Isn't it great how fast the propeller spins even though I turn the handle slowly Yes it's
a gearbox and you probably think that there are some kind of gears or something like that inside.
But this gearbox is a little bit different and it's actually not a mechanical gearbox. This is
a magnetic gearbox. Although both mechanical and magnetic gears actually serve the same purpose
magnetic gears work on a completely different principle. a mechanical gear mechanism inevitably
requires physical contact during engagement magnetic gears however use the interactions
of permanent magnets so there is absolutely no physical contact between the gears as a
mechanical ones. if there's no physical contact there is no wear or mechanical damage and so no
need for lubrication isn't it great this Flux modulated concentric magnetic gearbox basically
consists of three concentric rotors I designed all these in Fusion 360 than 3D printed them with pla
this is the Sun Gear there are eight magnets on the sign gear and normally these eight magnets
are four pole pairs so for mechanical teeth but this sun gear is a little different because I
didn't arrange these magnets alternately like one north and one south as in this ring here
the magnets in the sun gear are arranged in groups of two, two North and two south
so that in total there are two pole pairs
and that means 2 teeth instead of 4 teeth. the reason I arranged it this way is to get more gear
ratio in the same valume. the other component is the ring there are 20 magnets in the ring gear and
this time unlike the sun gear I arranged these magnets as one north and one south alternately
as you can see on this magnetic field viewer the magnets in The Sun Gear are in groups of two
but here each magnet is separate
in this case 20 magnets make 10 pole pairs and this means 10 mechanical teeth
the last component is the flux modulator what does this modulator do
it's just like the planetary gears in mechanical ones it converts the
magnetic flux in the ring gear into a magnetic flux that can match the sun gear
and finally when the sun gear is added this inner modulated ring gear flux and the sun gear can work
together and the gear ratio can be achieved so actually all the work is done by the modulator
if there was no modulator anyway the sun and ring gear would rotate together at the
same speed and direction like a magnetic coupling
the modulator owes this flux modulation work to its 12 metal
segments on it there have to be exactly 12 set screws otherwise the flux of the
ring gear cannot be converted into a flux compatible with the sun gear
it's converted into a flux of different order and so the gearbox will not work properly so
there has to be exactly 12 metal segments and this value comes from the thing that there are two pole
pairs in the sun gear and 10 pole pairs in the ring gear so 12-pole pairs to have teeth in total
okay
okay this is the second order radial Flux concentric magnetic gearbox it's radial
flux because the fluxes of these magnets are moving in a radial direction towards the center
that's why it's called radial flux okay let's give it a spin I'd better fix it
so okay wwhen I turn this modulator the sun gear will
here we have the sun gear this can be rotated with the orange handle here the inner modulator
with the gray and finally the other ring gear with the blue handle the gear ratio depends on
which gear is stationary and which gear is moving before we start remember that the gear ratio is
output divided by input so the output teeth, speed or Torque divided by input teeth speed or Torque
when the modulator is stationary turning design gear causes blue ring gear to spin as you can see
so for the ring gear to make one turn the sun gear has to make 5 turns this means a
gear ratio of 5 times and in this case we get 5 times more torque than the input the sign gear
but in return of course the speed will slow down 5 times
and check out the gears are rotating in the opposite direction this time something more
interesting I'll keep the ring gear fixed not the modulator the input will be the sun gear and the
output will be the modulator what will happen now the gear ratio was output divided by input so the
modulator has 12 metal segments and the sun gear has two teeth in this case the gear ratio should
be six and as you can see when the propeller made six turns the modulator made only one turn
and in this case the gears are rotating in the same direction
Now The Sun Gear is fixed the ring gear is input and the modulator is output
the modulator didn't even complete one turn these three cases we have seen so
far were cases where torque increased and speed decreased now let's see the opposite
whoa it's really fast
although I can't count it now there is six times a gear ratio between the sun
gear and the modulator and because I'm now turning from the modulator
side the speed increases 6 times but the torque also decreases 6 times
as a result a total of six different gear ratios can be created three of where the speed increases
and the torque decreases and three of which will be the case where the speed decreases
and the torque increases this is just like in mechanical planetary gear sets there is no need
to mention the last two combinations where the speed increases only the ratios are different
this motor can go up to a maximum of 3000 RPM and with 6 gear ratio
magnetic gearbox in front of it it can theoretically go up to a maximum of 18
000 RPM and I really wonder what happens at such high speeds with these 3D printed parts
to be honest it's not what I expected there's a
little bit of wobble and look at the particles flying in the air
although the design looks easy it can be challenging to get precise tolerances with
3D printers and if there's also wobble on the mechanism we may face these kinds of results
also the bearing noises are terrible there is a loss of about 6
000 revolutions which is too much for a magnetic transmission
oh