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| kvom:
Did a couple of small tasks on the engine: First I remade the crank pin a bit longer so that I could tighten the screw without binding the piston rods. There is really no reason that it can't be longer than the plan's dimension. I "discovered" that I had failed to machine the pocket in the head that I was test fitting the pushrods on. That meant that the rocker and its arms were .05" too high. Hopefully the next time I put it together things will fit better. As far as I can tell, I have everything set to try a test run the next time I get into the shop. |
| kvom:
I did the recommended tuning and adjustments as recommended by Liney for the first cylinder, and after some fiddling got a runner. Here's the evidence: http://www.youtube.com/watch?v=IvhgMdTBUYM To get enough flywheel weight I clamped my tapping station chuck onto the shaft. On the video, I started it at 40 PSI and gradually reduced the pressure to 20 PSI at which point it stops. With more cylinders and some run-in I expect it will run at a fairly low pressure. For other builders I will reiterate the setup process and some issues I encountered. My first "concern" was realizing that the pushrod holes in the cam housing are not centered on the cylinder. It seems that my setup on the rotab was a bit off. While the drawings from Liney show the pushrod for the inlet valve connected to the rear hole, I decided to reverse this to make the rods more upright. Since the cams are symmetric, this isn't a problem as long as all cylinders are set the same. The first adjustment is to set the crank pin/conrods relative to the cams. This is the sole timing adjustment and is needed only for the first cylinder. I slightly loosened the screw that holds the crank to the shaft and then turned the shaft until I felt the inlet cam contact the ball bearing that pushes the inlet rod. Holding the shaft steady, I pushed on the crankpin so that the piston was at TDC (i.e., you want the inlet valve to start to open at TDC). Now it's time to tighten the crank to the shaft; however, the conrod blocks access to the screw head, so I needed to slowly rotate the shaft and crankpin together until I could get to the screw with a small screwdriver. It's for this reason that you need some friction with the screw initially: loose enough to be able to adjust the crank pin but tight enough so that the pin turns with the shaft. Note that I set it up so that the engine turns CCW as seen from the front; to reverse this direction turn the crank pin 180 degrees relative to the cam. Next, the travel of the rocker arms needs to be adjusted. Connect air at low pressure and turn the shaft until the inlet valve is open. Then adjust the outlet rocker via the SHCS until air is coming out of the exhaust. Next back it off until no air is exhausting. The exhaust pushrod length is now set. Now you can lock the adjustment screw with a 2-56 jam nut. The small issue I had with this is that the screws supplied may not be long enough to protrude out the top of the rocker. For this reason, I plan to use longer screws on the other cylinders and cut off any excess once the jam nuts are in place. A 3/16" nut driver is an excellent tool for tightening these small nuts. The same procedure is followed for the other pushrod. Turn the crank so that the exhaust is open and adjust the inlet pushrod until air enters the inlet valve; then back off and lock the jam nut. |
| Bernd:
ALL RIGHT Kirk. :bugeye: :thumbup: :beer: :bow: :ddb: :nrocks: Lookin' good. Bernd |
| NickG:
Wow Kirk, looking very good. How far away are you from a run with all cylinders? It sounds fantastic even with just one! Nick |
| kvom:
My first 5-cylinder trial was not a success. :scratch: First I had to remake the skewed rocker arm, and the blank I had left over from the first batch was too thin. So I spent probably an hour making one from a bit of 1/4" thick aluminum. Note to self: finally buy a set of thin parallels. Once assembled, the last head seemed pretty leaky on the output valve, but I decided to hook it up anyway. Applied air up to 60 PSI without a runner. Then I noticed that the crank had become loosened from the shaft so that it wasn't turning. By then it was to late to pursue a readjustment. With all cylinders attached, there is a fair amount of force needed to turn the shaft by hand. |
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