Bafang G310 geared hub - 11:1 reduction ratio!!!

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Bafang G310 geared hub - 11:1 reduction ratio!!!

Post by neptronix » Dec 29 2017 8:05am

Was going over vendors' pages looking for new stuff. Came across this interesting geared hub. Figured i'd kick off a thread about it.

It's got two gear reductions inside for a overall reduction ratio of 11:1. Very cool.
It to be rated for around 350 watts continuous and comes in at 5.6lbs or 2.55kg.

Image

ebikes.ca seems to be the only vendor i can identify so far.
http://www.ebikes.ca/shop/electric-bicy ... 0-std.html

And of course, ebikes.ca already simulated it.. results with boosted power already look pretty impressive. This motor looks like a real sleeper.
2017-12-29 05_47_25-Motor Simulator - Tools.png
2017-12-29 05_47_25-Motor Simulator - Tools.png (78.57 KiB) Viewed 5174 times
I haven't been impressed by a geared motor for a while. If anyone has any more info, let's hear about it here!
My first major build: 8T MAC motor on a Trek 4500.
The new all-arounder: Leafmotor 1500w on a Turner O2 full suspension.
The wheelie machine: 20" Rear Magic Pie II on a Trek 4300 MTB

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Re: Bafang G310 geared hub - 11:1 reduction ratio!!!

Post by Triketech » Dec 29 2017 9:56pm

Nice discovery I know a few folks who would like it.

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Re: Bafang G310 geared hub - 11:1 reduction ratio!!!

Post by neptronix » Dec 30 2017 9:38am

Yeah. I've always been attracted to the Cute Q128H... but the eRPM is too high because of the 16:1 or so reduction.. therefore it only comes in a terribly slow 201rpm at 36v wind. Also, that motor doesn't seem to be built very sturdy.

I spent a while trying to explain to BMSBattery that the motor could be perfect with just a few tweaks, but as usual they're too dense.. :lol:

This motor seems like what the Q128h should have been. 8 magnetic poles with a 11:1 reduction will give you just 10% more eRPM per rotation of the wheel than the MAC. So basically, any controller that can handle the MAC/BMC/eZee motors should be able to handle this bad boy. 30mph in a 20" wheel might be where most controllers start to choke, which is perfect because you can't really expect a motor this small to do that job anyway.

I'd be the test hamster for this motor, but i already have an eZee sitting here that i used. hoping someone else takes up the torch for this round.
My first major build: 8T MAC motor on a Trek 4500.
The new all-arounder: Leafmotor 1500w on a Turner O2 full suspension.
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Re: Bafang G310 geared hub - 11:1 reduction ratio!!!

Post by Triketech » Dec 30 2017 11:49am

We're pretty satisfied with our MAC motors, but I do like the lighter weight option.

Among our circle of geriatric-larva stage of recumbent trikers most with any interest in boosters are looking for assist climbing hills, and maybe a little bit of boost when riding with a group of uprights. No cogging drag is desired but simple installation and light weight is vital.

Mid drives eliminate triple rings and have a few other issues on trikes. Magic Pie Edge is nice for easy installation but has just enough cogging drag to be undesirable, and its a bit too heavy.

I've bought & tested over a dozen drive systems looking for the best solutions for us old farts on trikes. This one is tempting.

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Re: Bafang G310 geared hub - 11:1 reduction ratio!!!

Post by fechter » Dec 30 2017 1:04pm

Interesting how the motor is an inrunner on this one. A little oil in the case would make for pretty good cooling.
"One test is worth a thousand opinions"

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Re: Bafang G310 geared hub - 11:1 reduction ratio!!!

Post by robbie » Dec 31 2017 2:22pm

I've been testing one of these for a few months now. The low level of noise that comes from the motor (when loaded - it can be a bit noisy running unloaded) is impressive. On my aluminum framed commuter bike paired with a phaserunner this motor is effectively silent. Any sinewave controller should provide a low noise level experience as well. I can't comment on a basic trap controller.

I did have an experience where I damaged the gears on one of the motors, while I was late, I increased my phase current limit to 70A, and also removed my speed limit (36V battery, 35A battery current limit). Going up a steep (12% grade according to google maps) I blew the gears. I suspect I was sitting at around 80-90C (I had previously hit the thermal limit on my CA of 100C). I was traveling around 12-15km/h when it happened, so ~55-60A phase current.

Luckily, the motor is quite easy to open (without delacing the wheel), and the gear set is not too challenging to replace, provided one makes sure that the gear tooth indicators all line up with the sun gear. Due to the gear ratios of the motor and the double reduction, there's not very many locations where the teeth will perfectly mesh!

Setting my Phaserunner to a 50A phase current limit has had zero problems. It may be interesting to do some experiments to see if there's a significant gear strength reduction at higher temperatures.

Bafang rates this motor at "30Nm", which would translate to approximately 28A of phase current (simulator derived value), so I can see why 70A would have damaged the gears (http://www.bafang-e.com/en/components/c ... 1250d.html).

I hope to hear other users feedback as more people get this awesome little motor. It's been the perfect light weight commuter for me! Its only downside is that due to the helical gears, I don't think locking the clutch for regen would be very smart, the gear set has axial bearings *and* thrust bearings to deal with helical side-forces.

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Re: Bafang G310 geared hub - 11:1 reduction ratio!!!

Post by Triketech » Dec 31 2017 2:42pm

Thanks Robbie, nice update.

What kind of top speed do you see motor power only on a flat?

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Re: Bafang G310 geared hub - 11:1 reduction ratio!!!

Post by fechter » Dec 31 2017 3:14pm

robbie wrote:
Dec 31 2017 2:22pm

Setting my Phaserunner to a 50A phase current limit has had zero problems. It may be interesting to do some experiments to see if there's a significant gear strength reduction at higher temperatures.

Bafang rates this motor at "30Nm", which would translate to approximately 28A of phase current (simulator derived value), so I can see why 70A would have damaged the gears (http://www.bafang-e.com/en/components/c ... 1250d.html).
From what I've been able to research, temperature is a critical factor in the strength of plastic gears. They can handle a lot more when they're cold. Some of the heat comes from the motor and some is generated on the teeth by friction. A long hard climb can get them above the safe limit. Anything that reduces heating will help.
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Re: Bafang G310 geared hub - 11:1 reduction ratio!!!

Post by robbie » Dec 31 2017 7:44pm

Triketech wrote:
Dec 31 2017 2:42pm
What kind of top speed do you see motor power only on a flat?
I run about 5A of fieldweakening current through my PR, and a speed limit of 40km/h on my CA3 with 30A/36V battery, most of the time I'm averaging around 30km/h here in Vancouver commuting.

I'd guess around 36-37km/h (22-23mph).

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Re: Bafang G310 geared hub - 11:1 reduction ratio!!!

Post by Buk___ » Jan 01 2018 3:11am

neptronix wrote:
Dec 30 2017 9:38am
Yeah. I've always been attracted to the Cute Q128H... but the eRPM is too high because of the 16:1 or so reduction..
Could you explain what's bad about the Q128H's eRPM?

From what I can make out it has 9 pole pairs rather than the 8 above; is that such a huge bad difference?
neptronix wrote:
Dec 30 2017 9:38am
therefore it only comes in a terribly slow 201rpm at 36v wind.
BMSB also offer a 36V/260?

neptronix wrote:
Dec 30 2017 9:38am
Also, that motor doesn't seem to be built very sturdy.
Which part(s) do you see as fragile?

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Re: Bafang G310 geared hub - 11:1 reduction ratio!!!

Post by neptronix » Jan 01 2018 4:08am

Buk___ wrote:
Jan 01 2018 3:11am
Could you explain what's bad about the Q128H's eRPM?
The eRPM is too high for most controllers to handle. BMSBattery recommends one specific controller for the motor in their lineup, and refuse to sell a higher speed winding for this reason. The motor is crippled by design. They also removed all sorts of info on that motor off of their listing. The reduction being 16:1 is just from memory..

Now in theory, you could get an expensive high eRPM capable controller and shove 72+ volts into that motor to find it's true potential.
From what I can make out it has 9 pole pairs rather than the 8 above; is that such a huge bad difference?
Not sure how you're getting that. I see 16 magnet sections, so divide that by 2 and you get 8. The MAC/BMC/eZee are all 16 pole motors.. 32 magnets divided by 2.
BMSB also offer a 36V/260?
I don't see a Q128H with that RPM anywhere on their webpage. Do you?
neptronix wrote:
Dec 30 2017 9:38am
Which part(s) do you see as fragile?
I've seen plenty of complaints of clutch and gear issues with the Q100H and Q128H. Might want to read around about these motors if you want to find out more.

Nonetheless, given that BMSBattery doesn't understand their own products, and they're the only vendor who carries the Q***H series, i decided years ago to take a hard pass on their double reduction geared motor for the reasons i outlined above.
My first major build: 8T MAC motor on a Trek 4500.
The new all-arounder: Leafmotor 1500w on a Turner O2 full suspension.
The wheelie machine: 20" Rear Magic Pie II on a Trek 4300 MTB

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Re: Bafang G310 geared hub - 11:1 reduction ratio!!!

Post by neptronix » Jan 01 2018 4:26am

robbie wrote:
Dec 31 2017 2:22pm
I did have an experience where I damaged the gears on one of the motors, while I was late, I increased my phase current limit to 70A, and also removed my speed limit (36V battery, 35A battery current limit). Going up a steep (12% grade according to google maps) I blew the gears. I suspect I was sitting at around 80-90C (I had previously hit the thermal limit on my CA of 100C). I was traveling around 12-15km/h when it happened, so ~55-60A phase current.
No surprise! if it took a super steep hill at ~1260W to make the gears look like the aftermath of a war zone, AND the stator/halls survived, i'd call that a testament to a motor of this size. I think it was right in thinking of it as a sleeper.

I've managed to get a MAC pretty hot on that sort of power. It took 5 minutes of 4000w continuous to get my old 0.5mm lam MAC's gears to melt ( the stator also survived, so the motor failed in the least expensive way possible.. good job, MAC motor co! )

It's funny that bafang markets this as a 250w motor on their page. I wonder if there's some Chinese version of the gentlemen's agreement..
https://www.caranddriver.com/news/japan ... t-car-news
My first major build: 8T MAC motor on a Trek 4500.
The new all-arounder: Leafmotor 1500w on a Turner O2 full suspension.
The wheelie machine: 20" Rear Magic Pie II on a Trek 4300 MTB

"The best time to plant a tree was 20 years ago. The second best time is now."- Chinese Proverb

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Re: Bafang G310 geared hub - 11:1 reduction ratio!!!

Post by Buk___ » Jan 01 2018 5:06am

neptronix wrote:
Jan 01 2018 4:08am
Buk___ wrote:
Jan 01 2018 3:11am
BMSB also offer a 36V/260?
I don't see a Q128H with that RPM anywhere on their webpage. Do you?
Update: Actually, no. I was looking at the Q100H 260 by mistake!

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Re: Bafang G310 geared hub - 11:1 reduction ratio!!!

Post by cwah » Jan 01 2018 5:42am

I think it could be good for my brompton.

It has 16" wheel and I need it to spin to 25mph.

Where can I buy with the relevant controller?
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Re: Bafang G310 geared hub - 11:1 reduction ratio!!!

Post by amberwolf » Jan 01 2018 5:49am

neptronix wrote:
Dec 29 2017 8:05am
ebikes.ca seems to be the only vendor i can identify so far.
http://www.ebikes.ca/shop/electric-bicy ... 0-std.html

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Re: Bafang G310 geared hub - 11:1 reduction ratio!!!

Post by neptronix » Jan 01 2018 6:32am

cwah wrote:
Jan 01 2018 5:42am
I think it could be good for my brompton.

It has 16" wheel and I need it to spin to 25mph.

Where can I buy with the relevant controller?
11 reduction x 8 poles x 540 rpm = 47520 eRPM.
You're absolutely going to need a controller that's capable of a little beyond 50,000 eRPM..
phaserunner, or one of kelly controls' high eRPM upgraded controllers is the ticket..

Also you'll need the fast winding and 55-60v..
My first major build: 8T MAC motor on a Trek 4500.
The new all-arounder: Leafmotor 1500w on a Turner O2 full suspension.
The wheelie machine: 20" Rear Magic Pie II on a Trek 4300 MTB

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Re: Bafang G310 geared hub - 11:1 reduction ratio!!!

Post by Papa » Jan 01 2018 9:52pm

neptronix wrote:
Jan 01 2018 4:08am
I've seen plenty of complaints of clutch and gear issues with the Q100H and Q128H. Might want to read around about these motors if you want to find out more.
I did search, rather extensively, but unearthed no Q100H users who damaged gears. However, a few Q100H "hot rodders" did report clutch failures. I did NOT research the Q128 so cannot comment on it.
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Re: Bafang G310 geared hub - 11:1 reduction ratio!!!

Post by Triketech » Jan 01 2018 11:16pm

neptronix wrote:
Jan 01 2018 4:08am

Not sure how you're getting that. I see 16 magnet sections, so divide that by 2 and you get 8. The MAC/BMC/eZee are all 16 pole motors.. 32 magnets divided by 2.
The number of magnets to pole pairs on a 3 Phase motor...

When one pole pair is aligned directly with the magnet it switches to the next phase. Now if the number of magnets is divisible by the number of poles, the next phase is already aligned with the magnet. The field may rotate while it locks the rotor in place with the stator. To achieve motion between the stator and rotor, the succeeding phase pole needs the next magnet to be retarded.

And since there are 3 Phases the number of poles will be divisible by 3. Usually there are 2 more magnets than there are individual poles. That gives the shortest distance between "the next magnet" without confusing the rotor on which way to rotate during the moment of switching phases.

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Re: Bafang G310 geared hub - 11:1 reduction ratio!!!

Post by neptronix » Jan 02 2018 1:48am

Hm, that's contrary to how i was taught to count poles. You could be right, i could be wrong.. but..
What i find is that magnet sections divided by 2 = the pole count for every motor i've seen where the manufacturer specifies the number of poles.

Example: the MAC motor has 32 magnet sections but 36 stator teeth.
2018-01-01-23_40_58-IMG_6373.JPG-(JPEG-Image,-500 × 667-pixels).jpg
2018-01-01-23_40_58-IMG_6373.JPG-(JPEG-Image,-500 × 667-pixels).jpg (88.81 KiB) Viewed 4555 times
The vendor claims it's a 16 pole motor.

Nonetheless, there's no harm in calculating the eRPM controller wall based on 9 poles instead of 8. The further you are away from the eRPM maximum of your controller, the better the throttle response will be on a motor like this.
My first major build: 8T MAC motor on a Trek 4500.
The new all-arounder: Leafmotor 1500w on a Turner O2 full suspension.
The wheelie machine: 20" Rear Magic Pie II on a Trek 4300 MTB

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Re: Bafang G310 geared hub - 11:1 reduction ratio!!!

Post by cycborg » Jan 02 2018 9:46am

Triketech wrote:
Jan 01 2018 11:16pm
The number of magnets to pole pairs on a 3 Phase motor...

When one pole pair is aligned directly with the magnet it switches to the next phase. Now if the number of magnets is divisible by the number of poles, the next phase is already aligned with the magnet. The field may rotate while it locks the rotor in place with the stator. To achieve motion between the stator and rotor, the succeeding phase pole needs the next magnet to be retarded.

And since there are 3 Phases the number of poles will be divisible by 3. Usually there are 2 more magnets than there are individual poles. That gives the shortest distance between "the next magnet" without confusing the rotor on which way to rotate during the moment of switching phases.
You may come from a background with a different terminology, but I've never seen "poles" meaning anything other than "magnets" in a BLDC/PMSM motor. That's certainly the case for the vendors we typically use here, as well as PhaseRunner settings, Grin simulator settings, etc.
Last edited by cycborg on Jan 02 2018 5:01pm, edited 1 time in total.

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Re: Bafang G310 geared hub - 11:1 reduction ratio!!!

Post by Triketech » Jan 02 2018 1:14pm

cycborg wrote:
Jan 02 2018 9:46am

You may come from a background with a different terminology, but I've never seen "poles" meaning anything other than "magents" in a BLDC/PMSM motor. That's certainly the case for the vendors we typically use here, as well as PhaseRunner settings, Grin simulator settings, etc.
Apology for the confusion, its an old habit from back when I worked with induction motors. Stator Poles and Rotor Poles.

And the number of magnets to coils can either be + or -, as Neptronix pointed out on the MAC having 36 coils and 32 magnets.

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Re: Bafang G310 geared hub - 11:1 reduction ratio!!!

Post by neptronix » Jan 03 2018 2:48am

Oh, that makes sense that induction motor thinking is different.
My first major build: 8T MAC motor on a Trek 4500.
The new all-arounder: Leafmotor 1500w on a Turner O2 full suspension.
The wheelie machine: 20" Rear Magic Pie II on a Trek 4300 MTB

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Re: Bafang G310 geared hub - 11:1 reduction ratio!!!

Post by slacker » Jan 09 2018 11:23am

Wonder how this would be on a catrike expedition. Been thinking about going electric but would like to still pedal the majority of the time. Will be following this and if i pull the trigger on this will post up my thoughts. Looks promising.

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Re: Bafang G310 geared hub - 11:1 reduction ratio!!!

Post by molybdenum » May 19 2018 8:41pm

I might have to try this motor.

I've been using the Q128c sourced from BMS battery, as it was the only geared hubmotor around this power level that accepts a cassette. Since I live near Grin, the savings on shipping make this option competitive, tough I'll need to re-lace a wheel. Also nice is the replaceable parts on this motor. I have found the Q128 a bit fragile even when run at specified power levels and would like to run something a bit more robust.

Here are the three possibilities:

G310_fst (10.5kV) in 700c wheel with 35c tire, 48V battery

Bafang MG310 fst = 10.5 RPM/volt x 48V = 504 RPM
= 504 x 2.2 m/min (2.205 m diameter at 700c with 35c tire)
= 1108.8 m/min
= 18.48 m/s
= 66.528 kph unloaded, which suggests full power assist up to just above 55 kph.


MG310_STD in 700c wheel with 35c tire, 52V battery

Bafang MG310 STD = 8.5 RPM/volt x 52V = 442 RPM
= 442 x 2.2 m/min (2.205 m diameter at 700c with 35c tire)
= 972.4 m/min
= 16.2 m/s
= 58.3 kph unloaded, which is still quite fast, but might be better efficiency for urban riding where I average 40-45 kph on the flat with 500W motor power.


MG310_STD in 700c wheel with 35c tire, 48V battery

Bafang MG310 STD = 8.5 RPM/volt x 48V = 408 RPM
= 442 x 2.2 m/min (2.205 m diameter at 700c with 35c tire)
= 897.6 m/min
= 15 m/s
= 54 kph unloaded, which is certainly suitable for my uses. Also, 48V batteries are a bit cheaper and more readily available.

Now here's the oddity. When modeled on the motor sim with the power levels I plan on using, the slower motor is predicted to overheat more quickly at the same power levels. This difference is more pronounced when modeled with the default 20A controller. It's almost as if the two motors are reversed :shock: Am I missing something?
MG310 std vs fst.jpg
2012 Kona Dew Deluxe, Q128C and 9spd cassette, S12S sinewave controller, 48V Panasonic battery

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Re: Bafang G310 geared hub - 11:1 reduction ratio!!!

Post by neptronix » May 20 2018 7:33pm

G01 is a different motor.. single reduction as far as i know.
So there you go, the difference between spinning a motor up to really high RPM with two reductions versus not.. :)

I wanted to go with this motor myself but i've decided to build an ebike oriented around getting as much exercise as possible so i'm going with the Xiongda YTW-06 for it's super light weight.. but i'm still excited to see what you guys come up with, and if this is really the 750-1000w continuous sleeper i think it is based on graphs.

It would probably be my primary choice for building a bike for someone else, over what i usually go with, a MAC.
My first major build: 8T MAC motor on a Trek 4500.
The new all-arounder: Leafmotor 1500w on a Turner O2 full suspension.
The wheelie machine: 20" Rear Magic Pie II on a Trek 4300 MTB

"The best time to plant a tree was 20 years ago. The second best time is now."- Chinese Proverb

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