Introduction: Tesla Turbine From Old Hard Drives and Minimal Tools
Tesla Turbines promise up to 92% efficiency of converting air or fluid flow to rotational energy and its use can also be inverted for use as a pump with exceptionally high efficiency too. With compressed air becoming recognised as a feasible form of energy storage, we can see this device in everyday life soon as a source of locomotion. Factoring the simplicity, robustness and resillience to ingress of this design and you have something ideal for pumping heterogenous fluids like sewarage or fluids with suspended particulate. As a pump, this device has an important role to play in the developing world. More about it here: http://en.wikipedia.org/wiki/Tesla_turbine
Step 1: Tools That You Will Need
1. Torx set of screwdrivers to disassemble the hard drives and to build the rotor
2. Circle cutter - get this from you stationary shop for 1.99
3. Engineering Compass - optional, you can use the circle cutter to mark the workpieces
4. Sheet-metal drill bit and a 5 mm drill bit
5. Half-round file
6. Hole file
7. Craft glue or hot-melt glue
8. Epoxy glue to bond aluminium (that's aluminum to you lot in the US/Canada!)
9. Gaffa/Bodge/Duct/Electrical tape
10. Hacksaw with metal blade to cut aluminium (see proper pronounciation in item 8)
11. Pillar drill
12. Compressor to supply the air to drive the turbine. You can also use a drinking straw and blow really hard 'till your eyes pop out.
13. Some spare hard disk platters (chances are that you will have a couple of attempts to cut the right shape of slots in them)
Step 2: Materials That You Will Need
1. Two hard drives.
2. Erm... that's it.
Step 3: Disassemble the Hard Drives
You will most certainly need the Torx screwdrivers to this. Remember that there also screws under the label, sometimes just one, mostly two.
The magnets and the armature assembly needs to be removed. Often, the top magnet is not screwed on at all but held on using (you'll never guess!) its own magenetism. Strip the hard drive right down - you should have a between 2 to 4 disks per hard drive.
Step 4: Build the Casing
With the 2 hard drive cases, use the bhack saw to cut each one in two so that when the parts are joined together they form a circular casing in which the hard drive motor can be mounted.
Cut along the red lines indicated on the pictures and start by making the larger half first - that way, if you bollocks it up, you can use this bit for the smaller half and reattempt to make the larger half from the second hard drive.
Then assemble with two halves with epoxy glue, making sure that you can spin a disk platter inside the newly-formed circular enclosure without it touching the sides. Clamp it and let the epoxy glue cure.
While you about with the epoxy glue, fill any gaps on the side with it to prevent air leakage and to reduce turbulance.
Form an air nozzles into the circular enclosure where the air filter is and drill a 5mm hole where the air inlet is going to be (see last picture)
Step 5: The Back Plate
The back of the disk drive enclusure may be stepped and the drive motor will probably have a step in its shaft too. The solution is to glue a stationary back plate in the casing over the motor.
Enlarge the hole in one of your platters to fit around the step in the motor shaft.
Mount the hard drive motor back in the glued-together casing. Glue the back plate in.
Step 6: Mark the Slots on the Rotors
This is the bit where craft and patience becomes important: It is imperative that the platters are kept flush during the cutting of the slots.
Use the circle-cutter or an engineer's compass to mark 3 circular slots on 4 platters. First, mark out 3 circles or 20mm, 25mm and 30mm radius. Then devide the middle (25mm) circle into 6 equal parts using the compass (set to 25mm if you did not do this while being bored in geometry class).
You now have the 6 drilling points where you will make 10mm holes using the sheet metal drill.
Step 7: Make the Slots on the Rotors
Drill the 6 marked holes on each of the 4 disk platters with a sheet metal drill bit. Do not use a steel drill as you will twist your disk when the bit binds to the thin sheet metal.
Join the holes up so that you form 3 equal slots using a hole file. Finish each curved slot off with a half-round file. Mount the disk in a wooden-clad vice and work as close as possible to the lip of the vice. Be careful not to bend the work piece.
Step 8: Make Disk Spacers
There is a fair bit of interesting math and physics involved which determines how far the disks need to be spaced. Since we are just prototyping here, it is sufficient that the disks are spaced by 2 thicknesses of the average postcard (how scientific is this? Well, that's what the formulas indicate).
So, using the hole cutter, cut at least 12 washers with inner radius 15mm and outter radius of 20mm.
Step 9: Assemble the Rotor
Start by stacking one standard, unslotted disk on the rotor.
Continue the assembly by stacking:
2 paper disk spacers on the rotor shaft.
Then stack slotted disk #1
...2 paper disk spacers
...Slotted disk #2
...2 paper disk spacers
...Slotted disk #3
...2 paper disk spacers.
...Slotted disk #4
Finally, add 2 or more paper disk spacers so that when the disk retaining ring is screwed back on, it will compress the disks so that they won't be able to slide past each other.
Align the slots on the disk with a pencil before tightening the retaining ring.
Step 10: Put a Roof on It!
Cut the top blanking plate from one of the recycled disk drives to the size of your turbine assembly. Make a hole in the middle so that it alligns with the slots when mounted.
Tape the whole thing together using duct tape or whatever tape you have on hand
Step 11: Test It!
Remember that hole you drilled in the side near the beginning of this project? You have probably coverd it up with duct tape. Find the and cut the coverting tape away. Stick a drinking straw into it and blow! The turbine should turn. Slowly.
You will now probably want to hear this thing sing like a canary: Apply a 80PSI air stream to the turbine for 10 seconds for it get up to speed and then listen to the beautiful sound. This one goes up to 22,000 RPM.
Then hold it in your hand and feel Carioli's forces.
Since the disk drive motor is a permanent magnet DC motor, you can also generate a current from it.
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