2000W MAC lawnmower motor

[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.

[youtube]p5k3O3no8Ic[/youtube]

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 :lol:

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/pro...de_Adaptor_for_Freewheel_Sprocket-888-27.html

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

 

[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.

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.

I was forgetting about the higher rpm, but the peak efficiency in the mid eighties isn't encouraging. We've gotta keep in mind that being designed for a lawnmower the money was spent on durability and toughness, but for a fixed rpm. At least it came in under the weight Nep was expecting.

Regarding efficiency compared to hubbies, speak for yourself. I've got 3 hubbies in a higher power range than this motor that have a peak efficiency of 93%, and after 5 months of testing my opinions about motors are quite colored. High efficiency motors is the path forward, because the thermal limitations are too great for motors with peak efficiency in the mid eights like are broadly available. The motors I have prove that better is possible and still be economically priced, so we should expect no less.

John

 

[toolman2]

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.

I was forgetting about the higher rpm, but the peak efficiency in the mid eighties isn't encouraging. We've gotta keep in mind that being designed for a lawnmower the money was spent on durability and toughness, but for a fixed rpm. At least it came in under the weight Nep was expecting.

Regarding efficiency compared to hubbies, speak for yourself. I've got 3 hubbies in a higher power range than this motor that have a peak efficiency of 93%, and after 5 months of testing my opinions about motors are quite colored. High efficiency motors is the path forward, because the thermal limitations are too great for motors with peak efficiency in the mid eights like are broadly available. The motors I have prove that better is possible and still be economically priced, so we should expect no less.

John

the 100w of rpm loss that neps measured (and loaded to a further 100w of copper loss, takeing us to the the peak efficiency point) and 2000-4000w would yield 90% - 95% efficiency, and yep i still believe THAT to be more efficient than any of our hubs, not the criro one, but ours. but those potential numbers are not known or real untill we get a resistance check to go with the no load test that has been done.

likewise going with number like 93% efficiency from a chinese hub motor spec sheet, and haveing complete faith in it by 'proving' this to be accurate with a side cover plate magic finger temperature test is equally doubtful.

i believe in the real world this is a low budget motor of around 85% efficiency at best, and if you want to compare this to your hub, then lets at least try and do it right and use the same method for both. all you need is a no load test and a resistance check john, easy to do and im keen to know, with actual tested readings you may well end up in front here and we will all learn some stuff..

 

[neptronix]

I agree that "doing science" is important here

So even though i was a bit nervous about plugging my iCharger into my phase wires, i did your test and here are the results:

The voltage would not go up to the 5v i set the 'foam cut' mode to. It just slowly rised up to 10A and maintained a certain voltage.

Mind you, the phase wires are about 3 times longer on the hub motor, and about half a foot is only 16ga, where the rest is 16ga. x 2. I don't know if that makes a big difference.

I don't know how to interpret this data, so let me know what you think, toolman.

 

[toolman2]

fine work neps, so heres the deal,
you have .0305ohlms winding resistance, and to get to peak eff we need the resistance losses (notice the 4.5w reading on the icharger, this is that loss for 10a)
to equal the 106w rpm losses.

it tuns out thats 59A (59*59* .0305 =106w of winding loss) of phase current.

its a 70kv motor so 1 divided by 70 * 9.6 =.137NM/amp -this is good to know, you get .137NM of torque per phase amp.

59 of them gives you 8.1NM output for 106W of winding loss (kinda regardless of rpm)

so to put that all together for this 38.6v setups peak efficiency spot, 8.1NM * around 2400rpm loaded *.1047 = 2035w output @peak eff of around 90%
you have put in 2277w (38.6v and 59 amps) you get all of that as output accept the two lots of 106w losses so you get 2035w output.

this maths is not spot on (but should be, when corrected by someone like miles who actually went to school!)
and even then its not taking magnetic and other losses into account, but its a really good ballpark, and prolly the same as the basic simulators.

so 90% peak eff, pretty dam good neps, better than i thought, and you are only dissipating 212W of heat, that i reckon it could do continuously without additional cooling, so this point of operation is going to be really easy on the motor.

you could go to 50v and about 85A to get more like 4000w and a bit higher efficiency, with i bit of air directed through it i reckon this motor could do say 11 NM at around 3000rpm on a light bike and be somewhere its thermal limit (depends on a bit more size/weight info), be good if folks could just double check all of that, it was a rush job.

but its looking pretty good for this motor, also with key ingredients like easy single stage reduction and cheapness.
and come on john, why not feed in the readings and join all the fun!

 

[torqueon]

Sounds good thus far, any up dates on this motor, as to what it can do, and where it can be found. I have a really light weight moped, just begging for a motor like this.

Thanks to all for the foot work.

 

[neptronix]

Thanks toolman2, maybe this motor has hope
I look forward to seeing what it does at 78v and 57v, i guess i have to order up the bits and pieces for a secondary reduction system.

Torqueon, i am waiting on parts at the moment.

http://endless-sphere.com/forums/viewtopic.php?f=6&t=40327

I will update this thread, as well as my killabicycle jr. build thread above, when i get something actually on the road.

 

[zappy]

Good work nep

Thanks for all the constructive input Toolman




Neptronix at that lowish (3000) rpm you should be able to to get a way with a single stage kart 219" chain. 800kg-1000kg break.
Go karts put out about 20Nm at very high rpm. Ebay or online kart shops have a better range of ratios than most other pitches availble.
A medium size outrunner with a single stage reduction is probably a really good middle of the road between obese hub motors and the very small outrunners with multi drop gear sets and an erpm most availble controllers can't keep up with.
You would need to make up a kart sprocket to disk adaptor somthing like this and than your motor options are large.
It almost makes it worth welding up a motor test bike?

Zappy

 

[magudaman]

Hey guys just wanted to let you all know I am the one who purchased one of the motors from neptronix and will be making some postings about my experience with the motor. I received the motor on Friday (amazingly fast thanks neptronix) and looks great. The plastic case is actually well made and may end up staying on mine. The phase wires look pretty tiny though and I may consider replacing them.

I will be opening the motor up hopefully tomorrow and be taking some picture next to my BMC 1500W/2000w unit to contrast the two. I am also going to be machining the shaft down on the MAC to 5/8in and adding a 3/8in keyway (looks smaller currently. I'll have to look a bit closer but that bolt hole on the shaft look pretty large, and I hope 5/8in will work. I would also love to make a new mount plate for the motor but out of aluminum but I'll see if I'm feeling up for that.

Lastly I was thinking about adding some small fins on the magnet assembly to create a centrifugal fan of sorts. My BMC is currently cooled by a 12V fan, which sort of works but needs the air flow reversed.

I do intend (just as my BMC) adding a temp sensors a some winding and another for general air temp/magnet temp.

I am sure hoping this MAC has similar power as the BMC. I have pushed that old BMC upward of 8KW peaks and it just continued to seem to get more and more torque. Not to mention it has had a very hard life of too much heat and well over 1000 miles of really tough off road.

 

[neptronix]

Zappy: that is an awesome adapter, damn!!
You could run a huge sprocket on that with such a huge inward offset.

I did not know that such a thing existed nor do know a machine shop locally who could make one ( would probably be rather spendy ). I wonder if the chain would then rub on the tire, lol.. or maybe that's a 150mm wheel..

Anyway, i did order a sprocket from here: http://kingssalesandservice.com/. I ordered a 39t 40 pitch sprocket and will be using 12t. at the motor.

Yeah i agree that a mid-speed motor is really desirable. There aren't many of these out there. Come to think of it, the supply of cheap, lower KV BIG outrunners is kinda drying up these days, isn't it?

http://www.hobbyking.com/hobbyking/...SK3_6374_149kv_Brushless_Outrunner_Motor.html

There are these - you'd just need a lot of them in parallel, and double reduction for sure.


Magudaman: Glad you got the motor in one piece

Hey, wasn't it you that melted the magnet epoxy off a 1.5kW rated BMC motor? Did you ever fix that motor?
Can't wait to see what you come up with.

 

[fizzit]

This motor looks pretty cool. Thanks for all the info, Neptronix. I wonder how well an HV160 could drive it?