Converting a hubmotor to a middrivemotor

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Re: Converting a hubmotor to a middrivemotor

Postby Altair » Tue Feb 16, 2016 12:54 pm

I wanted to have a 2:1 reduction ratio before the crank, just to be sure I had enough torque.
Besides, if I run the chain directly from motor to the rear wheel, when I'm on the lowest gear the chain will rub the tire.

I bought the motor 3 months ago but I think I didn't get the latest version. At least, I have the blue composite gears but I learned from EM3EV that the new version has 2 smaller bearings supporting the rotor, while the older version had one large bearing doing the job.
And my motor winding is made of 3 smaller gages of wire instead of a single larger gage. But that doesn't necessarily indicates it's newer or older.
I ordered a spare stator that I'll wind as a 9t I think. I also have a set of new hall sensors that I'm going to put in, hence my presence here to gather info on exactly where I place them.
Last edited by Altair on Tue Feb 16, 2016 1:04 pm, edited 1 time in total. View post history.
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Re: Converting a hubmotor to a middrivemotor

Postby Altair » Tue Feb 16, 2016 1:03 pm

I think that the Adaptto limits the max RPM of the motor, maybe because it measures increased inefficiency past some RPM.
Early on, when I began tuning the controller, there was times during auto-detect where the RPM went to twice the normal maximum I get now.
But I never saw that again. The motor speed is still reasonable now, it's just that low RPM behavior that drives me nuts.
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Re: Converting a hubmotor to a middrivemotor

Postby Altair » Tue Feb 16, 2016 1:08 pm

Oh and another reason why I have 2 chains. I needed a jackshaft to put the freewheel for the pedals. So now I can interchange the pedals or the footpegs easily.

Changing the gear ratio is also very easy, I machine my own sprockets for the primary chain, it's a #219. With the adjustable length motor mount, I do not need a chain tensioner for the primary chain.
Last edited by Altair on Tue Feb 16, 2016 1:12 pm, edited 1 time in total. View post history.
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Re: Converting a hubmotor to a middrivemotor

Postby Altair » Tue Feb 16, 2016 4:10 pm

I'm wondering why this MAC motor is so difficult to drive for a controller.
Could it be because it has concentrated windings?
Do any of the other popular hub motors also have concentrated windings, or never?

The freewheel is in for something anyway, it greatly reduces the inertia in one direction only, maybe that confuses the controller.

Would there be still a better placement for the hall sensors? Maybe they get adversely affected by the changing magnetic fields there right on the edge of the stator. Bury them lower on the face of the stator?

Slot spacing for the sensors should be in multiples of 3, right? But what slot to use as the #1? (Assuming that we're gonna place the sensors into the slots)
If we refer to the winding scheme:
MAC winding.jpg
MAC winding.jpg (114.03 KiB) Viewed 579 times


Placing the sensor between poles #36 and #1 will have varying magnetic fields constantly affecting the sensors.
But if the sensor is placed between poles #1 and #2, its electrical environment will be much more quiet because, due to the concentrated windings, the pole #1 is always of the opposite polarity from the pole #2.

If we're gonna place the sensors on the face of the pole, then pole #2 has the advantage because it is flanked by two poles of opposite polarity, always.
I didn't think about this during the time that my motor was dissassembled but it would be interesting to know where the sensors were placed exactly, by the manufacturer. Anyone has a MAC on his bench?

I don't know much about motor design but I wanted to get this out, just in case...
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Re: Converting a hubmotor to a middrivemotor

Postby izeman » Tue Feb 16, 2016 5:49 pm

@altair: i dont know if you followed all the thread, but if you look at post #905 you can clearly see where i moved the halls. this was a picture of the new stator.
@crossbreak: good to know that you tried the kelly kls with the mac now as well. i was waiting desperately for your result. good (bad?) that you confirmed my findings: it's impossible to go above 2krpm. at least not sustained. when i release the throttle at wot it revs up to 2.3k for the blink of an eye. also if i test it from a stand still with the tire lifted. going wot makes the motor rev up to 2.3k and fall back to 2k almost instantly.
i manged to find some settings for the kelly that works nicely (still to be tuned). check my last post of the third link in my signature.
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Re: Converting a hubmotor to a middrivemotor

Postby izeman » Tue Feb 16, 2016 5:54 pm

@cb: my mac runs super quiet and super smooth from zero rom to full rpm. can't confirm that this is because of my halls shift, but it was necessary anyway as it was almost impossible to run auto-detect w/o the mod. now it works great.
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Re: Converting a hubmotor to a middrivemotor

Postby izeman » Tue Feb 16, 2016 5:56 pm

Altair wrote:At least, I have the blue composite gears but I learned from EM3EV that the new version has 2 smaller bearings supporting the rotor, while the older version had one large bearing doing the job.

correct. and the color of the gears says little about the motor itself. :(
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Re: Converting a hubmotor to a middrivemotor

Postby Altair » Tue Feb 16, 2016 7:20 pm

@izeman, yes I have read most of the thread, and I was aware of the change that you made to the placement of your halls.
I am very happy to learn that it solved your problem. I will probably do this mod to my motor.
Can you tell me if you placed your sensors in the center tooth of each group of 3, or if you placed them in either the first or the third one?
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Re: Converting a hubmotor to a middrivemotor

Postby izeman » Wed Feb 17, 2016 5:45 am

I just removed the halls from the slots and moved then about 4mm cw looking from above. I didn't cut slots for them but just put them onto the lams directly. So the magnets don't move along them directly but the magnetic field is strong enough to switch the halls.
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Re: Converting a hubmotor to a middrivemotor

Postby Altair » Wed Feb 17, 2016 8:27 am

OK izeman.
But are they still standing up, or you laid them flat on top of the laminations?

I wonder what the magnetic fields look like there on the top edge of the lams. Who has the software to simulate it here on ES?

I also wonder how it would work if they were placed further outwards, right over the magnet line, in a quieter magnetic environment. They could be supported by a PCB that is centered on the shaft of the motor for easy advance adjustment.

EDIT: Now that I have read the thread referred to by Fechter earlier, many of my questions have been answered. Thanks Fechter.
Last edited by Altair on Wed Feb 17, 2016 9:13 am, edited 1 time in total. View post history.
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Re: Converting a hubmotor to a middrivemotor

Postby izeman » Wed Feb 17, 2016 9:52 am

It is quite easy. Take a heat gun and soften the epoxy. Then lift the hall's board with halls still attached to it. Heat the solder and move the halls further to the board (about 4-5mm). Move the board some degrees CW and glue it to the windings. That's how i did it. So the halls moved 5mm up and 4mm to the side. They were NOT bent. This would not be good as they imho sense the magnetic field on the small flat side normally facing to the magnets.
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Re: Converting a hubmotor to a middrivemotor

Postby izeman » Wed Feb 17, 2016 9:53 am

Btw: i don't think that the magnetic field is much different where the halls are located now. Maybe the timing changes because of that as well.
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Re: Converting a hubmotor to a middrivemotor

Postby Altair » Wed Feb 17, 2016 11:30 am

OK thanks for the explanation izeman.
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Re: Converting a hubmotor to a middrivemotor

Postby izeman » Wed Feb 17, 2016 11:38 am

Altair wrote:OK thanks for the explanation izeman.

you're welcome. i hope you can sort our your issues, and together with CB's findings we can nail down the MAC's strange issues.
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