Tesla CD Turbine At The Science Fair

[dlchambers]

I'd guess it goes backwards because the turbine magnets pull the bottom side of the ball in the direction that the turbine rolls, causing the ball to spin as if it were actually touching the top CD () that is, the ball's bottom surface moves in the same direction as the turbine). But because the ball is touching the plexi plate, friction causes the ball to move in the opposite direction. Cool how the magnets keep the ball from flying off the plate - sort of like a satellite in Earth orbit.

[fancytableshoes]

Try it with a flat magnet - won't happen. The ball is a magnet, right (not just magnetic steel)? What you're seeing is due to inertia. At slow speeds, the ball is not rolling. It is coupled to a magnet below and simply dragged around. At a certain speed, the lower magnet will outpace the ball, pulling the ball's magnetic axis off vertical, setting it spinning (rolling) about it's own axis. In a perfect world the ball would just sit and roll in place - friction gives it forward motion.

[fancytableshoes]

Try it with a flat magnet - won't happen. The ball is a magnet, right (not just magnetic steel)? What you're seeing is due to inertia. At slow speeds, the ball is not rolling. It is coupled to a magnet below and simply dragged around. At a certain speed, the lower magnet will outpace the ball, pulling the ball's magnetic axis off vertical, setting it spinning (rolling) about it's own axis. In a perfect world the ball would just sit and roll in place - friction gives it forward motion.

[retrorecycler]

I'll bet it goes backwards because it takes a shorter time to reach the magnetic field then if it were following the magnets.

[PerfectParasite]

You should try a tesla turbine only using two magnets. I think that it would generate an interesting affect for the ball.

[geekwes2]

what type of magnets did you use: blocks, spheres, or discs?

[MrfixitRick]

@geekwes2

We used 1/32 inch thick x 1/4 inch discs as spacers between the CD discs. We also used 1/2 x 1/2 inch neodymium cylinder magnets as the top drive magnets.

[MarkRiverbank]

From your instructables, it appears you are orienting the magnets so that the polarity is the same direction for all of them. What if you alternated the polarity of the magnet stacks [of the 6 stacks, 3 would be north, 3 south], could you get an alternating magnetic field and from there generate electricity?

I believe Tesla's original turbine did not use magnets at all. Someone could build a similar cd turbine using small washers instead couldn't they? [minus the cool rolling ball effect]

[MrfixitRick]

@MarkRiverbank

Yes, alternating magnets would be better for generating electricity. It is problematic to use alternating magnets as a magnetic drive, however.

No supermagnets in Tesla's Turbine, but it requires a shaft, bearings and shaft seals mounted in a strong case in order to get the power out. A mag drive doesn't need these things!

Washers could work as spacers between discs along with drive magnets, perhaps.

[igokebutuoy]

This will be a great experiment to do for my science fair next month, can you give a simple part list so I can get work on. Thanks.

[09205479428]

Very interesting theories.

One important factor could be the mass of the ball. Once the rotation of the disc exceeds the critial mass it can pull, the object halts and keeps pace again. This time it can not be held along the disc rotation so it has to keep pace on the other direction to maintain Rotational Equilibrium. Furthermore, in centrifugal equilibrium two attached bodies must move on opposite direction.

[the88thcrazy]

You should try this in a vacuum with the magnet set as a pendulum instead to see if it still spins backwards.

You should also try this with a cone shaped magnet that has a base with the same diameter as the magnet used in this movie, but with the same height as the radius of the turbine. I think this would be interesting because it would change the center of mass greatly.

[MrfixitRick]

I did try a magnet on a string, and after an hour of trying, did convince it to go backwards. More experiments need to be done in this area...

[the88thcrazy]

How far (in terms of height) did you hang the pendulum? As seen with the sink science 11 video, the relation seems to have some relation to height, with a mixture of speed.

My theory is that it has something to do with breaking away from the magnetic field. You would think that when the speed of the turbine exceeds the resistance of the magnet, it would break away with a similar pattern of tangental velocity, but this isn't the case. the magent still has attraction as it breaks the resistance

[MrfixitRick]

The height of the magnetic ball above the turbine magnets, as you mention, is critical to obtain the effect. I used in the range of 1 inch gap to get the reversing action.

[the88thcrazy]

Ok cool, i was just wondering.

See, if my theory is correct, you should be able to get an entire disc of magnets (such as in the vortex video) to spin backwards as well, just as long as it is high enough above the magnets, and you have the turbine spinning at a rate high enough so that it can exceed the velocity between the two magnets.

try it out some time, i could think of a few uses of this in a factory setting if manipulated properly.

[MrfixitRick]

I could get a magnetic disc to go slowly backwards above the turbine only when the centre post was sloppy enough to allow a slight wallowing motion, and therefore the CD's had some traction against the post, it seemed.

[the88thcrazy]

(continued)...breaks the resistance, so it starts heading in the opposite direction. imagine there is a net force of 0 between the free moving magnet and one of the magnets on the turbine, as the turbine moves forward, the magnet will idealy move with the the speed of the magnet on the turbine.

Let's assume that we know the velocity of the magnetic attraction. let's call this Va, and we'll call the tangental velocity of the turbine Vb. once Vb exceeds Va, the magnet should break away.

[the88thcrazy]

Once it breaks away, it is moving in the opposite direction of the turbine, once it gets far enough away from the turbine, it is attracted to the next magnet in line, which starts building accelleration. i'll have to go into greater detail of this later, i need to head to class.

[LittleBigKRATOS]

Where can I buy those magnets?

The ones at home depot are ceramic magnets but they don't sell this kind.

[MrfixitRick]

@LittleBigKRATOS

These are neodymium magnets and can be ordered through the K&J Magnetics link in the "more info" box.

[LittleBigKRATOS]

Oh, I missed that part on the info box.

Thanks.

[syaoran02sakura]

the truth is when water compressedthrough the chamber, it spun the magnet through the coils then when the magnet spun aound the iron, it produced magnetics field and when the magneic field is greate and bigger, it produced electricity when spund around the iiron (it's called electromagnetic) and the elcetromagnetic distract the magnetic field so the magnetic field is affected by the elcetricity movement (from negative to positive)

[themarksmann]

I think FritzLaurel has got it. My thoughts originate from much more of a layman's viewpoint: comparing it to a spinning fan. When slow, the blades appear to go one direction; sped up, they seem to go in reverse since your eyes make a logical connection between the current and previous image. Sped faster, the fan blades seem to spin in the original direction again. Perhaps with the ball a similar connection is made, and the pull is stronger coming from a magnet headed to the ball vs against.

[salzahrah]

bs

tht girl doesnt noe anything bout her project

teacher did all of it

[MrfixitRick]

That was a foolish thing to say.

First, its a boy not a girl. (duh!)

Second, he knows more about the CD turbine than anyone else but me. (very bright kid)

Third, he built his own turbine with my guidance...

I am his teacher.

Got anything else negative to say?

[salzahrah]

ok then why didnt he go to the intel science fair and win $100,00

[crackpiperomance]

erm im no physicist but it jus looks like the the magnet is pulling the underside of the ball in the direction that the magnet is spinning which is causing the the ball to simply roll the oposite like if u hold the ball flat on ur pal, them move your palm towards you fast the ball wil roll the oposite way and fall off your hand it wont go the same direction that your hand is going

[Choowbz]

I live in Australia.

Water and Magnetism go the opposite way here.

I wonder if a unit made in the North would behave differently if brought to the South?

And could that polar difference have something to do with it?

[MrfixitRick]

Good points. I think those effects would be too slight to affect the running of this machine. However, at very high rpm's the polarity of the magnetic turbine vs the earth might make a bigger difference.

[FritzLaurel]

The ball follows the path of least resistance which is caused by the NET magnetic field at the position of the ball created by the rotating magnets. If you could calculate what the field at the ball is and how it changes as the magnets rotate, you'd see the ball's path.

I wonder if there's an upper RPM threshold where the ball goes with the turbine again? Might be a small window.

I like this stuff. Very nice!

[MrfixitRick]

Good thinking! The net magnetic field changes with the lag built into the system. The inertia of the ball, the centrifugal forces on it, and the sliding resistance, also come into play in calculating the ball's path.

I believe it's correct that the ball will go with the turbine again at higher rpms. That would require running on air pressure to test, and the possibility of catastrophic failure! (hmm, sounds like a good movie...;)

[stop4stuff]

Q. Why does the ball go backwards?

A. Because the magnetic attraction to the lower half of the ball is similar to the forces put on a cue ball on a backspin shot, i.e. the ball skids on the surface when travelling in the same direction as the magnets, then friction takes over and the magnets make the ball backspin against the surface causing the ball to travel in the opposite direction whilst still attracted to the magnets.

(I maybe wrong, tho logical to me)

[afrojoe90]

attracted to the previous magnet the faster you spun the turbine the ball cant quite keep up with any thing but as you noticed when you slow it down the ball spins faster . i believe this is because the magnets start to meet the ball at a more disireable point. kinda hard to explain but yer thats my thoughts

[MrfixitRick]

"the magnets start to meet the ball at a more disireable point" That pretty much describes it!

[afrojoe90]

does the ball rotate beacuse of a similar effect to that ofa camera filming a spinning wheel you notice that when the camera is if filming as the wheel acellerates it seems to go one way then reverse direction this is beacuse as the camera works it takes pictures and if the weel is spinning fast enough it starts appear to go backwards. i think the ball does the same thing. the magnets are spinning around so fast that it cant keep up due to friction, wind resistance and inerita so it becomes

[Flipp2w0]

what is the polarity of rhe top magnets. is it + - + -? or ar they all the same?

[MrfixitRick]

The only way I found it will work as a magnetic coupling is to have all same polarity. The Turbine has N-N-N-N-N-N up. The coupler put on top of the turbine has N-N-N-N-N-N down to engage the magnets of the turbine in REPEL mode.

To make electric power, it would be better to have N-S-N-S-N-S and produce a full AC sine wave.

[903harman]

cant you make it run on the turbines power instead of outlet? im sure it can be done..

[MrfixitRick]

Like you, I think it can be done too. (opposite rotating magnetic fields are the key...)

Unfortunately, that is usually called perpetual motion and is generally considered impossible. However, I do specialize in doing the impossible with next to nothing, so you never know what I will come up with!

In my later videos, I do show a re-circulating bucket Tesla CD Turbine system, that runs off of solar energy stored in a battery. Close enough?

[903harman]

cool :D i subed...i like your projects.

[gblackhead]

PART3:

The rotor speed for direction change and oposite rotation speed is depending on the number of rotor magnets used,

the size (diametter) and weight (in the earth's gravitational field) of the rotating ball and the distance of the ball-surface from the rotor magnets.

The speed and direction of rotation is dependent on how and where the ball's magnetic lines/field penetrates the magnetic lines/field of the rotor magnets.

[gblackhead]

PART2:

When you speed up the rotor a bit, the ball will turn toward approaching rotor magnet.

But like it's going under the ball, the ball tryies to find it's best-opposite position and rotate in oposite direction on the top of the surface.

But when it reaches the next magnet it tryies to spin again to achieve best position for the next magnet.

[vipersrules]

Where can I get neodymium magnets?

[vipersrules]

Ahahaah Ima totally make one of these :D

[seddarcheese]

Could I use this as a motor to something?

As in could I make this a circular saw?

[MrfixitRick]

Haha, that's the first thing I did with this concept!

See YouTube/watch?v=SPN8WmKG1LM for the idea,

and YouTube/watch?v=Dn6MR0Wslf8 for the bizarre and dangerous test run.

[HelloBrainMind]

Most likely, like others have stated, has to do with the ball being driven to the oncoming magnets, but interesting none-the-less. It really doesn't make sense.

It would be interesting if you could find the speed at which the ball would "stall" and prefer neither direction.

[MrfixitRick]

The "stall" speed of the magnetic ball depends on the height above the turbine that the plate is held. It ranges from about 400 rpm to 900 rpm.

[therealskunkyjo]

i would hazard a guess as to the polarity of the magnets makes the ball rotate the opposite way, sinse the ball itself is magnetic (i'm guessing by how it was described as a magnetic ball) with the magnets all spinning it would attract the pole on the top of the ball towards the oncoming magnet causing it to roll backwards and towards the next magnet. hard to explain what i mean without diagrams. tesla is the shizny tho.

[NiNjA410404]

I think the ball being magnetic may have an oppisite charge magnetic field from the disks field.

[c1b3rz]

Have you ever thought that, if they roll backwards, their approaching speed is higher?

[frzn4ever]

it's the same as if you took a roll of toilet paper and pulled the end of it. pull slow and the roll moves toward you, pull fast and it moves away from you. that's the best I can describe it. The magnet pulls the bottom of the ball causing it to roll backwards. Rotational inertia takes it from there.

[MrfixitRick]

Thanks for that quite visual contribution. I can see that a peer-reviewed paper takes on a different meaning here.

[hypnotekk]

HAHAHA! welcome to the internet, where the phrase "some say..." qualifies as academic reference :)

nice video by the way, and i would be interested if you know why the ball rotates the other way.

[MrfixitRick]

There are lots of interesting theories and ideas, but do I truly know why it rotates backwards...no!

[hypnotekk]

what is this effect called, and do you have a link or reference i could look at the maths?

[MrfixitRick]

Since I discovered this effect, I have not been able to find any literature on it. The only side reference is from Tesla himself, when describing the effect of increasing the frequency in an AC motor.

Tesla said,

"When the speed of rotation of the poles was increased, the torque would diminish, would finally go down to zero, become negative, and then the armature would begin to rotate in opposite direction to the field."

[JonathanJams]

GREAT JOB !!!!! CONTiNUE on this way

[windoes98se]

you should make a coul of wier above the magnets , then you might be able to produce n electriacl current, but the poles of thr magnets willprobly have to alternate (i am not exactly sure this is an educated guess)

[MrfixitRick]

That's right, a coil of wire will work and I have lit LED's that way. The magnet poles should alternate NSNSNS to make it more effective, instead of the NNNNNN they are currently.

[bestamerica]

thank rick to set up a closed captioned for the deaf / hearing impaired people,,,

big thank rick,,,

rate top 5 stars

[electricmic]

The rolling spherical magnet changes its orientation as it rolls. Wow! that is a complicated interaction. Does it skid around or is it really rolling? Perhaps it stabilizes in a horizontal orientation? I'd like to see the sphere painted to identify its polarity during a retest.

Great stuff!

[MrfixitRick]

It is indeed complicated to ponder the forces involved...yet so simple in it's resultant vectors!

The ball can skid or roll, depending on the height above the magnets of the turbine.

I have a couple of other videos I will release soon with a bobbing styrofoam-encased magnet in water, and one suspended on a string above the magnetic turbine.

[GSol17]

I think i know why it goes backwards. It's because it's attracted to the magnets and at some point it goes so fast that the one in front is closer then the one behind it. therefore it goes backwards.

[NOCNOTCAUGHT]

Each magnet has two poles. When rotated there is a shifting effect. The effect of the induced emf from the leading pole is always in opposition to that pole and all other leading poles provided the magnets are all glued to the CD in the same N-S orientation. That primary emf would also attract the opposite pole during the rotational cycle. Remember though there are static magnetic forces at work in combination with the induced emf making this a very complicated process overall. Fascinating!

[NOCNOTCAUGHT]

Suspend a neodymium magnet tied or taped to a long string from something high - ceiling or light fixture. Place very in very close proximity to the bottom of the suspended magnet but not touching - something like a block of aluminum - a soda can or something non-ferromagnetic but electrically conductive. Now swing the magnet on the string and watch how the non magnetic aluminum stops the magnet. This demonstrates the counter emf principle from Lenz's law.

[MrfixitRick]

Thanks for comments...that makes sense. I have shown this principle in one of my first videos, "Neo Magnet Floats Down A Tube" ...YouTube /watch?v=a5BtjZWkua0

It's amazing to see a heavy, solid, magnet float down an aluminum tube like it was a feather!

How does the ball magnet sometimes go faster backwards than the turbine turns forwards ?

There must be complex resonant interactions involving inertia and centripetal forces, and the intensity and shapes of the magnetic and electric fields.

[NOCNOTCAUGHT]

I would suspect that faster backwards is a result of the overall gain of the emf effect. The turbine magnets become a linear physical accelerator as well as an induction accelerator or generator simultaneously adding more energy of a different type to the overall motion. Again - there is a LOT going on at once here!!!

[NOCNOTCAUGHT]

The more I watch this video, I'm thinking automotive transmission applications. What do you think Rick? MrfixitRick's Magnetic Hydroglide Accelerating Transmission? I saw it here first!

[HandsHeldHigh1]

if you make that the Government will kill you

[whatevtube]

I'd still like to see valves that require no lubricant and instead glide frictionless via EMF.

[stop4stuff]

"Neo Magnet Floats Down A Tube" = eddy current repulsion (or eddy current braking)

"How does the ball magnet sometimes go faster backwards than the turbine turns forwards ?"

backspin of the ball going faster = gearing (your disc of magnets has a bigger circumference than the ball hence the rotational speed of the ball is geared up compared to the rotational speed of the turbine)

[MrfixitRick]

Thanks for the comments!

It seems the process of pondering various answers to this question leads to visualizing and a better understanding of the forces involved. Which is a good thing, I believe!

[MrfixitRick]

Now that you mention it, I also have a movie of a ball magnet suspended on a string above the magnetic turbine, that I will edit and get out soon. It shows some interesting behaviour as well.

[NOCNOTCAUGHT]

There are two types of magnetism at work here - plain physical - magnets to ball and electromagnetic - magnetized ball to magnets - all due to the initial motion of the magnets. When the turbine rotates fast enough the positive physical magnetism is overpowered by the opposing electromagnetism. Great demonstration!!! Keep up the good work!!!

[NOCNOTCAUGHT]

The backward motion of the ball is due to induced counter emf. While the ball is magnetic it is also a conductor. When the magnetic field passes the conductor it induces a counter emf opposite to the direction of the magnet - see Lenz's law.

[electricmic]

If this explanation is correct then any non ferrous metal ball (brass, aluminum, copper, gold) should also rotate in the opposite direction of the turbine rotation, right? Can you think of a commonly available non-ferrous sphere? Do you think a wedding band might work if a ball is hard to get?

Fix-it-Rick called it a "magnetic ball" Does that mean it is itself a neodymium magnet or just steel? That would be interesting to see how a rolling magnet would interact with the magnets on the disc.

[MrfixitRick]

The ball is a magnetic sphere, magnetized axially with a north and south pole.

At a certain higher rpm, the ball will just sit there and vibrate. I suspect that at certain higher harmonic frequencies the ball goes backwards, stops, and then goes forwards. An AC motor will do a similar thing with "currents of differing phase", Tesla found, in "Notes on a Unipolar Dynamo".

An aluminum pie plate seems to only spin in the direction of the turbine.

[wiscokiddd]

Hi Rick: Cool experiment. Yeah I can't figure out the reverse of the steelie or round magnet with the variance in speed of your turbine humm I'll have to think about this...PL&H K

[spinafire]

One of your coolest experiments yet. Good job to both of you!

[unclewooly]

Good stuff. Great to see the turbine back in action

[markuks]

Interesting... I had the same design as her. Unfortunately, I lack 2 of the most important parts. The magnets which is very difficult to find it here, and water pressure, i'm still looking for a pump with a considerable power.

[Individualism101]

Try ebay.

[KanineKruizer]

How much did it cost you to make this Tesla-type CD turbine?

How did you make sure the space between each disc was just right, or did you not worry about it?

[AdminOnDuty]

Maybe its following the magnetized water vortex... :-D

Actually it is the shape of the fields that causes that. Imagine each of the internal fields has an invisible apple on top of it (you know, with that dimple where the stem goes on top) and the external magnet keeps rolling inside that dimple as it moves from apple to apple. I call that region the catenoid region because it has that shape through the magnet which extends beyond each pole. The top edge is the event horizon. The ball is inside

[MrfixitRick]

Thanks for comment. Admin; I knew I could rely on you to provide a clear explanation!

[m4lvolio]

I'm finding it a bit hard to visualize Admin's explanation.

I see it as a sort of gear mechanism: the magnets on the turbine form the first gear. The ball represents the second. It will spin in the opposite direction and, thus, travel the same way.

Maybe if there was considerably reduced friction between the ball and the surface on which it's traveling and the ball wasn't a ball, but rather something magnetic with wheels on, it would go in the same direction. :)

[MrfixitRick]

The gear visualization works...except when the ball suddenly reverses from one direction to the other.

Perhaps we can think of the dimple in admin's apple as a gear...one side of the dimple gives one direction, the other side reverses the direction. The side of the apple's dimple/gear that the ball magnet contacts is related to the lag in the system.

I encased the magnetic ball in styrofoam and put it in water and it still goes backwards.

[m4lvolio]

Interesting. Does it spin in the water ?

[MrfixitRick]

The styro ball/magnet bobs, mostly. But it will pull the water in a bowl into a vortex when it begins to move around. I will release a video of it soon.

[m4lvolio]

sounds awesome

[reinheart767]

very cool stuff, thx for the vid upload :)