Mars Electric LLC Axial Flux Motor

[Jeremy Harris]

Please dont skew the rotor teeth....

It will only help with the torque ripple at the cost of efficiency, and mimimaly effect the noise.
Remember, the cogging isnt what causes the noise, its the alternating push-pull of the torque producing magnetic field flexing the rotor back and forth a whisker, much like a speaker.

A little acustic dampening material on the back of the rotor, or altering the rotor design would be better options IMHO.

Thank goodness for some more voices of sanity on this. I've done some work on trying to reduce the noise level from this motors big brother and the only thing that made an appreciable change to the motor noise was adding damping to the rotor disc. Changing controllers, even using an expensive sine controller, didn't make a massive difference to the motor noise, certainly not as much as damping the rotor.

It may be that the rear case acts as Bigmoose suggests, too, amplifying the noise somewhat.

Either way, I believe that it's an intrinsic property of a single-sided axial flux motor, so something that we've probably got to live with.

Jeremy

 

[jmygann]

Is the "Planet Rider" motor noisy ?

 

[Ypedal]

the cell phone mic does not always pick up accurate real life sound, but to me that was not offensive at all.. a low pitched hum is ok imo....

 

[Miles]

Is the "Planet Rider" motor noisy ?

No, it's pretty much inaudible, outside (circa 1800 rpm).

 

[jmygann]

Can it be reproduced ?


"The rotor is made from precision machined steel bar and has twelve high-temperature (180°C) neodymium-iron-boron (NdFeB) magnets mounted on its circumference. The magnets are retained with stainless steel bands and the rotor is balanced prior to assembly.
Following our commitment to high quality, high performance materials and components, Nachi bearings are used throughout our product line. 30mm double-row angular contact bearings are standard.
The rear cover is comprised of glass-filled, high temperature thermoplastic, which is precision machined. A magnetically coupled coolant pump may be added, when necessary.

 

[Miles]

Of course. You just need a suitable stator to start with....

 

[johnrobholmes]

For my use, I will gladly take an efficiency hit for less noise from the motor. The motor makes as much or more noise as my 3 stage chain drive reduction with an astro motor, but there isn't reduction added to the motor yet.


If you have further suggestions on reducing the noise, I am all ears. I say that it is the detent of the motor causing the noise because the motor was noisy during rotation with no power applied. I am sure that changing the case and rotor can reduce a good bit of the noise as well, as they are acting like a speaker from the vibrations caused. The question is what is a cost effective way to reduce the noise without throwing out the tooling that Mars already owns.

Bigmoose, could you try flicking the rotor and seeing if it rings like a bell? Maybe some holes in the rotor could make a significant effect.

 

[Jeremy Harris]

Of course. You just need a suitable stator to start with....

Wasn't this based on a modded car alternator stator, fitted with a PM rotor designed for use as a wind generator?

I've seen these kits on places like ebay from time to time and thought they might make reasonable BLDC motors. An alternator can usually run up to around 12,000 to 14,000 rpm, the stator on even a small car alternator is good for at least 50A, some are good for around three or four times this current.

Jeremy

 

[Miles]

Of course. You just need a suitable stator to start with....

Wasn't this based on a modded car alternator stator, fitted with a PM rotor designed for use as a wind generator?

Yes, it was a stator from a Ford, I think.

It would be nice to start with one of these: http://www.globaldensoproducts.com/em/a/sc_alternator.html

 

[recumpence]

Of course. You just need a suitable stator to start with....

Wasn't this based on a modded car alternator stator, fitted with a PM rotor designed for use as a wind generator?

Yes, it was a stator from a Ford, I think.

It would be nice to start with one of these: http://www.globaldensoproducts.com/em/a/sc_alternator.html

Wow, the copper fill looks awesome!

Great find, Miles. Now you just need to get one and convert it for us...........

Matt

 

[TylerDurden]

Bigmoose, could you try flicking the rotor and seeing if it rings like a bell? Maybe some holes in the rotor could make a significant effect.

Maybe measure movement in-situ (it might take drilling a hole or two in the case for the gauge).

 

[bigmoose]

Bigmoose, could you try flicking the rotor and seeing if it rings like a bell? Maybe some holes in the rotor could make a significant effect.

John, I'll make an appointment with myself to take it apart again on Wednesday and try to "ring the rotor" with an impulse. I still owe you guys the motored scope traces... "The faster I go the behinder I get!" ... kids coming home from college this week are throwing off my schedule. Lastnights snow storm didn't help either... spent a couple hours plowing snow today.

 

[liveforphysics]

http://www.globaldensoproducts.com/em/a/brushless_alternator.html

Perhaps permanent magnet as-built?

 

[jmygann]

Perhaps like this ...
http://www.survivalunlimited.com/windpower/pmas.htm

 

[Jeremy Harris]

http://www.globaldensoproducts.com/em/a/brushless_alternator.html

Perhaps permanent magnet as-built?

Interesting find. My guess is that this would work fine up to the sort of rpm it runs at on the truck, probably quite high, as these things are usually geared up to run a lot faster then the engine.

I wonder what trucks they are fitted to? Might be an idea to do a tour of the local vehicle dismantlers and see what they've got.

Perhaps like this ...
http://www.survivalunlimited.com/windpower/pmas.htm

I've had a look at something similar, including some PM rotor replacements for standard alternators. I also looked at some of the big purpose built PMAs sold by wind power companies, some of which have ratings in the kW range. The problem will all the wind power offerings seems to be that they are optimised for low speed (typically less than 2000rpm) and good start up. This latter point means that they deliberately "detune" the thing by skewing the magnets in the rotor, so that the detent torque is low. Whilst OK for a wind generator, where they want the rotor to start turning at low wind speeds, it's not ideal for a motor at all.

It can't be too hard to make a PM rotor for an alternator. I have two or three old alternators that are rated at around 50 to 70 amps, if I get any spare time I make take a look at what it would take to do this. We know it works, because others have similarly made "altermotors" like this. The restriction has always been the relatively thick lamination thickness and relatively poor copper fill, both issues that seem to have been addressed in that Denso SC design.

Jeremy

 

[Harold in CR]

New Delco 12 Volt Brushless Industrial Alternator 1117641
Used onn Caterpillar, Chevrolet Truck, Cummins,GMC,IHC,Mack,
Massey Ferguson,Caterpillar Marine Engines

The Denso is on Cat engines as well.

I have been waiting for a Brushless Motor Controller to show up, so I can mess with an Alternator rewind. I also have a 24V 250 A Leece-Neville Alternator, just waiting for a suitable controller.

I also have been wondering, what about using 2-3 Alternator Stators, fastened together, and just make a longer shaft, and use 2 same type Alternator bell ends with the larger bearings. Just wind the coils as needed ???

 

[Jeremy Harris]

New Delco 12 Volt Brushless Industrial Alternator 1117641
Used onn Caterpillar, Chevrolet Truck, Cummins,GMC,IHC,Mack,
Massey Ferguson,Caterpillar Marine Engines

The Denso is on Cat engines as well.

I have been waiting for a Brushless Motor Controller to show up, so I can mess with an Alternator rewind. I also have a 24V 250 A Leece-Neville Alternator, just waiting for a suitable controller.

I also have been wondering, what about using 2-3 Alternator Stators, fastened together, and just make a longer shaft, and use 2 same type Alternator bell ends with the larger bearings. Just wind the coils as needed ???

Thanks Harold, I'll have a look around and see what I can find locally. My guess is we're going to be short on Jimmys, Chevys and Macks around here, but there may well be some Caterpillars, MF and Cummins parts around.

Looking at some of the PMAs being sold by the wind turbine folk it looks very much as if they might be doing just as you suggest, putting a few alternator stators together and rewinding them. I was looking at these yesterday: http://cgi.ebay.co.uk/500W-WIND-GENERATOR-TURBINE-PERMANENT-MAGNET-ALTERNATOR-/250741346231?pt=LH_DefaultDomain_0&hash=item3a61594fb7 and whilst googling around found a photo of the stator (I can't find it now!). It looked pretty much like two or three alternator stators stacked and rewound to me.

My simple (relative term, I know) home made brushless controller is now working, BTW.

Jeremy

 

[Harold in CR]

I saw your Brushless Controller thread, Jeremy.

I have tried, several times, to learn Electronic stuff. Only thing I did learn, was, they sure pack a whole bunch of Magic Smoke in some very tiny parts.

All you Electronic guys simply amaze me. Nice job, jeremy.

 

[bigmoose]

Gent's on that denso alternator. Just because it said brushless, might not mean it is permanent magnet. On large alternators, think 60 cycle "generators" in the larger sizes, the rotor field windings are energized through inductive coupling. There is a separate stator that acts like a transformer. Primary in the energizing stator and the secondary is on the end of the rotor that powers the main rotor's field. ... did that make sense? This way the brushes are removed for higher reliability.

 

[Jeremy Harris]

Nice tip, Bigmoose. That would make perfect sense for a vehicle alternator, where they would want to use it as a charge controller as well.

Depending on the rotor design, it might well be worth looking at anyway, as you can still get higher flux densities (and hence greater potential torque) from electromagnets than you can from permanent magnets. I haven't checked lately on the current state of the art when it comes to neodymium and other rare earth magnets, but when I looked into it a couple of years ago a good electromagnet could be around 40 to 50% better than a permanent magnet using the best grade neodymium.

Jeremy

 

[jmygann]

Nice tip, Bigmoose. That would make perfect sense for a vehicle alternator, where they would want to use it as a charge controller as well.

I haven't checked lately on the current state of the art when it comes to neodymium and other rare earth magnets, but when I looked into it a couple of years ago a good electromagnet could be around 40 to 50% better than a permanent magnet using the best grade neodymium.

Jeremy

maybe these ...

http://www.survivalunlimited.com/windpower/pmasc.htm

 

[olaf-lampe]

To overcome the noise of the mars motor, he should make it a two disk rotor. This would eliminate the 'drum' effect.
But that's a complete different housing a.s.o.
-Olaf

 

[jmygann]

Anything happening with this motor ? .......or are we back to an alternator motor ?

 

[johnrobholmes]

I haven't heard anything from Mars addressing the motor noise lately, but I haven't pushed the issue too hard. If you wanted to pick one up for yourself, contacting them would get you a motor pretty fast I imagine.

As-is, I have no doubt it could make an awesome ebike motor for 1hp average use. Run it through the derailleur and it would make a pretty potent setup.

 

[neptronix]

I saw your Brushless Controller thread, Jeremy.

I have tried, several times, to learn Electronic stuff. Only thing I did learn, was, they sure pack a whole bunch of Magic Smoke in some very tiny parts.

All you Electronic guys simply amaze me. Nice job, jeremy.

I can identify with this :lol:

That's why i keep a magic smoke refill on hand at all times.