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

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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).

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## 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

Participated in the
The Instructables Book Contest

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## 340 Discussions

You cut it from a bigger piece

Where did u get the acrylic sqaure from? They seem a little hard to find on with estimated deminsions that are not over 6" in any three angles

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???

2 replies

It potentially could. It may not be very effecint though. U may need "fins" like that of a compressor wheel in a turbocharger.

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.

If u use a tap and dy set then just thread the shaft and use very small, light ,thin nuts like wat is used with potentiometer on soundboards.

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?

2 replies

U need more surface area while the disks are smooth. So a few more this disks could help. This is a tesla turbine. If u add fins it would be called "tesla's fan pump" whcih ,1, isnt right, 2nd, it doesnt work the same way, 3rd -its a whole lot louder then the actually turbine speed. The fins can also cause a very large resistance. It will spin slower thin it is capable. This can also lead to lots of rattling if the fan is unbalanced. Also the fan may act as a compressor wheel like one in a turbocharger. This will create more resistance to work against. How ever if u ruffed up the disks with sandpaper, it will have more torque, but again, it will mess with the air flow a little bit. So u may need to do some slightly bigger exhaust ports for better flow. As asked, a gear box or gear ratio added to it can greatly increase. For more torque, the ratio of the turbine shaft to the slave shaft will need to be greater thin 1:1.1 gear ratio. So if the drive shaft (turbine) is connected to a pulley or gear that is 1.1 times bigger (.1 change difference in size) then the torque wull change. In this example of 1:1.1, u will not see a noticable difference. I would do a ratio greater then 1:2. This can drematicly increase the torque. It will be a very slow speed but it will be strong with turbine at high speed. That number can increase if there are more gears. Like 1:2 gear to a another 1:2 and so on... it gets stronger and stronger. (At least till the final slave pulley brakes because of the torque load lol). If u do the gears the other way then the speed increases while torque decreases. ( just if u want your turbine that spins 70 thousand rpms to increase to 120 thousand rpms)-(insane) ur ideas would work. The "fin" one just wouldnt be a tesla turbine. (Remeber sand paper) sorry if the explenation is sooooo long, so ill just make it loooooooonger lol

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

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.

U just need a good round housing. He used clear acrylic to see through (which is kind of cool). But something round could work just as well if done right. Also the square acrylic piece he used made it easier for making it stand upright withou falling over and he could use it mounting hardware for the other pieces. But as i said someyhing (like pvc) could just a little harder to work with.

Its hard for me to get some of the stuff in my country..
Is there any posibble way i can buy it..

Hello,

I was wondering how can you calculate the power output of such a turbine and how big would if have to be in case your input is compressed air at 210 l/min with an 8 bar pressure. I am trying to reach an output of at least 4 kWh. Any help would be appreciated, if there are any formulas you can help me with the better.

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.

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