2000W MAC lawnmower motor

[neptronix]

Allright, finally got some pics. Had to work all day and had the motor box sitting in front of me all day! time to check out the new toy!



Two big MACs. One to blow up finding it's limits, one to ride with on a permanent basis



First note is the huge black plastic case and 12 gauge phase coming out of it.



The axle is flipping huge.



22.3mm.. that's a 7/8" shaft size in inches, which seems to be fairly standard.



70mm width, so ~2.7 inches. This would fit inside a bike triangle pretty well.



I'm missing my tape measure and my caliper is maxed out. I'm gonna guess this is 165mm in width ( 6.5 inches ). The plate adds quite a bit of extra width too, maybe the total diameter is 180mm or so ( 7 inches ). I'll get more exact dimensions later.



Ghetto rigged boat chair seat swivel from wal-mart fits over it..



And fits under it.. i could sandwich the motor between these if i wished. Cool!



mock bike mount..



mock bike mount showing chain line..



Okay, opened up now and oh no, shrinkage! apparently the case is very oversized. Oh well, i was warned.



Cooling holes pre-drilled, sorta like the BMC motors..



Magnet diameter, about 23.5mm or so ( hard to measure here )



Total stator circumference is 135mm.



22mm stator width.



Or 28mm with copper..



Hall sensors and what looks like maybe.. a thermistor?



Okay, back to the case... looks like there is a groove that you could use to seal the motor up by inserting an o-ring, or throwing in some RTV gasket maker, to waterproof the motor.



And last but not least.. showing how oversized the motor cover is.

Overall first impression... this is most definitely a lawn mower motor. It's very overbuilt. If redesigned, it could easily shed pound or two for eBike usage. The case size could be drastically reduced as well. I think the 7/8" shaft is going to have to be cut down for eBike usage, and maybe a custom case could be made as well.

Should have some actual motor tests in a few weeks. Life's a bit hectic but you will definitely hear more about these later

[Miles]

neptronix,

Please could you measure the core lamination thickness? 0.35mm? I tried counting....

[neptronix]

Miles, how do i do that?

BTW, user 'ohzee' mentioned that his MAC hub motors have identical dimensions, except the stator + copper width is 1mm less..

[TylerDurden]

Magnet diameter, about 23.5mm or so ( hard to measure here )

Looks good!

FYI: You can use the tang of the caliper to measure depth.

[Miles]

Miles, how do i do that?

Count how many laminations there are, then divide the total width by that number. Or, set your calliper to 10mm and count how many laminations there are within that.

[Miles]

It's an 18t stator. 16 or 20 magnets?

[neptronix]

You mean each layer of ~1mm steel that makes up the stator then?



I'll have to take the motor part again tomorrow. Let me know which dimensions/counts you want in advance then.

[Miles]

The plastic bowl looks to be useful - elsewhere.....

[neptronix]

[Miles]

You mean each layer of ~1mm steel that makes up the stator then?

That's right. Magnet thickness would be useful, too.

[Jeremy Harris]

Looking at that motor it would seem that you might be able to remove the shaft. make a new, longer, one and stack another motor on top, with the new shaft connecting the two rotors together................

[bzhwindtalker]

This looks quite promising to me, a quite ligthweigth 4kw motor that you can fit on a bike with a single stage #35 chain drive, that is serviciable and easy to rebuild is something a lot of people here are after. Now, is is easy enough on controllers? I would like to see what kind of power this can make paired with an inexpensive hua tong 27$ 18fet. Price?

[neptronix]

Well, i've got bad news..

2 people ( ohzee and andynogo ) have confirmed that their MAC hub motors have the same stator diameter, circumference, and almost the same copper fill, about 1mm less copper

This motor is going to be hard on our eBike-tailored controllers, for sure. You will need a controller that is capable of pushing high sustained amps. This is a low turn count motor - would be equivalent to a 4-5 turn MAC hub.

An ideal controller would be a 18-24FET with 3077 FETs with upgraded phase lines & phase/battery amps tuned to 200+ at 36 or 48v. The 3077 FETs have 25% lower RDSon than 4110's and should have no problem flowing at such a high amp rate.

http://www.irf.com/product-info/datasheets/data/irfb3077pbf.pdf

http://www.irf.com/product-info/datasheets/data/irfb4110pbf.pdf

A 4110 FET controller will do, but consider it as pushing 25% less amps, so a 24-36FET would be more ideal.

To give you an idea of how fast a winding this is.. it will do 2750RPM unloaded on only 36v. With a 5:1 ratio ( just like the hub motor version ), it is pushing out 550RPM. That translates to 42.5mph unloaded on 36v with a 26" wheel. That probably makes for 35mph ( or 54kph ) on 36v with a 26" wheel.

The reason this motor was chosen is because it has a much lower RPM per volt than the BMC can motors. A single stage reduction is fine here.

I believe that the 2kW constant rating may only happen at 48v, which means you get 3500rpm unloaded. a 6:1 or 7:1 reduction would be needed to hit that lofty 35-40mph figure.

This motor's advantage over the MAC hub motor may be this:

+ Higher RPM per volt should mean for better power per weight.
+ No gears to worry about melting. No clutch to worry about killing. Pump as much stupidly high peak power into it as you want. This is overbuilt and can take it.
+ Looks easier to seal than the MAC hubs..
+ Looks like half the pole count so i would assume the electrical RPM is half. This is going to be much easier on controllers.
+ Low voltage is easy to live with when it comes to charging, not having to worry about precharge resistors, etc.

But so far, i am disappointed by the high weight. This will end up being 2-4lbs. heavier than a regular MAC motor.

[neptronix]

Jeremy, i like your idea .. but when you add the weight up, you might be better off just getting the motenergy 4201.

http://www.electricmotorsport.com/store/ems_ev_parts_motors_pmac-ss.php
http://www.cloudelectric.com/product-p/mo-me4201.htm

The end result might end up being rather wide too. Wider than said motenergy ( which isn't a small motor! )

And BZH, these motors are gonna be cheaper than a BMC 1500w motor from the superkids:

http://www.thesuperkids.com/15wabmcbrmos.html

But i don't know what the end-price will be if we get a large sale going. I can work with cell_man later on to get a good price for folks who are interested, after the testing is done. ( I don't want to arrange a sale if this motor is a dud and not a stud. )

[liveforphysics]

I bet the continuous power with that cover on is less than half of the power with it off. That tooth has a lot of air space around it, like they were going for saving $2 in copper over adding 20-30% continuous power.

[bzhwindtalker]

I'll stick to a mid drive hubbie as a big/cheap outruner then. Super easy on controllers, widely available, well documented. I would like to know where the mechanical/ iron loss limit is on a typical hub, anybody have an idea??

[voicecoils]

Even pulling a hubmotor motor out of it's geared motor case, the ability to shed heat should vastly increase and any cooling methods should be easier to implement. Fan forces for example.

I still think brushed motor is an easier option in the bike you have planned nep. It's just that the thin pancake and high efficiency options are not cheap.

[neptronix]

I'll stick to a mid drive hubbie as a big/cheap outruner then. Super easy on controllers, widely available, well documented. I would like to know where the mechanical/ iron loss limit is on a typical hub, anybody have an idea??

In that case, you want a 12T MAC motor, or one of the slowest Crystalyte 4xx's you can find.

[neptronix]

Very possible, Mr. coils. I bet you could dump some serious peaks into this stator that way.

Sorry i did not get measurements today, guys. Motivation to toy with this motor is down considerably after discovering that the stator is the same size as the hub motor i already own. I don't see how this motor can be rated for double the power as the hub.

Would it be conceivable that a really large case and approx. 1.5x the RPM of the hub could really push an identical looking stator to produce double the power?

Still waiting on cell_man for a hall wiring combo.

[liveforphysics]

Would it be conceivable that a really large case and approx. 1.5x the RPM of the hub could really push an identical looking stator to produce double the power?

Nope. That really large case is a big power hurter on the motor rather than helper.

Still waiting on cell_man for a hall wiring combo.

You don't need anyone to tell you a hall wiring combo bro. Just hook up wires and start testing until it spins the right direction, then make sure it's not a damn false-positive (make sure no-load current is like sub 1amp), and you're set.

Y-pedal made a really handy spread-sheet for trying combos and crossing them off one at a time. I've used that sheet like 20 times. lol

[neptronix]

yeahh.. but do i risk damaging the hall sensors themselves with the wrong combo?

Fechter says this:

Be very careful when swapping the hall signal wires around. If a hall signal wire makes contact with the hall supply, there is a good chance of blowing the hall sensor. Best disconnect all power before swapping wires.

I cannot tell what the 5v lines are. Brown, red, orange, yellow, green.. i don't see any correlation. What happens if i reverse the polarity on the hall lines, since it is not apparent at all?

Guess i could pull apart my MAC hub motor once i am done moving, maybe the board is similar enough that i can figure it out.

http://endless-sphere.com/forums/viewtopic.php?f=16&t=3484

^-- this idea of looking up the datasheet won't work because there aren't any markings on the back of these halls.

Any other ideas other than disassembling 2 motors, copying the wiring scheme, and hoping i don't blow some brand new halls?

Feelin' noobish over here..

[Chalo]

I bet the continuous power with that cover on is less than half of the power with it off. That tooth has a lot of air space around it, like they were going for saving $2 in copper over adding 20-30% continuous power.

You don't think air gaps in the armature help cooling? Seems like they might.

Chalo

[Miles]

You don't think air gaps in the armature help cooling? Seems like they might.

Better not to make the heat in the first place.....

[auraslip]

Not really surprised. Lawn mower engines have a habit of being overrated. Toro was sued for it. My "2.5hp" toro mower is actually more like 1hp! If I actually cared enough I could of gotten free mower maintenance out of the lawsuit.

Again, I'm not really surprised. If you think about how a lawn mower is setup and used. 2kw peak is plenty for residential use. Especially in an electric mower. Most people mow for 20 minutes. Most people don't push their mower through thick grass that requires a 2kw motor. Mostly through grass that'll be the equivalent of running at no load. And Only for enough time for the motor to start to get really warm. And also, I think some mowers use the blade itself to cool the motors. That's a a TON of air to cool the motor.

But listen, don't be too bummed out. If it's rated at 2kw... that's probably somewhere between continuous and saturation.

And think about this statement:

Okay, back to the case... looks like there is a groove that you could use to seal the motor up by inserting an o-ring, or throwing in some RTV gasket maker, to waterproof the motor.

You could concievably fill the case with ATF, and then you'd be able to run the motor at pretty much saturation.
Or at the very least you could properly cool the motor with a fan. Remember, geared hub motors can't really be ventilated. So even though it's the same size as it's ebike cousin, doesn't mean it will only be capable of what a hub motor will be.

[magudaman]

Where exactly can you get these motors? I looked at getting one directly from mac for testing but they didn't even have that plastic case, just exposed, there price wasn't too bad though! It looks very internally similar to that BMC 2000w superkids has that I have been using for a couple years. The BMC has been a great motor and really took some crazy abuse.