Motor size vs Power

[PeeHell]

OK guys I'd like you to clarify this for me : Is the diameter of a hub motor more important than its width to create torque, efficiency and power ?

I mean how does the large Magic Pie (18mm width) compares with 9c (28mm) or a Hx35 (35mm) in terms of power handling ?
Does the width of the magnets is proportional to the saturation current ?

You'd be nice to help me out with these technical questions.

 

[Drunkskunk]

The short answer is Yes. the long answer is No.


Larger diameter hub motors will make more starting torque than smaller diameter motors of the same power rating. Thats the short easy answer, applying to hub motors.


But the width of the stator and the magnets are a bigger factor in the power a motor can make. Ultimatly, its all about copper mass, and having a good ratio in favor of the copper between the stators as opposed to the copper going around the ends. and its a lot more complicated than that. So the long answer is No.

Its easier to make a large diameter motor than it is to make a extra wide motor, when they all have to fit in the same dropouts.

 

[PeeHell]

What would you guys choose for the best bang for the buck hub motor ?
My setup is a 700c wheel with 18s lipo and I'd like 60km/h (37 mph) hot off the charger. Montreal is pretty flat so overheat is not a much of a problem . I hesitate between :
-MXUS/9c 9 turn
-Magic Pie
-MAC 10t 1000w (cellman)
-Large diameter cromotor
-Any suggestion

What's your opinion about the best torque/speed setup possible ?
Thanks

 

[dogman dan]

Well, now that you restate the question in terms of bang for the buck, it's obvious.

I definitely settled on the Muxus/9continent as the motor cheap enough for me to melt some.

I don't know where you get the 6x9 muxus/ 9c, but if you mean the 9x7( 2807) winding that would be my choice for the speed at voltage at rim size you are looking for.

Cellman for the win again. Run it on the Lyens 12fet or similar controller. You'll see less speed if you run only 20 amps.

Equally obvious that the Hs clyte would be a contender, painfully obvious that the cromotor is not in the same price category as a muxus. Bottom line for me is, the 9c is quite up to the goals as you just stated them.

Of course, there is what you say you want, and what you really want. If you go for what you really want, just start closing your eyes, clicking buy, and plan on having some charge card bills for quite awhile.

 

[PeeHell]

The choice I wrote above is to replace my front 9c 2806. I have a 15 FET Hua Tong controller modded to ~50A and I wanted a new rear hub deal with that power. So you think the 100$ more of the magic pie over the MXUS DD is not worth it ? I only want a cheap hub to handle the acceleration and cruise efficiently. Any idea of the potential price of the narrower cromotor ?

 

[MadRhino]

What is best for you, has to be according to your desired performance and budget.
Montreal is not flat, well it may be that your commute is on the flat, but there are some serious incline in the city.
When you mention in the same sentence, the Cro-motor and the MXXUS, it makes me think that either you don't know at all what kind of power that you want, or you have a big budget and don't care if the motor is worth 1K or 100.

 

[PeeHell]

Well it's just that I don't know the price of the large diameter Cromotor. I guess it's cheaper than the wide one. You're right, Montreal isn't flat ; there's a hill on the middle of the island that is easy to avoid.
I was just wondering what would be the best hub suited for my needs for <300$

 

[MadRhino]

If you avoid the Mont Royal, buy the kit from Cell-man. The Cro-motor is for those who are after performance, and it is much more expansive, the like of 1000$ with a good lacing job and shipping,

 

[PeeHell]

Thanks for the advice. I didn't know the thinner Cromotor was that expensive. What would be the difference between Magic Pie and the MXUS/9c with similar windings (except $100) ? MadRhino, what are your setup ?

 

[dogman dan]

Well, back to post one. By now I'm clueless what it is you really want. Is it bang for your buck, or you want a cromotor for $210? What you said so far is easily in the range of a muxus.

Larger diameter will improve the way a motor leaves the line. I don't know if it's really more torque, but it seems that way to me. So maybe what you want is there in the magic pie. But 18mm wide magnets just doesn't sound like any kind of advantage to me. Magic pie with 28mm magnets would interest me.

Sounds like you already have a muxus or similar motor, and run it on 50 amps. Who knows what voltage, but if it's not now then go for 72v. If that's too slow for you then try 100v is all I can say.

You are running a 700c wheel, and a 2806. Well, good thing you aren't climbing my mountians. It's steep here, and I like much lower speed windings. But I'm looking for something different than you are.

 

[PeeHell]

That 's what exactly what I was thinking Dogman ; the Magic Pie diameter sure is great, but the 18mm width isn't. I am looking for the best motor possible for the price so I'm not thinking of the Cromotor anymore. All I want is good acceleration up to a top speed between 35 and 40 mph
As stated above, my current setup is 18s Lipo with a 15 FETs 50A controller. I just found an MXUS motor on their site that looks like a good compromise between diameter and width. It's the 266mm stator MXUS DD : http://mxusebikekit.com/shop_show.asp?cid=57

Available in 12" to 28" rims


23mm stator width ??


Nice performance curve compared to others chinese cheap motors


Well if it's true and available at low price this motor could have good potential...

 

[MadRhino]

Thanks for the advice. I didn't know the thinner Cromotor was that expensive. What would be the difference between Magic Pie and the MXUS/9c with similar windings (except $100) ? MadRhino, what are your setup ?

I am building with the Cro-motor now
I have 3 Chrystalyte X5, and 2 of the H series, with various windings
Then, 2 of the big X54 are coming soon

 

[parabellum]

As stated above, my current setup is 18s Lipo with a 15 FETs 50A controller. I just found an MXUS motor on their site that looks like a good compromise between diameter and width. It's the 266mm stator MXUS DD : http://mxusebikekit.com/shop_show.asp?cid=57

Available in 12" to 28" rims

tmpphpigeWQo.jpg

What you are looking at is a "ESCOOTOR MOTOR", I believe you need "bicycle motor"
Here are Mxus DD kits for 175U$, by cellman. http://www.emissions-free.com/catalog/i14.html
They are 500w rated, but motor takes 2KW continuous easily if you do not bog it down, and I run setup peaking at 8KW (at my own risk). Stator is 26mm width. Filed with oil it can handle up to ~4 KW continuous at higher speed.

 

[neptronix]

The magic pie is freaking amazing, but it needs very high voltage to really perform.
If you want 30-35mph, 72v is what you'll need.

But my first choice would be the tall motor from greyborg that i like to call the "deep dish". ~22% more magnet than the magic pie, which is already a pretty damn strong motor. Should be a true beast - i think it may stand right up there with the crystalyte 53xx, at a notably lower weight. Continous power is quoted at 1700w. Most motors are rated at 500w-1000w.

My second choice is the MAC motor due to it's weight, broad efficiency band, stealthyness, and low power requirement. I can average about 26mph, with peaks up to 29mph on 36v with a 8T motor; very satisfactory for quasi-USA legal speeds.

What you will end up with depends on your requirements for power, speed, and efficiency. There are dozens of options.

 

[PeeHell]

The hub I've shown the pictures of shows a 136mm width on the diagram. Maybe I've read wrong. The MXUS site writes "Specitication:12"-28". That's why I thought it could fit a bicycle.
I've read a lot of good thing about the mac. It seems to be very torquy and fast but I'm scared of overpowering it with 18s and Lipo and 45-50a max...

 

[neptronix]

How fast do you want to go and are you dealing with straight flat land, a little hilly, or very mountainous?

 

[PeeHell]

I aim 35-40mph with a relatively flat terrain. The off the line torque is important but I'll never have to go up long steep hills.

 

[neptronix]

Then your motor requirement is going to be very relaxed and you won't have to overspec a hell of a lot like me.
No geared motor in production will do 40mph for very long. Maybe 15-20 minutes and it's time to cook your breakfast on it

Not many hub motors will do this either; you need something like a Crystalyte 5xxx, maybe a magic pie on a stupid amount of volts ( no guarantee )? the deep dish cromotor should do it, and the hubzilla cromotor will definitely do it..

40mph is 2500w continuous on a lot of motors. 35mph is more like 2000w continuous. 30mph is more like 1250w continuous.

You will definitely need a bad boy of a motor to do that 40mph constant.

 

[PeeHell]

I'd be happy with 60 km/h (37.5mph) off the charger. Because this large hub can tolerate more heat longer than the geared, would you recommand me the Magie Pie over the MAC ?

 

[neptronix]

For that speed, i would recommend the pie over the MAC, yes.

oooScorpioNooo is the only member on here that i know who has really pushed his magic pie to high speeds, on i believe a 26" wheel. You may want to send him a PM.

I am running a 20" wheel, so i need a higher voltage, and the results i can give you on the pie are going to be different. For my wind, I would require i think.. 24S / 91.2v nominal to pull that off. I know a 26" wheel is a little faster per volt.

The pie might do what you want.

But if you can wait, the deep dish motor by cromotor should be awesome. i will likely dump my magic pie for it.

 

[PeeHell]

Yeah I thought about the big dish but people have written above that it's going to be very expensive. Do you have any ideas about the possible price and release date ?

 

[neptronix]

If you avoid the Mont Royal, buy the kit from Cell-man. The Cro-motor is for those who are after performance, and it is much more expansive, the like of 1000$ with a good lacing job and shipping,

I think madRhino was not aware that there are two greyborg hub motors going up for sale.

The 50mm magnet hubmotor that's roughly the diameter of the Crystalyte 5xxx motors is rumored to be about $595 plus shipping.

The large diameter ( i like to call it the deep dish; it looks like a wider Magic pie ) motor's price is *completely* unknown.
I'm thinking it will be under $400 - just a guess.

 

[parabellum]

I'd be happy with 60 km/h (37.5mph) off the charger. Because this large hub can tolerate more heat longer than the geared, would you recommand me the Magie Pie over the MAC ?

60kmh is not a big deal for any bigger DD hub.
1)9C/Hx/Mxus/GM(not MP version) are same construction with only relevant difference of stator/magnet wight all can do that
2)Sure MP will do that as well at certain voltage.

Real life data.
1)If you lase 20" (low wind) Mxus DD hub into 26" wheel, you get ~60kmh top speed at 60V (15s LiPo), consuming ~1.8KW continuous (on flats).
2)If you run 26" hub to 26" rim you will come to 60kph at 20S LiPo for sure but will be just little under 60kph at 18S. (I get 40kph at 12S and speed will not grow in linear proportion)
3)Must also say, have GM DD (48v1000w marked motor, 30mm stator) and it is little more efficient than Mxus.
4)Less efficient motor I ever had is HS35 (32mm stator), it manages to turn more W in heat in any conditions and quality of inner construction is worst of all.

Hope it helps.

 

[MadRhino]

If you avoid the Mont Royal, buy the kit from Cell-man. The Cro-motor is for those who are after performance, and it is much more expansive, the like of 1000$ with a good lacing job and shipping,

I think madRhino was not aware that there are two greyborg hub motors going up for sale.

The 50mm magnet hubmotor that's roughly the diameter of the Crystalyte 5xxx motors is rumored to be about $595 plus shipping.

The large diameter ( i like to call it the deep dish; it looks like a wider Magic pie ) motor's price is *completely* unknown.
I'm thinking it will be under $400 - just a guess.

Only one right now, and if you add shipping, good rim and spokes and lacing job... It's a 1000$ wheel
Mine comes a tad over that, and I laced it myself.

There are 2 other Cro-motors that should be available later this year. One higher KV version of the one that I have, as a pre-order and more expansive, the other we don't know yet but will be expansive too, compared to all the small hubs mentioned here.

I don't see why someone who is not after performance and says being on a budget, would buy an expansive powerful motor, that is not yet available. I personally, if I was building with the OP target performance, would prefer to use a lighter weight hub and leaning toward cell-man motors, maybe even thinking of the geared hub kit.

 

[dogman dan]

Still say your target speed is totally within the range of a muxus- 9c motor in the 2807- 9x7 winding when fed 72v 40 amps.

Yes, it will melt if you run it too long like that. Ventilate the hub covers, and run it on no more than 10 ah, and you will not hit the melt point sooner than you hit the stopping point. If you have to run 15 ah to make your range, slow down to 35 mph crusing speed and you won't melt it so fast.

So many people have done this standard 40 mph club recipe succesfully. It's cheap, and just makes the speed.

You could go to the Cylte Hs model, but it cost more than 9c. I'd call a pair of 9c motors affordable. a spare if you do melt one down.