All turned around.

Do these numbers of turns vs. rpm/v make sense as is:

48V 290RPM motor's winding is 19turns, 6.04kV
48V 320RPM motor's winding is 18turns, 6.67kV
36V 290RPM motor's winding is 13turns, 8.06kV
36V 320RPM motor's winding is 12turns, 8.88kV

Or is the absence of any information regarding the wire diameter making them opaque?

Looks plausible to me why do you ask?

Assuming its all the same stators... then yes, wire diameter goes down as turns increase.. otherwise the extra turns won't fit in the slots.

Rather than wire diameter going down, most builders use multiple strands of the same wire, so the strand count goes down as the number of turns increases.

flat tire said:

Looks plausible to me why do you ask?

Click to expand...

I currently have a 36v battery and I am looking to buy a motor to suit.

But, in the long term I'm aware that the limited top speed of a 36v setup will be a limiting factor I will want to overcome by moving to 48v when resources permit.

I'm trying to work out the pros and cons of buying a 36v-wound motor and later running it at 48v vs buying a 48v-wound motor now and running it at 36v until I buy a bigger battery.

I suspect that either wind would work at both voltages, but if I buy the 36v, the supplied controller may not be up to handling 48v later; but if I buy the 48v motor, performance at 36v will be abysmal.

That is further complicated because I was considering an XD2speed; but then the supplied controller is matched to the motor to ensure that the switch from low to high takes place at an appropriate point; so switching voltages without also switching to (the appropriate, proprietary) controller would almost certainly screw things up.

So now I'm (somewhat reluctantly) moving away from the XD2 and looking at a Q128H
Q128H; but that introduces a different bunch of unknowns that I am struggling with.

What does the H in the designation stand for? (Hall sensor?)

The Q128C (rated at 500w) offers the choices of 36 or 48v; and either a 201 or 328 wind.

But the Q128H (rated as 800w) only offers a 201 wind (regardless of voltage). Why?

And then the Q128 front hub offers only 36v; but either a 201 or 328 wind.
(Why the range 400w-500w? does that depend on which controller you get?)

It seems the more I read the less I know...

(It stopped raining; I'm going for a ride.)

I would go for a slower wind that works better on higher voltage since if you start riding the bike frequently you'll probably get a better battery / controller asap. And then ditch that tiny motor! So it probably doesn't matter too much. Also it may be worth getting a hubmotor already built into a wheel since they're available for not too much more.

Thanks for the reply; but to be honest, it doesn't help much. No direct answers to any of my questions, and what you did say only raises more questions.

flat tire said:

I would go for a slower wind that works better on higher voltage

Click to expand...

Why would "a slower wind work better on a higher voltage"?

flat tire said:

if you start riding the bike frequently you'll probably get a better battery / controller asap.

Click to expand...

Better controller than which? I haven't specified a controller yet; so if you could tell me which one you think I would need to replace, then I could avoid buying it in the first place.

flat tire said:

And then ditch that tiny motor!

Click to expand...

The small motor is what I want. Most of the time the 20 to 25kph it will give me is more than enough for the type of riding I do; and with the battery pack off the bike, the lightweight, freewheeling geared hub means the bike would remain usable as a bike.

Occasionally I would like to do longer runs on long, mostly flat roads where I would like to be able to get nearer to 40kph.

flat tire said:

Also it may be worth getting a hubmotor already built into a wheel since they're available for not too much more.

Click to expand...

The problem(s) with buying a pre-built wheel are: 1) you pay substantially more for shipping; 2) they tend to get built with heavy gauge spokes and (reportedly) not well aligned and trued.

Note: Going by what I've read; mostly here.

Slower winding gives the torque higher voltage will make up for the speed hit. And you will pay more or spend more of your own time to get a wheel built than you would just buying it like that in the first place. The shipping isn't even that much. Just tighten the spokes and it should go a long ways. If you're ok with slow then controller choice and battery don't matter as much as long as they're not bottom dollar.

H in Q128H is the high torque version. It gets its higher torque than the cooking version by using a higher reduction ratio and spinning faster.
The 36v 201 rpm Q128C is actually 260 rpm, which means 328 rpm at 48v, so the 36v 201 rpm and 48v 328 rpm are probably exactly the same motor with different labels. If you run it at 36v, you get around 22 mph on the road. At 48v, you get around 25 mph, though it wil assist to about 29 mph. You get 30% more torque and power at 48v..

The Q128H is for freewheel gears up to 7-speed and the Q128C is for cassette gears of any no of speeds.

The Q128C is a lovely motor when paired with a 15 to 20A KT sine-wave motor - perfect at 48v.

Thanks Dave, that helps a lot. But ...

d8veh said:

H in Q128H is the high torque version. It gets its higher torque than the cooking version by using a higher reduction ratio and spinning faster.

...

The Q128H is for freewheel gears up to 7-speed and the Q128C is for cassette gears of any no of speeds.

The Q128C is a lovely motor when paired with a 15 to 20A KT sine-wave motor - perfect at 48v.

Click to expand...

That implies that you can only have the high torque version with a freewheel and the "cooking" version with a cassette?

Can you buy a cassette that is directly compatible with a 7-speed derailleur, chain, shifter etc?

"Can you buy a cassette that is directly compatible with a 7-speed derailleur, chain, shifter etc?"

Yes, you can. The shifter and chain can't tell if it's a cassette or a freewheel.. as long as it 7 speed it's all all the same. 8 speed actually works too.. you just a gear you cant get to with your shifter, and you can pick whether its the big or the small gear depending on how you adjust it.

Voltron said:

Yes, you can. The shifter and chain can't tell if it's a cassette or a freewheel..

Click to expand...

Of course. But I read somewhere that cassette systems use thinner chains, thus more closely spaced sprockets, thus smaller indexing movements.

I have now (since your comment) read that by using the right combination of spacers it will work.

Buk___ said:

Of course. But I read somewhere that cassette systems use thinner chains, thus more closely spaced sprockets, thus smaller indexing movements.

Click to expand...

Not anything I have here. The 7 speed cassettes are spaced the same as 7 speed freewheels, etc.

When you get into 10, 11, etc., *then* it's different (and would be the same way with freewheels as cassettes).


some info
https://www.sheldonbrown.com/k7.html
https://www.sheldonbrown.com/speeds.html

The answer to your question is pretty simple..

You want fast, so buy the faster wind motor. Then if 36v is not enough speed for you, run it on 48v.

Don't worry about the voltage rating of the motor, because there really is no such thing. Only thing is, rpm rating IS stated @ a particular voltage. So 320 rpm @ 36v and 320 rpm@48v are NOT the same winding.

Again, just buy the fast one, since you want fast. If you want more power, then you buy the big fat motor, again, in the fast winding.

Don't sweat torque, or wire size, since none of that matters. The same motor with different wind will have near the same torque.

If you need more torque, you buy the big motor, with the big magnets and tons more wire inside. The tiny motors you are looking at are completely unsuitable, if you need big torque and big speed. But the fast version tiny motor will work fine even on steep hills, provided you do not weigh over 200 pounds. You won't need such big torque unless you are big. If you weigh more than 200 pounds, then you need to look at bigger motors,, period. Or, you need to be a very very fit cyclist.

dogman dan said:

The answer to your question is pretty simple...

Click to expand...

Hm. What you say contradicts pretty much everything that those that use the Q motors tell me.

Is there some problem with me trying to use the collective expertise here to understand what the various options available will give me, before I buy?

It may all be old hat to you, but you don't have to read it, and you don't have to answer. I been reading thread after thread here along with wiki pages and blogs going back years, but there is a lot of information amongst even more misinformation; and an ever changing state of play.

The sources of these motors rarely give accurate information on their websites; you get pictures of one motor in a wheel that is entirely different to the (apparently) same motor shown right next to it without the rim attached: (eg. A silver mini-motor with rim fitted, next to a black pancake motor without.)

The "same" motor for front fitting offering more (and more desirable) options than that for the rear-fitting which I need. 201RPM actually means 261 where 328 actually mean 290 (or something like that).

The same motor on different sites with different names, different power ratings; and different speed designations.

I cannot afford (retired early on a minimal fixed income prior to my achieving the official retirement age) to buy half a dozen motors and see which one suits me, so I need to understand what my options are and what they will give me.

Sorry of that doesn't gell with your '70-esque 500ci V8 shopping car attitude of "stick a bigger bloody motor in it"!

You are tripping out hard about this. You want to spend once and you're worried your motor won't perform like you want, so buy a decent size motor and be done with it. Try a Leaf 1500w. 18 lbs, high efficiency, and up to 60 mph if you're a lunatic and put 7kw thru it. Or you can cruise efficiently at 15 mph on 48 volts. Climbs pretty much any hill. The leaf is only $200 (plus shipping) and kicks ass.

This guy is selling a 1KW QS motor for $190 each in usa.

https://electricbike.com/forum/forum/for-sale/parts/47284-qs-v1-1000w-205-35h-hub-motor-8-5kv

From what you've said I wouldn't get a motor less powerful than those. You can always run a motor at less power than it's capable of but you'll have a very bad time trying to get a 500W motor to climb hills or move around with any kind of urgency at all.

amberwolf said:

Buk___ said:

Of course. But I read somewhere that cassette systems use thinner chains, thus more closely spaced sprockets, thus smaller indexing movements.

Click to expand...

Not anything I have here. The 7 speed cassettes are spaced the same as 7 speed freewheels, etc.

When you get into 10, 11, etc., *then* it's different (and would be the same way with freewheels as cassettes).

Click to expand...

Isn't this guy having exactly the problem that I was worried about? Or am I misreading those posts?

No... his problem is trying to make a 7 speed cassette (or freewheel, it doesn't matter) work with a nine speed shifter. It would work with an 8 speed shifter, leaving an empty click, but with 9 speed the spaces between clicks is different., and it won't line up.

The only difference between cassette and freewheel is the racheting mechanism is built into the gear cluster and the whole thing screws onto the hub. With cassette, the racheting mechanism is built into the hub, and the gear cluster cassette slides onto splines on the spinning part. But there's no special spacering needed between between the two types. FYI cassette with freehub ( the racheting part built onto the hub) is better than freewheel... the final bearing is closer to the end of the axle, reducing bending loads on it.

Voltron said:

No... his problem is trying to make a 7 speed cassette (or freewheel, it doesn't matter) work with a nine speed shifter. It would work with an 8 speed shifter, leaving an empty click, but with 9 speed the spaces between clicks is different., and it won't line up.

Click to expand...

Ah. T'other way around to me. Got it. Thanks.

Voltron said:

FYI cassette with freehub ( the racheting part built onto the hub) is better than freewheel... the final bearing is closer to the end of the axle, reducing bending loads on it.

Click to expand...

I read about that applicable to normal wheels with QR axles; but does it also apply to a hub motor?

Usually an ebike axle is stout enough that axle bending is less of an issue, so the benefit is not as great as on a normal mountain bike wheel. But you usually find higher quality gears for cassette than freewheel, but again, maybe not much benefit unless you actually pedal hard.

Usually.

(though this failure wasn't from the same loads as those that bend axles from pedal chain torque)

https://endless-sphere.com/forums/viewtopic.php?f=2&t=67833&p=1311210&hilit=%2A5304+axle#p1310982