm afraid people just won't want to pay an appropriate amount for friction drive components. Heck, the bearing is $10, the hardened shaft will be around $5, and I have yet to get quotes on having the sleeves hardened. And that's before the machine work, price of stock, etc... I can see a roller easily being $40 or $50 before it's done. Man, I wish I would have snagged all of the ev warrior rollers when I had a chance.

Now making them in aluminum would be a different story but they're not going to last anywhere near as long. Maybe I'll whip up a plain steel one and see how long it lasts. I have a couple of different ideas for rollers I want to try anyway.
New Tidalforce friction drive build: http://endless-sphere.com/forums/viewto ... 28&t=28029

My Friction Drive Outrunner Setup: http://endless-sphere.com/forums/viewto ... &start=330

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Re: Friction drive outrunner setup. New DJ bike.

Post by mani9876 » Jul 26 2010 3:16am

Hello!

I have seen that there are some different one way clutch bearings, for the same shaft size like these two:
http://www.vxb.com/page/bearings/PROD/Kit8239
http://www.vxb.com/page/bearings/PROD/12mm/Kit7646

One is the HF1216 and the other is the HFL1226, I only see the difference theat the HFL1226 is longer, and on the border they have normal needle bearings, so that the shaft will slide on this, when the motor doesn't turn but the wheel do, is that right?

So am I right, that the HFL1226 are much better to use for us?

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Re: Friction drive outrunner setup. New DJ bike.

Post by spinningmagnets » Jul 26 2010 12:24pm

Mani, I don't know, but your guess makes sense to me. And in my opinion, the more rollers the better (to spread out the load).

Todd, using a one-piece roller would avoid future problems with sleeve-to-roller fitting. But then, if you want to develop a reputation for making a product that is long-lasting, it would seem that the final driving surface should be hardened steel.

For any type of production volume, I think you'd be best served by maching the ID of a soft steel roller (and also shaping the traction surface) for the proper one-way bearing press-fit, and then having them hardened. I personally like removeable sleeves, but after some thought, the average customer shouldn't be given too many choices.

The tires I bought recently have a round cross-section (for better cornering grip on unavoidale wet turning), so Larrys "self-centering" concave roller is something I really like. But, it shouldn't be difficult to carry several styles of roller? (customers are often fickle and stubborn,...sell what they want)

I strongly suggest you use two of the one-way bearings (rather than one bearing and a 3/4-length bushing). From what I've seen the shaft will slide in and out of the bearing ID easily.

Some people will always be willing to just pay a high price for a complete plug-and-play drive unit. Others can construct a drive unit with a hacksaw and drill, but can't machine the difficult part. I am interested in someone producing the one-way rollers at the very least. Better you than me, but I will make a few if you don't. (though I am low-production, and expensive).

I will be happy to sell "Todd drives" to the local college students and soldiers (Manhattan and Ft-Riley, central Kansas). I can purchase entire drives from you, or just the one-way rollers if you like.

Edit: what is the best interference-fit for something like this (0.005")? if all unassembled parts are room temperature? Roughen-up the OD of the bearing and the ID of the tube...heat the tube to expand it, and then insert?

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Re: Friction drive outrunner setup. New DJ bike.

Post by spinningmagnets » Jul 26 2010 8:20pm

I went to the local hardware store with one of these bearings and my caliper, and the bearing would not lock-up on shaft diameters of 0.495" and smaller. On shafts of 0.496"-0.500" it has a suprising amount of grip. Found one that was 0.503" and the bearing wouldn't even slide on. The one-way bearing OD's are 0.750" right on the nose.

Concerning me using a split-bushing to take up the slack in supplier dimension variations, when factoring in the shipping costs, its cheaper for me to buy tubing nearby at retail prices. I looked at brass pipe from the plumbing section of the local hardware store, and the wall thickness was roughly 0.100"-0.110"

That would give me an OD of bearing/bushing of 0.950", which could be shaved down to an interference-fit to match the ID of a steel roller (or in my case, an Al-roller with separate steel sleeve?). So, I'm looking for roller stock with an ID of 0.850"-0.900".

Somewhere a few pages back is a post about making hard plastic urethane rollers from car-suspension bushings. Those could have their ODs cut to a concave shape, and an aluminum roller could be shaved to an OD that the urethane could slide onto?...

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Re: Friction drive outrunner setup. New DJ bike.

Post by spinningmagnets » Jul 26 2010 8:25pm

Todd, concerning interference-fit, what is the OD of the roller that you pressed the bearing out of? Since the bearing I have (the exact same part number) has a 0.750" OD on the nose, I would assume the tube ID to be 0.748" or less?

I would assume that EV-Warrior had experimented with several fits, and had already settled on the right amount of tension?...

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Re: Friction drive outrunner setup. New DJ bike.

Post by EVTodd » Jul 27 2010 10:46am

spinningmagnets wrote:Todd, concerning interference-fit, what is the OD of the roller that you pressed the bearing out of? Since the bearing I have (the exact same part number) has a 0.750" OD on the nose, I would assume the tube ID to be 0.748" or less?

I would assume that EV-Warrior had experimented with several fits, and had already settled on the right amount of tension?...
Hmmm, my bearing's od measures .753 and the id of the roller is .75. Doesn't sound like much but that's a crazy tight press fit. Now you have me worried. I'm hoping the bearings have a consistent diameter. I would sure think so.

As far as machining the rollers... Yup, you would have to make them before they're hardened for sure. I wouldn't want to try to knurl a hardened roller. I like my lathe too much. lol :D

I also did some research and the brass bushings are actually there for a reason. From what I have been reading, clutch bearings won't work very well (if at all) if they are held tight on the shaft in one location. The brass bushings are machined a tad larger than the shaft so that the roller has a little float in it both directions. It makes sense if you read up on how clutch bearings work. You'll notice that your bearing also has a little play in it on one side.

The only reason for using two clutch bearings would be if you're having a problem with them holding the amount of power your motor is producing. I'm still surprised they hold up as well as they do. I think they're only rated for around 5.8 ft/lbs of torque.
New Tidalforce friction drive build: http://endless-sphere.com/forums/viewto ... 28&t=28029

My Friction Drive Outrunner Setup: http://endless-sphere.com/forums/viewto ... &start=330

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Re: Friction drive outrunner setup. New DJ bike.

Post by spinningmagnets » Jul 27 2010 6:01pm

The online-metals website states that their tubing (Al and also Steel) dimensions are consistent within a 0.011" variance. If the press-fit has to be a fairly precise 0.002"-0.003", then I would definitely need to add a custom-shaved split-bushing, as I will soon have some type of OD shaving capability for brass/aluminum.

Of course, with your experience and lathe availability, you could make a one-piece steel roller with the proper ID interference fit, with whatever size parts you had been shipped.

In view of shipping costs for bushing stock, it would be cheaper for me to buy retail brass pipe (from the plumbing section of the local hardware store) with a wall thickness of 0.100"-0.110", then each bushing would cost me about $2 (shave to proper wall-thickness, chop to length, then add a split). The 0.250"-wall Al-tube would be $7 a foot (plus shipping and tax).

If you begin selling them , I will probably just make only one of the style I'm interested in for myself. How soon before you think you might have a few for sale?

edit: a note, the online metals website states that their "pipe" is made with the ID being closer to the nominal size (rated for flow, regardless of OD), and the "tube" OD is made closer to the nominal size (must fit OD connectors regardless of flow).
Last edited by spinningmagnets on Jul 29 2010 4:53pm, edited 1 time in total.

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Re: Friction drive outrunner setup. New DJ bike.

Post by EVTodd » Jul 27 2010 10:17pm

spinningmagnets wrote:The online-metals website states that their tubing (Al and also Steel) dimensions are consistent within a 0.011" variance. If the press-fit has to be a fairly precise 0.002"-0.003", then I would definitely need to add a custom-shaved split-bushing, as I will soon have some type of OD shaving capability for brass/aluminum.

Of course, with your experience and lathe availability, you could make a one-piece steel roller with the proper ID interference fit, with whatever size parts you had been shipped.

In view of shipping costs for bushing stock, it would be cheaper for me to buy retail brass pipe (from the plumbing section of the local hardware store) with a wall thickness of 0.100"-0.110", then each bushing would cost me about $2 (shave to proper wall-thickness, chop to length, then add a split). The 0.250"-wall Al-tube would be $7 a foot (plus shipping and tax).

If you begin selling them , I will probably just make only one of the style I'm interested in for myself. How soon before you think you might have a few for sale?
Good question. I found 2 local shops that do heat treating. I need to contact them to see what kind of quantities they will work with and what kind of steel they suggest for this application. I have been working with aluminum for many years but steel is kind of new to me.

Once I get everything worked out I should be able to make a batch pretty quick. I could probably make 50 a day once I get going. My main concern is still pricing and I have my doubts about how many people are really really interested in friction drive. There are a few people on here that seem excited about it but it appears to only be a handful at best.
New Tidalforce friction drive build: http://endless-sphere.com/forums/viewto ... 28&t=28029

My Friction Drive Outrunner Setup: http://endless-sphere.com/forums/viewto ... &start=330

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Re: Friction drive outrunner setup. New DJ bike.

Post by etard » Jul 28 2010 12:17am

Todd,
I'm looking for something more like the concave sintered roller that is 3/4 the size of the EV Warrior roller. But now that you mention the brass bushings as a "guide" for one way bearing to lock onto the shaft, I'm not sure this is best. Maybe there is a reason the warrior roller has to be the size it is even though the roller only contacts the tire in a 3/4" section. Is that what you are finding?
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Re: Friction drive outrunner setup. New DJ bike.

Post by EVTodd » Jul 28 2010 11:20am

etard wrote:Todd,
I'm looking for something more like the concave sintered roller that is 3/4 the size of the EV Warrior roller. But now that you mention the brass bushings as a "guide" for one way bearing to lock onto the shaft, I'm not sure this is best. Maybe there is a reason the warrior roller has to be the size it is even though the roller only contacts the tire in a 3/4" section. Is that what you are finding?
I think it needs to at least be big enough for the bearing and a couple bushings. I'm not sure the bushings need to be quite as big as the ones they used but I would keep around that range. The bushing are a tad over 1/2" in length if I recall.
New Tidalforce friction drive build: http://endless-sphere.com/forums/viewto ... 28&t=28029

My Friction Drive Outrunner Setup: http://endless-sphere.com/forums/viewto ... &start=330

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Re: Friction drive outrunner setup. New DJ bike.

Post by Jamzz » Jul 29 2010 6:50pm

Todd,


I'm keeping my fingers crossed that you get a batch made. I think your friction drive out-runner setup is awesome. I would love to buy one and try to mimic your success.

Cheers

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Re: Friction drive outrunner setup. New DJ bike.

Post by etard » Jul 30 2010 2:26am

Now here's an idea:

What if you concaved one half of the roller and sintered or gnarled that side, which would be smaller in diameter than the other side which would be left intact. Now I'm thinking a rack mounted design that could be shifted over between the two roller profiles, much like a typewriter, effectively giving you a two speed transmission based on different roller diameter. My main concern would be whether it would be worth it, and how much low end torque you would actually gain. But as you have stated earlier, you're practically doing wheelies as it is. :mrgreen: Maybe this could allow you to use a higher KV motor and still have the same great acceleration. A much easier way might be to just use a tiny roller, like the scooter roller I have that is .778" diameter stuck directly on the shaft for hill climb , next to the Warrior roller. Use one of those hi torque servos for movement between the two. Or even have a cone shaped roller with a servo tester potentiometer knob, where you can infinitely vary the roller diameter while you vary roller speed with the throttle! Too complicated? I know, but one can always dream. 8)
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Re: Friction drive outrunner setup. New DJ bike.

Post by spinningmagnets » Jul 30 2010 9:33am

etard, a few pages back, someone suggested some type of "rocker arm" that had the motor in the middle, HTD belts to a small roller on one tip, and a larger roller on the other. Perhaps direct-drive (like todds) on one roller, and a single belt to the second speed? Which design are you the most serious about making? I don't think many people would buy those, but a 2-roller/2-speed is fun idea.

The more I consider other ideas, the more I come back to Todds original design. 36V cordless drill batteries, 30-MPH, small enough and light enough to pull off of the bike and carry inside/upstairs.

Currently investigating polyurethane bushings and longboard wheels (skateboard wheels , 2-1/2" wide) for an optional roller...

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Re: Friction drive outrunner setup. New DJ bike.

Post by EVTodd » Jul 30 2010 10:29pm

Jamzz wrote:Todd,


I'm keeping my fingers crossed that you get a batch made. I think your friction drive out-runner setup is awesome. I would love to buy one and try to mimic your success.

Cheers
Thanks Jamzz. It's still possible that I'll make a few of these from time to time. In fact, I'm finally making my girlfriend's drive so I'm going ahead and making two more. I'm not sure what I'm going to do with the extras yet but we'll see.

Etard, I'm with you (you too spinningmagnets)... I've tried to think of a million different ways to improve the drive from different kinds of rollers that have varying diameters across them to using a multi-speed hub as a roller (actually not my idea but I thought about trying it). For me it just came down to what I wanted from an e-bike. 30 mph was more than enough for me. I already had the ev warrior rollers so I just matched a motor to the bosch fatpacks I found cheap. It's so much easier to do it that way.

Since I'm making a few drives I decided to tear mine apart to see how everything looked after all the miles I put on it. Everything looked great. The sliding mount had very little wear even though I have to admit I've been lazy about greasing it from time to time. In fact, I only did once and that was when I assembled it.

The one thing I was afraid to look at was the motor but it looked brand new inside. The original bearings still feel great and the epoxy I added seems to be holding just fine. I guess you can use cheap motors if you do it right :D . Seriously, I think these TowerPro motors possibly have the worst method of holding magnets out of all the outrunners I've seen and they're still just fine. I'm not chalking it up to luck any more. If you do it right you can use cheap motors. Heck I wouldn't have been THAT upset if I had to replace this motor right now. I've put a lot of miles on it already but it sure looks like it's ready for more. Not bad for 48 bucks.

Sorry to go on and on but it made me happy.
New Tidalforce friction drive build: http://endless-sphere.com/forums/viewto ... 28&t=28029

My Friction Drive Outrunner Setup: http://endless-sphere.com/forums/viewto ... &start=330

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Re: Friction drive outrunner setup. New DJ bike.

Post by etard » Jul 31 2010 3:53pm

Good news Todd, it is amazing how good these motors are, ESPECIALLY at that price. I mean, you add I'm the other materials and fadteners and your drive prolly comes in under $100. Hubbies can't compete with that, and certainly chain driven isn't even close!

You are completely right about keepin it simple, I just like to brainstorm and see if we can't come up with the perfect solution for speed, acceleration, torque, and efficiency.

Now your motor, has it seen much rain or dirt or even mud? Do you blow or flush it out every so often?
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Re: Friction drive outrunner setup. New DJ bike.

Post by EVTodd » Jul 31 2010 3:58pm

etard wrote:Good news Todd, it is amazing how good these motors are, ESPECIALLY at that price. I mean, you add I'm the other materials and fadteners and your drive prolly comes in under $100. Hubbies can't compete with that, and certainly chain driven isn't even close!

You are completely right about keepin it simple, I just like to brainstorm and see if we can't come up with the perfect solution for speed, acceleration, torque, and efficiency.

Now your motor, has it seen much rain or dirt or even mud? Do you blow or flush it out every so often?
No rain or mud but lots of dust. I never took it apart or cleaned it until last night. Just gave it a quick blast of air. It wasn't really that dirty. I was kind of surprised since I've been riding some dirt trails quite often lately. most of my motor is inside my panniers though so maybe that kept some of it out. My sliding mount had some dust build up, not bad enough to hurt anything, but I should clean and re-grease that from time to time.
New Tidalforce friction drive build: http://endless-sphere.com/forums/viewto ... 28&t=28029

My Friction Drive Outrunner Setup: http://endless-sphere.com/forums/viewto ... &start=330

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Re: Friction drive outrunner setup. New DJ bike.

Post by EVTodd » Aug 03 2010 10:43am

Ok... A little update on the rollers.

I have 20 hardened shafts with machined ends (like the ones in the ev warrior roller). I'm now going to do a little experimenting making an aluminum roller with a clutch bearing inside that uses standard size sanding barrels around it. I've found them down to 36 grit which is very coarse and should give great grip.

I've never been a big fan of using a sleeve around a roller since I don't want anything that might slide around on it (of tear apart) but I think it may just work if the barrel has a tight enough fit. Maybe... I'm hoping I can make it work without using glue or adhesive strips. Maybe a straight knurl on the aluminum roller.

I do think it would be nice to be able to change out the roller surface if needed. Especially with something cheap and readily available. Any thoughts?
New Tidalforce friction drive build: http://endless-sphere.com/forums/viewto ... 28&t=28029

My Friction Drive Outrunner Setup: http://endless-sphere.com/forums/viewto ... &start=330

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Re: Friction drive outrunner setup. New DJ bike.

Post by spinningmagnets » Aug 03 2010 5:20pm

Just saw these today out of polyurethane for $6 each, many different sizes. They are keel-rollers for a boat trailer.

Image

I think I understand what LFP was saying, and if I'm correct, I agree with him on concave rollers. The center of the roller is moving at the speed of the center of the tread (of course). The sidewalls of the tire are moving at the same speed as the center of the tread...so...the outer edge of the concave shape is a larger diameter than the center of the roller, meaning that the outer edge would be travelling at a faster speed than the center.

This would mean that if the concave shape was in full contact with all of the rounded cross-section of the tire, the sidewalls would be getting "scrubbed" by the outer edges of the concave roller. Good for traction, bad for sidewall wear.

Todd, your original cylindrical roller on a relatively flat cruiser tread is a proven combination, however...

Since your drive has the feature of sliding deeper onto the tread when it encounters resistance, a capstan shape (meaning a cylindrical center with flared-out sides) would only have the center of the roller driving the tire most of the time, and the edges would only engage and "scrub" the sidewalls on rare occasions, only when you needed the extra traction?...

I am only pursuing this line of thinking because I believe some customers will strongly desire a rounded tread profile option...

Image
Last edited by spinningmagnets on Aug 10 2010 2:04pm, edited 1 time in total.

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Re: Friction drive outrunner setup. New DJ bike.

Post by EVTodd » Aug 03 2010 5:53pm

I've never thought the concave roller idea was bad. In fact, I really like the idea that it would help keep everything centered. Of course you would REALLY have to make sure your mount and alignment was perfect or you would be scrubbing the tire all the time. Keep in mind that very few rims are perfectly straight. I'm sure that's the reason the ev warrior roller can float from side to side.

My main issue with it is that it would be hard to have a traction surface made into a concave shape. Knurling is out. The stippling idea is great but I'm not sure how hard it would be to do on steel.

You would also have to make different rollers for different tire shapes.

I was thinking about my sanding sleeve idea again. I'm not sure that's going to work well on an aluminum roller unless it's glued on. I seem to recall reading rubber cement worked great to hold the sleeves on aluminum. Hmmm, something to try anyway I guess.
New Tidalforce friction drive build: http://endless-sphere.com/forums/viewto ... 28&t=28029

My Friction Drive Outrunner Setup: http://endless-sphere.com/forums/viewto ... &start=330

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Re: Friction drive outrunner setup. New DJ bike.

Post by EVTodd » Aug 03 2010 7:05pm

Ok, I've done some searching and I'm not quite finding an answer...

I'm going to try mounting hall sensors to one of my outrunners. I think I have a pretty good understanding on how to do it but I have a question about the controller I'm going to try.

I have the old model e-crazyman 6-fet, 36 volt controller. Here's a pic:

Image

The sticker that had it's specs on it is long gone but if I recall it was rated for 350 watts and 20-25 amps (I used it with my old Kollmorgen setup).

My question is. Will this controller work ok since it's only rated for 350 watts? I know people have said they use this controller with outrunners. Are they modding them? More solder on the shunt?

I'm sure I'll be asking 100 more stupid questions during this little experiment. This controller has a pedal assist function that I thought would be fun to try which is why I'm messing with it.
New Tidalforce friction drive build: http://endless-sphere.com/forums/viewto ... 28&t=28029

My Friction Drive Outrunner Setup: http://endless-sphere.com/forums/viewto ... &start=330

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Re: Friction drive outrunner setup. New DJ bike.

Post by mwkeefer » Aug 03 2010 7:10pm

That controller is an unknown but some things (thankfully) remain constant - providing you get the halls positioned correctly, then yes it should work with your outrunner...

It will be a good test controller for no load atleast :)

Note: The ebike type controllers like that seem to prefer and operate much more efficiently with a Wye terminated motor than a Delta, not sure what your motor defaults as but...

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Re: Friction drive outrunner setup. New DJ bike.

Post by etard » Aug 03 2010 8:52pm

Hey Todd, hopefully gwhy or Thud will chime in ( maybe pm them) they seem to be pushing these 6 FETs to the brink and also using them on RC motors. Although, Thud might have a differing opinion seeing how he blew his easily. I think Knuckles has posted some good info on modding the shunt. If you make a successful hall sensor arrangement, I would be interested, cuz I believe we have the same motor, and I've always liked the size of those.

I never thought about the wobble of an untrue rim, that is a valid point on the ev roller sized for wander side to side. I guess it would be a maintenance issue to have a concave roller, but having a nice straight rim all the time could be a plus. :D

In order to get the sand paper to hold onto the roller maybe you could gnarl the roller? Or maybe some heat shrink tubing, if you could find it that big. I wonder if they make heat shrink bands?
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Re: Friction drive outrunner setup. New DJ bike.

Post by spinningmagnets » Aug 10 2010 1:54pm

Todd, been searching constantly the last few weeks. I want to make something that I can sell to local college students, and I believe I should be driving what I am selling. I cannot improve on what you have engineered, so, much of my searching has centered on copying something similar to EV-Warrior roller with the freewheel-bearing inside it. I found several individual used units on the web, but no supplier for future builds.

I was frustrated upon hearing that your bearing was 0.753" OD, and the three bearings I ordered were precisely 0.750" on the nose. But now, after talking to local machinists, that is too large a discrepancy to be an accident. An interference-fit must have a vital set of precise dimensions (taking into consideration the elasticity of the metals involved). Too loose or too tight, and you will have problems.

I am now convinced that EV-Warrior ordered those bearings as a 0.753" OD, so that the hole in the rollers can be machined to 0.750" ID. Cheaper to special-order a drawn-cup sizing swage for a custom bearing OD, than to special order a 0.747" drill. (Also drills wear out and must be replaced, an OD-swage will last a very long time). The drilled rollers were likely heated to expand them, then the bearing+bushing would easily slip in. Once cooled, the pieces would be a in a very tight grip.

I am now committed to using a 1/2" drive shaft, a solid and removable hardened-steel roller fixed to a live shaft, and an external belt-drive using 5mm-HTD (motor on top), with a freewheel bearing inside the HTD pulley ID.

I may end up with nobody else interested (not a problem), but "if" there is any interest, there will be no parts supply problems. The drive I am envisioning will be easy to copy, however it will certainly be larger, heavier, and uglier than yours! Thanks for your help and inspiration (also thanks to Kepler and Grinhill)...

I will start a new thread when I have something to show. (edit: aug 12th, this will be useful as an odd-roller and motor test rig, not good for sale to the public)
Last edited by spinningmagnets on Aug 12 2010 11:53am, edited 1 time in total.

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EVTodd   10 kW

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Re: Friction drive outrunner setup. New DJ bike.

Post by EVTodd » Aug 10 2010 2:40pm

Hmmmm. That´s strange. Now I want to take another roller apart to measure it´s bearing. I looked up the specs and sure enough it´s supposed to be .75. Hopefully they don´t vary that much from batch to batch.

I really doubt ev warrior had the bearings special made. That would cost a fortune. Having drills (or a reamer in this case) custom made isn´t really that expensive (not around here anyway).

Most places would actually drill it out to a smaller size then bore it to the correct dimension. A drill would never be accurate enough for a press fit even when it´s new.

I actually hate making anything that has to have a press fit. Even room temperature while you´re machining it can make a difference.
New Tidalforce friction drive build: http://endless-sphere.com/forums/viewto ... 28&t=28029

My Friction Drive Outrunner Setup: http://endless-sphere.com/forums/viewto ... &start=330

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spinningmagnets   100 GW

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Re: Friction drive outrunner setup. New DJ bike.

Post by spinningmagnets » Aug 10 2010 9:07pm

Perhaps you're right. I believe It would be easy (but time-consuming) to make split-bushings (as an OD spacer) that have been shaved to any wall-thickness needed to mate up the press-fit in-between a needle-bearing shell OD and the ID of a purchased roller.

One of my concerns was that when a roller becomes worn (or someone simply wanted to try a different roller diameter or type), changing rollers would require pressing out the bearing from one and re-pressing it into the other. Also, the "other" roller may not have the same precise ID as the first one. Replacement rollers would each require their own one-way bearing and custom split-bushing, raising the price.

It may sound like a minor concern, but I believe this is one of several reasons potential customers have shied away from a friction-drive (no matter how well engineered it may be).

I have seen computer printers sold at very low prices, only to find that the ink cartridges are pricey. Whether a customer should or should-not be worried about a hardened steel roller wearing out, I very much want to advertise that the solid rollers I stock will slide onto the shaft very easily, and the rollers are very low-priced.

If I contracted a local machinist to make rollers from soft steel, have them bored to precisely press-fit a box of needle-bearings (sorted by OD size), then have the rollers hardened, also have him make the bushing for the other end...I would have to order 30 of them (cash up front) and charge customers $30 each to make it worth my while. The thing that really sinks this potential plan is that I can't count on the bearing ODs being consistant. My three are 0.750" and yours is 0.753"

I want to re-emphasize that if I only wanted one for myself, I'd buy a couple of EV-Warrior rollers from Ebay and copy your drive. I've pondered several dozen potential changes that all came up short in one way or another, and your current version continues to remain simply brilliant...

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