I didn't find any cam grinding in the issues that you mentioned, but did find one in issues 39, 40, and 41. There is also a very simplified cam "jig" in issue 6. The more complex cam grinder looks pretty capable, with its own grinding head.
Really, the "jig" setup should be more than adequate for anything except production. The jig consists of a hand-cranked rig with a master cam pattern and uses a regular 6" bench grinder.
Strictly IC serialized the creation of a 1/6 scale deHavilland Cirrus which I built a few years ago. This is an inline 4, requiring an 8-lobe tiny cam shaft perhaps 5" long. The author described a way to make the camshaft with an EXTREMELY simple cam jig using a slotted hand-wheel setup with a dowel pin to restrict the rotation of the handwheel through a predetermined arc. The entire assembly is placed in the mill beneath a regular mill cutter, and the lobes are roughed out by feeding slightly, then rotating the camshaft with the handwheel through the arc limited by the dowel pin. It looked crude as hell but I did it, and amazingly it worked fine! All that was required was a little hand smoothing at the end, and polishing of the cam.
The really "funny" part was after I had this pretty little camshaft, I was putting the engine together partially and checking the valve timing to be sure all was OK, and noticed that the cam was backwards, and would have caused the engine to run in reverse. I wrote the magazine pointing this out, and the response was "No way. But I'll forward your letter to the author". The author, Eric Whittle, confirmed my observation, and they posted a correction later. Yes I had to start over with the cam. I point this out because it is one additional way to make a camshaft, simple but functional. Get the deHavilland Cirrus 1/6 issues if you want to pursue it.
Don't let commercial cams for racing engines throw you. They expend big $$ on R&D to tweak the last Newton out of their engines. It is very easy to make a cam that will reliably run the engine if you are not after power. All you need is valve lift. Blend the peak with the flanks and the base circle, and your engine will run.
The one radial engine cam ring I've made was simple. 4340 steel round with two cam "peak" circles turned on the perimeter. Chucked in a R/T on the mill, and a keyway cutter is used to mill away the correct portions of the cam down to the base circle. The flanks are then blended with a dremel sanding drum to a roughly correct shape. The cam was heat treated to Rc 43. Like I said, not rocket science, get some valve lift at the correct points and the engine will run fine.
HTH |