Q128 CST / Top Speed / P1 - Reduction Ratio

[Ltc433]

I bought a 201 RPM Q128CST with a 10.5 reduction ratio. Comparing it to the Q100CST it appears slower but that's due to the reduction ratio. (i think)

Firstly:
P1 Setting

Q100CST Magnets = 16 * 14.2 = 227.2
Q128CST Magnets = 16 * 10.5 = 168. Is that right? Does it have the same number of magnets?

Second:

The top speed unloaded on the Q100CSt was about 27mph.My Q128CSt unloaded is maxing at 23mph. When I change the pas assist level it makes no difference.. Is about 23mph unloaded normal?

 

[motomech]

Doesn't seem like folks are that interested in mini geared hub motors these days, but here is an "oldie but goodie";
https://endless-sphere.com/forums/viewtopic.php?f=2&t=70369&hilit=Q100+reduction+ratio
Another good search-word is Cute, that's what a lot of people refered to them when they came out.

 

[E-HP]

Hard to say what's normal without additional information, like the voltage. In any case, it looks like based on their specs, the 128 has a lower RPM/top speed by design.

 

[Ltc433]

Doesn't seem like folks are that interested in mini geared hub motors these days, but here is an "oldie but goodie";
https://endless-sphere.com/forums/viewtopic.php?f=2&t=70369&hilit=Q100+reduction+ratio
Another good search-word is Cute, that's what a lot of people refered to them when they came out.

Yes I really did a lot of searching but couldn't find a definitive answer because they apparently changed magnets and versions.

Hard to say what's normal without additional information, like the voltage. In any case, it looks like based on their specs, the 128 has a lower RPM/top speed by design.

The Q128CST is running at 48V in a 700C wheel. I got a response from the vendor and they said P1 = 147

147/10.5 (reduction ratio) = 14 magnets vs 16 in the Q100CST.

Edit: I am not sure that is correct..

 

[motomech]

Yeah, That link was at a time where we were taking Q100's apart left and right, but not many Q128's. I always just assumed they were like Q100's, only bigger

 

[Ltc433]

I was right about it not being correct.

The reduction ratio is 10.5 but the number of magnets is 16. However the supplier has said to set the P1 to 147 for Q128 CST.

10.5 x 16 = 168.

 

[Ltc433]

Yeah, That link was at a time where we were taking Q100's apart left and right, but not many Q128's. I always just assumed they were like Q100's, only bigger

Ive now got it built and have been reading a lot:

I just recently converted my bike with a Q128C. I love it. It's powerful, smooth and silent. I'm using the 36v 201 rpm one at 48v with a 14 amp sine wave KT controller. I get a top speed on the road of about 38km/h with 26"wheels. I think the most suitable controllers,if you want more power, are the 17A and 20A sinewave ones you get from PSWpower.

I get about 20mph. Seems a little slow. Q128CST 201 RPM KT 20A sinewave in a 29inch rim at 48V

Sounds like something is wrong.
My Q100's will spin almost as long as the bicycle ASM.
Are you sure the washers/spacers are connecting the wheel bearings and nothing else?
I would probably would flip the bike up-side down, loosen the axle nuts and see if it will free-wheel better.

My wheels, both the q100 and the Q128CSt dont freewheel that much. with the wheel suspended, a light push from my hand will make the wheel rotate for about 1/2 a turn and thats it. If everything too tight? It was the same with the Q100CST.

Would bumping up the voltage to 52V make a difference? I was thinking of getting a 21ah battery anyway...

 

[Ltc433]

https://www.youtube.com/watch?v=zOubH5zmtTc

I found this video and it seems similar to my freewheel CST speed ...

Compare Q100H and Q100CST

https://www.youtube.com/watch?v=a96wRJ2Rzis

 

[pullin-gs]

I get about 20mph. Seems a little slow. Q128CST 201 RPM KT 20A sinewave in a 29inch rim at 48V

Q128CST 328RPM 22MPH w/36V pack on a 20"wheel. Using an 11S (40V) pack, I get 25MPH fresh off charger.

My wheels, both the q100 and the Q128CSt dont freewheel that much. with the wheel suspended, a light push from my hand will make the wheel rotate for about 1/2 a turn and thats it. If everything too tight? It was the same with the Q100CST.

Would bumping up the voltage to 52V make a difference? I was thinking of getting a 21ah battery anyway...

My 128C is sluggish also during freewheel.....although it has freed up a bit after about 1000 miles. The rubber seals are pretty tight and drag the wheel a bit.
Suggest running ebake.ca bike motor simulator to see if upping voltage will help much. I found results were very close to actual results for my motor when I plugged in good numbers.

 

[Ltc433]

the odd thing is from pas 3 to pas 5 i didnt get much increase in speed. Torque, yes, but not speed. with my 1000w ddrive 30a from 3 to 5 pas gave a significant incease. Id be happy around the 22/3 mph mark but just seemed a bit slow.

 

[motomech]

PO has asked me about the lack of free spinning by hand of the motor wheel. It only turns a half turn or so and he thinks it may be too tight.
Well, when it's installed correctly, it really can't be secured too snugly, short of ripping off the axle threads.
Where the wheel comes in contact of the inside of the drop-outs, it usually will be against a nut on the axle (this should not be tightened hard against the bearing, but just located next to the bearing). It may have come with a washer over the nut and sometimes an extra washer may be needed so the rotating bits, like the end of the cassette spline/free whl. end doesn't rub on the inside of the drop out.
At any rate, I would suggest inside the drop-outs is the area to look for any binding.

 

[Ltc433]

it usually will be against a nut on the axle (this should not be tightened hard against the bearing, but just located next to the bearing). It may have come with a washer over the nut and sometimes an extra washer may be needed so the rotating bits, like the end of the cassette spline/free whl. end doesn't rub on the inside of the drop out.

On mine I did not use any washers on the inside. The dropouts rest on the hexagonal nuts that are on the axle. Is that correct or should washers be placed on the inside? I checked and there is no rubbing on either side.

 

[Ltc433]

Q128CST 328RPM 22MPH w/36V pack on a 20"wheel. Using an 11S (40V) pack, I get 25MPH fresh off charger.

I think i have figured out whats gone wrong. I ordered a 48V 201rpm Q128CST when I should have ordered a 36V Q128CST and run it at 48v. The website I was ordering from did not have a 36V Q128CST.

 

[Ltc433]

The 36V Q128CST 201 RPM, runs at 260rpm at 48V. So it is equivalent to a 48V 260 rpm or a 328 rpm?

i found this:
"I'm pretty sure that the 201 rpm 36v Q128c is actually 260 rpm and it's identical to the 48v 328 rpm Q128C, i.e. they're the same motor."

"By all accounts, the 36v 201 rpm and the 48v 328 rpm are in fact the same motor apart from the label, so you can take your pick. I have the 36v 201 rpm at 48v in a 26" wheel. I have it limited to 15.5 mph, but even at that speed, it seems to be pretty efficient. It has plenty of torque, but I have a feeling that it would work better in a 26" wheel than 700C."

"how 201rpm at 36V equates to 328 at 48V. I make it roughly 268"

"Simple. The 201 rpm 36v motor is not 201 rpm. It's 260 rpm!"

https://www.pedelecs.co.uk/forum/threads/q128c-motor.28061/

So Should i have gotten the 36V Q128C 201 rpm running at 48V or a 48V 260RPm or the 48V 328 rpm?

 

[molybdenum]

I have a 36v 201 rpm Q128c in 700c wheel, and as far as I can tell according to the ebikes.ca simulator, it spins true at around 260 rpm at 48V. I've never tried the 48V 320rpm model.

I also know that you can often just swap the cores of these motors, re-using the shell laced in the wheel. I've done this before when I fried my first one, and it saved me a lacing job. These motors are quite cheap, and I have about 14000 km on my 2nd one (babied, and never used over 540W at 10A).