Modifying a Hub Motor

The bloke wants to go faster, he'll need more power, I mean it is rather the point of his post.
If he really want to keep the motor then the easiest way is to add a battery in series, assuming he has spare amperage capacity, as he says, and assuming his controller can handle the voltage.
Assuming he actually wants to re-wind the motor (which is unlikely but an interesting discussion) then fewer turns of thicker wire at the same voltage will give him more power with the same fill
Here's a Grin simulation of the same battery (something like his 72V 350A capable setup) with a 4T and 3T motor, just as an example as they are about the same copper fill and same motor
With the 3T (thicker wires, three turns) he gets 2.8 Kw instead of 1.8 Kw = more power from the same voltage, only by changing the windings
4T Vs 3T.JPG
 
fatty said:
BobBob said:
To be clear, you are not rewinding the motor to be more "powerful" unless you achieve more copper density but you are changing the amount of voltage and current to suit your power supply
This is nonsensical. Motor winding is independent of supply voltage and current. As explained above, rewinding only exchanges kV for kT.
Motor winding is not independent of supply voltage and current. It is the thing that determines the relationship between the two.
Sorry I didn't make myself clear enough, it is not that it is nonsensical it is that you haven't understood me.
The chap wants to go faster - that is the aim of the exercise and his question is can he re-wind the motor to achieve this
The battery is a 72V 350A (from 25 KW spec) capable and we are assuming that the new purchased controller will be capable of providing the additional current that our new winding will require.
This means that he has spare current capacity - his system can provide more amps than he can use
His system only provides 72V
So, if you re-wind the motor with fewer turns of thicker wire then it will draw more current at this 72V
He will use more amps and get more power at the wheel
So he goes faster which is what he wants
So the answer is yes - he could re-wind to go faster and have more power

fatty said:
BobBob said:
If you want more current you need thicker wire, not thinner wire, you need to go to a 3T from a 4T or 5T.
Gotta go, will re-edit later but you've got your calcs the wrong way round.
Read my post again -- I address both these points. You continue confusing two different procedures/mechanisms:
Rewinding for higher kT = lower kV, requires more turns, and possibly thinner wire with side effect of higher electrical losses -- relevant only at maximum motor torque (not maximum controller current)
Rewinding for higher kV = lower kT, requires less turns, can possibly use thicker wire with side effect of lower electrical losses -- relevant only at maximum motor torque (not maximum controller current)
This is where the simulator might help you, the power curve is different - the bit in the middle not the bit at either end
The peak power output is higher
fatty said:
Distinct from
Rewiring with thicker wires because you burned out your old windings with too much current in a current/temperature-limited (not flux-limited) motor design. Thicker wires fit less turns, with side effect of reducing kT, thus requiring more current for the same (previous) torque, thus requiring much thicker wires to increase current capacity to result in net torque increase. Much thicker wires decrease electrical fill factor.
1. He didn't burn out his old windings
2. Yes he risks melting the thing because he's putting more power through it of course
3. The MXUS 4T has a better fill factor than the 3T or 5T so no, it doesn't always decrease fill factor
4 Yes - he requires more current and he has the same voltage so he gets more power which is what he wants.
More power = more speed - exam question answered
fatty said:
Please take a second to re-read through this carefully, so we don't continue to talk past each other. You are overgeneralizing a rare corner case (rewiring) and thus missing the big (motor constant) picture.
I'm using Grin simulations and simple examples to illustrate a fundamental of motors.
There's pretty much no difference between a 3T driven with 4S and a 4T driven with 3S - see my 12 strands example above
I suspect you may be limiting your analysis to one variable at a time such as KV and KT without understanding the relationship between them and thus missing an understanding of the system performance at mid range speeds. See graph above
 
fatty said:
markz said:
https://youtu.be/c96n0Ma2rLY?t=8174
Exactly :thumb:
Most of this is about high T vs low T being the same so long as you drive them with the equivalent Voltage and Current
Summed up perfectly 2:22:35 the winding makes no difference, you just trade voltage for current
It's just a small logical step hopefully to realise that if you have a non optimal setup then changing something can make it better
The perfect example being a system that can deliver 350A but us only using 20A
fatty said:
markz said:
https://ebikes.ca/tools/simulator.html?motor=MX4506&batt=B7208_DT&cont=cust_21_42_0.035_V&hp=50&cont_b=cust_40.5_81_0.035_V&motor_b=MX4503&batt_b=cust_45_0.1_8&hp_b=50&bopen=true&throt_b=92&throt=100&grade_b=0&autothrot=true&autothrot_b=true
**********Range is different because the batteries are different total Wh.

Exactly :thumb:
Here is a customized chart with the OP's fatbike and battery pack.
Here's your original - you have the 3T motor running at half throttle but are trying to say that the 6T one at full throttle is faster to make them look the same but they're not.
This shows that the thicker wire, lower turns of the 4503 (3 turns) rather than the 4506 (6turns) can achieve your top speed by only using half throttle - it half proves my point not yours.
Original.JPG
So when we get rid of your fixed throttle output, to answer the bloke's question of can I go faster; guess what? Yup, the one with fewer windings goes faster
WOT.JPG
fatty said:
This is why I always recommend selecting the lowest kV suitable to reach desired maximum speed:
It's just not clear why. Perhaps for efficiency at a target speed but ignoring power in mid range.
He didn't give a desired maximum speed, he wanted more power and more speed.
Your solution is slower and less powerful
fatty said:
lower kV = higher kT
= lower current for same torque = lower electrical losses = higher efficiency (as seen in simulator above)
AND
= higher torque from same current
Yeah but we don't want to use the same current, we have 350A available and youve limited it to 40 A LMAO
You're not answering the exam question
So, to explain again, if you want more power from the same voltage you need more current so you need a controller than isn't limitiing it
if you want more power from the same current you need more voltage
Now lets try your simulation with, hmm, lets say a 100A controller, to make use of the additional spare current and give the chap more power - see the difference that rewinding makes ?
We just managed to increase power from 2.2Kw to 3.4 and top speed from 29 to 44 Mph from just changing the windings
Quetion answered - using your own simulation
100A.JPG
 
You want more torque, why not set the controller for higher amps? what is your current maximum amperage?
 
fatty said:
serious_sam said:
I never made any claims about power.
In fact, I've explained higher kV at equal torque = more power.

Yeah, you did and you got it wrong

fatty said:
EpicShelter said:
If I'm not mistaken, I should be able to rewind the hub motor to draw more current at 72V effectively making it more powerful (increasing its wattage).
Does anyone have any resources on how to rewind a motor for increased current draw?
No, as was correctly posted above, you can only trade speed for torque.
Your answer was incorrect, the key word is "effectively"
The question you answered was "will I get a more powerful motor" to which the answer is technically no
The question he was asking however was "will I get more power out of my 1.5 KW motor by winding it differently" and given my 350A capacity battery but at a fixed 72V and buying a new controller, to which the answer is "yes you could"
 
neptronix said:
You want more torque, why not set the controller for higher amps? what is your current maximum amperage?
He's blown his controller and has a 25Kw capable battery at 72V so 350A available apparently
Sensible answer is get a better controller, see how it goes then get a better motor.
Re-winding is an intellectual side track. (yeah I know winding motors is tricky, did some work on F1 and some bigger in wheel systems)
 
John in CR said:
You can't rewind a motor to make it able to make more torque at any voltage. A rewind accomplishes nothing that you can't accomplish by changing the voltage and current, unless you are able to fit more total copper around the stator teeth than the factory.

If you want better performance from the same motor, the best way to accomplish that is increasing voltage and decreasing wheel diameter.

This is the correct answer, although i'd add that in motor simulations, lower kV windings can be a few % more efficient in the low RPM range. In the real world, this small difference is likely due to things like wire diameters and component selection in the controller.

Rewinding a motor is a massive job with very little benefit, versus other solutions for increasing power.
 
Yes rewinding just trades voltage for current
The voltage is fixed, there is spare current capacity (350A) and the controller can be purchased to suit the solution
To draw more current you could use thicker windings and get more power from the system flat out
This is the academic answer to "could it be done" not "should I do it"
 
There's a lot of advice in this thread and some of it is a bit iffy.

John in CR nailed the theory and Dogman the practicality of the OP's situation.

To make the bike go faster you need more volts and/or bigger tire size. More torque will need more amp and/or less tire size. Motor winding only determines how many amps the motor will accept. Getting carried with any of these 3 variables(Volts, Amps, tire) will toast your motor/controller system on hills.

My advice to the OP is to get comfortable with Grin's simulator and pay special attention to "time it takes to meltdown @ 100% throttle". Start out imputing the values of what you already have then change just one at a time until you get the results you want.

My thoughts on rewinding is to forget about it unless you enjoy wasting time and money. I don't think I have heard of anybody having success without trying multiple times. It's so much simpler buying a new or used one and selling what you have. Get the best controller you can afford. You can always limit the amps if you can't keep the front wheel on the ground or it overheats. For sure buy a cheap Digital thermometer and put the probe inside the motor.

Good luck and HAVE FUN!
 
My chat about theory is not advice. Most of this thread is theory not advice
When I'm saying what's possible and what's advisable, those are two different things, hpefully that's clear
Nobody on this thread has said that rewinding is a good idea though I'd love for him to succeed
I have a soft spot for nutters, especially the ones who build fantastic crazy stuff and I'm gonna support that, so shoot me
I am probably the most positive on the subject and I've said if you reallly want to then why not. You will probably F it up but I know one person who rewound a precision motor when it blew, and it works, and it works well, and why the hell not.
He is kinda exceptional and the jig he built was something else. this is more difficult

Yeah, John nailed it but it is only the first step.
The trade off of V vs A is useful if you have spare Amps

The guy asking the question wanted to know if he could get more performance from his bike - the answer is yes, in theory
You will get different performance from different windings
Sometimes that performance will be "better", What's the chance it was already perfect
English time. gonna crawl off to bed. Thanks for the discussion
Yeah I agree it's not sensible. I'm not a fan of sensible - agreed - it's for fun
 
https://youtu.be/dxJe_gygRGU?t=2679

https://youtu.be/dxJe_gygRGU?t=4217

edit
I am not retyping it out here but link to what I did type out.
https://endless-sphere.com/forums/viewtopic.php?f=3&t=111422#p1651119
 
serious_sam said:
If you never admit when you've put your foot in your mouth (and you never do), you'll never get rid of that bad breath.

And your breath stinks bad.
I think we disagree enough not to add your lack of reading comprehension to the list:

fatty said:
Again, I'm not disputing that higher kV = more power at fixed maximum motor torque (obviously, power = torque * rpm). But nobody asking such beginner questions is holding their motor at the ragged edge of burning up.
 
fatty said:
serious_sam said:
If you never admit when you've put your foot in your mouth (and you never do), you'll never get rid of that bad breath.
And your breath stinks bad.
I think we disagree enough not to add your lack of reading comprehension to the list:
But it was you that were wrong on many of the points you made, specifically the one that Serious_Sam picked you up on - power.
You even admit this later so I guess you disagree with yourself as well?
1. Your first comment either was intentionally trying to belittle and mislead the OP by telling him he was wrong when he was right or
2. perhaps you failed to understand the question - this might be termed reading comprehension but could just be trolling
3. You then go on to explain how KV and KT are related and advise to use thinner wires, thus getting the technical aspect wrong as well as the comprehension bit.

Most important, what about the being nice to a newbie bit?

fatty said:
Again, I'm not disputing that higher kV = more power at fixed maximum motor torque (obviously, power = torque * rpm). But nobody asking such beginner questions is holding their motor at the ragged edge of burning up.
1. yes that is exactly what you started by disputing and got it wrong.
2. We dont have fixed torque, we don't have fixed current - you made that up and it's the best solution - use more current if you don't have more voltage
3. You got the answer to his "beginner question" wrong in several ways
4. He's planning on putting 2-3 Kw through a 1.5 Kw motor. How is this not "holding their motor at the ragged edge of burning up", thus you appear to be incorrect in this point as well, at least from my reading of the question.
Thus it appears that yes, the OP was asking whether he could get his motor to 3 KW by using thicker windings

For your subsequent answers you have confused increased windings with increased KT - you got the relationship the wrong way round which may be causing your confusion - suggest re-reading your own posts:
fatty said:
Rewinding a motor for more torque (higher kT) in the direct, textbook meaning of "rewind" is simply increasing turn count to trade kV for kT.

fatty said:
Rewinding for higher kT = lower kV, requires more turns, and possibly thinner wire with side effect of higher electrical losses
 
Read my post again and learn motor constants.
You have no idea what you're talking about.
 
BobBob said:
[repetitive]
I have you on ignore but keep getting repetitive notifications that I'm wrong "in several ways", without explaining (or indeed, understanding) why.

I'll try one last time. Read this carefully and think about it, and you might actually learn something. If you don't understand it, ask a specific question where you're getting lost. Isn't the chance to learn something worth at least a try?

BobBob said:
4. He's planning on putting 2-3 Kw through a 1.5 Kw motor. How is this not "holding their motor at the ragged edge of burning up", thus you appear to be incorrect in this point as well, at least from my reading of the question.
Thus it appears that yes, the OP was asking whether he could get his motor to 3 KW by using thicker windings
This is precisely my point. He's not limited by maximum motor current/temperature, but rather some lower controller current limit. If not limited by ultimate motor current/temperature, what determines motor torque? kT, right? Higher kT = more torque, right?

And what is power? torque x rpm, right? So what gives more power at the same speed, low kT or high kT?

Where are you getting confused? Make sure you differentiate between maximum motor current/temperature limited intrinsically by the motor, and operating current/torque as determined by the controller.

I'm unsubscribed and turned off notifications, so PM if you actually want to learn motor constants.
 
BobBob said:
For your subsequent answers you have confused increased windings with increased KT - you got the relationship the wrong way round which may be causing your confusion - suggest re-reading your own posts:
fatty said:
Rewinding a motor for more torque (higher kT) in the direct, textbook meaning of "rewind" is simply increasing turn count to trade kV for kT.
Actually, this conversation is probably pointless. If you keep arguing this point without understanding it, you're beyond reason:
I don't have the motor constant relationship "the wrong way round". Trade means to give up one thing for another.
As you quoted me above: Increase turn count = decrease kV = increase kT

Here's Motor Terminology for Dummies:
Turn Count

The more turns a motor has, the slower it will spin. Turn count is how many times the wire is wound around the tooth of a stator. It is inversely proportional to the Kv of the motor. For instance, a 3210 4T has a Kv of 339 RPM/V. From this, it can be determined that the Kv of a 3210 8T is 165 RPM/V (339 RPM/V * 4T / 8T = 165 RPM/V). Further, the turn count is also directly proportional to the Kt of the motor. Using the same example, a 3210 4T has a Kt of 4 Inch*Ounce/Amp, which means the 3210 8T has a Kt of 8 Inch*Ounce/Amp.

There is an common misconception that increasing the turn count is the same as gearing down. It is true that by doubling the turn count while maintaining the same input voltage and current yields half the RPM and double the torque, which is the same result as using a 2:1 gear ratio. However, spinning the motor at half the RPM will also half the maximum output power of the motor. This is because the maximum torque of all motors of a specific motor size (eg. 3210) is the same and unaffected by turn count (the reason they're all the same is because there is the same amount of copper loss).

For example, the 3210 4T has a Kv of 339 RPM/V. We have a 50V power supply to use and would expect to get about 17,000 RPM (339 x 50 = 16,950). However, 17,000 RPM is too fast for our application. We want to run our at half that speed, 8,500 RPM. To achieve this, we have 3 options: we can use a power supply of half the voltage (25V), we can apply a 2:1 gear reduction, or we can use a 3210 8T. We opt for the 3210 8T to avoid having to buy a new power supply and to avoid having to add a reduction system, but after looking at the application specs, we realize that we need 500 Inch*Ounce of torque for the product to work correctly. The 3210 series, however, can only supply 375 Inch*Ounces (any more and the excessive copper loss would cause the motor to overheat). The only option that will fit our needs is to use a 2:1 reduction on the 3210 4T. By doing so, we've achieved our desired RPM and also can afford a bit of overhead in torque (the reduction allows us to have a maximum torque of 750 Inch*Ounces).
 
Don't forget about COPPER FILL.

There was a post on using squared windings, I should try and find it after this zoom mtg I am on.
Wasnt long to find something.
https://endless-sphere.com/forums/viewtopic.php?f=30&t=103212&p=1541928&hilit=square+winding#p1541928
https://endless-sphere.com/forums/viewtopic.php?f=30&t=103212&p=1541928&hilit=square+winding#p1547731
It is much more expensive with square wire and i think it takes a lot more time to wind it. the thin wires can probably just be wrapped around easily vs the thick wire that needs to be formed, radius by radius, turn by turn

Ah yes, dont forget the wire gauge used
https://endless-sphere.com/forums/viewtopic.php?f=2&t=14482&p=218275&hilit=winding#p218275
The 6x10 winding won't really have any more torque than the 7x9 or 9x7 windings. You'll only get marginally more torque off the line and at a stall because the controller and phase lead losses will be somewhat less, but the effect is going to be pretty small, and can be negated with the faster winds by using heavy 10 or 12 AWG phase wire between your controller and the motor. As soon as you reach any appreciable speeds, then the slow 6x10 winding would have LESS torque than the faster windings for a given controller/battery combo.

The myth that more turns = more torque is deeply pervasive in this industry. I blame some well intended but ill-informed Crystalyte salesmen in the early 2000's for entrenching the entire ebike community with this falsehood, and it's forever an uphill battle to set the record straight.

Justin


A bit on copper fill, but its all within the Big Myth Thread
https://endless-sphere.com/forums/viewtopic.php?f=2&t=64907&p=984783&hilit=myth#p984783

https://endless-sphere.com/forums/viewtopic.php?f=2&t=24593&p=381600&hilit=myth#p381600


Read on
https://endless-sphere.com/forums/search.php?keywords=myth&terms=all&author=justin_le&sc=1&sf=all&sr=posts&sk=t&sd=d&st=0&ch=300&t=0&submit=Search
 
fatty said:
Read my post again and learn motor constants.
You have no idea what you're talking about.
Happy enough with motor constansts but the reason you keep getting this wrong it you rely on simple one dimeinsional retaionships too much rather than looking at the interaction between motor, controller and battery
 
fatty said:
BobBob said:
[repetitive yet stilll not getting through :)]
I have you on ignore but keep getting repetitive notifications that I'm wrong "in several ways", without explaining (or indeed, understanding) why.
If I have repeated myself several times and yet you still don't understand the difference between thick wire and thin wire it is becomming increaasingly difficult to explain to you.
I guess I could start with "do you think more or less current will go through a thicker wire"
fatty said:
I'll try one last time. Read this carefully and think about it, and you might actually learn something. If you don't understand it, ask a specific question where you're getting lost. Isn't the chance to learn something worth at least a try?
I do understand your confusion. You tend to try to optimise for efficiency by aiming for 85% of unloaded speed for a target speed.
Thus you aim for thinner wires and make up a target speed which is exactly the opposite of what someone who wants more power needs
Thus you get it wrong
I think you must know this because you tried to mislead the forum by locking the amperage output when the OP had high amperage capacity and locking the speed - pretty dishonest in my opinion.
fatty said:
BobBob said:
4. He's planning on putting 2-3 Kw through a 1.5 Kw motor. How is this not "holding their motor at the ragged edge of burning up", thus you appear to be incorrect in this point as well, at least from my reading of the question.
Thus it appears that yes, the OP was asking whether he could get his motor to 3 KW by using thicker windings
This is precisely my point. He's not limited by maximum motor current/temperature, but rather some lower controller current limit.
He doesn't have a controller, that's why your chart was BS, as I explained before with pictures
fatty said:
If not limited by ultimate motor current/temperature, what determines motor torque? kT, right? Higher kT = more torque, right?
You got the first bit wrong so this is all waffle, you didn't read the question but also no, at the same voltage, higher kT will result in lower torque due to the lower current (more turns of longer thinner wire)
fatty said:
And what is power? torque x rpm, right? So what gives more power at the same speed, low kT or high kT?
Either, more current or more volts. You haven't got more volts and you're proposing a solution to get fewer amps = fail
fatty said:
Where are you getting confused? Make sure you differentiate between maximum motor current/temperature limited intrinsically by the motor, and operating current/torque as determined by the controller.
He doesn't have a controller, he's going to buy one to suffice so that will not be the limiting factor
You see, you didn't understand the question, but following on from that (just for fun) you are also oversimplifying again, whether it's current, temperature or back EMF limited and whether that's because of battery, motor or controller depends on combinations of these depending on the speed and torque requirement.
As he doesn' have a controller and the battery is fixed it makes it pretty simple - more volts or thicker wire
fatty said:
I'm unsubscribed and turned off notifications,
I only reply to the stuff you say, I'm pefectly happy if you don't say it :)
fatty said:
so PM if you actually want to learn motor constants.
lol
The interesting challenge here is how to communicate with someone who thinks thinner wire will give them more torque.
Sometimes it's the humans that are the difficult bit and the engineering the easy bit, particularly when this simple.
He doesn't have a controller, he still needs to buy one and he has a battery which put ous 350A.
Yeah, you got it wrong again, the limitation is 72 V with his motor and the answer is up the voltage or (less sensibly) use thicker wire.
 
fatty said:
BobBob said:
For your subsequent answers you have confused increased windings with increased KT - you got the relationship the wrong way round which may be causing your confusion - suggest re-reading your own posts:
fatty said:
Rewinding a motor for more torque (higher kT) in the direct, textbook meaning of "rewind" is simply increasing turn count to trade kV for kT.
Actually, this conversation is probably pointless. If you keep arguing this point without understanding it, you're beyond reason:
Yeah, I know how you feel
fatty said:
I don't have the motor constant relationship "the wrong way round". Trade means to give up one thing for another.
As you quoted me above: Increase turn count = decrease kV = increase kT
Yeah, you're right, that bit was right, the next bit was the wrong way round
What you actually said was "Rewinding a motor for more torque (higher kT) "
In this example rewinding for higher kT will result in lower torque not higher torque because the voltage doesn't change

fatty said:
lol - was this all a wind up? if so, good one :)
Turn Count
The more turns a motor has, the slower it will spin.
lol
It's just a trade between voltage and current
fatty said:
Turn Count
Turn count is how many times the wire is wound around the tooth of a stator. It is inversely proportional to the Kv of the motor. For instance, a 3210 4T has a Kv of 339 RPM/V. From this, it can be determined that the Kv of a 3210 8T is 165 RPM/V (339 RPM/V * 4T / 8T = 165 RPM/V). Further, the turn count is also directly proportional to the Kt of the motor. Using the same example, a 3210 4T has a Kt of 4 Inch*Ounce/Amp, which means the 3210 8T has a Kt of 8 Inch*Ounce/Amp.
Yup 2S is double 1S etc
fatty said:
Turn Count
There is an common misconception that increasing the turn count is the same as gearing down. It is true that by doubling the turn count while maintaining the same input voltage and current yields half the RPM and double the torque,
V=IR
Same V, Same I but different turn count so different R
Only way is if you have a controller running heavily throttled in which case just open the throttle for more power
If you ignore the copper losses then both motors will have double the torque at half the speed as you've said the power input is the same lol
fatty said:
Turn Count
which is the same result as using a 2:1 gear ratio.
No, the slower spinning motor will have higher copper losses and so will be less efficient
fatty said:
Turn Count
However, spinning the motor at half the RPM will also half the maximum output power of the motor. This is because the maximum torque of all motors of a specific motor size (eg. 3210) is the same and unaffected by turn count (the reason they're all the same is because there is the same amount of copper loss).
it's also less efficient at the lower speed so a little worse than half the power
fatty said:
Turn Count
For example, the 3210 4T has a Kv of 339 RPM/V. We have a 50V power supply to use and would expect to get about 17,000 RPM (339 x 50 = 16,950). However, 17,000 RPM is too fast for our application.
So the example application starting point is at no load? That's daft
fatty said:
Turn Count
We want to run our at half that speed, 8,500 RPM. To achieve this, we have 3 options: we can use a power supply of half the voltage (25V), we can apply a 2:1 gear reduction, or we can use a 3210 8T. We opt for the 3210 8T to avoid having to buy a new power supply and to avoid having to add a reduction system, but after looking at the application specs, we realize that we need 500 Inch*Ounce of torque for the product to work correctly.
LMAO, not only will it not spin at the unloaded speed when loaded but it won't spin at all
fatty said:
Turn Count
The 3210 series, however, can only supply 375 Inch*Ounces (any more and the excessive copper loss would cause the motor to overheat). The only option that will fit our needs is to use a 2:1 reduction on the 3210 4T. By doing so, we've achieved our desired RPM and also can afford a bit of overhead in torque (the reduction allows us to have a maximum torque of 750 Inch*Ounces).
That's great, in this example of how to use motor turns we will show you how you use a gearbox instead and the motor turns won't help.

Conclusion
If you need more torque than any of your motors can supply then you need a gearbox
Motors spinning faster can develop more power

I'm kinda convinced you must just be winding everyone up but sort of along for the ride

Back to the OP, Yeah, it will get hot, it's a 1.5Kw motor running over spec, This is the same as putting more voltage through it
It will be putting out more power and be less efficient but it will be putting out more power which is the answer to the question.
The best solution would need some actual numbers

Maybe he needs to add a gearbox to his DD hub?
 
markz said:
Don't forget about COPPER FILL.

There was a post on using squared windings, I should try and find it after this zoom mtg I am on.
Wasnt long to find something.
https://endless-sphere.com/forums/viewtopic.php?f=30&t=103212&p=1541928&hilit=square+winding#p1541928
https://endless-sphere.com/forums/viewtopic.php?f=30&t=103212&p=1541928&hilit=square+winding#p1547731
It is much more expensive with square wire and i think it takes a lot more time to wind it. the thin wires can probably just be wrapped around easily vs the thick wire that needs to be formed, radius by radius, turn by turn
Nooooooo - don't do it, well, I mean, ok, go for it, if you're even more brave than a simple re-wind lol
Square wire is just so more difficult to work with as you have to get the twist right as well as everything else

markz said:
Ah yes, dont forget the wire gauge used
https://endless-sphere.com/forums/viewtopic.php?f=2&t=14482&p=218275&hilit=winding#p218275
The 6x10 winding won't really have any more torque than the 7x9 or 9x7 windings. You'll only get marginally more torque off the line and at a stall because the controller and phase lead losses will be somewhat less, but the effect is going to be pretty small, and can be negated with the faster winds by using heavy 10 or 12 AWG phase wire between your controller and the motor. As soon as you reach any appreciable speeds, then the slow 6x10 winding would have LESS torque than the faster windings for a given controller/battery combo.

The myth that more turns = more torque is deeply pervasive in this industry.
Yeah, wow, I was expecting a "whoops, my bad"
markz said:
I blame some well intended but ill-informed Crystalyte salesmen in the early 2000's for entrenching the entire ebike community with this falsehood, and it's forever an uphill battle to set the record straight.

Justin


A bit on copper fill, but its all within the Big Myth Thread
https://endless-sphere.com/forums/viewtopic.php?f=2&t=64907&p=984783&hilit=myth#p984783

https://endless-sphere.com/forums/viewtopic.php?f=2&t=24593&p=381600&hilit=myth#p381600


Read on
https://endless-sphere.com/forums/search.php?keywords=myth&terms=all&author=justin_le&sc=1&sf=all&sr=posts&sk=t&sd=d&st=0&ch=300&t=0&submit=Search
Always sanity check with a Grin sim :)
 
markz said:
https://endless-sphere.com/forums/viewtopic.php?f=2&t=64907&p=984783&hilit=myth#p984783
I have to admit I had no idea this was contentious, I'm new to this ebike business.

In science, reducing variables is useful when analysing something
Perhaps a solution is a motor / system that can be re-wound by thought alone. Lets make one:

The mobius motor

Lets say I take an 8T motor and rewind it with exactly the same wire gauge but as two coils in series and take the tails out of the motor so it comprises two sets of 4T in series. (yeah, this is not a good idea but it illustrates a point if you bear with me)

I then take a battery (lets say a 72V 20S8P) and chop it in half to form two batteries which in series make the original one (for example 2 off 10S8P to form the 20S8P)
First I wire up the motor with two battery halves (B1 & B2) in series followed by the coils in series (T1 and T2) and the FETS in parallel (C1 & C2)- this is the original motor configuration and the motor works the same (using better connecting wires etc)

I then take a nice, high-enough current, high-enough voltage, 12 FET controller, and chop the power circuit in half.
The power FETs are now in two banks.
Each half of the motor coils, goes through one FET (x 6 for the two directions of 3 phases)
Again there is no change to performance because the same current and voltage go through every component
One half battery is then moved in the circuit, so that the circuit goes B1 T1 C1 B2 T2 C2 and backt to B1 etc

The motor behaves exactly the same as for the previous wiring - each half battery drives half of the overall coil and they're all in series

I then connect the circuit (anywhere will do and with anything) in parallel, lets say between the two positive poles of the two battery halves with a nice fat busbar.
Or with a voltmeter. The voltmeter always reads zero, the halves are identical, there is no voltage difference or current flow.
We now have a motor that is two half batteries in series with two half coils in series
It is also a two half batteries in parallel with two half coils in parallel


It may be stretching it a bit but you could argue it's both a 4T 36V system and an 8T 72V system at the same time and you can think of it either way depending on your mood.

Hopefully this illustrates the trade off in motor windings arguement - it's the same thing in this example - exactly the same thing

The overall current through all turns taken in parallel is what matters, voltage just drives it

I considered adding a cat in a box to make the parallel connections but decided on calling it the Mobius motor instead, as I like cats

We could do some experiments switching between 4T ans 8T configurations, using thought alone, to see whether we can get some performance improvements from exactly the same motor in exactly the same configuration yet in 4T vs 8T winding :)

I probably need to add a circuit diagram
 
The next step is of course two switches and some relays to put the batteries or motor turns in series or parallel (not both)
Both series is of course identical to both parallel and equivalent to the mobius
Series coils with parallel batteries makes it go slower,
Series batteries with parallel coils makes it go faster and potentially melt (more copper losses, more power, overheating etc)
 
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