50 mph friction drive? Possible or just impractical

[DesignerDan]

What do you think? I'm not talking about accelerating power. Just a friction drive that could sustain 50 mph. Think it's practical or am I wasting my time?

[neptronix]

tire shredder, is what i'm thinking.

[Bluefang]

Well some guys are hitting 30+mph with just a 63-74 sized motor so i would think its easily possible with a 80-100. I remember seeing some videos on youtube of someone using a C80-100 motor and he was going damn fast.

http://endless-sphere.com/forums/viewto ... er#p430334 and here it is

[Dauntless]

So you need Rearengine in here giving an update on his.

[adrian_sm]

[spinningmagnets]

For a friction drive (FD) it doesn't matter what diameter tire you have. Roller circumferential speed is your road-speed. I agree for 50-MPH you'll have to start with the 80mm motors. The low 130-kV of the 80-100 is your best bet. So, lets do some math.

Since the diameter is roughly 80mm, then times it by 3.14 gives us an approximate circumference (one revolution) of 251.2mm

You want 50-MPH when loaded on level ground, so it would be very roughly 65-MPH when unloaded with the tire in the air (just to find the ballpark for now).

Gotta be 10 ways to figure this, how about: 65-MPH = 104.6 kilometers per hour, also a kilometer is 1,000 meters, so, 104,600.0 meters per hour, or, 104,600,000mm per hour.

One volt will get the 130-kV motor (130 X 251.2mm per minute)...= 32,656mm per minute...X 60 = 1,959,360mm per hour.

So, you want to travel 104,600,000mm per hour with a motor that will produce 1,959,360mm per hour (per volt)...= 53.4 volts

(for 180-kV = 45,216mm per minute...X 60 = 2,712,960mm per hour...= 38.6V...which is really too low for the kind of wattage you need).

If you use the type of RC controller (ESC) that this motor is designed for (Castle Creations HV-160), the most voltage I'd recommend is a 44V LiPo pack(42-MPH?) . In order to use a voltage from 48V up to 100V, you would have to add sensors (halls or optical) to the motor, which would allow you to use a Lyen E-bike controller.

You will need Moped tires, because bicycle tires will fly apart at 50-MPH...maybe not immediately, but soon enough.

[rearengine]

DesignerDan

Hey there ... I believe 50 mph F/D is very possible ... My HILLHELPER goes 28 mph on just 18 volts , 63 64 280 motor on my RECUMBENT.. I run on the can without friction tap ( no tire shredding ).. I'm sure there is some slippage on acceleration, and believe that's a good thing for the controller & motor.. More motor , more controller, more battery , 50 very possible ...
I hope you build it , and keep us informed ... You may be the first 50 mph F/D ... I'm with SPINNER 50 mph on bicycle tires ... Bill

To Dauntless ... Thanks

[neptronix]

I can imagine that rocks and road debris would be flying at a pretty damn high speed and you'll go through so many tires, something like a new rear tire in the hundreds of miles.

You'll have to figure out how to prevent it from slipping at such insanely high power. People with less power already have slippage problems, particularly if you are on anything other than perfect pavement.

Ever considered just driving the wheel via chain?

[bzhwindtalker]

Search rock and solex on youtube, there is plenty of guys going really fast and racing those pumped up 35cc moped, with a max roller diameter of 40mm. I was there last weekend, I had a good kick trying a friends prototype that did 73kph on the speed event. I'm going there next year with an electric one.

[def215]

ive built a friction drive bmx bike capable of 30 mph running 6s and a 50-55 series motor:

i believe that 50 mph is feasible, just that someone needs to do it.

[Hillhater]

Use a speed /power calculator..
30 mph needs 1kW ....on the flat
50 mph needs 4kW ..on the flat. ... that is a big jump in power.
Im sure its possible, ..but i doubt its practical for any realistic length of time or tire life !

[Dauntless]

I can imagine that rocks and road debris would be flying at a pretty damn high speed and you'll go through so many tires, something like a new rear tire in the hundreds of miles.

Well, I'll say I've been getting the idea that friction drive is sort of counterintuitive: All these things you THINK are supposed to be a problem don't seem to be. A kid around here built a friction drive BMX with a weedeater and the knobby tire has held up just fine. He built a crude but effective version of the release arm as these people depict, seems almost as though his SHOULDN'T work but it does. It does occur to me that if the contact point for the friction drive is more than 60 degrees after the friction patch on the ground, the junk should have cleared the tire if it's not stuck in the tread.

However, if you don't want to follow Mr. Magnets advice on the moped tires, there are kevlar/aramid tires that are durable. If you ever get to working with composites you'll see kevlar just plain doesn't let you cut it. I've never seen it get unraveled. I don't know ANYTHING about what these hookworm tires people talk about are made of. But your more mainstream cheap bike tire will mean that less than double the speed brings less than half the life.

Meanwhile I read about the RC plane crowd occasionally bending the shaft on their 80100 engine planes, I couldn't imagine that it could survive a few hundred miles as a friction drive, but that and smaller are apparently working out for people.

Ever considered just driving the wheel via chain?

Well, the friction drive is tantalizingly simple, what an accomplishment he's going after. You're asking him to walk away from a challenge.

I just got a cheap little RC motor and controller to run at 12v to build my first throttle grip for an RC controller and in general to see how it holds up as a friction drive. The idea is it would make a $60-80 modification to make anyone's bike electric, at least for getting around local. Make it chain drive and you run up the price some. Then the guy that lost his job, lost his car, went to work at the convenience store on his bike would have a cheap way to get a little farther from home. (I know a few of those; as do we all at the moment, right?) Wish I could see def215's, but everything is the same shade in the pic; he seems to have beat me to it.

To Dauntless ... Thanks

Me? You're the one sharing in here. How is the housing itself holding up?

[rearengine]

Picture 015-5.jpg (124.96 KiB) Viewed 1712 times

Big 10-4 on the above ...

Def215... can you take more pix of your F/D drive, and tell what it is ... Does the roller free wheel, or come off the tire when coasting ? looks pretty stealth ... Like EV Todd , Kepler ,Adrian, and Spinner ...

This picture was my first drive with one way roller ... Then wanting to make it simple, and lighter I now run off the can .. Bill

[rearengine]

Dauntless... The housing is fine so far, but keep in mind it's 18 volts only , and no friction tap on the can so works like a slip clutch... up to speed no noticeable slipping... Ya!! this old man doesn't ride in the rain Bill

[DesignerDan]

Thanks for the advice guys. I never use cheap tires on an e-bike. I always use the quality tires with kevlar and they hold up just fine at 40 mph. I have over 1,500 miles on them without a problem. And in terms of slippage, why don't people just limit the amps? I'm just looking for crazy acceleration; just enough power/grip to sustain high speeds. I'll going to attempt this project and I will report results.

[def215]

...Wish I could see def215's, but everything is the same shade in the pic; he seems to have beat me to it.

Def215... can you take more pix of your F/D drive, and tell what it is ... Does the roller free wheel, or come off the tire when coasting ? looks pretty stealth ... Like EV Todd , Kepler ,Adrian, and Spinner ...

sure. heres some more detailed pics of it:

the motor mount is made out of angle iron from the hardware store.

everthing on the bike

this was really an experimental rig for me. the set up on this bike is 6s 6ah lipo, exceed monsterpower 46 (50-55 670kv) motor, 0.750 drive roller, 80a mystery brushless esc, 555 timer based throttle. the drive system was a fixed system, so once you set it, it was staying there. i wasnt able to make a more sophisticated drive system like adrian, todd, kepler, or spinningmagnets. i just dont think i have the skills that they have to do so. i wanted to make a cam-type manual "clutch system" engagement lever for it, but i never got around to it. at the moment, its in pieces. ill be getting a new motor to have it back together soon, because my experiment with high kv/small drive rollers didnt pan out so well .

[spinningmagnets]

I don't think a friction-drive is for everyone, but it appealed to me enough that I researched the experiments here on ES and made some choices for a drive that was a long-term robust solution for me.

The motor-shell drives (Kepler/Adrian) are wonderful. They are the smallest and lightest a drive can be. I don't want anything I say to sound as though its a negative against them (its like a discussion of geared-hub vs Direct-Drive hub, each has its strengths).

When I saw how Keplers drive could be attached to the seat-post, it meant that when coupled with a lever-style clamp, I can easily attach and remove the drive from a bike, or swap to another bike (I have an aluminum 20-inch BMX inside my RV).

The 63mm motors have a larger diameter rotor (the magnets in the shell) compared to the 50mm motors, and that gives them a leverage advantage, meaning they produce more torque per a given watt (bog down less under load). Plus the larger mass of copper in the 63mm motors make them more capable of some abuse when tackling the occasional hill.

Having the roller be a separate component than the motor-shell was a conscious choice. This way the motor doesn't need a skirt bearing, and that means that any 63mm motor will work. I admit that this choice adds cost and size/weight, but I feel the choices it provides are well worth the downsides. The 63mm kVs available are 150-295, and when compared to practical voltages, this is perfect.

If the roller is housed and supported on both ends with bearings, there is no deflection pressure on the motor-shaft. I wanted a system that would last, regardless of abuse. Rollers can be had from 5/8-inch diameter up to 1-1/2 inch. I liked EVTodds design using a roller-clutch bearings to allow the roller to remain in contact with the tire (no external clutch, or lever-linkage).

A smaller diameter roller allows the same speed from higher volts/RPMs, and sometimes higher volts means that you can support the same load with fewer amps. I've tried a couple and I like the hill-climbing ability of the one-inch roller (climbs well while drawing fewer amps).

I'm very happy with the 63mm Exceed 295-kV motor. I had tried it using 24V on a 1-1/4 inch roller to get 20-MPH. It climbed OK, but I was uncomfortable with the amount of heat on a steep hill. Warm is good, hot is bad. I now use 36V on a one-inch roller for 22-MPH. I feel I can throw anything at it, steep hills, etc...I haven't tried 44V-48V, but that should result in around 28-MPH.

Castle Creations ESCs have data-logging, and that verified what Todd had posted. Peak amps on hard acceleration were 60A, and constant draw was around 10A. The Castle ESC I tried tops out at 28V, so I tried the Hobbywing HV-70A to reach 36V (capable of up to 48V). That proved to be the final piece of the puzzle. If I was starting out from scratch, I would just get the Castle HV-80A...since at low volts I had a problem with a loss of sync with the "affordable" generic ESCs. I sincerely wish the cheap ESCs had worked well, but they didn't for me.

Low amps across the RPM range when under load is always a good thing, but it also means that the battery is not limited to only using LiPo for a high-C-rate.

Hobby King has 63mm motors with kV of 250 that have skirt bearings (if you wanted a shell drive). It should provide 50-MPH at 44V, but only on flat land. Once you put a 50-MPH load on it (or a mild hill), the motor and controller will get hot. Much less copper mass than the fattie 80mm motors.

[Punx0r]

If more power is required, surely two rollers/can drives would solve the problem of slippage and tyre-shredding?

[rearengine]

Hill Helper thread

download/file.php?id=70837

Bill