APL's DIY axial-flux motor

[fechter]

But I did look up your BMC motor on the calculator, (I think it's the one), and see the three tooth pattern. Seems
like it might be a higher torque motor that way? I do like the winding factor!

That's it except the BMC is delta connected. I think the main advantage is ease of wiring and slightly less wire between coils.
The windings are a single layer of some pretty stiff wire.



My guess is you could use your same cores and just space things a little differently to get a more symmetrical and easy to build pattern.

 

[amberwolf]

Thanks for the info. amberwolf, I know that the H35/40 series Cryt. has 51 coils, but I was never quite sure about the
pole pairs. I put my motor back together, and only have photos, and can't make it out.

Looks like it's 48 magnets, so 24 pole pairs, if I counted correctly
https://endless-sphere.com/forums/download/file.php?id=248480
could be 46 and 23 pole pairs, which is more likely, as I am having a hard time keeping track of where I am when switching between the actual magnets and the reflections for those not directly visible, and the edges of those I can't see the face of.

Strangely, I have never been able to find a stator wire diagram for one, so I still don't know how it's coils are wired.

Pass a current thru one phase from phase input to star point.

Use a tiny compass and hold it over each pole or coil or stator tooth, and mark whcih ones react, and what polarity.

Repeat for the other two phases.

Now you have a wiring map.

 

[APL]

Sweet Success!

Break out the cigars boys, and pass them all around! Baby's got a spin going on!

A little wobbly, noisy, and way to fast, but spinning all the same.





So, what was the problem? Well, it's the old assume thing, makes an a-s-s out of u-m-e. Larsb was right about the
reversed poles, and the compass test told all. (except that if you get it too close, the field will override the compass)

When I wound the coils, I wound the black sets from right to left, and the red sets left to right, thinking that it would
reverse the field. But it don't work that way. My bad.

Anyway, I just flipped the black core sets over, and put it back together, and it took off like Lance with his pants on fire! :lol:
A special thanks for all of you for helping me out! I couldn't have done it without you.

I have a video of it running, but can't seem to get Youtube to load it. It just 'spins' forever. 33MB, and 33 seconds,.. do I
need to compress it ? And if so, how do I do that on my Mac? I left it load all night, but still no go.

 

[sleepy_tired]

Such a bad-ass accomplishment. Very good.

 

[neptronix]

Rad.

On the mac, try a program called handbrake to recompress videos. I've been using that program for many years.

 

[fechter]

Nice work.

Do you have a way to measure the battery current?

 

[APL]

Finally figured it out, this PC stuff is like a bad easter egg hunt!

[youtube] P3ECmh6AG84[/youtube]

I'll be doing some testing, and hook up the CA to it,.. give the RPM and specs soon. Plus I have some tweaking to do
to straighten it out and run smoother, I just kind of tossed it together for the test.

I don't really need it to run that fast, so maybe a few more winds would help? Like maybe twice as much.
But then the real test will be to mount it on the bike and run it. Yee-Ha, can't wait!

Todays a fish'n day, I need a break.

 

[APL]

Dang it! OK, well do it the old fashion way.

Youtube Video; https://www.youtube.com/watch?v=P3ECmh6AG84

 

[Archer321]

 

[wturber]

Finally figured it out, this PC stuff is like a bad easter egg hunt!

Almost there ...

Your code:

[youtube] P3ECmh6AG84[/youtube]

should be .. You have an extra "space" in front of your code.

[youtube]P3ECmh6AG84[/youtube]

[youtube]P3ECmh6AG84[/youtube]

 

[wturber]

Finally figured it out,

Awesome!!!

 

[damirsky]

Dang it! OK, well do it the old fashion way.

Youtube Video; https://www.youtube.com/watch?v=P3ECmh6AG84

congratulations!

 

[larsb]

great news!! :thumb:
What's the kV now?

There's some runout visible in the video, plates are not 100% nomal to axle. do you have some way of correcting that built into the design?

 

[j bjork]

Very nice

 

[APL]

Thanks for all the thumbs up! Geez, it only took 17 pages!
Well, thats what happens in real time, we just call it entertainment.

And thanks wturber, for helping with that again, I didn't realize that I was one space off. I think I finally
have all the pieces of the puzzle now. Let the videos roll! I'll try to make one of the bike in action
when I get that far. ( Should be pretty soon, since I'm getting all gitty over it!)

Larsb, I'll get the KV next,,, it will be very interesting to know, although I suspect that it's still fairly low,
that is 14 X the .30v that we had before. It is actually making more sense to me now that I realize how fast
the motor spins. I measured it at 1110 RPM. with a 40v battery pack.
Before I charged the batteries,which were pretty low, it got up to 1500 RPM. Go figure.

The less wire winds, the more speed, and less KV. Thats 'open' speed not under load, so I'll put it on the bike
and see how it performs first, and then think about adding some more winds. I only really need 3-400 RPM.

I'll have to go back and read my own post, but if I remember right, more winds don't give me more torque,
just less speed, and less heat?

I'm still trying to figure out where I went wrong on the coil wind direction, according to the right hand rule,
changing direction of turns, changes direction of poles. But that's not quite true. I think it doesn't matter
which way you wind a coil,.. only the direction of voltage. That's where I went wrong. lesson learned.



The runout is the result of the design change I made way back in the build when I decided to move the
back iron from the outside of the rotor, to the inside of the rotor. This placed the drive bearing in a different
position on the axle,.. and since the axel was already made, theres no easy fix. At least, I think thats the deal.
I'm pretty sure that I have to go back and bond in some material, and re-turn the axle a little in that spot.
Like I say, the first one is the worst one, and it seems to spin alright. I'll see what I can do, but I'm looking
forward to V2,.. as so many things are out of spec. on this one.

I know it's pretty motor, but it's an experimental at hart, and it's made for proof of concept, and to extract
all the information needed for the next one, which hopefully, will be much better. Both in design, and construction.

 

[APL]

Another curiosity that I should mention, is that it doesn't matter how I connect the phase wires, no matter what
combination I try, it still runs the same, except for direction of turn.
Normal for a sensoreless motor?

 

[larsb]

Yes, it's normal
You should fit all the possible copper on the cores, either by many parallell wires and a low number of turns or the opposite.

KV is not a performance figure, it's only a constant to match to your controller and battery spec.

This post and the following ones might be useful:
https://endless-sphere.com/forums/viewtopic.php?f=3&t=99566&start=25#p1484693
On kV and battery+controller output:
https://endless-sphere.com/forums/viewtopic.php?f=3&t=99566&p=1484693#p1484786

You will be able to gear motor down anyway so keep the rpms high but reasonable for the design. Right now with unbalance it's wise to not go higher but in ver2 you can increase rpm to whatever you can gear down to the rpm you want.

 

[APL]

Not that easy to gear 'down'. The smallest motor cog is a 16T before the chain starts rubbing mounting bolts,
and the rear 'low' cluster cog is a 28-30T, I'd have to look. The 400 RPM (aprox) motor on there now takes it up
to 21 mph, in that low. The bike has lots of high gears, but low's are running out.
I hate to use 34 and 40T cogs, because the der's for them kind of suck. The more chain I have for the large cogs,
the more likely it is that the motor will cause the chain to jump the cogs in rear higher gears.
It gets complicated.
Mid drives have the torque to jump chains in the rear, which is why I have a downhill Zee der. with a locking clutch
cage on it

Thats why I'd like the slower RPM,.. it works better with this system.
If a Shimano IGH hub has lower gears, then maybe I could also put a larger cog on the IGH and get by with higher
RPM's on the motor. (more stress on the hub though)

First things first, I'll put it on the bike and see how it goes, maybe under load, it's not a problem.

Thanks for the links, I'll take a read, perhaps I should have used another word for Kv..

 

[larsb]

I understand, that's a different picture - and difficult as you need your motor effective and powerful at low speeds as well as matching the setup you have now.

I'd think about designing a new system around your motor for rev2 as that can be tweaked to match well.

It'll be interesting to hear the verdict after your first ride

 

[madin88]

Nice to see you got it working now. Good job :thumb:

I measured it at 1110 RPM. with a 40v battery pack.
Before I charged the batteries,which were pretty low, it got up to 1500 RPM. Go figure.

The less wire winds, the more speed, and less KV. Thats 'open' speed not under load, so I'll put it on the bike
and see how it performs first, and then think about adding some more winds. I only really need 3-400 RPM.

I'll have to go back and read my own post, but if I remember right, more winds don't give me more torque,
just less speed, and less heat?

Yes for sure the kV is quite high for beeing a replacement for the Crystalyte Hub.
If you want to get the same torque on the wheel you would have to double the phase current or gear ratio.

To get an idea of the current it can take (or torque output) it would be useful to know the phase to phase resistance.

 

[APL]

Back to the ohm meter that I don't have.

Well, I had the thought that we could do it theoretically at least. I know approximately how much wire I used,
so I looked up a wire resistance calculator on line, and found one that was simple to use.

I know that I used around 4 foot of wire for each coil, give or take an inch or two, and theres 21 coils, so that comes
out to 84 feet of 14 awg wire. Divide that by three for each leg, and I get 28 ft.
One phase is two legs, so that brings it to 56 ft. of wire.

According to the calculator, it comes out to .1414 ohms per phase. Not a real world number, but should be pretty close.
Of course theres the phase wires and solder and such, but it should get us close enough for a rough idea?
As always,.. my logic could be completely flawed.




Taken from Inch calculator.com: https://www.inchcalculator.com/wire-gauge-size-and-resistance-calculator/

 

[APL]

Also, I just ran the phase voltages with the new cut plates, and motor working;

YG.- 6.56v
YB.- 6.61v
GB.- 6.46v

All at 296 RPM. 74.4 degrees start temp, 78.2 degrees after 3 minutes of being externally turned.

 

[larsb]

a 5 minute driving motor at noload test with rotor temps before and after and noload current measurement would be good, it would tell if you need to improve.

phase resistance is high, you won't be using a lot of current before overheating, an example:
60A gives 500w copper losses, let's assume it can be shed and neglect the other losses.
kV 45
continuous torque(60A)= 9,55/45*60=12,5Nm
power 12,5*(1500/2)/9,55=980W
efficiency about 66%

the assumption that max power is at half noload is correct but i'm not sure that the torque assumption is correct in the power calc. The losses will be higher than this in real use.. try the motor simulator at ebikes.ca with your parameters!

 

[APL]

Thanks larsb, for doing the math, not too good of an efficiency.

I did the 5 minute no load test at full rpm, and it was a bit disappointing as well.

77.5 degrees start temp.
After 5 min.
Copper 135 degrees.
Stator 127 degrees.
Rotor 102 degrees.

Those readings are not that precise, as the thermometer will vary with positions. But I would say they are average.

So your right, it won't take long on the bike before things will get HOT.

I also did a smoke test on the cooling system, and although it makes plenty of air around the radius, there doesn't
seem to be much movement through the side holes. So it's not clear if the coils are actually being hit with air yet.

I guess I can see the light, but I'm not out of the woods yet, on this.

So riddle me this,.. supposing I double the windings, wouldn't it roughly double the phase volts, to 13v,
double the resistance to .077, and half the RPM to 550 RPM?

And if so, would your calculations produce a higher efficiency? Any help would be much appreciated. :thumb:

I'll take a look at the motor simulator, I haven't used one yet,.. should have checked it out long ago.

 

[neptronix]

A MAC motor does the same thing on the bench at no-load. It just takes longer. And that's a pretty decent motor, efficiency wise.
Some high efficiency motors do that.

Just FYI.