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

[molybdenum]

Silly of me to select the wrong motor in the sim Definitely apples and oranges...
Here's the sim comparing the two MG310 motors under my anticipated running parameters.





I am wondering about the differences in predicted final temps. Is this the slight difference in efficiency? Ideally I would have a motor which spins at 9 RPM/V; as the STD is a bit too slow and the FST is a bit too quick.

Also, for the purposes of the sim, I set wheel size to 26". I am running a 700c wheel, but with 35c tires. My wheel circumference works out to 2205 mm, which is nearly identical to that of a 26" wheel with 2.25" mountain bike tire. I'm assuming that the 26" wheel best fits my actual wheel size and hope this is correct. I would like to see the option of setting actual wheel circumferences in the sim, as this detail is very important and impossible to get right otherwise.

 

[neptronix]

Yeah, two windings at different speeds.. one is capped on amps and should be going faster, and might actually increase in efficiency if you give it more amps and allow it to run closer to it's top speed on 48v.

You might also see different results modeling a single motor instead of two at once.

 

[tomjasz]

I really want to like this motor, but given my history wish the trail of broken promises for efficient parts access...I went eZee. But it still entices me. And Justin jumping on helps hugely!

 

[1N4001]

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.

What did you find fragile about the motor itself? Genuinely curious.

 

[molybdenum]

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.

What did you find fragile about the motor itself? Genuinely curious.

I guess it's not fair to say yet. I got 6300km out of my first Q128c at 10A 48V before it started to make a constant high pitched singing sound, which increased in pitch along with speed. Although mechanically inclined, I have been very short of time. I swapped the core in my laced wheel with that of a new Q128c. The old core was clean as a whistle, looked well lubed, and the gears seemed fine. I will definitely post pics on a relevant thread when I get around to the teardown and look at the clutch.

Meanwhile, my second motor at 3700 km has started to protest a bit when cold. It's kind of like a grinding vibration that goes away in a couple minutes.

For the price and the ease of swapping cores, getting 10k km (or even 6k km) would seem fine for a $120.00 CAD motor, and it works out to less than I spend per year on brake pads! The price Grin charges for the MG310 plus local pickup and parts availability does make this seem like an attractive alternative. I still think the Q128 is a great motor and would definitely keep using it.

In addition, my bike is a light weight high speed road eating machine, and I pedal very hard - routinely pushing my Q128c 201RPM@36V (268RPM@48V) well past the unloaded speed on the flat or slight descents (registering 0V at WOT). I'd like something with slightly higher KV that would still assist at the top speeds I travel, but think the Q128c 328RPM@48V KV may be too high and prone to overheating. As near as I can tell, the MG310_STD should assist to 45 kph (at 52V) before hitting the cliff, which suits me better.

 

[neptronix]

Yeah, i've heard plenty of the negative experiences with the q*** motors on this forum. Kinda sad because the dual reduction ones looked tasty a while ago, but it turned out they had low efficiency ( under 80%, whereas a motor like this can peak around ~84%.. which is a very big deal considering how poorly the heat of that other 16% can be shed in a geared motor )

 

[1N4001]

I'm having a closer look at the G310.

The specs on the product page mention an OLD of 135mm, yet the diagram shows a whopping 138mm. Which one is correct?

 

[molybdenum]

I'm having a closer look at the G310.

The specs on the product page mention an OLD of 135mm, yet the diagram shows a whopping 138mm. Which one is correct?

The pdf diagram linked through Grin states "OLD 138 mm" in its measurements, which seem to measure outside to what look like lawyer lipped washers on either side of the axle. I'm not sure what to make of it either.



The standard wind is backordered atm; I may email Grin and ask how this fits a standard 135 mm dropout.

 

[davideserin]

Is it possible to put a temp sensor in this motor?

 

[1N4001]

I've found a detailed info page on the G310. It explicitely mentions the 138mm OLD: http://www.ebikes.ca/product-info/geared.html

 

[lightrush]

We got it installed in an 135 mm frame with a minimal difficulty. There are some spacer washers that can be removed which may reduce the OLD but we shoved the whole thing in because we didn't know the purpose of the washers.

 

[1N4001]

I've ordered a G310 and will try to fit an 11-speed MTB cassette to it. I'm fairly confident that it'll fit. Will provide feedback once that's done

Is it possible to put a temp sensor in this motor?

Yup. I've asked Grin and (very quickly!) received an answer from Justin.

You can indeed add a temperature sensor if you want to forgo the internal speedometer sensor. That requires opening up the motor, removing the white wire from the internal speedo and instead hookup up a thermistor between this lead and Gnd, and then similarly reconfiguring the motor controller so that the pass thru of this signal goes to the CA's temperature sense input rather than the speedo input, and wire up an external spoke magnet style wheel sensor for the CA's speed reading. It's not a service that we offer but it's certainly something that someone who's not afraid of opening up a motor can do.

The shop page now also shows the correct OLD.

 

[lightrush]

Does anyone know what the "specially made inside torque arm that replaces the left side anti-rotation washer" mentioned here: http://www.ebikes.ca/product-info/geared.html#washer-stack-and-torque-arm is and where can one buy it?

 

[zukster]

I'm going to give this a bump re torque arm ideas for the rear G310.

I want to try the G310 on my carbon frame mountain bike but am concerned about rear spin out. I currently run a Q100CST with a torque arm attached to the 10mm slotted 12mm axle. This works very well.

I had emailed Justin previously, but only got a partial response, most likely because he was off to France for the Suntrip solar ebike race. So I thought I'd follow up here when I saw the above post.

My Idea was to use a torque arm held to the motor axle by double-nutting it firmly in place by really tightening the nuts on both sides of the torque arm, while making sure that the inside nut does not turn in, which would pinch the carbon drop-out too much. A delicate operation, but doable.

Justin guessed that the friction between the nuts might be able to get you up to 30 Nm of spinout strength.

I can't really use the anti-rotation washer because my dropouts are to shallow.

So to take this idea a bit farther, one could use two torque arms (one on each side of the axle), and metric high grade 10.9 nuts, to avoid stripping them, and to be able to tighten them up more. So maybe this way you could get 60-80Nm of spinout strength.

Another idea would be to grind the ends of the axle with 8mm flat spots for torque arms to fit onto. Similar to how the Cute motors have 12mm diameter axles and 10mm flats. But in this case you would have a 10mm axle and 8mm flats at the ends of the axle only. Of course one would have to make a torque arm specifically to fit this, but it should work if done right.

I might just have to try one of these methods out or switch to a different bike. But I though I'd post the ideas here for comment first.

 

[lightrush]

There already is a flat on the axle - it's where the anti-rotation washers catch it. One can replace an anti-rotation washer with a torque arm.

 

[1N4001]

There already is a flat on the axle - it's where the anti-rotation washers catch it. One can replace an anti-rotation washer with a torque arm.

Yes, but I suspect that one would have to custom-machine torque arms, as they sit on the inside of the dropouts. It could be a tough fit. See these pictures I took:

one, two

 

[zukster]

Much thanks for the comments. I have not seen the hub up close, so I didn't know there was a flat on the axle for the anti-rotation washer. That does look like it would be a tough fit. I'll think about this a bit more now.

 

[lightrush]

Yes, it would be a tight fit. Grin were working on an arm that replaces the torque washer, but I'm not sure if that panned out yet.

 

[zukster]

Is that slotted anti-rotation washer a standard one made for a hub with a 12mm wide axle and a 10mm flat spot width, or is it smaller and specially made for the G310?

If its the 12mm/10mm size, I have some 1/8" titanium torque arms I bought last year from a guy in the UK that look like they'll probably fit on one side or another of my bike on the inside of the drop-out. They're much thinner than the Grin ones. I'm pretty sure I can get at least one side to fit, maybe with some spacers.

It occurred to me that if one was concerned with the 138mm dropout spread, that one side of the axle could be ground round to 10mm where the square part is. Then you'd be back to about a 135mm dropout again, and could use a torque arm on the other side to prevent spin-out. Then using some more thin spacers on the other side to fit the torque arm would also not be a big deal.

 

[Jean]

Thanks for this topic about the new BAFANG G310. It's really interesting. I think i will buy one for my carbon mtb. I want a small motor but powerfull enought witch is hard to find. First i wanted a xiongda ytw06(1,35kg), it would be perfect but it look too much noisy. Then i am also very interested by the jiabo JB-75 T2 wich is tiny and light weight (1,9kg):

https://app.alibaba.com/dynamiclink?touchId=60785317806&type=product&schema=enalibaba%3A%2F%2Fdetail%3Fid%3D60785317806%26ck%3Dshare_detail&ck=share_detail&shareScene=buyer







The BAFANG G310 seems to be very silent and quiet powerfull. I will add a 52v battery and a sempu torque sensor but i wonder about wich converter i can buy with it because i don't want any display so maby any cheap 48v/52v sinwave controller would fit?

 

[neptronix]

jiabo is a company i have never heard of or seen before.
The claimed >82% efficiency for such a small geared motor is fairly impressive and i would guess it has 0.35mm laminations inside; not bad for a cheap motor.

The 6.9:1 reduction is a nice compromise but i imagine that's a single reduction and you might find that such a big reduction ratio is a weak design... just a speculation. "one test is worth a thousand opinions", right?

If you decide to be the test hamster on that motor, it would be cool to start another thread on it.

That being said, i have a G310 wheel from ebikes.ca on order, just in time for Utah to freeze over.
More data from me next year :lol:

 

[Adamlivi]

So, I'm setting up a G311 standard wind front hub with a Phaserunner (throttle only) and a 52v 6 ah Samsung 30q battery (one mounted and one spare) on my "pub bike".

Currently have a tangent ascent with CA3 that I have become pretty comfortable programming but was hoping for the "secret sauce" settings for the Phaserunner with the G311. Justin had suggested keeping the max phase current to 40A if I want to eliminate chances of gear failure. Any other insights appreciated.

Thanks in advance!

 

[neptronix]

I also have a phaserunner here, waiting to get hooked up to the G310 series motor.. although i may revert to using the usual infineon clone type controller that runs the rest of my fleet. Depends on the noise level and how well the oldschool controller can handle a motor like this.

Let me elaborate a bit on what Justin had to say about phase amps while we're talking about a motor with two sets of planetary gears to be concerned with.
I've long been a fan of making big power with geared motors like the MAC/eZee/BMC series and found that there's a recipe for finding the sweet spot between reliability and power.

You can think of phase amps and battery amps as a ratio that adjusts the torque curve of the motor.
Here is what you can expect from tuning based on that ratio.

1:1 ratio: The motor has almost no initial torque at all and shutters and stalls because of this. Like a 1990's Honda Civic with 500,000 miles on the motor and an exhaust and intake that's 2 times larger than it should be.. even the mid range torque suffers..
2:1 ratio: This is more like a typical internal combustion engine where the torque from a stall is weak, and by the mid to high range is pretty strong.. this is ideal if you're trying to force yourself to pedal from a start.
2.25:1 ratio: This is a flat torque curve on most motors.
2.5:1 ratio: This is where the motor starts having more low end torque than mid and high.
3:1 ratio and beyond: Wheelie time!

Most absolutely stay away from 'wheelie time' on a geared motor.
Torque is the biggest challenge for your nylon gears and the most torque can occur in the lower section of the power band.

Start at 2.25:1 ( IE 18A batt, 40.5A phase ) and adjust for taste.

 

[docw009]

Too bad Grin is back ordered on the G310, or I might have bought one. Maybe CNEbikes would carry them. I bought a fatbike bafang motor there once, and they keep sending me email. They carry generic 250W hubmotors for about $40-50. Really shows how cheap these things are in quantity.

By the way, I have three 260 rpm Q100H's running on 20" wheels, 36V and 20A controller. Occasionally, I'll take them up to 48V/52V. Not a lot of miles. About 800 on all three this year.

 

[Alan B]

The real issue isn't so much the ratio, but the actual torque on the gears which is proportional to motor current (often incorrectly referred to as phase amps). So with the geared motors we want to strictly limit motor current to a safe value. This is straightforward on the PhaseRunner, since it has a phase current limit setting, and it actually measures motor current.

The Infineon type controllers don't measure motor current, and they don't have a direct limit for it. They estimate it with a calculation cased on battery current, and have the ratio plus the battery current limit. Their ability to limit motor current is based on the accuracy of their calculation.

So you decide what your motor current limit should be, say it is 50 amps, and your battery current limit (which sets the power limit), say it is 25 amps. Then set the ratio to motor current limit / battery current limit. In this case 50 / 25 = 2. So 2:1 would be the limiting ratio. If you decide to change your power and thus change the battery current limit you will have to adjust the ratio to keep the same torque / motor current limit.

Ideally we would limit the torque and motor current based on the motor temperature, that's what really determines how soft the gears are. A temperature sensor and a conservative temperature limit could protect the gears from damaging torque.