# Zero Air Gap Electric Motors could be improved?

#### Fulano

Joined Feb 16, 2024
1
Hello, I've been looking into online scientific articles and I was able to find a few ones about the subject. On these articles it is normally observed that the torque value of the motors doubles or even quadruples with the direct contact of the rotor and the stator while consuming the same amount of energy.

Some articles:
https://www.mdpi.com/1996-1073/13/17/4286
https://www.researchgate.net/publication/322650195_Airgap-less_Electric_Motors_with_External_Rotor
https://ieeexplore.ieee.org/document/8002357

However, I really can't find anything but a few articles, so I'd like to ask around and see if someone can help or give an educated guess.

For example, I was thinking of making the rotor rotate just like a hypocycloidal drive. On top of that, I was also thinking on making the stator and rotor into gear-teeth.

But I'm not qualified enough to even guess how this would improve the performance of the electric motor, nor I feel confident on even attempting on designing such thing.

What are your thoughts on the subject?

#### crutschow

Joined Mar 14, 2008
34,454
torque value of the motors doubles or even quadruples with the direct contact of the rotor and the stator while consuming the same amount of energy.
Yes the torque value may increase, but the output power will still be some less than the input power if the motor is driving a load.

#### LowQCab

Joined Nov 6, 2012
4,075
Magnetic attraction or repulsion is Mathematically multiplied, not simply added to, versus distance,
but just how much You can practically reduce that distance,
reliably, and at a practical cost, is the sticky point.

It would be great if You could design a 0.0001" clearance Motor, but it would be highly impractical.
Any contact between fast-moving parts generally results in eminent catastrophic failure.
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.
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#### Lightium

Joined Jun 6, 2012
169
When you increase the path length along the circular circumference, what's the point?

#### Alec_t

Joined Sep 17, 2013
14,318
Moving mechanical parts will soon wear out if they're in actual direct contact. A lubricant film between them would be necessary. That would introduce viscous drag losses.

#### BobTPH

Joined Jun 5, 2013
8,989
And the best motors now are about 95% efficient, so there is not much gain to be had.

Torque can also be increased by using stronger magnets, without the disadvantages if direct contact of moving parts.

#### MisterBill2

Joined Jan 23, 2018
18,535
It appears that what you have seen and read is found on the cartoon channel and not tied to reality. If the concept were valid then such products would be available.
What the image looks like is the classic "flex-spline speed reducer, not an electric motor. what it would require to operate as a motor would be a totally different scheme to produce the magnetic field. In addition the vibration would be a whole lot.
And besides all of that, the precision machining needed to produce an electric motor with close to zero air gap would be incredibly expensive.
So if the concept was at all possible the product would already be available.
This is typical of what is found on that "cartoon channel".

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#### Externet

Joined Nov 29, 2005
2,221
I believe it is not about a small air gap; it is about reducing the distance between magnetic poles from the stator-to-rotor. And it is not possible to make it near zero because the magnetic poles are zones, not points.
That hammered my mind for a while loooong ago; could just think of how to bring the poles closer with mechanical interlaced shapes with voids and prongs.

#### MisterBill2

Joined Jan 23, 2018
18,535
The motion of the rotor in the animation will produce a huge amount of vibration, and in addition, the motion of the magnetic field will be very expensive and complex to produce. In fact, I want to see the TS or somebody elsce describe how they can reasonably move a magnetic field in a circular path, like that motor appears to use, in an efficient or economical manner.