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| kvom:
I have been working on the crankcase over the past few nights as time permitted. I'm sure John will make this a lot differently as he has 6 to do, but here's my effort. Since I had a precision 1" bore in the rotab chuck's soft jaws, I chucked a piece of 2" dia. aluminum rod in the lathe and turned down one end to 1" diameter. On the other end I turned down 1" in length to the required diameter of 1.65". I then bored the interior to .75" for a depth of 1". I don't have a good boring setup for the lathe as yet, so further boring will be done on the mill. Having previously dialed the rotab in to work on the cam housing, I was able to chuck the raw crankcase without further ado. I then used an endmill to enlarge the bore to just over 1". Since all of the holes to be drilled and tapped into the interior will cause burrs, I plan to bore to the final diameter of 1.25" after all the drilling is done. This will remove the burrs, which might be difficult to access otherwise. Next the mounting holes for the cam housing were drilled. With the crankcase still in the chuck, I tilted the rotab to the vertical position. Here's my method of squaring it to the mill table: The mounts for the cylinders were machined next. I used a .75" endmill that was actually only .725", so each flat needed two extra passes to attain the necessary width. I spot drilled the five holes needed in each flat, then drilled and reamed the center hole to .500". Next there were 20 mounting holes to be drilled with a #50 drill. I have two of them, but somehow I have lost or misplaced one of them. Since there are a lot of holes this size to be drilled I hope I find the spare. Given the angles of the mounting holes, I just tapped them 2-56 using the guide I had previously made to tap on the mill or lathe. It turned out to be very easy to tap aluminum with this setup. The weight of the chuck was enough to start the tap cutting, and the taps cut very well. Less than minute for each hole. Trial fit of some screws: Unchucked the crankcase and put it on the tapping stand to tap the 5 holes for mounting the cam housing. The next step will be to bore the interior to final dimension. I will hold off parting off the crankcase as long as possible. Maybe bogs can send me one of his cylinders for a test fit. :thumbup: |
| chuck foster:
very nice build :thumbup: :clap: i just didn't realize how small this engine was :bugeye: (well small to me) :) keep up the good work (and photos) i will be following this build very close :nrocks: chuck :wave: |
| sbwhart:
Good job :thumbup: Nicely done and shown, great work with the RT :thumbup: Have fun Stew |
| spuddevans:
Looking good there :thumbup: I'm enjoying watching this come together. Tim |
| Gerhard Olivier:
My mind is boggled Amazing :bow: :bow: :bow: Gerhard |
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