2000W MAC lawnmower motor

[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.

[neptronix]

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.

There is no formal dealer for these motors. I got mine by saying the magic words and knowing the right people in order to get a sample from 'cutler mac'. What they want is large quantity orders, ultimately.

Retail cost might be around $200, maybe less if the one time sale occurs.

[el_walto]

Does cell_man sell these? I wanted to build a lawn mower, maybe these are they way to go. Looks like you might be able to directly mount a blade on them.

[neptronix]

No, he does not. I am trying to convince him to sell them if they turn out to be useful as eBike motors.



Well, i took a chance and plugged the hall connector straight in. I got grumbling on the first throttle twist, so i knew that was a good sign. Swapped the yellow and blue phase lines and she spun up.

2700rpm @ 38.6v unloaded. 80% should translate to 2160rpm; with a 5:1 ratio, i estimate that the speed on a 24" wheel will be 33-35mph.

No-load amps are 2.75A @ 38.6v.

There is tons of extra weight in this motor. I estimate that 3-4lbs could be shaved off if you took a machine shop to it.

Will provide pics and additional measurements later on.

[Hillhater]

Nep, ..one major advantage with that motor ( and part of the extra weight) is that huge output shaft ....with proportionately larger bearings too i assume ?
That is going to be a lot easier to mount a sprocket on than a hub motor, will stand up to a ton of abuse, and help transfer heat away from the stator.
Frame mounting will be easier than a adapting a hub motor also.

[toolman2]

fine work neptronics,
this motor has some potential, if you are able to measure phase resistance, (by putting around 5amps dc across any phase and measure the voltage drop by probing at a nearby bit of the same phase wires) then there would not be much need for destruction, as we can then work out nearly everything about its abilities.
-or another way of putting it, we can calculate for say 2kw of output power weather you have just 150W of heat build up to shed or 500w+ ?

and what was the weight again of just the necessary motor bits?

[John in CR]

No-load amps are 2.75A @ 38.6v.

Low efficiency, so Luke was right about that air gap. It's not worth your time.

[toolman2]

No-load amps are 2.75A @ 38.6v.

Low efficiency, so Luke was right about that air gap. It's not worth your time.

100ish watts for 2700rpm is not necessarily a problem john, and i believe a bigger air gap would actually lower this reading (not saying its a good move though).
-you realise that 100w alone lost out of 2000-4000w has the potential to be more efficient than any of our hubs?
its all down to the phase resistance from here.

im thinking its well worth the 3mins to check it.

[neptronix]

Hm, attached is the motor performance graph @ 48v. Efficiency at no load is apparently 16.9%. Peak efficiency is 84.7% on 32A / 48v.

The MAC hub has a slightly higher no load current ( 3 amps? i forget ) at 1600rpm versus the 2700rpm this motor is putting out at the same voltage.

I don't have a weight on things yet, sorry. All my stuff is packed and we are about to move. Maybe i should hop over to wally world and get a fishing scale if they have one. Too hard to excavate mine from the boxes.

But the metal plate that the stator bolts on to is pretty heavy, feels like 3lbs on it's own, and is steel.
The shaft itself has to be quite a bit of weight on it's own, and is made of steel as well.

The giant stator support could be cut down too with the right machine shop tools.

Some more pics..



42 laminations.



Motor with the mounting plate taken off, showing the rediculous size bearing.



Comparison to the magnets of the MAC 500W hub. These are over 2mm but i am having a hard time measuring due to the fact that they are flush with the case that holds them in, sorry miles.



Showing how excessively long the stator support is... this could be cut down quite a bit.



The housing for the neo magnets is oversized given that they are about the same dimensions



Another magnet shot.



Stator comparison.



Another stator comparison.

[neptronix]

toolman2.. what would be the best way to do your 5A test? i have an iCharger and can use the motor drive mode to pump constant current.. but i've never done this.. would i risk damaging the iCharger?

[neptronix]

okay, got the scale from wally world. This motor is only 9lbs, 2oz / 4,139g rather than the 11lb/5kg quoted.

Face plate: 2lbs / ~900g
Axle and neo magnet assy.: 2lbs / ~900g
Plastic cover: 1oz / ~28g
Stator + wiring + stator bolts: 3lb, 14oz. / ~1757g
Stator without bolts: 3lb. 12oz. / 1700g.

OK, now this motor seems like it's got a decent power to weight ratio then, even if it is only capable of pushing out 1.5kW continuous ( worse case ), considering that you can shave a few lbs. off and get the motor down to 7-7.5lbs pretty easily.

Am now feeling better about this motor. Perhaps i will get a BIG sprocket ordered and sent to the new place, run high end BMX chain on it, and see what happens around 4-5kW.

[toolman2]

toolman2.. what would be the best way to do your 5A test? i have an iCharger and can use the motor drive mode to pump constant current.. but i've never done this.. would i risk damaging the iCharger?

maby not motor drive, but wire cut function on the icharger should work, any way of putting even a few amps across a phase, 5 or 10 is better(its resistance should be way under .2 ohlms so is near enough to just a solid length of wire) anyway just measure the amps you get and the few tenths of a volt that you will get across it as a result, volts divided by the amps =ohlms.

[Miles]

Thanks!

So, 0.5mm laminations. That's going to limit things a bit...

[neptronix]

Am shipping out one of these motors to magudaman. He will probably be able to provide some proper test data on this thread faster than i can

I am stupid when it comes to chain drive. I am still trying to find the proper bits and pieces for a 6:1 gearing at this point , so i can test the motor out

[auraslip]

I am stupid when it comes to chain drive. I am still trying to find the proper bits and pieces for a 6:1 gearing at this point , so i can test the motor out

Building a drive system capable of 10hp peaks onto a modified bicycle frame has intimidated the hell out of me.

[neptronix]

I am stupid when it comes to chain drive. I am still trying to find the proper bits and pieces for a 6:1 gearing at this point , so i can test the motor out

Building a drive system capable of 10hp peaks onto a modified bicycle frame has intimidated the hell out of me.

Yeah... it's another world. I guess if you are familiar with motorcycles, scooters, go karts, ATVs etc then you already know what's up, but from a hub perspective, you're a total damn noob

I've had various go kart, motorcycle, scooter, and lawnmower repair places give me dumbfounded looks and no answers.
I did find one place who recommended a jackshaft system and gave me an idea of what i needed, but not the complete picture.

http://www.staton-inc.com/store/products/7_8_ID_x_1_2_wide_Adaptor_for_Freewheel_Sprocket-888-27.html

Staton inc. has some interesting bits and pieces, but not the entire shebang.