The original project was made from closely spaced, cardboard discs centered on a threaded steel rod. The rotor assembly was suspended in a bathroom tissue role by a supporting assembly. The aviation grade bearings were housed in retaining assemblies. When a stream of air from an electric air pump was injected into the manifold, the stream spiraled inward between the discs toward exhaust ports surrounding each disc's center. The stream exited the turbine along the axis of rotation. Peak rotor speed was measured at 2,220 RPM. Note that the following instructable assumes that you have a fully functioning CTT that is ready for painting and customizing.
Anything attached to the rotor shaft could fly off suddenly if not properly secured. In addition, the sudden decompression of CO2 as the gas escapes from the cartridge produces extreme cold. Use heavy gloves when handling the cartridge.
Step 1: Items You Will Need
300 Grit Sandpaper
Ceramcoat All Purpose Sealer (http://www.deltacreative.com/pcid/86/Tips-Technique.aspx) or something similar
Hobby Paint Brush
Silver Marker Pen
Spray Paints: Black, Blue, Brass, Clear Enamel, Copper & Silver
Spray Paint Safety Mask
Popsicle Sticks to Use as Rotor Shims (4) - 1.5 mm thick
25g Threaded CO2 Cartridges w/Regulator (http://www.innovationsaz.com)
38 cm plastic zip ties (2)
Plastic Propeller & Mounting Hardware
Step 2: Disassemble & Prep Components
Prep all cardboard surfaces w/a coat of Ceramcoat. Sand w/300 grit when dry. Remember not to saturate the cardboard! Ceramcoat is water based and can seriously warp (and ruin!) your turbine as it dries.
Step 3: Spray Painting
Base - gun metal blue
Bearing Retainers, Manifold Straps & Support Assemblies - gloss metallic brass
Manifold & Plastic Spacers - gloss metallic copper
Rotors - high gloss black
Turbine Housing & End Seals - textured metallic silver
The rotors require special attention. According to the helpful folks at the Tesla Engine Builders Association website, turbines work better when the rotor discs are as smooth as possible (http://www.teslaengine.org/page/bi.html). Apply 3 coats of high gloss paint. Gently sand each coat w/300 or higher grit paper when dry. The paint manufacturer recommended a clear top coat to preserve the gloss finish; so I added 2 successive coats of clear enamel. I used a silver marker pen to ID proper orientation of each disc and facilitate rotor reassembly. BTW, one rotor was ruined when I applied too much Ceramcoat. I painted it before realizing the extent of the damage ...
Step 4: Reduce Rotor Gap
Step 5: Rotor Clearance & Alignment
Secure manifold to turbine housing w/zip ties (I held ties in place w/two plastic cable clamps bolted through the support bar as shown). Trim excess w/scissors. Make sure all components are thoroughly dry before moving to next step. If any components become paint stuck, it is nearly impossible to separate them (words of experience!).
Step 6: Reassemble Remaining Components
Step 7: Detailing
BTW, wording on the manifold reads: "CAUTION HIGH PRESSURE VENT." When your lettering is complete, apply a protective coat or two of clear enamel.
Step 8: Preliminary Test
Step 9: Results: CO2 Vs Air Pump
The maximum rotor speed of nearly 300 RPM when measured by a Digital Mini-Tach (http://www.towerhobbies.com) was disappointing. There just wasn't enough gas in the 25 g cartridge to drive the turbine. Compared to an electric air pump (PolyGroup, Model AP-01; no pressure specs) which spooled up the turbine to over 2,000 RPM in seconds, a CO2 powered CTT is unusual but unimpressive.