Bafang 20” motor in a 24” rim

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Exobio   1 µW

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Bafang 20” motor in a 24” rim

Post by Exobio » Nov 27 2019 10:41am

Hi Forum,

I am brand new in this forum, I am from Denmark and has just begun my venture into the electrical bike world..

I have just received a rear hub drive motor from Bafang 36v 250W, my problem is i ordered the motor as 26” and received a 20” motor in a 26” rim.
The whole plan was i was going to rip the motor out of the rim and re-lace the 26” motor into a 24” rim on my cargo bike (see the attached photo). I had specifically ordered the 26” motor since i am after torque and don’t care about top speed, the bike is going to be used for hauling kids and dogs.. on of my friends has the the set up with 26” motor in a 24” rim on the exact same bike, and i works beautiful..
But how will it work with the 20” motor the by mistake send me, the whole process of returning is troublesome Chinese shop sending through Germany🙄🙄..

Is the setup going to work with the 20” motor in 24” rim, will i draw too many amps, will the range suck, will i have too little assistance moving from standstill.. Etc, etc.

Hope you can help..

Kind regards

Ulrich
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amberwolf   100 GW

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Re: Bafang 20” motor in a 24” rim

Post by amberwolf » Nov 27 2019 1:49pm

If the motor is a different winding or planetary gearing (intended for a different speed/torque at the same voltage) than the one you ordered, then no, it won't work the same way you planned, with the same controller and battery voltage.

Exactly how much difference in performance there will be depends on what the difference in the winding or gearing is.

If they sent you the same motor you ordered, but in a 20" wheel, then it doesn't matter; it'll still do what you want.


If you have the motor specs for what you have and what you ordered, you can go to http://ebikes.ca/simulator and see if they are both listed in hte mtoor dropdown. If they are, you can simulate your system wiht each one to see about what the differences should be.


I suppose you ordered from BMSBattery? They are unfortunately well-known for (at least sometimes) sending whatever the hell they feel like, instead of what was actually ordered. :/

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Re: Bafang 20” motor in a 24” rim

Post by john61ct » Nov 27 2019 2:32pm

Is there a payment platform they accept that will force a refund when they do that?

Other than a proper credit card of course.

Exobio   1 µW

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Re: Bafang 20” motor in a 24” rim

Post by Exobio » Nov 27 2019 2:43pm

Hi Amberwolf,

Thanks for your reply, the thing is I ordered a 26” motor i thought, what they did is they send me a 20” motor laced in a 26” rim. At least that is what i think, there is a sticker on the motor with the number 20 on it.. (see photo)
I have no idea other than that what the specs are, i deliberately ordered the 26” motor because i wanted more torque when i relaced in to a 24” rim, i now have quite the opposite, at least that what i think i got. I have no idea with regards to windings it says the reduction is 1:4,42.. Maybe it is the same motor no matter what size rim one uses, when i look at other dealers the same motor with same specs goes for everything from 20” to 28”

Here is a link to the motor in the shop where i bought it:

http://www.pswpower.com/ven.php?cargo.2017-7m-dfwv
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Thanks

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amberwolf   100 GW

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Re: Bafang 20” motor in a 24” rim

Post by amberwolf » Nov 27 2019 3:00pm

If your friend that did this used the same motor, you can check what labels his motor has, and if they match yours, you're ok.

Otherwise, unless you talk (or already have) to the vendor to find out what they shipped and why and what they will do to fix the issue, your best option is to just lace it up and see if it works like you want.

If it doesn't, then you can try a different seller and see if you can get the actual motor you're after. Places like Grin Tech should be reliable; I"m sure there's others.

Bafangs seem to use a "code" system that describes which winding they have, which helps determine what speed they will give at a particular voltage. IIRC, the last digit of the serial number, the -6, is what "code" they are. So yours is probably a "code 6" BPM, if I understand the nubmers.


I use my SB Cruiser trike for dog-hauling (and cargo); I ended up going with direct drive (DD) hubs and much more power, mostly because I've broken clutches / overheated smallish geared hubs doing this.

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Re: Bafang 20” motor in a 24” rim

Post by docw009 » Nov 27 2019 4:15pm

I bought a bare SWXH hub motor for about $130 USD shipped in 2016 from BMSbattery.com. I spun it in a 700cc rim. Haven't ridden it in two years. It still has all its stickers. including your "20". However, as they no longer carry it. I don't know if mine was wound for a smaller wheel. I intended it for a large wheel though, and that's where it is.
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It's a mild mannered motor, rated for 250W. On 48V, my wife had no problems climbing moderate 5% hills with it. With me on it, it tops out around 18-20 mph on 36V. I would have chosen the Bafang BPM or CST if I were doing a cargo bike.

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Re: Bafang 20” motor in a 24” rim

Post by motomech » Nov 27 2019 10:01pm

If you look at the spec ratings on the PSW Power webpage, it's listed as a "261" motor, which I assume means 261 RPM @ 36 Volts.
Since I only have experience w/ the Q series of minis (mostly Aikemas), I can only make some more assumptions, like;
The 261 Would equate to the "260" mid-speed range, the other two being the "201" low-speed range and the "328" high-speed range.
The OP's motor is probably a mid or a high speed version and if a Cute came w/ a 20" sticker on it. it most likely would be a 328, high speed.
But the fact that Doc's works fine in a big(ger) wheel on low Volts leads me to believe that, His at least, is a mid-speed motor.
The Cute 328 in a big whl. on 36 Volts has all he zippyness of a speedy glacier.
Motomech

'03 Rocky Mountain Edge 2WD 260 Q100H frt and Ezee V1 rear 2 Elifebike 20A & 25A 9-FET controllers 12S/10Ah Multistar Lipo rear 4Ah Turnigy frt Luna Cyclops Extra lite Alex 24DM rims, Crazy Bobs run ghetto tubeless. 25 mph. Mean Well HLG-320H-54A
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'07 GT Idive 4 4.0, Q100C 201 14S LiPoly elifebike 9-FET 20A controller. 23 MPH.
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Re: Bafang 20” motor in a 24” rim

Post by goatman » Nov 27 2019 10:40pm

I have a bafang and it has a stamp (T12) on the inner surface where your 20 is but theres also T10,T8, T13. there is a list of what speed the motor does in a 26 inch wheel by the T-code here on ES somewhere, I don't know if it applies to your motor but a T12 would be 32km/h? in a 26 wheel, T8 50?km/h in a 26 wheel etc.

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Re: Bafang 20” motor in a 24” rim

Post by Exobio » Nov 29 2019 8:49am

Hi All,

Thank you for taking the time to answer me..

I have mailed with the company, but have gotten no where they simply dont understand what i am asking about.
They keep answering me that the motor will ride faster in a big wheel.... 👍🏻. Figured that part out my self🤦🏻‍♂️.. But why my motor with a 20” sticker is laced in a 26” wheel they can not answer.. I told them i ordered the 26” since i thought there was a difference in the motor... I suspect the stick the same motor in no matter the size wheel the customer orders..

Anyway i will try to lace it up and see what happens..

Thanks

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Re: Bafang 20” motor in a 24” rim

Post by docw009 » Nov 29 2019 12:03pm

Greenbikekit.com sells the SWXH in 201 rpm and 260 rpm versions. Usually, 20" wheels will use 260 rpm motors.

That would mean mine (and the OP's) is likely 260 rpm. Higher speed, but lower torque. Not an issue for me, not so good for a heavier bike, but the 24" wheel will help here.

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Re: Bafang 20” motor in a 24” rim

Post by 999zip999 » Nov 29 2019 1:19pm

Nice bike . What battery and controller . Amp rating of controller ?

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Re: Bafang 20” motor in a 24” rim

Post by Voltron » Nov 29 2019 11:13pm

Don't know what your test bench setup is, but if you bolt it into a frame or a bench mount jig, then use a laser tachometer to get the rpms, you could figure out the kv (rpms/volt) and see if matches a spec sheet, before going to the trouble of lacing it up.
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They're like 10 or 20 bucks and come with little reflective stickers to bounce the laser back better

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Re: Bafang 20” motor in a 24” rim

Post by neptronix » Nov 30 2019 1:34am

^-- bingo
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Re: Bafang 20” motor in a 24” rim

Post by amberwolf » Nov 30 2019 1:34am

There are also phone apps to do RPM; don't know anything about them but there's discussion in some threads around here about them.

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