## Introduction: Build a 15,000 Rpm Tesla Turbine Using Hard Drive Platters

Here's a project that uses some of those dead hard drives you've got lying around.

In the Tesla Turbine, air, steam, oil, or any other fluid is injected at the edge of a series of smooth parallel disks. The fluid spirals inwards and is exhausted through ventilation ports near the center of the disks.

A regular blade turbine operates by transferring kinetic energy from the moving fluid to the turbine fan blades. In the Tesla Turbine, the kinetic energy transfer to the edges of the thin platters is very small. Instead, it uses the boundary layer effect, i.e. adhesion between the moving fluid and the rigid disk. This is the same effect that causes drag on airplanes.

To build a turbine like this, you need some dead hard drives, some stock material (aluminum, acrylic), a milling machine with a rotary table, and a lathe with a 4 jaw chuck.

Wikipedia has a good review article (http://en.wikipedia.org/wiki/Tesla_turbine), as well as articles about

Nikola Tesla http://en.wikipedia.org/wiki/Nikola_Tesla,
the boundary layer effect (http://en.wikipedia.org/wiki/Boundary_layer),
and Reynolds number (http://en.wikipedia.org/wiki/Reynolds_number)
(which determines if the fluid flow is laminar or turbulent).

I run my turbine on compressed air (40 psi), and it easily reaches speeds of 10-15,000 rpm. While the speed is high, the torque is low, and it can be stopped with your bare hand.

I have more details on my webpage (http://staff.washington.edu/sbtroy/turbine/turbine.html).

## Step 1: Make Ventilation Holes in the Platters

Step 1 should probably be to disassemble some hard drives but I assume that if you read Make, you've already figured out how to un-Make a hard drive.

The easiest way to make vent holes in the hard drive platters is with a milling machine and a rotary table. Center and clamp a stack of several platters to the rotary table and then you can cut any radially symmetric pattern fairly easily. Just be sure that you use aluminium platters because ceramic platters will shatter when you drill into them.

I made two sets of platters; one with a radial array of holes, and one with radial arcs. The platter with radial arcs in the picture was on the top of the stack and took the most damage. The platters beneath it have very little tear-out and look much better.

## Step 2: Make or Reuse Spacers

The ideal spacing between the platters depends on several variables including the fluid viscosity, velocity, and temperature. You could go through the calculations (http://en.wikipedia.org/wiki/Navier-Stokes_equations) and make a set of spacers, or be lazy and just reuse the spacers from the disassembled hard drives.

I was lazy and reused the spacers that were originally in between the platters. The advantage to this is that they'll have the same inside diameter as the platters. They're about .050" thick where the ideal spacing is closer to .012" but the increased distance doesn't make that big a difference in this case.

## Step 3: Make the Shaft

This is just a piece of aluminum stock turned on a lathe. The center diameter is about .98" (which is the inside diameter of the platters) and about 1.77" long (so it will fit in a piece of 2" thick acrylic).

The thinner sections on each end are turned to fit the ball bearings I pulled from a box of scrap.

## Step 4: Make Collars

The collars are made from more aluminum stock are wider versions of the platter spacers. The inside diameter is also .98" but they're about .3" thick to hold a #10-32 set screw.

## Step 5: Rotor Assembly

Center the platters, spacers, and collars on the shaft and tighten the set screws to hold everything together. I used 11 platters, and 10 spacers. Try to line up all of the ventilation ports. If there isn't enough tension between the two collars, the platters can rotate around the shaft instead of with it.

## Step 6: Make the Chamber

This is a 4.75" x 4.75" x 2" piece of acrylic that was bored out on a lathe using a 4 jaw chuck. The intake hole is taped for a 1/4" pipe fitting and all of the other holes are 1/4 - 20.

I used acrylic because it's what I had around and because it's going to be used for lecture demonstrations. You can use metal or even wood. However, if you plan to use steam instead of compressed air, wood might expand too much.

## Step 7: Make the Side Panels (stators)

The side panels are 4.75" x 4.75" x 0.47" acrylic with untaped .25" holes to screw to the main chamber. The center hole is 0.6" and the counterbore is 0.28" deep.

The two 0.6" holes (one on each side) are the ONLY exhaust ports. The air spirals inwards across the face of the platters, through the ventilation ports, around the air spaces in the bearings (2nd picture), and finally out through these two holes.

However, more exhaust holes in the side panels might improve efficiency.

## Step 9: Complete Turbine and Movie

Please post (or email me) any questions or comments and I'll do my best to answer them.

Steven

How much did it cost to make it from scratch?

calskin (author)2017-09-22

If you keep your eyes open, you could make this out of found materials, so essentially zero.

I work on computers, so I constantly have hard drives I need to destroy. Speak with your local IT guy.

I'm also part of a makerspace, so the acrylic and tools wouldn't be hard to scrounge for me.

This is my anecdotal account, but I don't think I'm that unique.

GokulK27 (author)2016-03-25

Will a 12 v cigarette car charger attached tyre inflator br able to run this ???

With low rpm but yes.... probably.

harshilp3 (author)2016-03-28

CalebB10 (author)2016-03-04

i cant understand what your pdf says.

CalebB10 (author)2016-03-04

Cant wate to try

CalebB10 (author)2016-03-04

cant

waterbear226 (author)2016-02-10

Is it possible that instead of using acrylic plastic entirely, that I could use the right sized clear PVC pipe to enclose the discs? Please do not respond to my email, is expired and cannot get on. Please respond by comment.

juliozz (author)2015-08-25

Hi there, I'm interested to know whether or not is it possible to substitute the platters with custom cut aluminum.

Oh, and can you please specify what kind of compressor do you use to power it in the video, including its pressure and type? Is the power generated by the air flow from the compressor varying in different pressure?

Also, do you know how to calculate the power by using the tachometer?

Sorry for asking too many questions, and thank you for posting this!
athan9 (author)2014-04-23

do you know if it can work with a water exit hole?

SammerrA (author)2015-05-10

It has an exhaust hole. Can it use water? Sure. Will it lose efficiency? Maybe.

fasterthanfalcon (author)2014-11-10

Maybe instead of using water or air you can use another kind of gas or liquid that might produce more friction on the platters and create more torque. I really have no idea what... Just trying to think outside the box here....

SammerrA (author)2015-05-10

Increasing pressure, disk spacing, temperature etc all change the reynolds number and therefore the flow. Matching this to the turbine is the difficulty of the design. You can technically make any fluid match the turbine in use but it requires changing these parameters.

poikilotherm (author)2013-12-13

Would it be possible to, instead of having the exhausted air be released, have it be forced into another tube to re-use it? (I'm toying with the idea of using this as a drive for an airsoft minigun, with the exhaust air propelling the BBs)

SammerrA (author)2015-05-10

If the turbine is very efficient, the "air" that is being exhausted will have to be re-compressed. Conversely, if you used the turbine to compress air to drive the minigun, then you simply need a power source and strong arms.

WarriorStudio (author)2014-06-17

Is it possible to add more torque by attaching a gear system, or by adding "fins" to the disks. I realize that it will lose a lot of speed, but will it gain torque?

SammerrA (author)2015-05-10

Adding fins changes the flow and reynolds number. You want more torque increase disk number and diameter, given that all other factors are perfect.

andras.nolsoe (author)2014-12-07

How are the discs attached to the shaft? are they welded?

praneeth93 (author)2015-02-16

same doubt can someone reply to my mail chilumulapraneeth93@gmail.com

SammerrA (author)2015-05-10

This design uses collars that utilize screws to hold the disk together with friction. Tesla's design uses a keyed shaft. Another method is to use something like a dove tail and collars. This method is very simple and cheap.

I just want to purchase one of them .

WSF (author)2015-01-24

star washer actually helps the rotation buy guiding the air/water to the vent holes as the star extends above the vent holes. If you can see what difference that makes in the rpm.

nerd7473 (author)2014-04-16

I want one!!!

Pie Ninja (author)2010-06-08

There is no such thing as a free lunch.

KimberlyP (author)2011-04-25

I don't know about that. If you look at energy we are just fractioning it.
You just don't always get the choice of what you want for lunch :)

I'm a science person but there is a paradox which binds me to my religious brethren and sisters.

Which is more troubling a God which always was.

Or Infinity and or something created from nothing.

God would have to be infinite and spring from nothingness
&
Science can choose one or the other.

redrooster (author)2013-08-19

Isn't it strange how religion insinuates itself in the most unexpected places like some undiagnosed disease.

Pie Ninja (author)2011-04-25

I honestly have no idea what you just said.

KimberlyP (author)2011-04-25

You said there is not such thing as a free lunch.

I'm saying there is always a free lunch, you just don't always get to choose what you are eating.

I was trying to be funny at first. (MY Geek humor sometimes does not translate well)

And then I got serious. In the end there are things we cannot know or comprehend. --- Paradox.
What created something out of nothingness?
If you are infinite then you have no creation or end.

Pie Ninja (author)2011-04-26

KimberlyP (author)2011-04-26

Causality is a paradox is the sense if you have a finite universe, then something must have created it. (It need not be God) The problem is that at some point you are down to where there was nothing before, and then how does something spring from nothingness?

If not you are dealing with infinity. With infinity nothing has ever been created or destroyed its just changing form?

Still infinity is a paradox for causality because its saying their is no beginning or end, just points between numbers.

Some things are unknowable, and non computable.

Whitehead in the Principia tried to save us but failed.

Schrodinger6 (author)2012-05-10

Something comes from nothing all the time, easy example is the spontaneous creation/destruction of particle and anti-particle pairs. That's why we have the PROVEN concept of vacuum energy. Also, why we can theoretically have the big bang springing out of nothingness and in this light we have no need for a god to exist...other than the "god-particle", kinda need that guy ha.

Pie Ninja (author)2011-04-26

I'm going to go over there now.

KimberlyP (author)2011-04-26

http://en.wikipedia.org/wiki/Kurt_G%C3%B6del

Godel The man who reduced the principia to ashes.

aearly92 (author)2012-01-09

Makes complete sense to me, as long as you think of infinity with a positive and negative span. What kimberlyp is saying is that something infinite does not have a beggining... I personaly think infinity to be an endless forward reach that starts at a given point and then never stops so in my eyes the paradox isn't a paradox at all but I do respect the alternative view point. Thanks for making me think about it.
Can god create a rock larger than he can move? lol

KimberlyP (author)2012-01-10

Yes, well with causality we can pick a particular point and go forward on that point towards infinity.

But Causality is always a function of the state before that point in time.

Maybe its a circular function? Symmetrical on the macro scale, and non symmetric locally. IN which case we keep returning to 0 and all numbers are positive? We descend into a world of fractals. An infinite rabbit hole that keeps Excedrin selling well.

Something without a true beginning or end is as wacky as any religion!

Causality either maps to infinity or God or it breaks down and is no longer valid.

Causality needs time but if there is no change in time, ie: the universe is reduced to a single common state variable, then all we need is activation energy based on a density function of that state variable, which results in a second state variable.

Then you can map it all with a circular function and say everything is infinite and be satisfied. Except I would say why is there anything?

Science shows us how things work or can work, and philosophy and or religion tells us why?

So to rephrase: How is it that we can get something from nothing?
In the Universe I live in energy and matter are the same thing in different clothing. Practical physics deals with finite measurement. Mathematical abstractions do not have this limit.

Can god create a rock larger than he can move? lol

I would say no based on the 1st law of Thermo. It would be over unity!

nedesico (author)2012-03-12

I agree o.O

dombeef (author)2010-06-15

Or free pie...

Pie Ninja (author)2010-06-15

Oh, woe is me.

dombeef (author)2010-06-15

What did he say?

Pie Ninja (author)2010-06-15

dombeef (author)2010-06-16

Oh ok So he probably said that you could connect the end pipe to the opening pipe to get free power?

dombeef (author)2010-06-15

Yeah

TheStudio7 (author)2013-08-18

Nice, though I stopped reading the comments when some one started the god bs thing. Can we keep reality and stupidity separate please?

maikel2 (author)2013-05-04

a conventional rotary compressor runs more than 100k rpm to develop vacuum to sucks outside air continuously thus compressed it.if this device run at that speed can it become a compressor???

bulsatar (author)2013-02-19

For those that don't like math but are still confused: notice that it is basically a closed system (rotationally) from the point of force (the air being blown in). The air circulates in the first platter set until the air pressure is too great and it escapes through the center holes of the platters (ignoring air escaping from the outside edges). This creates a pressure differential between the side of the hole being "pushed" on and the "back side" of the hole, inducing a spin. The pressure differential builds in the next platter layer and then moves out again, and again, and again until it escapes freely from the last platter set's center holes.
Because of energy loss from air escaping around the platters, friction from the bearings and other natural energy sinks, the inside platters exert more torque pressure than the outside ones (math stuffs go here for proof).
Good thing about this design is that you can use some "simple" thermodynamics to have a relatively low pressure, large area front condensed into a high pressure, small area front to get your air pressure from the wind for "free" (think of a properly tuned funnel) to drive an electrical generating motor thingy off of the axle with those new found magnetic thingies...

FlashSC (author)2009-12-08

I'd like to ask the silly question here, but, where does the pressed air comes out?
Maybe i missed something...

Thanks for the tuto.

.:FFH:.

Science4fun (author)2010-12-27

You're not!
This IS a stupidly designed device.
the air actually escapes thru the shaft hole.

CapmBattleship (author)2011-07-21

This is actually correctly designed, with the exhaust escaping through the shaft hole.

The Tesla turbine relies on the boundary layer effect and centrifugal force. The air gets forced to the center and out the shaft hole. An exhaust port on the side would ruin the design of the turbine.

jhardee (author)2012-08-05

no. CENTRIPETAL. not centrifugal. why does everybody think its centrifugal??