Tesla Turbine - Part 4

Photos and drawings by Author

Nozzle

Start with a 4" to 4.5" length of 0.500" diameter brass rod. Mill a flat on one end, which will be used to align the nozzle for a couple of operations. Clamp the rod upright (using the flat) in the mill and line it up with a square (Photo 99). Center it up under the spindle as shown in Photo 100. Drill the two 0.109" holes to a depth of at least 1.5" (Photo 101).

Now we'll set things up to cut the 3.563" radius curve. First, locate the edge of the vise with an edge finder (Photo 102). Move the table left by 3.463" (accounting for half of the 0.200" diameter of the edge finder). This places the center of the spindle 3.563" away from the edge of the vise. Install a boring tool in the mill, and insert a boring bar sideways as seen in Photo 103. Adjust the boring tool until the cutting edge just makes contact with the edge of the vise. Tighten the boring tool, now properly set to cut a 3.563" radius. Please note that, in order for the boring tool to cut, the mill must be run in reverse. This was the only way I could get this boring tool to cut a 3.563" radius.

Next, clamp the nozzle in the vise, using the flat on one end for alignment. Clamp it so the 0.109" holes are aligned as shown in Photo 104. Use an edge finder and align the center of the spindle to the end of the nozzle. Clamp the mill table in the X-axis so it cannot move left or right. Put the previously set up boring tool in the mill. Move the table out so the cutting edge, when rotated by hand, just makes contact with the edge of the nozzle. Start the mill (remember, in reverse!) and take a series of small cuts, moving the table out by 0.05" or so each time, until you've moved out a total of 0.313". The last cut is shown in Photo 105. The curve in the nozzle should now match the curve in the inside of the runner casing.

Switch to the lathe. Cut the nozzle down to the final length of 3.500". Center drill and drill a 0.344" diameter hole to a depth of 2.188", as measured from where the tip of the drill first makes contact with the face of the nozzle (Photo 106). Turn down 0.375" of the end to a diameter of 0.375" (Photo 107).

Check the nozzle for fit in the runner casing. The curve on the nozzle should match the inside curve of the casing (Photo 108). Clamp the casing in the mill vise. With the nozzle in place, locate and drill the No. 43 hole through the casing and nozzle (Photo 109). Use a 0.250" end mill to cut a flat in the casing (Photo 110). Remove the nozzle, then drill out the hole in the casing to 0.125". Tap the hole in the nozzle 4-40.

Assembly

Now, we finally get to put some of the pieces together. The bearing frame should already be together at this point, having mounted the tachometer sensor block and wheel. Bolt the runner casing on the bearing frame using 3/8-16 bolts. The disk and hub assembly can now be screwed onto the end of the shaft. Mount the nozzle in place with a 4-40 screw using the hole drilled previously. An end view of the assembly is shown in Photo 111.

Runner Cover Plate

This part is made in a similar fashion to the runner disks. Resurrect the old disk tooling, now somewhat the worse for wear (Photo 112). Drill a 1.000" hole in a piece of 0.125" brass sheet 8.5" x 8.5" (I purchased it cut to this size, like the runner disk material). Photo 113 shows this operation. Center the spindle over the rotary table. Clamp up the disk tooling as it was used for the runner disks and place the brass sheet over the 1.000" center (Photo 114). Remove the brass sheet. Move the table left by 1.000", then turn the table until the spindle lines up with one of the 8-32 tapped holes already in place (Photo 115). Place the brass sheet on again, and drill a No. 19 hole (Photo 116). The hole in the sheet should now match up to the 8-32 hole underneath. Bolt the brass sheet down. Drill two more No. 19 holes, spaced 120° apart, and bolt these holes down as well. Move the table left an additional 2.781". The spindle will now be a total of 3.781" from the center. Drill six No. 19 holes spaced 60° apart (Photo 117). As with the runner disks, cut the cover plate roughly round while still on the rotary table. Leave the diameter greater than 8.000" (Photo 118). Using a center in the lathe and the faceplate, attach the disk tooling as shown in Photo 119. Attach the cover plate and turn the outside to the final diameter of 8.000" (Photo 120). Remove the cover plate from the lathe. Take the runner casing and bolt it to the faceplate and center it up (Photo 121). Now bolt the cover plate to the runner casing (Photo 122) and bore the central 2.750" diameter hole (Photo 123).

Next time, we will conclude the project.