Leaf hub motors any good?

[2moto]

Hi all, newby here.

I am starting another electric bike project, an electric trials bike this time. Was looking to use one of the higher powered hub motors this time, almost certainly a direct drive, as geared ones tend to have longevity problems in serious off-road use. Have been looking at Golden Motors, Conhis, and various other Chinese makes. However, Leaf seems to have a more powerful one then the others. Link here: http://www.leafmotor.com/hub-motors/rear-electric-hub-motor.html

For trials, it's low speed torque that's critical and Leaf claims 44 Nm versus 29 Nm for the Golden Motor Mag Pie as the next closest. Does anyone know if this is real or just specmanship, i.e. bullshit? Anyone used one of these?

The plan is to motorise a bicycle first to gauge performance, and then build a purpose made trial bike from scratch. Any help is greatly appreciated. Thanks.

[Spicerack]

They look just like every other cheap hub motor out there. I would tend to take any performance figures with a pinch of salt. They also state how their "highly powered and low noisy hubs" attain even 20mph. Phew!

[bearing]

Looks like they were very inspired by http://www.goldenmotor.com when they did the website. Apart from that, no alarm bells from me. It looks OK.

There are some good pictures of the insides of their big hub motor.

7-electric-hub-motor[1].jpg (151.97 KiB) Viewed 2283 times

If I count correctly, this motor has 51 teeth and 46 poles. Looks like a very good combination. Very low cogging, and high winding factor.
EDIT: apparently the same as 9C 2806 viewtopic.php?f=30&t=25562

Slots 51 Magnetpoles 46
This slot/magnetpole combination will have 2346 cogging steps per turn.
And its windingfactor is: 0.94378
AaABbBbcCcaAabBbBCcCAaAabBbcCcaAaABbBCcCcaAabBbcCcC
http://www.powerditto.de/bewicklungsrechner.html

Leaf claims 44 Nm versus 29 Nm for the Golden Motor Mag Pie as the next closest. Does anyone know if this is real or just specmanship, i.e. bullshit?

http://www.leafmotor.com/electric-bike- ... -motor.pdf

At 44Nm the motor has lost more than half it's max speed, and has an efficiency of 57%. I don't think it handles that torque continuously. Do you have a link to the Magic pie numbers?
Something is a little strange about the data though. Torque and current doesn't have a constant relationship. I think they have measured battery current, and not phase current.

[waynebergman]

Looking forward to see how this project works out for you 2moto. I love putting around slow myself and would love a hub solution with even a 15mph top speed that had some good torque and smooth power that does not heat up from the bursts you would want from a slow to standstill start. I am a newbee myself so I am not sure about this, but just going by what I have read over the last 6 months it seems its very hard to find a quiet DD hub motor that is happy enough giving good torque at slow speeds. Its a shame because I love the simplicity of my DD Hub build but in the end it is a motor that is happiest going faster than trials type riding. Also the DD Hub motors I think would want to heat up being put through a trials style power demands. I have wondered if a mid drive style using DD hub would be an option for you. More work but you could house the motor with a dual purpose bash guard in front of the BB area for bashing over logs and stuff. There is a mid drive in progress on the forum here using a Mac. I think its from Whiplash......check out this link if you are interested in a mid drive viewtopic.php?f=28&t=34158

Good luck with this one.

[Farfle]

I would do a mid drive slow wind hub motor with some reduction, 2:1 or lower. I think a 9c or magic pie would be more than adequate with a reduction.

[2moto]

Many thanks for everyone's input. Lots of food for thought. The data for the Magic Pie DD motor is here: http://www.goldenmotor.com/magicpie/MP-performance%20data%2048V.pdf

Yes, at full torque the efficiency drops off significantly but that's not surprising. The speed drop-off is not too concerning as it's the torque at zero speed that critical for trials. And yes, I wouldn't expect the max torque to be continous. Do you think it could provide 1000W continous?

And, lastly, the "gear reduction" will hopefully be enouth by using a 16" rear wheel. You see, it will be a kids trials bike. Using the Leaf Motor data, this would give a theoretical max speed of about 22 MPH, which more then sufficient.

I'll start posting build pictures as soon as it starts in earnest.

[waynebergman]

My son used to ride a little Magamo trials bike and it was very cool with that small back wheel and the big fat tire back there as well. If you are going with that small of a wheel my guess is the larger diam DD hubs will mean a radial lace, how about the mac geared hub so you can maybe cross the spokes with a one cross? I am not sure about how the one cross with a 16 inch and a mac but pretty sure a bigger hub on a 16 will not let you cross your spokes at all which wont be ideal for trials.

[Farfle]

The 16" magic pie has a mag rim, and its pretty wide.

[2moto]

My son used to ride a little Magamo trials bike and it was very cool with that small back wheel and the big fat tire back there as well. If you are going with that small of a wheel my guess is the larger diam DD hubs will mean a radial lace, how about the mac geared hub so you can maybe cross the spokes with a one cross? I am not sure about how the one cross with a 16 inch and a mac but pretty sure a bigger hub on a 16 will not let you cross your spokes at all which wont be ideal for trials.

Yes, the 16" wheel is "cast" unit bolted to the hub motor, so no spokes.



And this is the Magic Pie version:

[toolman2]

yes well, that first pic of a downhill bike with the 18" rear wheel is mine!
it seems the guy used to work at golden motor, and has now started his own web shop selling the same and some similar stuff, he used the photo without asking but
i just spoke to the dude "peter" and he was a friendly dude, apologizing etc, so i told him i didnt mind.
-pretty rough looking machine for the front page of your website! but whatevs

[full-throttle]

he used the photo without asking

'they' do it quite often - hyena spotted my old bike on this one http://www.alibaba.com/product-gs/521590971/spoked_type_Rear_hub_motor_for/showimage.html

[neptronix]

Looks like rebranded golden motor stuff.

If it fits on a 14" wheel, it is most likely identical to the GM pro hub, 9C, or MXUS direct drive family of motors.

Nothing new here, IMHO.

[toolman2]

Looks like rebranded golden motor stuff.

If it fits on a 14" wheel, it is most likely identical to the GM pro hub, 9C, or MXUS direct drive family of motors.

Nothing new here, IMHO.

ah yes, i just re read the original question, and no theres nothing better about this leaf stuff -any specs that say better numbers are prolly just made up.
in the "normal" 7ish kg hub motor range the magic pie has the highest peak and continuous torque from what ive tested due to the being the largest diameter
it has greater leverage, and more surface area for cooling.
from what i remember testing them they can make around 28NM continuous (max 150deg winding temp) and around 120NM peak (less than 10 seconds)

[neptronix]

toolman2; while i have you here.. what do you think the continuous wattage that the pie can put out is? I'm thinking upper 1000w figure.. i ran 42mph continuous for about 10 miles and it didn't get all that hot really..! 100deg F on the cover.

Is your 150 deg. figure in Celsius or Fahrenheit?

[jonescg]

toolman2; while i have you here.. what do you think the continuous wattage that the pie can put out is? I'm thinking upper 1000w figure.. i ran 42mph continuous for about 10 miles and it didn't get all that hot really..! 100deg F on the cover.

Is your 150 deg. figure in Celsius or Fahrenheit?

He's an Australian, so it's probably Celcius

I've ridden Toolman's machine and it's quite a wild beast. well more than a kW continuous, based on my seat of the pants dyno...

[neptronix]

Thanks for the feedback Jones.
I've got mine up to 100F/37C at the covers. If the winding temp is double that, then i've still got tons of thermal headroom.

Is his magic pie modified in any way? cooling holes, etc?

[jonescg]

I don't recall any cooling holes. All I know is that it felt funny to ride cause it was a 20" wheel on the back of a downhill mountain bike...

[Philistine]

I have had the pleasure of riding Toolman2's bike (and meeting the good man), it does have both cooling holes and an internal (winding) temp sensor. It throws wheelies like no-bodies business. Smokes my Greyborg with HS3540 in 26inch (both of us running 72v nominal him in a motorcycle minibike wheel, slightly larger than a 20inch I believe with the motorbike tire, in a modified Norco Aline), up to about 30-40kph then my Gborg/HS3540 takes over the show. I must say I have been a bit surprised by the recent hype people on ES have been showing for the Pie as if it is a new discovery, considering Toolman2 has been trumpeting the virtues of the Pie since I have been on this forum. But that is OK, I am sure Toolman2 is cool with that. He is sort of like a Yoda figure (but quite tall actually, taller than me and I am 6 foot, and he isn't green either.... and he doesn't talk in a weird Kermet like tone using aphorisms either).... He also isn't really a Jedi Master.... In fact, now that I think about it the Yoda bit is kind of a bit of a stretch really....

Anyway, he has been trumpeting the virtues of the Pie since I met him - the meeting of which was precipitated by me joining this forum over a year and a half ago.

But certainly of all the people I have seen on this forum (and I explicitly exclude Farfle for obvious reasons), I consider Toolman2 to be Professor Pie. At the very least we should let him sew material elbow patches made from a suit jacket onto one of his leather jackets, effectively ruining two jackets ala homer......

And he definately gets a pipe.... Oh yeah he gets a pipe....

[Miles]

Credit us with some intelligence, James....

[Philistine]

Credit us with some intelligence, James....

But he has been saving up his first post just for this!

[Miles]

[Cicada]

What? James you just pissed off so many buyers with this two lines of your commercial.
Can you prove what you stated? For my little knowledge in advertising that would be important after such a claim.
In what exactly is Leaf hub perfect? Can you feed it with water?

[toolman2]

yes, thanks for the kind words (i think) and ill admit that i do like the pie, ive had one set up on a dyno with a torque arm to measure NM etc. in one of the low speed torque tests i ran it at 55rpm with an output torque from 2NM through to 100+NM, the idea was to measure everything like input power, amps, winding temps, etc and then calculate the losses and see how the motor copes for an extended time at each point.

it was at 32NM that the winding temp got to 150deg c, and stabilized just above that forever, as in below that torque the temp dropped, above that it rose (about to fry the windings) but 32NM was the maximum CONTINUOUS output that could (just) be sustained indefinitely.

remembering that we have kept the revs so low that there nearly no rpm related losses to confuse the results.
32NM at 55rpm required 475w of power in to the battery, and 185w of output power, 290w of heat loss for the motor to shed (and evidently this 290w is now known to be the maximum waste heat that a pie with no holes or forced cooling can cope with) and is prolly not wildly different for most of the 6-7kg hub motors

this means all sorts of things, like you can run with double that amount of torque 64NM, producing 4 times the heat loss, and is therefore only sustainable for a quarter of the time (say for 5 seconds pinned, 15 seconds off to cool and repeat) it sounds low i know but this (helped along by the large thermal mass) is very roughly what we all are doing with our hub motors.

so at 27kph (with a 20" rear wheel at 300rpm) and 32NM you get 1000w output, you need about 1330w power in, losing 290w to ir losses and 40w to rpm related losses, the motor is 75% efficient here, and you run run it all day neptronics, just.
and sure, my bike along with everyone elses here may run 2 or 4 times this, but not continuously.

then we drilled the covers (just recently) mounted 4 mini computer fans inside, etc, etc.

sorry to hijack the thread with all this crap, now back to you james.

[neptronix]

Hijack away! You are the only person on this forum that knows this stuff about the pie. I had not really taken the motor seriously until liveforphysics kept beating it into my head that it would be far better than the MAC hill climbing setup i was planning.

Otherwise, cheesy marketing, bashing of golden motor, bashing of golden motor canada, etc. had me basically writing that company off 100% until i took the dive. I followed the herd mentality. Which is right about 90% of the time. Not here.

toolman; could you post some pics of your cooling setup? i thought about the computer fans inside the case ideas as well.

I was thinking of using a push-pull setup.. as close to the windings as possible. Buncha tiny little fans on each side.. sorta like a sideways ram air..

[2moto]

Sorry to reseurrect this thread, but decided to take a chance on the Leaf motor. Motor (48V/1000W) has arrived and seems reasonable. Although, I don't think I'll end up using it eventually, I am planning on running it through a set of test like toolman2 describes to see if comes anywhere near the datasheet that Leaf publish on their website. Going by there respective datasheets, the Leaf motor is supposed to have a better torque constant, but only dyno testing will give a true piucture. Will report finding here, hopefully in a couple of weeks.

Toolman2: Would be willing to share any further information about your dyno setup?