Build an Amazing Tesla CD Turbine

Step 7 Assemble The CD Disc Pack

The CD Disc Pack is the rotating part that is made of CD's. It spins inside the CD Case. There are several options for CD Disc Packs.

The easiest thing to do, is...nothing! That is, just stack the CD's on the spindle post without gluing or using magnets...about 10 CD's in this case. You can use more CD's if the CD Spindle is taller.

Disc Packs can also be built by simply gluing together discs with a few drops of Methyl Chloride (available at a plastics shop). Methyl Chloride is the solvent glue for CD Disc polycarbonate-type plastic. Put the glue on the raised ring, which you can feel near the centre of the CD, to bond each CD to the next. The glue sets fast. Try to keep the Discs centered on the Spindle as they are glued together. A couple of wraps of paper around the Spindle to take up clearance before gluing the discs might help keep the Disc Pack aligned best.

Let the glue set-up and get ready to assemble and test your Tesla CD Turbine!

Install the recently modified CD Case (with Cover and Nozzle) onto the CD Spindle and Disc Pack. Make sure the Disc Pack spins freely on the Spindle and in the CD Case. Hook up the water pressure supply, adjust the water pressure with the Shut-Off Valve, and the CD's should start to go around!

The speed of the CD Disc Pack is dependant on the water pressure, controlled by the garden hose shut-off valve. It should be able to go over 1200 rpm on garden-hose water pressure.

Welcome to the wonderful world of the Tesla CD Turbine!


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Comments

[skibum97]

My science fair partner and i are working on the tesla turbine and we were just gluing on the magnets with Methylene Chloride and we waited for a couple of hours but it still wasnt sticking, they came off when we tipped it up on edge.
How would you go about getting the magnets to stick?

[mrfixitrick]

There are a couple of ways to glue the magnets on.

I generally use a good quality grade of Crazy Glue. The magnets need to be cleaned with solvent and scuffed for best adhesion.

For the larger drive magnets I sometimes use Marine Goop in addition. For example, I put a 1/4 inch bead around the base of the 1/2 inch magnets to support them.

Goop pulls tighter when it sets up after a couple of days, and sticks really good to both surfaces.

Methylene Chloride works for gluing polycarbonate, but not for the nickel plating of the magnets ;)
Also, the polycarbonate CD discs are coated with a resin, making poly solvent less effective.

[______]

can you cut noches into the cd? to increase speed

[11vs11]

Ok that’s sweet I’m sorry that my questions are so sporadic, just that I’m flat out with study wish I’d gotten into engineering now L; (It is also interesting to me that am I correct in thinking that salt increases the boiling point of water therefore some kind of change in rpm should be expected, yes?) What I really want to know is how exactly would you convert the spin of this type of turbine, but let’s say bigger maybe a 50cm (radius), into energy for the ordinary grid or power battery? (Please don’t tell me magnets because there must be a better way and what would be more efficient for getting good psi from steam; concave mirrors or a focus lens?)

[mrfixitrick]

To convert the spin of a Tesla Turbine to power requires rotating magnetic fields of some sort. Magnets don't have to be used, but an alternator will need copper windings to produce a magnetic field. A 50 cm turbine with a few discs is capable of several hundred horsepower when going "full steam" as they say. It would have to be a big alternator for that, complete with a voltage stabilization system to put out 120 volts. I don't know if a mirror or a lens would be more efficient to generate steam. It would likely depend on the particulars of the materials used and the location. Someone mentioned using the heat stored in sand and low-temp fluids that boil at room temperatures.

[11vs11]

Ok that’s sweet I’m sorry that my questions are so sporadic, just that I’m flat out with study wish I’d gotten into engineering now :( (It is also interesting to me, am I correct in thinking that salt increases the boiling point of water therefore some kind of change in rpm should be expected, yes?) What I really want to know is how exactly would you convert the spin of this type of turbine, but let’s say bigger maybe a 50cm (radius), into energy for the ordinary grid or power battery? (Please don’t tell me magnets because there must be a better way and what would be more efficient for getting good psi from steam; concave mirrors or a focus lens?)

[11vs11]

Hi, am just wandering how would salient water would contribute to the spin seeing as EC is increased with increase in water salinity. I mean obviously it would mean the salt water would eventually eat through the glue but thats besides the point.

[mrfixitrick]

That's an interesting question. A greater viscosity or density will make a difference to the operation of the turbine.

The discs rotate due to the kinetic energy of the fluid, and the kinetic energy is 1/2 MV^{2. If the velocity was the same, but the mass was increased, it would give a corresponding increase in power, I would expect.}

Since the density of seawater is 1.025, there would be about a 2.5 percent increase in power with those assumptions.

I used marine "GOOP" glue, so that should not be a problem with salt water use!

[11vs11]

Are these the types of turbines that are employed in solar radiation harvesting? if not can they be and what would the conversion factor be between steam pressure and electricity output be?

[mrfixitrick]

Generally you will not find Tesla Turbines used for solar power, although they are a cheap and reliable form of turbine that is perfect for the application. However, there is an entire infrastructure devoted to the complex and expensive bladed type turbine already, so there has been no incentive for the testing and development of an upstart Tesla Turbine. I've made it my mission to change that, even if I have to start out building turbines with CD's to do it! hehe Tesla, almost exactly 100 years ago, had visions for the Tesla Turbine to be used for solar and geothermal applications. The Tesla Turbine can run on any fuel, or pressurized liquid, or compressed gas. Steam is one good source that Tesla experimented with extensively. Tesla often ran at 180 psi steam pressure. His smallest commercial turbine was 110 horsepower. There was some problems with disc stretch and warpage with the early materials. As far as efficiency, the Tesla Turbine varies wildly in the approximations of efficiency. It depends on the type of application, disc size, spacing and rotation speed, nozzle design and more. Generally the estimates range from 15% to 98% efficient (Tesla claimed could be as high as 98% ) 20 - 40 percent would be the norm. The generator or alternator attached to the turbine might give a 80 to 90 percent efficient conversion of the mechanical energy to electrical. So, by multiplying the above variables, we get a range of 12% to 88% efficient. Or more likely 16% to 36%, depending on the numbers. That's a big spread, but there are many variables for such an apparently simple turbine! It is the most complex turbine to model in a CFD flow analysis program.

[Tanners]

so for the pack were you glue em all together there wont be any space in between the discs right? so its pretty much just a cylinder?

[mrfixitrick]

There must be space between the discs; a cylinder won't work in the correct manner. In a Tesla turbine, the fluid must spiral inward through the discs, imparting it's energy to them, until it leaves through the centre exhaust. In the non-magnet disc pack, I did glue the discs together...but only after carefully grinding about 8 to 10 shallow grooves across the thin circular ridge that is close to the centre hole on each CD. Some CD's have this ridge on both sides of the CD, and they work better. The grooves allow the fluid to pass through to the centre hole of the disc and out through the drilled centre post of the turbine. I used methylene chloride as glue, which is the recommended solvent for polycarbonate, and made sure it didn't get in the grooves.

[Tanners]

yea so i just tried building it using penny's as spacers and used super glue to glue it all together and it worked pretty good.... for a while but the top disc broke off and then it all didn't work so I'm going to rebuild it this weekend because I'm building it for school and this project is due next Monday due you have any suggestions for what i could use as spacers that i might have lying around or could pick up at longs or homedepot or do u have a suggestion for a type of glue. i would use magnets but i don't have a lot of money and i don't have time for them to ship. thankyou

[mrfixitrick]

Are you sweating yet? hehe Dimes will work better than pennies, because they are thinner and lighter. (10x more expensive though!). Thin stainless washers are available at Home Depot, and would be better than pennies or dimes. 3/16 to 1/4 inch diameter could work ok. The gap-filling type super glue is best, or Marine Goop can be used but needs 1-2 days time to dry. Scratching the discs and spacers(pennies, washers) with some sandpaper beforehand makes the glue stick better. Some craft/hobby stores have 1/2 inch x 1/8 inch neodymium magnets that work ok for the top disc magnets for light applications. (4 magnets are about $5.)

[PKTraceur]

Actually, dimes are created using 5 cents if matreial, whereas nickels use 10 cents. Weird huh?

[mrfixitrick]

Yup, and we wonder why the economy is in trouble, hehe!

[astrozombies138]

I just got my magnets, wow their a bit smaller than i originally thought, so its ok if i dont glue the magnets on or anythingi just just put them on the cds? or should i glue them in place?

[mrfixitrick]

The magnets will stay on without glue if there are multiple layers of discs and the magnets are strong enough. But it can't be revved past about 800-1000 rpm. Sudden surges in water pressure or from a sudden stop of the magnetic coupler will dislodge the magnets as well. Glue-less is not a great solution except for limited testing, especially since the spindle cover requires a bunch of work to properly seal it with hot-glue. I use the thicker Crazy Glue, and scratch the magnets with medium grade sandpaper where they bond. Sometimes I use Marine Goop for bigger magnets and let it set a couple of days.

[astrozombies138]

awesome, im gonna be using a loctite marine epoxy, as soon as i get you approval for it to work, until then im just going to try some test runs without the glue. thanks for all the help so far too :D

[mrfixitrick]

That should work for you. Good luck & let me know.

[astrozombies138]

wooo, It's working great! Ill upload a video now.

[mrfixitrick]

Hey astrozombies138, that's terrific! Welcome to the small club of Tesla CD Turbine builders!

[Mr. Twist]

ooooohhhhh i hope to be part of that club to. I'm building mine right now but it won't be as good as any of for because 1. I have a very small amount of time 2. I dont have very many tools (my dad isn't much of a DIY guy) all i have is a leatherman knife and a glue gun but I hope it works out ok. I talked to you before asking you about it as a science fair project and the fairs coming up.

[mrfixitrick]

You can use the tip of the glue gun to pierce the CD case to mount the nozzle. Only the very tip of the nozzle should be inside the case, so it doesn't hit on the CD's. You will still need to cut part of it away, or use sandpaper. It's a little tricky and frustrating, but take your time and make sure the glue covers well, building up in layers.

I have one student, and he is now building a turbine for a science fair project. He will be featuring the reversing magnetic ball experiment...http://youtube.com/watch?v=HEY0jpsnwbg