ES DIY Motor Challenge

[fechter]

Since the objective is to make a motor that can push a bike, I think it's fair to include the overall gearing to the wheels in the efficiency measurement.

One measurement would be the watt-hours per km at a specific speed. Anyone with a CycleAnalyst or similar device can make this measurement. This is really what we're after in the end.

Here's an interesting motor design: http://www.evilmadscientist.com/article.php/HomopolarMotor
I made one of these and it always got going so fast the rotor flew off. Now how do you make a brushless version of it?

I once tried taking an old car alternator and shorted the field winding on the rotor and fed the stator with 3 phase from my scooter controller. With the field coil shorted, the thing acts like an induction motor. I don't think I had the drive optimized and it was running open loop, but the thing got spinning really, really fast. So fast that I was worried about it flying apart. Had no torque however.

Alternator test setup.jpg (65.66 KiB) Viewed 944 times

Here's an interesting coreless axial motor. The magnet is a solid ring that's magnetized with poles in a Hallbach array. There is non-moving back iron behind the coils, so I don't think it is very efficient. You can see the hall sensors in the middle of the upper left coils.

Axial ironless axial motora.jpg (37.83 KiB) Viewed 977 times

Here's another good motor, the AstroFlight AF3210. This has overlapping windings similar to a Crystalyte hub motor. I wonder how they keep the rotor from flying apart at high rpm?

AstroFlight_AF3210-12T-02.jpg

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One of my earlier motor projects was my Zappy motor. After burning it up twice, I replaced the wimpy ceramic magnets with some really strong Neodynium ones that just happen to fit the curvature of the motor housing. This allowed me to rewind the armature with about half the turns of much heavier wire. The result had at least 5x the power of the original motor.

A-0059.jpg (68.05 KiB) Viewed 945 times

[Thud]

Looks like we have a 3rd, Welcome LFP!

Miles, Are you building a motor?

Roll call: every one/anyone who wants to build a motor chime in. what do you need?

I did finish that eddy brake, But I kinda over tested it- dynoing my lathe. (melted the glue holding the rotor assembly togeter)lathe-1 dyno-0.

I plan to build a reasonably sized unit for testing my motors, so that is an option.

Let the debate begin on testing parameters

[Miles]

I'm not sure we need to test efficiency directly for the challenge?

If you achieve the highest sustainable specific torque, that will be largely due to having the best efficiency, I would have thought?

It would certainly be good to have the data. I'm not sure efficiency needs to be a challenge parameter, though..?

[Miles]

Here's an interesting motor design: http://www.evilmadscientist.com/article.php/HomopolarMotor

Thanks for that. I love it

[Malcolm]

I might just stand a chance of competing if you change the challenge parameter to "number of motors built in five minutes".

I just built two of the homopolar motors. Brilliant

[etard]

Why can't we test it the same way the rc guys do and just set a limit on rpm/volt? A simple test stand with a digital weight scale to measure the pull of the prop for 30 minutes. I also am throwing the hat in the ring simply because I want to learn more about the science and tolerances of these motors. I just want to keep this fun, we font need to get hung up on rules and cheating and loopholes, rather we should be a community that shares and gives good ribbings.

We should also standardize the controller to be used for testing. We also need somebody to come forward who knows what they are doing to set out the rules in stone and volunteer to test and devise the rig for testing. Next all entrants chip in for the test rig and send the motor along with payment for return shipping. I think we need 10 entrants to make this interesting and then set a date in the not too distant future.

John,
I think the weight limit is fair, it's just that you are trying to build a train motor and the rest of us would like to build a BICYCLE motor. Maybe we can set a secondary test that will award the entrant with most power so that larger motors will win this shootout?

[Miles]

Why can't we test it the same way the rc guys do and just set a limit on rpm/volt?

Hi etard,

What's that to do with?

[etard]

Miles,
Nevermind, that's gonna be a measurement of thrust and not really comparable to our purposes. I was mostly pointing out a method already in use.

I might just have a go at rebuilding my Hacker motor and submitting that. I wanted to delta/wye it anyway. Is that permissable? Or what if I overbuilt it with better and bigger bearings, and a stouter shaft with better magnets, maybe add sensors do you guys have any objections to this approach?

[John in CR]

John,
I think the weight limit is fair, it's just that you are trying to build a train motor and the rest of us would like to build a BICYCLE motor. Maybe we can set a secondary test that will award the entrant with most power so that larger motors will win this shootout?

Etard,
No, not a train motor...motorcycle motor maybe. My advantage is the lack of e-bike rules here in Costa Rica, so all I need is pedals and it's legally a bike as long as it doesn't have a piston displacement > 49cc. I have no interest in electric motors with pistons.

Miles,
Won't a larger diameter result in greater torque for a given weight more than higher efficiency would? If it's not as efficient then it just needs better cooling.

[Miles]

Miles,
Won't a larger diameter result in greater torque for a given weight more than higher efficiency would? If it's not as efficient then it just needs better cooling.

The dyno and the scales will be the judge of that..........

Certainly, you'll get higher sustainable torque level through a better heat dissipation rate.

[enoob]

4Nm of continuous rated torque per kg of motor weight - passive cooling only - for a motor weighing under 3 kg?

miles correct me if im wrong but i think what he wanted to start was a collaborative effort among those trying this with the end result of moving ebiking in general along.

it makes for a good target . and rather than making it a contest to see who is the best id rather see it as a more of a club . you get in "the club" by meeting the challenge as laid out and using this forum and open source to design and build a motor . if it makes 4nm of torque per kg of motor weight your in.

whomever makes the bestest most powerfulest one will most likely show itself without alot of testing and judging. i suspect. and i would have no problem copying that design for my own sick and evil purpose.

Other than a CA to see whats happening when i ride and sending one to thud (still not kidding T) i consider the best "test" to be real world. bolt it to a bike ride and see what happens. bench testing only tells you what happens on the bench not to say i wont bench test BUT how fragile is it ? 98.9 percent efficient and 20Nm per pound is great and all but what if the first bump in the road or the kick stand melting through ashphalt tips the bike and the motor bends ? wheres your efficiency then huh ?

i want some power . i want it to last more than 2 rides AND i want to be able to say its mine or copy it . wont be able to do any of those without seeing it on a bike or 3 for a month or 3

[Thud]

I am building a dyno.
#1 to get some #s from for compairison.
#2 we got 8 inches of snow last night. Its officaly building season.
#3 I am a tech geek who thinks having a dyno would be cool.
I have a laser tach on the way. touqe will be measured in ft pounds.
I am thinking an infra-red thermometer might be a nice add on to keep from smoking a motor on the dyno.


I will be happy to test motors & video the process.

I need some refinment on the eddy brake concept to be able to adjuste the brake effect. a simple brake dyno would be much easyer to fab.
keep an eye on the mule1.1 thread
I hope to have a nice addition by sunday

[liveforphysics]

That's awesome news Thud!

Put the magnets out at a big radius, then you can control torque by moving the aluminum sheet closer or further away. A little arm poking off the side of the sheet sitting on a digital scale will be all it takes to accurately measure torque.

[enoob]

yee haww.

i knew i liked you T.

makin lemonade baby.

the name hencforth will be- TTM1EBD = Thuds Test Mule 1 Eddy Brake Dyno.

or TED for short. Thuds Eddybrake Dyno

cant wait to see my motor getting shafted by TED

[Miles]

I will be happy to test motors & video the process.

Great! Thanks T. That's one problem solved

[Miles]

Other than a CA to see whats happening when i ride and sending one to thud (still not kidding T) i consider the best "test" to be real world. bolt it to a bike ride and see what happens. bench testing only tells you what happens on the bench not to say i wont bench test BUT how fragile is it ? 98.9 percent efficient and 20Nm per pound is great and all but what if the first bump in the road or the kick stand melting through ashphalt tips the bike and the motor bends ? wheres your efficiency then huh ?

That's why I added the "practical" clause....

How about:

Over 4Nm continuous torque per kg of motor weight.

Less than 3kg in weight.

No energy input other than that to the motor itself.

Capable of practical use on an electric bike.

[enoob]

looky there . missed that addition .

4 sentence rule book.

perfect.

[MitchJi]

Hi,

I'd eliminate all the rules. Everyone builds what they want and gets judged accordingly (kind of like pornography "I can't define it but I know it when I see it". The results could be something like:

Outstanding!
Excellent
Good
Poor
Failure

If one persons criteria are a cheap, simple DIY motor they get judged by how well their motor meets their criteria.

If Luke's criteria is under 4kg and under $4k cost with a power output of 10kw he gets judged accordingly.

If one motor is clearly more outstanding than all the others they could qualify for something like a "Best in Show".

[Miles]

If one motor is clearly more outstanding than all the others they could qualify for something like a "Best in Show".

So, how is it clearly outstanding? Because it looks cool?

Everybody is free to build whatever they want and invite comment on the forum, anyway..... I think I'd rather just do that than take part in a "dog show"

[adrian_sm]

Good work Thud

I am building a dyno.
....
I am thinking an infra-red thermometer might be a nice add on to keep from smoking a motor on the dyno.

Here is a couple of options for cheap infra-red thermometers in case your interested.
$47 - Digital InfraRed Thermometer with Laser Sight (-25'C~600'C/-13'F~1112'F)
$31 - Digital InfraRed Thermometer with Laser Sight (-32'C~380'C/26'F~716'F)
$25 - Mini Digital InfraRed Thermometer with Laser Sight (-50'~260'C/-58'F~500'F)

Hope this helps,
Adrian

[Miles]

I am thinking an infra-red thermometer might be a nice add on to keep from smoking a motor on the dyno.

This is something which needs working out, for sure.

Maybe a thermal sensor in the windings would be better?

Do we have a fixed maximum temperature? Which would have to be low....
Or, do we let the builder specify the maximum temperature?

[John in CR]

If one motor is clearly more outstanding than all the others they could qualify for something like a "Best in Show".

So, how is it clearly outstanding? Because it looks cool?

Since these are torque machines, then the highest torque density under continuous operation should win. The best idea to me was ES against all other groups so we can open source the build or several builds. It's that sharing aspect that make ES heads and shoulders above the rest. With tens of millions put on the road every year in China, the number working on the technical aspects of ebikes must number in the thousands, yet the open source approach is missing. Look at the result...pretty much crap and moderately efficient efficient machines with no good answer for multi-gearing and of questionable durability. I'm sure a number of posters here can do better going at it alone, but working together we can take a big step forward. To help satisfy the competitive need, how about top contributor and top builder awards?

Along the idea of an open source approach I'll pledge the purchase of one of the magnet sets, including shipping to whoever the group designates.

John

[Miles]

Since these are torque machines, then the highest torque density under continuous operation should win.

Then we have to wait until "everybody" finishes? Or what, a relay?

I still like the idea of a target to beat, myself..

[Thud]

Adrian,
Thanks, i am checking into it.

Regarding temps I guess I just want to see if the motor is really straining, if an eponential trend shows damaging heat iminent (temp ratings for the magnets) we'll shut it down. I was thinking non contact for ease.
I am also assuming that the builders will have plenty of bench runs on a submital before tourtureing their baby on a dyno

I have no issues with any of the parameters of this challenge & am trying not to dwell on the word "Win". As much as I would like to build the highest, tourqueiest, shinyest, gooderest motor this side of eternity, I still will have to give a bunch of credit to the forum as I suspect any one who participates will. I am thingking I have already won a huge prize just being able to contribute anything. If we happen onto an applicable design that will benifit the comunity here & abroad then the aknowledgmet will be enough. (untill the Nobel prize commitee calls )
The Kudo's are just frosting on the cake. & again the target will allways be moving. (next motor should allways be better shouldn't it?)

[Miles]

I was thinking non contact for ease.

I was thinking: the builder adds a thermal sensor to the windings during construction, so you just have to plug it in. Just an idea.