My hopes are to design a turbine system that is made from off the shelf materials. This project will not be easy but a good challenge is always fun. So far, there are really no exotic parts on the GR-1 and I hope to be able to prove that this can be done on a reasonable budget. The only hitch on my project is that more and more of my design is influenced by the use of the mill and lathe. These tools are proving to be essential to building anything rotary and I feel that I will use them a lot more than I anticipated before.
       By putting the exhaust diverter (elbow piece) on a turntable, I was able to locate the center of the housing on the back side of the elbow. This location is where I cut out for the bearing tube heat shield using a hole saw. The hole saw must be parallel with the flange so as to allow for the angle of the heat shield to the elbow.

       I took a piece of 2” EMT and welded a 1/4” steel plate on one end. I made the steel plate fit great by turning it on the lathe and I also bored a 11/16” hole in the middle of it for the drive shaft. After I ground off the rough weld, I chucked it up on the lathe and turned the face flat to mate with the turbine wheel. The heat shield is now ready for installation but there is one more thing to do before I weld it into place.
       I wanted to make the internal flow of the gas with the least amount of back pressure as This will make the engine run cooler and not overheat the bearing. I made sheet metal shroud that diverts the flow of gas around the bearing tube heat shield. I tacked them into place and fit checked the tube in the hole. After some grinding and alignment, I welded the tube into place.

       The alignment of the tube was difficult as I had to check it to be centered and perpendicular to the flange side so the turbine wheel will mate correctly. There are many variables working against the success of this project so I am sure that there will be some trial and error to experience. I ground the tube flush with the back of the elbow to finish the piece.

This completed part awaits further development of the turbine wheel and gearbox.

       I am now ready to start building the stator section of the turbine. The stator will mount inside of the expansion duct and will be removable so that I can experiment with other designs. I started by making a cone shaped center for the stator section. For this I used 2” EMT and made a template for the cuts needed to bring the pipe to a point.

       After making the cuts, I welded them together to form the stator nose-cone. Using the flap-disk, I touched up the piece to prepare for the stator blades to be welded on.

       I temporarily mounted the nose-cone to the heat shield for a thermal test run on the engine. After bolting on the housing to the GR-1, I ran the engine for a few minutes to see if there was any warping of the housing. After getting stung by a angry wasp, I learned that the jet blast had evicted a nest of wasps under the eve of my house :0(
       I disassembled the housing and started planning my stator section. One of the handy tools I bought was a rotary table. The table allows me to index parts to be machined by giving me a rotary plane that can be set to any of the 360 degree adjustments on the table. This means that I can build a jig to weld on my turbine blades at given places around the turbine wheel. This will allow me to get greater accuracy on the placement of turbine blades.
       I cut down the nose-cone to the final length and drilled a hole on the tip. this will allow me to use the tail stock on the lathe for support when I turn the blades.

       After I prepared the nose-cone, I needed to make my stator blades. I used some 1-1/4” (you guessed it) EMT and cut it length wise in 90 degree segments. This gives me the approximate curve for this size stator. I used a belt sander to make the segment as square as possible and then used the band saw to cut 18 even pieces. The pieces were then measured and 12 were matched for the stator section.

       I then set up my rotary table on a jig I made for blade placement. This jig will allow me to weld on each blade at the same angle and attitude on the stator nose-cone/hub. To place the twelve blades on the stator I divided 360 degrees by 12 and every 30 degrees will be placed one blade. I needed to center the stator nose-cone/hub on the rotary table so the blades will be perfectly radial. I did this with a dial indicator and patience.

You can see how the turbine jig holds the blade in place while it is welded on the hub. After the blade is welded, the table is advanced to the next position by turning the degree wheel.

The turbine jig worked like a charm and will be used to make the turbine wheel itself.

       The next step is to mount the stator onto the lathe and trim the blades to fit into the stator collar that will hold the stator in the expansion duct.

       I made the stator collar out of a short piece of 4” EMT and notched it to fit into the expansion duct. I welded the seam and prepared it for the stator to be mounted into it.

       The trimmed stator fitted snugly into the stator collar and was welded into place. This section will be held into place with 1/4-20 bolts on either side of the expansion duct.

       The stator fit perfectly into the expansion duct and encouraged me to test the back pressure of the turbine. I cut a short piece of pipe to gap where the turbine wheel would go and bolted it to the bearing tube heat shield. I then bolted the housing together for a test run. I was pleasantly surprised to see that the turbine ran very cool and was easy to start. I ran the GR-1 to full throttle and did not notice any warping.
       I am very happy that my effort is going as planned and I am looking forward to getting some power out of my home-brew gas turbine. Next time I will introduce you to my choice for a gear reduction system and we will get into the meat and potatoes of this project!

Till next time,

Don Giandomenico

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