Motor comparison spreadsheet

[crossbreak]

The geared motor is capable of being arranged in an equivalent model as an RC motors stator teeth on a radius of proportional length to become equal to the gearboxes net equivalent lever length.

sure, but a 16 times larger motor than a TP-100, is unrealistic. but is is necessary to gain the same magnet velocity and lever. A 1.6m diameter motor fits no rim.
Another thing is that all these materials used in motors are quite expensive. The cheap big motors are just so cheap since the people that produce these give a shit about environment. this has nothing to do with sustainability, it's a waste of material.
chains are cheap though

 

[Arlo1]

The geared motor is capable of being arranged in an equivalent model as an RC motors stator teeth on a radius of proportional length to become equal to the gearboxes net equivalent lever length.

sure, but a 16 times larger motor than a TP-100, is unrealistic. but is is necessary to gain the same magnet velocity and lever. A 1.6m diameter motor fits no rim.
Another thing is that all these materials used in motors are quite expensive. The cheap big motors are just so cheap since the people that produce these give a shit about environment. this has nothing to do with sustainability, it's a waste of material.
chains are cheap though

No No No.

Torque goes up at the square of the increase of the radius.

There for to get 16x increase to make a motor produce the same torque you only need to increase its radius by 4x and this doesn't mean it needs to be 4x as heavy as you can make the center mostly hollow.

 

[cwah]

Isn't torque dependent on the width of the stator? I've read 50mm stator is much better than 40mm

 

[Arlo1]

Isn't torque dependent on the width of the stator? I've read 50mm stator is much better than 40mm

Both the width and the diameter of the stator determine torque.

 

[cycborg]

... increase its radius by 4x and this doesn't mean it needs to be 4x as heavy as you can make the center mostly hollow.

4x radius means 4x circumference so 4x active material. And support structure volume would probably have to increase more like r^2 just to keep the same stiffness, and you'd need more stiffness since there's more torque. I don't see how it's possible for the mass to become proportionally lighter as radius is increased.

 

[cwah]

Isn't torque dependent on the width of the stator? I've read 50mm stator is much better than 40mm

Both the width and the diameter of the stator determine torque.

Is it better to increase radius or stator width?

If torque is square the radius, why don't we have like 26 inch motor that would have massive torque and be super efficient?

Weight would increase, but surely with right structural support it could work?

 

[liveforphysics]

Isn't torque dependent on the width of the stator? I've read 50mm stator is much better than 40mm

Both the width and the diameter of the stator determine torque.

Is it better to increase radius or stator width?

If torque is square the radius, why don't we have like 26 inch motor that would have massive torque and be super efficient?

Weight would increase, but surely with right structural support it could work?

When width grows, torque capability grows proportionally with width. When radius grows, torque grows at the square of the radius increase.

Neither is better than the other, both are needed. Low RPM applications tend to do better with growing radius and high RPM applications tend to do better growing motor length.

 

[crossbreak]

The geared motor is capable of being arranged in an equivalent model as an RC motors stator teeth on a radius of proportional length to become equal to the gearboxes net equivalent lever length.

sure, but a 16 times larger motor than a TP-100, is unrealistic. but is is necessary to gain the same magnet velocity and lever. A 1.6m diameter motor fits no rim.
Another thing is that all these materials used in motors are quite expensive. The cheap big motors are just so cheap since the people that produce these give a shit about environment. this has nothing to do with sustainability, it's a waste of material.
chains are cheap though

No No No.

You talk about torque, i talk about lever. You indeed need 16 times the diameter if you want 16 times the lever if you dislike gearing . Doubling the lever (or gearing ratio) induces four times lower copper loss. So more copper does not mean less copper loss automatically

Torque goes up at the square of the increase of the radius.

never questioned that fact, period

 

[Arlo1]

You talk about torque, i talk about lever. You indeed need 16 times the diameter if you want 16 times the lever if you dislike gearing . Doubling the lever (or gearing ratio) induces four times lower copper loss. So more copper does not mean less copper loss automatically

Torque goes up at the square of the increase of the radius.

never questioned that fact, period

Torque is a standardized term used to talk about "lever" we use standardized terms to help everyone world wide understand what we are saying.

Torque is a twisting force 1 ft/lb is 1 lb on a arm with a radius 1 foot radius from the fulcrum. 10 ft/lbs is 10 lbs on a arm with a radius 1 foot radius from the fulcrum (or 1lb on a arm with a radius 10 foot radius from the fulcrum) Some people use the term lbs/foot or some use ft/lbs its the same!!!!

When you grow the stator by 4x you get 16x the torque
So lets say you have 2 motors 1 with 100ft/lbs torque and another with 4x the radius of the first one. The one with 4x the stator will have 1600ft/bs torque.
Let say you use a 16:1 gear reduction on the smaller (100ft/lb) stator you will have 16x the torque - losses so < 1600 ft/lbs the smaller motor will have the potential to make less torque due to losses of the gear reduction. You can make both motors weigh the same and in that case they would have the same KW rating but the one with 16x the diameter of the stator will have lower losses and the total system will be lighter as it will have no gears for reduction.

Thing is you are not understanding this from a engineer point of view. When making a bigger motor you can rewind it for different KV when you do that you will get lower copper losses per unit of KW or HP when using more copper. But if you made it weigh the same then you would have equal copper fill and then the wind for the desired rpm would make the copper losses equal.

 

[Arlo1]

... increase its radius by 4x and this doesn't mean it needs to be 4x as heavy as you can make the center mostly hollow.

4x radius means 4x circumference so 4x active material. And support structure volume would probably have to increase more like r^2 just to keep the same stiffness, and you'd need more stiffness since there's more torque. I don't see how it's possible for the mass to become proportionally lighter as radius is increased.

Remember the torque on the stator/rotor is distributed by 3.14159 x the diameter.
Torque is not usually what the strength of the steel bell is needed for in a out runner.
Its usually to help the flux path and to survive the centrifugal forces at rpm but with 4x the radius and 16x less rpm the centrifugal forces would be the same.

 

[crossbreak]

torque and lever are two different things. i would never say that it's the same just to make people believe that they "understood" something. I like factual discussions.
Torque has the unit newton*meters, not ft/lb or ft/lbs that's simply wrong. lbs*ft would be ok for me, but lbs is a weight unit, not directly correlating with force well, as the gravity constant differs. Not what i think is a clean definition

kV is completely irrelevant for copper loss. It's always the same as long as you compare two same motors with the same fill factor.

Let say you use a 16:1 gear reduction on the smaller (100ft/lb) stator you will have 16x the torque - losses so < 1600 ft/lbs the smaller motor will have the potential to make less torque due to losses of the gear reduction. You can make both motors weigh the same and in that case they would have the same KW rating but the one with 16x the diameter of the stator will have lower losses and the total system will be lighter as it will have no gears for reduction.

what do you wanna tell me here? A four times smaller motor is more heavy than a big one?

Anyway, i posted facts here that are not so obvious. Took me quite some time to gain this knowledge i like share and discuss. There is quite a lot of half-knowledge out there (and here), which made me make false assumptions. For example that Km is a constant that is capable of comparing copper loss/ torque ability of different motors. But it's not. It's Km²

 

[Arlo1]

torque and lever are two different things. i would never say that it's the same just to make people believe that they "understood" something. I like factual discussions.
Torque has the unit newton*meters, not ft/lb or ft/lbs that's simply wrong. lbs*ft would be ok for me, but lbs is a weight unit, not directly correlating with force well, as the gravity constant differs. Not what i think is a clean definition

kV is completely irrelevant for copper loss. It's always the same as long as you compare two same motors with the same fill factor.

Let say you use a 16:1 gear reduction on the smaller (100ft/lb) stator you will have 16x the torque - losses so < 1600 ft/lbs the smaller motor will have the potential to make less torque due to losses of the gear reduction. You can make both motors weigh the same and in that case they would have the same KW rating but the one with 16x the diameter of the stator will have lower losses and the total system will be lighter as it will have no gears for reduction.

what do you wanna tell me here? A four times smaller motor is more heavy than a big one?

Anyway, i posted facts here that are not so obvious. Took me quite some time to gain this knowledge i like share and discuss. There is quite a lot of half-knowledge out there (and here), which made me make false assumptions. For example that Km is a constant that is capable of comparing copper loss/ torque ability of different motors. But it's not. It's Km²

Torque can be measured in NM (newton meters) of ft/lbs 10ft/lbs = 7.375 nm this is a standard. Yes they are talking force not weight. But a twisting force is what we are talking about and I went down the rabbit hole to explain it because you are missing something. I think you need to think is there a reason Tesla doesn use 1 motor 1mm in diameter and just spin it really fast then gear it down to get the same performance???
No I am not saying a smaller motor will weight more the a bigger one. I am pointing out a bigger diameter motor will not need reduction gears to produce the same torque at the end of the drive system. But I am saying the smaller one with reduction gears will do less torque because of efficiency losses and therefore the battery powering the bigger diameter motor will last longer producing the same torque at the end of the system.
https://en.wikipedia.org/wiki/Torque

 

[crossbreak]

these losses are small, but the weight reduction is great. Less weight = less consumption

Torque can be measured in NM (newton meters) of ft/lbs 10ft/lbs = 7.2 nm this is a standard.

Wikipedia says: "pound-force-feet" (lb⋅ft)

lb/ft is wrong

 

[Arlo1]

these losses are small, but the weight reduction is great. Less weight = less consumption

Torque can be measured in NM (newton meters) of ft/lbs 10ft/lbs = 7.2 nm this is a standard.

Wikipedia says: "pound-force-feet" (lb⋅ft)

lb/ft is wrong

No its not less weight its more weight for a smaller motor with a gear reduction. That is what I am saying. And the losses of the reduction make it worse.

ft/lb or lb/ft it doesn't matter as you end up with the same twisting force. 1000 lbs of force on a 1 foot radius vs 1 lb of force on 1000 foot radius is the same twisting force.

 

[crossbreak]

well, that's jut your opinion, man

 

[cycborg]

ft/lb or lb/ft it doesn't matter as you end up with the same twisting force. 1000 lbs of force on a 1 foot radius vs 1 lb of force on 1000 foot radius is the same twisting force.

The concept here is not in dispute, but the use of nonsensical units makes for confusing reading.

 

[speedmd]

If you have to argue about how you specify torque values, the argument on motor comparisons is lost. Pounds force is a simple measurement for most anyone here on earth. Newtons? Good luck with that one on your bathroom scale. If you need your slide rule to figure it out, you need to find a more common way to measure things. Now back to motors.

Interesting crossover going larger diameter vs gearing. We have had this discussion many times and need to explore what bottle necks need to be addressed to make the comparison more universal. Compact motor is simple as there is less material size so there is little penalty in over sized components. If the same errors become enlarged, you will also greatly enlarge the waste. A few grams extra iron on the rotor ring of a small diameter motor becomes kilos on a large diameter scaled version. A rim motor should be a good topic for ebike motor folks to bounce around a bit IMO. Lots of potential from a quick look at it.

 

[Punx0r]

ft/ln or lb/ft might not be mathematically correct but it's a well-known non-SI unit for torque and the meaning is clear to most technical people.

 

[major]

ft/ln or lb/ft might not be mathematically correct but it's a well-known non-SI unit for torque and the meaning is clear to most technical people.

ft/lb or lb/ft it doesn't matter as you end up with the same twisting force.

Guys,

ft/lb or lb/ft = feet per pound or pounds per foot which are not units for torque. Torque units are pound feet or lb.ft. Or Nm, Newton meters. Torque units are force times distance not force divided by distance.

See that difference?

major

 

[Arlo1]

ft/ln or lb/ft might not be mathematically correct but it's a well-known non-SI unit for torque and the meaning is clear to most technical people.

ft/lb or lb/ft it doesn't matter as you end up with the same twisting force.

Guys,

ft/lb or lb/ft = feet per pound or pounds per foot which are not units for torque. Torque units are pound feet or lb.ft. Or Nm, Newton meters. Torque units are force times distance not force divided by distance.

See that difference?

major

Nope Im saying ft/lb is the same as lb/ft. So ok the problem is in the / I can use a . or a : instead. But lb:ft and ft:lb are the same. Its force x distance lb x ft or distance times force ft x lb they both meen the same thing. I will try to use a : for now on.... ft:lb or lb:ft its still the same thing.

 

[crossbreak]

the : sign is still the divider. a bullet point or - "minus" or "x" or "*" would be ok, like justin does on his website. he uses a "-" as hyphen

 

[cycborg]

ft/ln or lb/ft might not be mathematically correct but it's a well-known non-SI unit for torque and the meaning is clear to most technical people.

Yes, the meaning is clear to us technical people because we are able to overlook the error and get to the meaning, after overcoming the cognitive dissonance. This does not mean the error is not an error.

 

[crossbreak]

exactly, as it leads people to false assumptions

 

[Arlo1]

the : sign is still the divider. a bullet point or - "minus" or "x" or "*" would be ok, like justin does on his website. he uses a "-" as hyphen

Lol Man oh man.... So I will use a minus (-) sign... I guess as that's what google says.... seams wrong... ft-lbs or lbs-ft.... it should not read foot minus pounds or pounds minus foot. :?

 

[Punx0r]

As I said, I get that it's technically wrong, but it's a common misuse and known to be synonymous with ft.lb (type ft/lb into google). I'm not advocating it's use, but given the context it clearly indicates torque and shouldn't be derailing this thread. ft/lb = ft.lb = lbf-ft = 1.356Nm. Get over it

Here's what's causing me cognitive dissonance!

A motor with 4 times the radius has 4 times lower Kv, if all the 4 parts are connected in parallel. Then it has 1/4th of the resistance. Km² = (60/2π)² * 1/(kV²*Rm), so the new motor has 1/(1/4²*1/4)=4³ = 64 times lower copper loss per Nm of torque. Not the same as the small motor that has 1:16 reduction, as reduction raises Km² quadratic, it has 16²=256 times lower copper loss per Nm!!!

Sorry Luke, gearboxes are unbeatable awesome!!