I have been working in my home shop (with help from a local sheet metal company and a friend that owns a good mill) to build a working disc turbine of approximate disc diameter 3-3/4" (95mm). Each disc has 4 each, 1/8" (3.2mm) ports near the hub for exhaust. There are about twenty discs en gang on the hub/shaft. The turbine case is 1/2" wall steel tubing, with a flat milled coaxial on the outside diameter for the fluid (air, water, and/or steam) nozzle. The nozzle itself consists of a 1/16" (1.5mm) slit cut through the casing on the flat using a ceramic cut-off wheel, as it enters the casing more or less on a tangent to the inside diameter. Nozzle block consists of 0.5" (12.7 mm) square stock with a slit cut the same width and length as the casing slit, cross drilled to allow fluid inlet.
End plates consisting of a steel band around a locked aluminum plate disc, with cutaway for exhaust directly to final end plate exhaust port turned from hard steel plate. The turbine assembled rests upon a poplar wood base, has aluminum flats for support legs (angled), and has outboard bearings that are basically "high end skateboard" bearings of 0.200" I.D. bearing race (shaft is sleeved to fit). The bearings are silicon nitride, and do not require lubrication, and are the self-aligning type, thus alignment is snap simple, even I could do it, with next to nothing for tools.
I used a Taig lathe, and cheap small drill press (Harbor Freight) for most of my tool work, but it is definitely a leap to turn some steel as large as the casing on that mini-lathe. I had to install reversible jaws on the lathe chuck. Due to the inability to lower rotation speed sufficiently for the size of steel, I was getting really proficient at burning up good cutting tools, including tungsten carbide ones. The way I slid past this, was to make "dusting" cuts only each pass, then let the thing rest a while and cool down. Finally I had the ID "bored out to specs", and then honed using a brake cylinder hone from local auto parts store.
One of the largest problems was getting threads of various sizes tapped, until I quit buying Chinese steel, and starting buying American, or Japanese, (although I have learned that in some circles German drills are best, and Swiss steel for taps and dies is Gans Uber. I am happy with results with American and Japanese stuff. Not so much the Chinese, where the kit I had virtually none of the taps work, and none of the dies were worth the weight of the steel. They seem to have been made to slow people down, rather than help them make progress. If this what the poor Chinese people have to work with, they have my sympathy.
Last night, at 20:45 CDT, in Lubbock, Texas, in my home work shop, I spun up the turbine for the first time, beginning with compressor off and empty tank (a smallish Husky brand compressor suitable for nail guns). Steady state air flow was between 10-20 psig showing on output gauge. Rotation started (only one bearing had been even close to aligned, and neither were optimized by starting torque measurement plots), almost immediately with air flow, and at ~20 psig, the speed was probably 1000-2000 rpm (no tachometer at hand, but have immediate plan to remedy this).
After allowing compressor to cycle up and top off at ~100 psig, when air was applied, the turbine must have reached speeds upwards of 20,000 rpm based on an extremely faint high pitch. With compressor switched off, the turbine is smooth and quiet as can be, mostly just an air flow hiss consistent with 1/4" supply tubing. At full speed at top pressure, the output torque was enough to instantly burn my finger tips as dynamic brakes.
I think I can come up with a better frictional dummy load than my fingers, sorry for the safety "violation". Maybe a speed reducing coupling to a water paddle mechanical equivalent of heat will act as dynamo-meter? Who knows?
Plans are to use an out-runner motor from RC plane/copter as a generator, due to its high speed abilities. I still have yet to build various burner heads, steam generators, disc turbine compressor (for Brayton cycle tests), etc. for this turbine.
Turbine Model: Stewart Disc Turbine (a Tesla form Turbine) Mark I (prototype)
Turbine Serial Number: 015 006 17-1 (not yet stamped)
There will be more to follow, including hopefully a You Tube video, and various build pics. I know I may be somewhat premature to start crowing, but I am sort of proud of my accomplishment thus far, although as do we all I stand upon the shoulders of industrial giants, many backyard tinkerers that are far more clever than me, and my own uncle William (WWII, US Army) who tried his best to teach me heavy machinery work,(his lathe and mills were about big barn sized stuff), my Brother-in-law, Leon the welder (he welded some platform stuff in the North Sea off Scotland and Norway.) who mainly tried to teach me some common sense, and my Dad, Charlie (Stewart), who was in the US Navy between WWI and WWII on a light cruiser, although the big guns on her were still 8", as best as I can recall from the stories of maneuvers.
Small Disc Turbine Build
Re: Small disc turbine build
