Tesla Waterpump/turbine- My first project. (Was fingertreadle engine)

[Blogwitch]

Orjan,

If you have an old hard drive, I reckon the plattens out of it would be perfect for your discs and if you are careful, they will be super highly polished, saving you a job. If you can get the bearings out as well, they might be good for use as well.


Bogs

 

[Orjan72]

Like that turbine tho, keep thinking to build one myself, might just be within my skill zone.

Robert

If I can do it, everyone can :big:
Get going,
Orjan

 

[Orjan72]

Orjan,

If you have an old hard drive, I reckon the plattens out of it would be perfect for your discs and if you are careful, they will be super highly polished, saving you a job. If you can get the bearings out as well, they might be good for use as well.


Bogs

Good thinking, I havent got any old drives laying about, but I think I know where to get some.
Doesen't hurt to have a look. Will scounge around, I might get lucky. If i get ready polished discs out of it It would be great.

Thanks for the tip!
Orjan

 

[Cheshire Steve]

I have a stack of hard drive disks here, with thoughts about a Tesla turbine in mind for the distant future. They look like chrome plated, but I suppose the finish must be a magnetic oxide, and who knows what underneath. OK if air is your driving medium. The bearings aren't really accessible being built into a central motor/bearing units. There are a couple of wicked magnets in each drive too.

One things about the Teslas is they tend to spin very fast which can be a test for the materials and bearings, and I assume is a function of the inlet air flow, which will be limited by the speed of sound if the pressure is above about 25psi. By my calculations this would mean 70,000rpm for a 3.5" turbine, which could burst it. Certainly I have heard concerns about overspeed if the load comes off suddenly. I was wondering if you could use an induced air bleed to (sort of venturi effect) at the inlet to bulk up the air flow but slow the speed, so that you get rid of the overspeed potential. You would still have the same air momentum, but shared with a larger air volume, so I would think you could get as much work out of it. Maybe someone here can tell me if it is a daft idea..

Steve

 

[Orjan72]

Hi Steve,
Not sure if I follow, but if I do (that would be a first...) ;D ,
Enlarging the input, or making an enlarged cavity with a venturi after it would possibly give you the opposite effect. My rationale:
The cavity would get pressurized and the venturi would speed up the airflow. The cavity would be pressurized at the running pressure of the incoming air and as long as the air is replenished there would be almost no lag in the pressure when load was taken off the turbine.
However if the venturi has a smaller diameter then the inlet (nozzle into housing) it would speed up the air. If the cavity was made as a wide nozzle it would reduce the chance of overspeed by reducing the general performance capasity of the turbine.

A flywheel would reduce the capacity for quick changes in rpm, but would result in higher inertia and possibly reduced overall performance. Maybe a seperate airchamber, sealed from the airflow, with a radial fan that maxed out at the required top speed?
The fan would probably run into max long before you would want the turbine too....

Keep in mind that I don't really know what I'm talking about and that this is just my take on it.

Orjan

 

[Stan]

One other comment about the strange action of the Tesla power turbine. When it is winding up and running it sounds like a jet fighter on take off. The instant the air is shut off, it goes completely silent, unlike a normal turbine which continues to scream as it winds down.

 

[Cheshire Steve]

That's interesting - I haven't had a chance to listen to one. I suppose it is the exit apertures that tend to make the sound. They could even act as a siren if you set them up right. I had never considered they might be noisy.

I have seen more than one safety warning on these beasties due to the extremely high speed they are capable of, and seen some rather questionable equations for the speed at which rotors fly apart. So there is a safety issue, and you need a substantial reduction gear before you let it drive anything outside the box that will fly apart at high revs.

As I think the action is mainly driven by momentum rather than pressure, I still hold that using some sort of eductor nozzle to entrain extra air might deliver similar power (momentum is conserved) but limit the top speed (velocity of the air hitting the rotors is reduced). One day I might get around to building one to test this.

Steve

 

[Orjan72]

Well, the QCTP finally arrived. It was the wrong one. Exactly the same as the one I had.
Its all a bit frustrating as I have been waiting for it for around 2,5 months.
The dealer has offered to help out (read fix his boo boo) by machining my topslide to fit the QCTP. This means reducing the spigot on the topslide from 26mm to 20mm. Not a lot, and I see many who customize their lathes in all sorts of ways. Its just that it doesn't feel right to modify the lathe to fit the wrong part... I guess I'll go along with it and make a shim for the spigot so I can use the original toolpost as well.
He offered a compensation of some sort, I'll see what he has to offer in terms of tooling and such.

Sorry for the holdup on the build, but I cant progress with the current toolpost. It just doesent work with the tools mounted too high.
OK, enough of my ranting.
All the best for now.

Orjan