Tiny 250 W hub motors

Jacq

10 mW
Joined
Oct 21, 2016
Messages
24
Location
Ireland
Hi
My plan is to build lightweight 28 inch wheel commuter and I asked Mrs China for two tiny hub 250 Watt motors ( 5inch/130mm diameter) .
I did not know that has to ask lower RMP to use them on 28 inch wheels, I asked for RPM when the motors arrived , the answer was RPM 365 . I do not know what to think about it , can I use them in that wheels ?
 
I hoped that the motors will be my legs and now I have to be pealing ,especially up the hill :)
 
At such low power, a BB drive is better for climbing hills. Yet, riding dual hubs should make the hills pretty easy to climb. Still, I would have recommended a single bigger rear motor.
 
I agree, but the big rear hub is 5-8 kilos and can be seen from far away vs double tiny hubs 2,2 kilo each + small battery pack (10s 6p ?) for 17 miles both ways, to work.
 
A have that costruction with Mxus 3K and motorcycle rims, 3inch tyres. I am looking for an ebike up to 40 pound/20 kilo. And I got that hubs.
 

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Tiny motor 250W --> you should have a look on the G310 Bafang (123mm diameter), I have it, it's small, light (around 2.5 kg) and still powerfull : despite its 250W rating, you can use it on flat lands at 5-600W without overheating, and around 3-400W on hilly areas. If you don't need more than that power, you don't need two motor, only one rear G310 will do the job.

I have it on my 29" bike.

See :
- this subject :https://endless-sphere.com/forums/viewtopic.php?f=2&t=92124&hilit=g310&start=75.
- the Grin simulator, very usefull to check at which power you can use it, depending on the speed and the grade, without overheating : https://www.ebikes.ca/tools/simulat...EZ&frame=road&mass=110&cont=cust_10_70_0.03_V.
- what Grin tells about it : https://www.ebikes.ca/product-info/geared.html
 
Sounds good, I am going use rear motor on a flat plus front motor up the hill.
Do you have any video ?
 
i think a rear motor is gonna wheelie and toss you off going up a hill
 
In general, using high-speed range mini motors (> 2.2 Kg.) in big wheels (<24") is not a good idea.
Without going into a lot of detail, the problem is they can't get up into the RPM range where they are most efficient. This is called a "Current limited system", whereas a mid or low-speed motor will rev till it just won't rev anymore (RPM limited system).
The way this plays out in the real World is that a mid-speed mini (260) powered by a 20 Amp controller on 48 Volts in a big whl. will top out in the 23 to 25 mph range and a high-speed mini in the same system will not go any faster, it runs out of Current. The bad effect is, the controller tries to supply max Amps most of the time (especially on hills) and this tends to melt things like the Phase wires and connectors and, in the worst scenaro, the windings in the motor.
Installing them (I'm assuming you are building a 2WD) in smaller wheels would certainly help, but if you can't, it still might work out. Your "saving Grace" is the 2WD set-up. As the motors work together, they tend "pull" each other up into a higher rpm range.
I rode a 2WD for a year and it consisted of two Q100's (2 Kg. ea.) high-speed (328) motors on 48 Volts in 24" whl.s. They mounted big tires so their overall height was like a 25" whl. w/ a 2.0" tire.
On a single motor (either one), top speed was around 23 mph, but together, it was a blazing fast, 27 to 28 MPH! It would take off well enough, but in the mid range (15 to 20 mph), it was really slow.
I now run two mid-speed motors (260's) and while I only gain a 1 or 2 mph using both, the bike pulls smooth and steady thru the entire rpm range. Where this set-up really shines is climbing hills and there is not much I encounter that I can't climb. The high-speed motored 2WD was so-so on hills at best.
If you think are going to be trying to climb steepish or long hills, I would rethink the high-speed motor/big whl. idea.
 
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