what is cogging torque?

[Chalo]

When you can feel or hear cogging torque, it's because some of that energy was transmitted outside of the system and therefore not conserved. Whether the energy is dissipated in your fingers as you turn the motor axle, your tires as you ride, or the groceries in your panniers as you bring home the bacon, is immaterial. It's dissipated now.

If you can notice it, it's drag.

 

[Hummina Shadeeba]

When you can feel or hear cogging torque, it's because some of that energy was transmitted outside of the system and therefore not conserved. Whether the energy is dissipated in your fingers as you turn the motor axle, your tires as you ride, or the groceries in your panniers as you bring home the bacon, is immaterial. It's dissipated now.

If you can notice it, it's drag.

The energy is lost as you say when cogging slows you down but what is that loss? Where is that energy going? It’s not converted to heat through eddies r hysteresis.

Just as the magnets in the motor are able to add to the motor’s force or torque through orientation at no expense, they can do the same if put in a bad orientation, no?

 

[Chalo]

I can't say one way or the other what's happening magnetically inside the hub, but once it's vibrating things outside the hub, that energy mostly leaves the system.

It's like hitting a bump in the road. You could decide hypothetically that the energy spent surmounting the bump on the front side is returned on the back side, but in practice it's mostly lost as hysteresis in the tires and rider. Put a nonstop row of identical little bumps one after another, and you have the road surface equivalent of cogging torque. Go slow enough, and they'll stop you in your tracks. But go fast enough and you'll skim the tops of all those bumps without too much rattling.

The faster the motor turns, the less the vibration shakes other stuff and the lower the effective drag torque. But at low rotor speed it's a significant source of energy loss, because the vibration happens at frequencies that interact more with the structural parts of the bike, and in turn with the rider.

 

[Hummina Shadeeba]

I can't say one way or the other what's happening magnetically inside the hub

How bout forgetting in a motor for a bit and tell me what you think of viewing a magnetic field in relation to a gravitational field. Both can create a force. Both are dependent on orientation. Both seem to break the laws of conservation of energy in that a force can be produced without having added energy and instead just related to orientation, for example:


satellites can piggyback off asteroids or whatever, then jump to another mass, etc., and ultimately could return to earth having travelled millions of miles with no force added. (Maybe not breaking the laws of conservation of energy in that the other masses that are interacted with would have their orientation slightly changed)..but still work is being done by forces that are already out there.

A magnet seems like a tiny yet huge mass with a polarity.

 

[Ianhill]

Rite lets gets this understandable for us dummys myself included.

We know a motor with no magnets does not cog and a motor with no iron will not cog either.

So its the interaction between the magnets and the steel thats causing the cog all agreed all say ai.

Soon as the rotor and its magnets are inserted in the iron it aligns the steels magnetic arrows we know about eddy currents and laminations keeping them arrows as many small ones rather than one large to minamize heat.

The rotor pole pair and stator teeth align so there's sections of the steal in north state and other south states as we turn that motor we flip the polarity of the stator teeth area as the magnets polarity is stuck by design.

So all we are doing is charging a bit of steel north south north south and so on but in sections across the stator and by hand we feel the hysteresis of the iron changing states across its stator teeth.

More iron stronger the magnets smaller the air gap stronger that interaction will feel and to overcome it by hand will take greater effort its not a bad motor it will be an excellent torque heavy motor.

Soon as the controller is turned on it pulses the coils and in turn thats removes the hysteresis in the steel with its own magnetic field so cogging torque is eliminated under power by the controller having advanced noticed from hall detection and back emf to make the motor flow round smoothly rather than cog around in a lumpy fashion.

Ive seen motors that have a humpy feel to them and theres many a reason why this can be but a decent motor and controller should only cog when its turned off and the basis of why cog happens is no mystery hopefully now.

The mxus 3k hardly spins with cogging torque by hand but when i was riding it sinewave controller i could freewheel decent on the flat and gather speed down a incline so i was not worried that im losing energy as what goes down must come back up and theres a flywheel effect going on with heavier objects its not all bad news.

 

[Hummina Shadeeba]

I’ll look elsewhere and they’re calling me a parascientist: https://en.m.wikipedia.org/wiki/Magnet_motor

That sounds kinda nice though.

 

[Ianhill]

I’ll look elsewhere and they’re calling me a parascientist: https://en.m.wikipedia.org/wiki/Magnet_motor

That sounds kinda nice though.

Quote the wiki (very much wrong)
Magnet motors are not to be confused with the commonly used permanent magnet motors, which are powered from an external electrical energy supply.

Theres no such thing theres many bullshit claims but not one has managed to even perform at unity let alone perpetual motion the quote itself is bullshit as magnets are in a permanent state they can not flip polarity and theres no mechanism to flip a magnet that does not take energy from the system.

Closest i think we can get is a finely balanced coreless superconducting axial motor with magnetic bearings held within a vacuum and even then theres still a slowing over time with the interaction with earths magnetic field theres no where in space a magnetic field does not exist so the best one can do is pinch moment from one to another but conservation always holds true.

 

[Hummina Shadeeba]

I got into the questioning of a possible “magnet motor” because of what I learned about cogging in a pm motor.

Someone will balk soon as I’m getting into pseudoscience or I guess parascience so I’m gunna give my final spiel one last time in this thread and see if anyone can respond related to specifically what I’m asking:


IF cogging is a loss of momentum alone and not an iron loss, which it seems to be, that says to me that magnetic fields are a source of force that in a way are not following the classic understanding of conservation of energy..otherwise where did that momentum go if not heat? This is similar to a gravitational field where force or energy or ..(whatever terminology is appropriate) is dependent on orientation. For example satellites are capable of dare I say doing work as they utilize gravitational fields of different masses out there and are able to get more speed or distance or whatever than was supplied by the initial rocket that set the satellite into its trajectory/orientation.

If someone who knows what they’re talking about can tear down my logic above please do but don’t want to go over the fundamentals of how a motor works or iron losses. Or if you have evidence that cogging IS an iron loss please then do go into it.

 

[Ianhill]

Ill keep answering till you get it no matter if you think im wrong as theres no trickery going on

Gravitational assist is swapping momentum everytime a rocket speeds up from earths mass, earth losses the equivalent kinetic energy from its rotation.

The earth is many many many tons of material vs the spaceship just a few tons, so the spaceship can gather alot of speed to the earth losing very little of its own thats a Gravitational sling shot i did briefly explain that but yout like ICP when it comes to magnets.

Your idea of magnetic fields is madness theres no lost energy its in a state of suspence the rotor is held in position by that LOST DARK ENERGY we call magnetism ive explained how metals work with fields present i suggest you look at some magnetic imagery of motors at work to get a clear picture of whats going on becuase your forst 2 paragraphs scream to me I'm dumb as fuk and believe anything.

By the way what did you learn about cogging from a PM motor that makes you think perpetual motuin is a possibility ? Please elaborate if im the silly billy narrow minded simplton prove it.

 

[Hummina Shadeeba]

Ill keep answering till you get it no matter if you think im wrong as theres no trickery going on

Gravitational assist is swapping momentum everytime a rocket speeds up from earths mass, earth losses the equivalent kinetic energy from its rotation.

The earth is many many many tons of material vs the spaceship just a few tons, so the spaceship can gather alot of speed to the earth losing very little of its own thats a Gravitational sling shot i did briefly explain that but yout like ICP when it comes to magnets.

Your idea of magnetic fields is madness theres no lost energy its in a state of suspence the rotor is held in position by that LOST DARK ENERGY we call magnetism ive explained how metals work with fields present i suggest you look at some magnetic imagery of motors at work to get a clear picture of whats going on becuase your forst 2 paragraphs scream to me I'm dumb as fuk and believe anything.

By the way what did you learn about cogging from a PM motor that makes you think perpetual motuin is a possibility ? Please elaborate if im the silly billy narrow minded simplton prove it.

Im not calling u anything abs sorry you are reading into what I write in that way. Telling me I’m dumb as fuk and believe anything...I’ve designed many motors with motor design programs and hand built over a hundred. I’m no expert I don’t need ur lessons on how a motor works and not what I’m asking about.


I’m not saying there’s any “trickery”. I am asking where the energy of cogging is lost to as well as other questions that are still unanswered. But leave ur crap paranoid attitude at home and I’m not interested in ur personal stuff just answers to the questions I asked. If you’re gunna write back please stop, think is this what the question asked, and am I answering that and that alone.

 

[Ianhill]

Ill keep answering till you get it no matter if you think im wrong as theres no trickery going on

Gravitational assist is swapping momentum everytime a rocket speeds up from earths mass, earth losses the equivalent kinetic energy from its rotation.

The earth is many many many tons of material vs the spaceship just a few tons, so the spaceship can gather alot of speed to the earth losing very little of its own thats a Gravitational sling shot i did briefly explain that but yout like ICP when it comes to magnets.

Your idea of magnetic fields is madness theres no lost energy its in a state of suspence the rotor is held in position by that LOST DARK ENERGY we call magnetism ive explained how metals work with fields present i suggest you look at some magnetic imagery of motors at work to get a clear picture of whats going on becuase your forst 2 paragraphs scream to me I'm dumb as fuk and believe anything.

By the way what did you learn about cogging from a PM motor that makes you think perpetual motuin is a possibility ? Please elaborate if im the silly billy narrow minded simplton prove it.

Im not calling u anything abs sorry you are reading into what I write in that way. Telling me I’m dumb as fuk and believe anything...I’ve designed many motors with motor design programs and hand built over a hundred. I’m no expert I don’t need ur lessons on how a motor works and not what I’m asking about.


I’m not saying there’s any “trickery”. I am asking where the energy of cogging is lost to as well as other questions that are still unanswered. But leave ur crap paranoid attitude at home and I’m not interested in ur personal stuff just answers to the questions I asked. If you’re gunna write back please stop, think is this what the question asked, and am I answering that and that alone.

Im not bringing my personal paraniod crap lol im telling you what your first 2 paragraphs reads as i believe in the electrical ghost worldtheres no amswer to the shit you spout unless you design an answer to fit the box you choose to see

 

[Hummina Shadeeba]

[no amswer to the shit you spout unless you design an answer to fit the box you choose to see

Again you didn’t answer the question as to where the lost momentum of cogging went and continue w the same.

I may be an idiot and incapable of understanding the most basic, but don’t say it and show it.

Or move it to the toxic thread section. Or the pseudoscience section. And then hopefully someone can explain

 

[Ianhill]

[no amswer to the shit you spout unless you design an answer to fit the box you choose to see

Again you didn’t answer the question as to where the lost momentum of cogging went and continue w the same.

I may be an idiot and incapable of understanding the most basic, but don’t say it and show it.

Or move it to the toxic thread section. Or the pseudoscience section. And then hopefully someone can explain

Face palm yourself becusee there's no lost momentum.

Please explain this lost momentum and prove ive not answered your question i think you will find i have.

 

[Hummina Shadeeba]

[no amswer to the shit you spout unless you design an answer to fit the box you choose to see

Again you didn’t answer the question as to where the lost momentum of cogging went and continue w the same.

I may be an idiot and incapable of understanding the most basic, but don’t say it and show it.

Or move it to the toxic thread section. Or the pseudoscience section. And then hopefully someone can explain

Face palm yourself becusee there's no lost momentum.

Please explain this lost momentum and prove ive not answered your question i think you will find i have.

Cogging is a loss of momentum which is obvious.
prove you haven’t answered the question? that seems backwards.

If u don’t have any evidence cogging is eddies or hysteresis how bout writing in another thread.

 

[Ianhill]

Cogging torque is the magnetic interaction between the steel and the magnet and if you csn prove there's more going on or explain in other terms than i like sudoscience im more than willing to try and help but i feel on the 4th page theres a lack of understanding im no pro but ill tell you theres no missing energy

Do a quick test have 2 differing motors that you know the layout of and have a think how many cogging spots will be on each then rotate the motor count the spots where each of these balance points where in regards to the magnets vs stator.

Where the motor sits the field is strongest to move forward to the centre of the cogging area requires torque to break free but once in the centre of the field the pushing force i apply swaps to a pulling force turning the motor to its next cog spot between teeth.

I shit you not its the steel and magnets as it moves forward your changing the polarity or the metal it takes energy and once the motor turns that energy comes from the controller and battery rather than the wheel forcing it past every cog location.

Motors turn smooth clearly defeating the cog torque dont you think ? Nothing is missing its part of the efficency loss.

 

[Hummina Shadeeba]

Cogging torque is the magnetic interaction between the steel and the magnet and if you csn prove there's more going... but ill tell you theres no missing energy

That doesn’t tell where the energy went.


As I understand it an esc must add current to overcome cogging torque. A motor with more cogging requires more current to overcome it. It is there at all speeds although the ripple aspect is generally smoothened.

Yes cogging is the interaction between the teeth and magnets but it is not net-zero and when you turn a motor and let’s say put some amount of energy into a spin of the rotor it will reduce speed more quickly to zero than is caused by eddies or hysteresis.

I’ve seen studies of skewed vs non-skewed stators showing less cogging with increased iron losses or greater cogging torque with decreased iron losses.

Is the loss of momentum in a motor actually due solely to iron losses and the study and people I spoke to wrong?


I don’t get your point in the two motor comparison and counting cogging spots

Yes the motor rotor must overcome the pull of the last tooth it was closest to but that pull strength seems to be greater than the pull force of that same magnet to the tooth it’s moving toward. The end result is not net-zero and the rotor will lose its momentum due to cogging. Where did that energy go?

 

[Ianhill]

Changing the iron magnetic state in areas of the stator steel will result in heating of the material the iron will hsve a reflection back on the magnets themselfs giving a miniscule amount of heating on them the system has torque been applied to the steel in a none uniform fashion that creates waves in the steel that become audioable and so on that represents some of that missing 7 or so % from a 100% efficent motor.

Id be concerned if i pushed the motor 2mm with 5nm and got back 2mm 5nm as that woukd be net zero id always expect 4.95737373nm or what ever but never equal or more.

Turning it by hand wont have the same losses as when its powered theres more losses again applied from being powered as you said we have to influence the steel to move the magnet

Brushed dc motors show on a half bridge controller when pushed backward the controller acts like a diode shorts the phases and locks up the motor with its own emf trapped in the copper and effecting the steel it sits in the core it takes a few seconds to bleed down like a cap almost so turning the motor takes alot of effort as we physically force the steel and copper to the magnet polarity with what ever force it takes to turn it.

 

[Hummina Shadeeba]

Changing the iron magnetic state in areas of the stator steel will result in heating of the material the iron will hsve a reflection back on the magnets themselfs giving a miniscule amount of heating on them the system has torque been applied to the steel in a none uniform fashion that creates waves in the steel that become audioable and so on that represents some of that missing 7 or so % from a 100% efficent motor.

Id be concerned if i pushed the motor 2mm with 5nm and got back 2mm 5nm as that woukd be net zero id always expect 4.95737373nm or what ever but never equal or more.

Turning it by hand wont have the same losses as when its powered theres more losses again applied from being powered as you said we have to influence the steel to move the magnet

Brushed dc motors show on a half bridge controller when pushed backward the controller acts like a diode shorts the phases and locks up the motor with its own emf trapped in the copper and effecting the steel it sits in the core it takes a few seconds to bleed down like a cap almost so turning the motor takes alot of effort as we physically force the steel and copper to the magnet polarity with what ever force it takes to turn it.

ur saying cogging’s loss of momentum is due to hysteresis or eddies or both? Do u have evidence? If the stator is skewered and results in almost no cogging are less hysteresis and eddies being produced?


capacitors or transistors or diodes or escs or whatever aren’t related to how cogging torque is produced and it’s as you told me a moment before: “ Cogging torque is the magnetic interaction between the steel and the magnet..”.

But I’m not looking for anything other than evidence. If you can find evidence of cogging’s loss of momentum not actually being a loss of momentum, or that it’s just iron losses, please post it. Not sure what you’re saying it is but don’t say it..show it.

 

[Ianhill]

The reason i said to do the motor test i said to you was you will see the motor lines up with the slots and them slots on a skewed motor move that line in a diagonal fashion meaning its over a larger area giving less cogging torque.

I think the way to imagine it is like ac electric on a graph its the overall area under the line that gives the total energy a skewed motor manipulates the peak torque need to turn down but the area under the curve is still equal therefore cogging is reduced with same torque load required to get from cogging spots but its spread over a larger area say many mm on a wide motor vs 2mm on a standard straight slot.

Really steal is the freind and the enemy all in one we need to move awsy from it for higher efficencys but for instant torque theres nothing like a guided field line.

Theres lots of fancy designs that go coreless but for general builds the cost is to high and the extra few percent just aint worth it.

By the way you keep asking me to prove it but its all research thats been done that we all got access to if you want to add a new additional force then you must try to explain it and document it yourself as i can not see any extra torque moments happening other than the actions we apply to the motor everything seems a ok in my eyes as to where the energy is going within the system at what rpm range and current points will the stator saturate etc i dont feel theres any science happening thats not explained thats not to say im a master and can build the best motor i the world no way lol but i can run what i got and get great results.

 

[Hummina Shadeeba]

So u won’t be bringing the evidence and instead rambling about what you vaguely know about after telling me I’m a fool. Get outta here with that. I had specific questions. Please answer them or don’t bother writing and not interested in simplified ramblings about things unrelated to the questions.

 

[Ianhill]

So u won’t be bringing the evidence and instead rambling about what you vaguely know about after telling me I’m a fool. Get outta here with that. I had specific questions. Please answer them or don’t bother writing and not interested in ramblings about things unrelated to the questions.

You cant even bring your specific question to the table my friend as your beat admit it your on the defense already.

 

[Hummina Shadeeba]

I just asked above. You need to look two posts up:
“ ur saying cogging’s loss of momentum is due to hysteresis or eddies or both? Do u have evidence? If the stator is skewered and results in almost no cogging are less hysteresis and eddies being produced? “

But please limit your response to relevant evidence.

 

[Ianhill]

Please do the experiment and see for yourself where the motor lands on its cog rotation spots then look at the the skewed slot spreads the cog over the tooth area and hopefully it clicks for you.

Of course theres no less heat build up from hysteresis as its still occurring but the time frame is longer so the ripple feels less or not even there if well designed.

To move the motor from point a to b on both motors will take simular energy overall but the skewed motor is a linear line of torque required compared to the straight slot that has a peak then jumps to its next spot.

You want the evidence ill try get you some but i can't quote reference papers off by hand and its easier sometimes to see something for yourself thats the only reason why ill keep on so you see what i mean its not something i can give the formula for as it quite a complex relationship going on in a motor and i don't pretend to be a master of it for one bit.

 

[Hummina Shadeeba]

What will “click”? When u spin a motor by hand it’s not going to reveal where the lost momentum has gone. But better yet just answer my questions directly.

But what are you saying you would bring evidence showing? What complex formula?

To move the motor from point a to b on both motors will take simular energy overall

A higher cogging motor takes more energy to rotate. That’s one of the reasons they bother reducing cogging.

Maybe cogging is due to hysteresis but I haven’t found anything showing that and instead found the opposite generally but I haven’t searched much. You say you have evidence or something saying something..post it

 

[Ianhill]

For a cleaner back emf ?
For a easier rolling system ?
For less wear on the bearings ?

Serious im done your full of it you follow sudoscience that's nothing but flat earth and you want me to give you a complex answer but can't even read the first line of Google on skewed stators its for a cleaner waveform on the back emf strange in it how the cogging effect is clean too guess i not answered your question though.