Where to get cheap and good motor for friction drive?

[ash ketchum]

I'm thinking of making myself a cheap and good friction drive, but the only problem is the motor. I need a cheap, good quality brushed motor; at least 300w but not more than 500W.

[moderator edit to correct spelling in thread title]

 

[Chalo]

I'm thinking of making myself a cheap and good friction drive, but the only problem is the motor. I need a cheap, good quality brushed motor; at least 300w but not more than 500w.

Why a brushed motor? What are you using for a roller?

Unite brand motors are cheap, decent enough, and available in lots of variations. Their shafts are all set up for proprietary sprockets, though, not rollers.

 

[wineboyrider]

A lot of people have built friction drives with RC motors and use the outside of the can to turn the wheel. Search Kepler friction drive for inspiration. The RC controllers are good for speed, but can fail from startup.

 

[ash ketchum]

A lot of people have built friction drives with RC motors and use the outside of the can to turn the wheel. Search Kepler friction drive for inspiration. The RC controllers are good for speed, but can fail from startup.

Although your idea sounds good, but I can't afford a controller. This is the reason why I'm thinking for a brushed one.

 

[spinningmagnets]

Maybe go to a pawn shop and buy a used 18V DeWalt cordless circular saw for $20. I just got a Ryobi to experiment with. Maybe it will work, maybe it will have problems...we will see soon.

 

[Ianhill]

When using rc cans the distance from the centre of the shaft to the outer of the can acts like a lever in contact with the tyre, so two motors of the same kv power etc one narrow and long the other short and stubby the stubby one would give best torque at the wheel.

A hoverboard wheel is super cheap, easy to obtain, and easy to power, it's super narrow and stubby plus it's in the power range you require and has tread to contact the tyre rubber to rubber so there's less wear than sandpaper but more grip in wet conditions than just the can surface, mind I've never built one and closest I've got to something like it is a granny bike dynamo that powers the headlight.

 

[Chalo]

When using rc cans the distance from the centre of the shaft to the outer of the can acts like a lever in contact with the tyre, so two motors of the same kv power etc one narrow and long the other short and stubby the stubby one would give best torque at the wheel.

The other way around. The larger the radius, the less thrust and more surface speed per volt, assuming same kV, shaft torque, power.

 

[Ianhill]

When using rc cans the distance from the centre of the shaft to the outer of the can acts like a lever in contact with the tyre, so two motors of the same kv power etc one narrow and long the other short and stubby the stubby one would give best torque at the wheel.

The other way around. The larger the radius, the less thrust and more surface speed per volt, assuming same kV, shaft torque, power.

Hmm having a think with the hamster wheel squeaking, the wheel size and the can circumference will act as a final gear ?
So even though the larger can has more leverage its geared itself higher with the cans added circumference so yeah i concour.

 

[Chalo]

Since the roller's surface speed corresponds to the surface speed of the wheel, the final ratio is independent of wheel diameter.

 

[Ianhill]

Im with you nw, unlike chain and sprockets it's only the roller that has any effect on gearing other than the effect of changing direction, The wheel itself can be bmx, mountain bike or penny farthing its the drive roller wheel that performs the gearing but i think a farthing wheel would need a bit more power for its weight I've never really looked at a friction drive until I seen a recent thread i didn't really analyse the design thinking it could be wasteful but a good setup could be quite efficent once upto speed and light too for a little top up to peddling to keep speed up on a road bike.

 

[spinningmagnets]

Since the roller's surface speed corresponds to the surface speed of the wheel, the final ratio is independent of wheel diameter

This is one of the quirks of a friction-drive (FD). If you are driving the tire tread OD of a 29'r tire, the leverage will actually be better than driving the OD of a 20-inch BMX tire.

IF...you are driving the AXLE of a 29'r (with a chain-drive), it will be worse than a 20-inch tire (the opposite of a friction-drive). Once you realize that, then....since my experience leads me to believe that the best possible scenario for a FD is about 1000W (due to traction limits between the roller and tire tread), then...the "best" FD set-up would be a small-diameter roller coupled with a large diameter tire (again...the opposite of an axle-drive). This would increase the motors "magnet-speed", and that is consistent with my personal research results, and observations of other builders' results.

 

[Chalo]

My point was that since the roller speed is the same as the tread speed, wheel size doesn't matter at all (with regards to gear ratio). Big wheels have all the usual advantages and disadvantages that they do in non-powered applications, but the motor-to-road-speed ratio does not change with wheel diameter.

 

[Ianhill]

I was watching one of AVE recent vijayo's on youtube and he blew me away with worm drive gears amazing stuff to be learnt from simple mechanical principles.

In his video he showed how a throated worm gear can apply more torque than a flat one the same will apply for the roller, a roller with a single throated cone matching the tyres inverted cone height and width is going to give better contact area allowing more energy transfer before slippage, the force pushing the roller to the wheel is going to have its perfect setting to much and the motor will lose energy fighting the extra added friction and the tyre will get hot, to little and the roller will slip on the surface and cause heat so the spring tension needs to be adjustable. All this will have the effect of gear down the roller a little two as it centre point is fractional smaller in diameter so its a win win really for added power id say try a wide wet tyre with minimal tread and soft compound it will give a lot of grip to the roller, the rollers surface material is where power can be gained too experiment a little.

It's suprizing what a 1000w motor and around 500wh batt can do, My controller on slow in my scooter is near enough 1000w and it goes up the the local mountain no sweat no incline can stop it, but i have no regen or sineasoidal controller so 500wh would have been more like 350wh amazing stuff, An electric scooter with decent bit of kit fitted these days really goes the distance compared to a stock razor e300 sealed lead acid gutless surprise.

 

[markz]

Could you use a ebike controller for an rc motor?
Or do you 100% need an ESC

AlienPowerSystems out of the UK has a good selection of RC motors.
You want an OUTRUNNER rc motor and I am unsure as to what KV you would need, I could only assume the lowest 50-90KV, or 150KV, KV = rpm/v

RC motors can run up to 10S but ESC's only really come in 6S for a reasonable price. That is why I ask about using a regular ebike controller for a RC motor, because you can buy them for cheap.

HobbyKing is a good source for RC motors as well.

I just got done looking at them.
KEDA 5364 190KV 2kW 8mm 90Amax 620g for $44usd good for 6-10S, while I found an ESC 2-7S 100A for $26.
But I like 10S

 

[amberwolf]

I'm thinking of making myself a cheap and good friction drive, but the only problem is the motor. I need a cheap, good quality brushed motor; at least 300w but not more than 500W.

See my DayGlo Avenger's last friction drive setup, either in the thread for it or on the http://electricle.blogspot.com site.

I used two pancake axial flux brushed radiator fan motors, with roller skate / skateboard wheels attached to the shaft as friction rollers.

Worked well enough once I got the mounting bugs worked out, but eventually the changes in pressure against the axles as the tire expanded in the areas away from bumps, fractured one ofthe axles along a weak point / stress riser at a c-clip / bearing junction. If I'd used a pillow bearing block at the other end that probably wouldn't have happened.

 

[spinningmagnets]

Could you use a ebike controller for an RC motor?

Thud and Burtie added hall sensors to RC motors and then ran them on 6-FET ebike controllers.

It has been proven many times that the friction drive will provide the speed of the roller, independent of the diameter of the tire. However, since the limit of a friction drives power is the traction of the roller against the tread? If conditions are optimal, I recommend using 1000W as a maximum of power application before traction becomes erratic and unreliable.

As far as a large diameter wheel applying less resistance to the FD roller, imagine the spoke length in a radially-spoked wheel as a lever. Put the roller at 12 O'clock, and imagine that the axle is the load that is being pushed forward. The longer the lever, the easier it is on the motor. The shorter the lever, the harder it is on the motor. If someone data-logged the amps between the same FD drive between 20-inch and 29-inch, that should settle it.

If you are happy with 20-MPH, 1000W using a 63mm diameter RC motor at 36V X 26A, driving a one-inch roller on a 26-inch wheel, climbed hills great. Didn't get hot, didn't bog down.

 

[markz]

Adding halls to outrunner
https://endless-sphere.com/forums/viewtopic.php?f=30&t=15686&hilit=hall+motor

what about running sensorless ebike controller that does not need halls?
https://endless-sphere.com/forums/viewtopic.php?f=2&t=23882#p347103
Yeah so adding halls is pretty easy Jeremy Harris states.


So........................... a cheap ebike controller off ebay, some fets for the halls and a rc motor and you'd be good to go OP. I will do that too, still not sold on friction drive tho.

KEDA 6364 190kv is the motor I am buying for $60usd shipped. Its 2kw 90Amax.

I wonder IF gear reduction is not an issue, would a higher kv motor be best for sprocket setup, then the exact same motor in a lower kv? for an ebike. This is leaning towards the higher torque, same motor "myth" again. I am just not familiar with rc outrunner motors at all. Looking at the rc motors on hobbyking the higher kv motor (160 vs 190kv) is listed as having a little bit more power. I emailed a guy about this from Alien Power Systems and he stated to go for the higher kv because it has more power. I am conflicted.

 

[spinningmagnets]

Hard to get excited over a max of 1,000W, and...it slips when the tire is wet. I've done it, and I have seen many others doing it (and I am doing it this week as we speak)

 

[markz]

Yeah SM that is true, wet puddles, rain, even light snow in April, slippage. Its hard for me to get excited over it. I thought there was gear reduction in FD, but its just whatever the drum on the motor spins at is your speed, dont matter what diameter the wheel is. Thats why I love ES I am learning lots.

If the key word is cheap, any old cordless tool would suffice. Ideally a mower, chainsaw or circular saw of the 6"+ variety vs 4" then less ideally..... trimmer, grinder, rec saw, drill. One fella was giving away a free cordless mower with dead battery, a cordless saw for $10 but most are $25-$40. I got a bad Mastercraft heavy drill thats 120V plugin I may open up and take a look at. I remember investigating corded mowers, tread mill motors and the like and they would be alright if you can snag one for el-cheap-o-mundo. Then you can tinker with them and research them on how to get them going on dc voltage. I cant remember off hand much about them, rectifiers, high voltage, high rpm's.

Its the day in age where people throw shit away when it doesnt work anymore, that is why battery powered stuff is good for us "pickers" because when the battery loses its uuummmmffffff the homeowner prices out a new battery and is sticker shocked then throws it away.


Happy hunting!

 

[wineboyrider]

If a cheap brushed motor is the way you want to go I recommend going for the used electric scooter type. I have several, because I bought them from craigslist really cheap with dead batteries. Look for one with a big shaft to hook your friction drive onto. Can also run with or with out controller.

 

[markz]

We need info from the OP to get a sense of terrain he/she will be riding, hills, windy, traffic, stop and go, long straight aways with no stopping. Also we need to know the total weight of rider and cargo + bike.

 

[Ianhill]

I think both Chalo and spinning magnets are both correct and I just been chatting along like I'm a player when I got not friction drive tech at all lol.

Here I go, spinning the hamster wheel in my head in friction drive mode i see the gearing is purely the roller and is independent of the wheel like chalo said, but the distance from the centre of the wheel axle to the rollers contact patch also plays a part like a lever, like spinning magnets said.

There's an advantage of having a larger wheel for the roller too the contact area of where the two mesh will increase slightly coupled with a shaped roller and decent tyre I could see it working decent on a bike that see no worse than a bit of rain or a dusty road.

There's also the flywheel effect with the wheel sizes increasing in size more power needed to break it's inertia but it helps when bursts of heavy load are applied when at higher rpms like climbing an incline etc.

So in my head i think slightly heavier flywheel fractionally longer lever and same gearing means added torque when at speed but slower to accelerate and initial jolt of the line will be less.