The basic idea of gears is to convert mechanical power from any rotational
speed and torque to another speed and torque and contrary what you see here
many machines today often need high torque and low rpm.
The linear actuator that I made before can be an example of this. Here i use the mechanical gearbox
to reduce the speed of the piston and increase the thrust so that could lift almost 100 kilogram.
It's well known that mechanical gears are very reliable and very high torques can be achieved
with all these drive systems. However they suffer from some inherent problems.
Because gear engagement inevitably requires physical contact and this causes wear on tooth
surface or damage to gear tooth. That's why gears must be constantly lubricated and periodically
maintained. Also as you see they have quite high noise levels because of the high vibration...
Since we can get such high torques, we could actually ignore all these problems. But on
the other hand a non-contact gearbox... This video is sponsored by pcbway more on them later.
Magnetic gears are very similar to conventional mechanical gears in terms of basic principle of
operation, geometry and function. the only difference between them is that the physical
contact gear engagement in mechanical gears is replaced by magnetic engagement in these gears
which is provided by a magnetic source such as permanent or electromagnet one of the most common
examples of this concept is this high magnet interaction concentric magnetic gearbox so let's
make a prototype the design basically consists of three concentric rotors and is very similar
to mechanical planetary gear sets there are two rotors on the inside and outside that contain
permanent magnets and act as sun and ring gears and between them is a flux modulator that acts
as a planet gears we know that a permanent magnet has two poles north and south and the same pose
repel each other but opposite poles attract in this case when the sun gear takes a small
step and aligns with the next iron segment in the modulator it attracts the south pole on the ring
gear towards itself. simultaneously it repairs the north pole which is right next to it these forces
create a tangential force in this direction and this force caused the ring gear to rotate
one of the remarkable things about this magnetic concept is that there is absolutely no physical
contact between the rotors the engagement is completely non-contact through magnetic forces
which gives them many advantages such as much quieter and lubrication free operation speaking
of the advantages pcbway has many services such as pcb manufacturing cnc machining or 3d
printing however they now offer a complete turnkey contract manufacturing service from the design to
mass production and they have a work that can be an example for that in the past months which is
electric floor fan as you see here you actually have all the machinery needed for your project
from the circuit boards to cnc machining even if you don't have professional machines it seems that
they have a capacity for many different ideas from the medicine to kitchen applications check
the link in the description for more on pcbway so let's start with these strong neodymium magnets
i arrange these magnets on the sun gear as one north and one south polarity
which will rotate at high speed the next step is to prepare the flux modulator
which is actually a very simple component in apperance and unlike the sun and ring gear
does not have magnet on it instead it consists of ferromagnetic and non-magnetic parts and which
plays a key role in the operation of the coaxial magnetic gear because if there was no components
such as a modulator the sun and ring gear would rotate together at the same speed and direction
like a magnetic coupling but thanks to the modulator the magnetic flux of each sun and
ring gear is modulated in the air gaps between them resulting in the gear ratio let's take a
closer look at this the ring gear contains 24 magnets in other words 12 pole pairs
and these magnets periodically produce a magnetic flux on the inner wall of the ring gear with a
wavelength of 12 harmonic order in other words 30 degrees the addition of the modulator to
the design causes 12 harmonic order flux in the ring gear to be converted into a fourth harmonic
or in other words the 30 degree wavelength is converted into a 90 degree wavelength
and at the same time this modulated ring flux is transmitted to the inner parts of the modulator
to the sun gear in the center here you may think that the gear ratio can be produced
because of the flux of the ring gear is modulated to a different order flux which it certainly is
but why and how did this flux modulated to a fourth harmonic order for the metal segments
in the modulator i used exactly 16 screws as many as some of the pole pairs in the sun and ring gear
so that these screws arrange at particular spacing on the modulator and that couse to have a
particular polarity pattern like south no field north and no field and if we look at a little
closer at this pattern thanks to the fact that some of the screws here have no magnetic field
we can see that this flux is actually corresponds to a magnetic flux at the fourth harmonic order
with a wavelength of 90 degrees long story short the magnetic flux in the ring gear
modulated to the fourth order as there were exactly 16 screws in the modulator
so when the ring gear takes a step or rotates 30 degrees the modulated ring
gear flux on the inside also must take a full step or rotate 90 degrees which as you
see means that the modulated flux must rotate exactly three times faster than the ring gear
this modulated flux is also same as the flux ofthe sun gear which is why the flux of the
ring gear is modulated to the 4th order because finally with the addition of the sun gear the
modulated ring flux interacts directly with the sign gear and causes to rotate
notice here that as a result as you see the sun gear now rotates three times faster than
the ring gear with the modulated flux resulting in a three times gear ratio between the gears
alright let's give it a run
okay this is an almost completely silent
lubrication free second order radial flux coaxial magnetic gearbox.
now i'm going to increase the speed a little bit
it is spinning around 12 000 rpm and the engagement still hasn't broken wow
that's really pretty awesome
but this is because i increased the speed gradually if i suddenly increase the speed...
it breaks okay so far it's working great it's just much noisier than
i expected especially at high speeds now i'm wondering how long it will last at this speed
so around 9000 rpm and after 10 minutes only the bearings got a little bit hot everything else is
almost cold where is the eddy current where are the losses why nothing melted hmm that's a
little strange okay by the way i chose the ring gear as the fixed component since it would be
difficult to get output from the ring gear in this case the sun gear and the modulator are
rotating in the same direction and this also caused the gear ratio to be 4 instead of 3.
it's actually just like the mechanical planetary gears and unlike these spur gear like designs in
this design we have a flux modulator so at any moment of the engagement all the magnets can
interact with each other and the torque capacity greatly increases speaking of the torque capacity
let's take a look at it by the way this large printing bed belongs to artillery sidewinder x2
this printer was sent by hekka.com and i printed most of the parts in the project with this printer
sidewinder x2 is a really high quality and pretty quiet printer we have a large
print volume and heats up very quickly it also has many important features such as
automatic bed leveling and direct drive extruder check out the channel for more about the printer
there should be a review video and there's a discount component below so definitely take a look
it's the fact that mechanical spur gears are so highly efficient that transmit power almost
without loss but it seems that magnetic gears are better at this because if we look at the results
we see that there is no loss between the input and output shafts okay this might sound crazy because
there can't be a lossless system and even if there is no physical contact friction or wear on
the magnetic engagement itself after all there are three crappy bearings in the system and they have
to create loss even the magnetic coupling itself have eddy currents or have hysteresis losses in
the bolts so it cannot be lossless probably the reason why the efficiency is so high is that
there is no load on the system anyway we have a more efficient gearbox than mechanical ones
but what i am actually more interested in that efficiency is the limits of this...
it's clear that the force will increase as the motor rotates but right after this peak
the magnets can no longer hold each other and the connection between them breaks
normally in the mechanical gears there should be damage at this point but there is no damage
here instead the magnets just slip over each other and jump to the next magnet
then the magnets interact again the force again rises to the maximum point
that the magnets can hold but reach the limit and slips again that's why we see these fluctuations
and these are also proof that the magnetic gears have an inherent overtorque protection
after a few tests the peak value is about 200 grams so before the magnets sleep the maximum
force that the torque arm can apply is 200 grams in this case the maximum torque is 0.05 newton 0.
it's really quite low and not even close to mechanical gears
it seems that it would be better for low torque and high speed applications but i still think it
has a potential because there are many reasons why torque is so low and one of the reasons
is that as you see we have a magnetic field outside as well as inside the ring gear and
not using that other one is a great loss but if i arrange these magnets in a particular way as you
see almost the entire magnetic field is now inside which will greatly increase the torque there are
many things that can be improved but that's all for now thanks for watching see you next time