The Craftmans Shop > Model Engineering

Side Valve i.c. engine from Bar stock

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Brian Rupnow:
And in case you are a bit confused about how this valve business goes together, here is a cross section thru the valves, cages, tappets, cams, etcetera.

Brian Rupnow:
Oh Heck--While I'm setting here waiting for a call back about gasket material, I may as well put up a drawing of the valve keeper.

Brian Rupnow:
We have valves and valve keepers!!! I had to order some gasket material and some extreme high temperature sealant and it won't be in until tomorrow, so in the interest of keeping things moving, I machined the valves and the keepers today. The valve on the right is open .080" which is the rise on the cam shaft, and the valve on the left is completely closed. Unlike an automobile engine, these valves set up a bit from the flat surface, even when they are closed.
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Brian Rupnow:
If you guys remember back to when I made the crankshaft, there is a .563" diameter spacer ring on the back side of the web on each half of the crankshaft. This web is in there to maintain some clearance between the revolving crank web and the inside of the crankcase, as well as to locate the crankshaft so it doesn't float back and forth in the crankcase as the engine is running, making a clatter. Due to accumulated tolerances when machining, the thickness of this spacer ring invariably ends up either too thick or too thin. I have made it a separate piece Loctited into place on the crankshaft and here is why. Since my crankshaft is a two piece and comes apart in the center, I can make up this "setting master" fixture, insert the large end into the cylinder, and let the small end hang down into the crankcase and put the crankshaft "throw" through the 3/8" reamed hole. The small end at 0.531" is exactly the width I want between the webs of the crankshafts. Then a bit of careful measuring done by sliding each end of the crankshaft to its extreme travel in both directions should let me know exactly how thick these spacer rings should be made.

Brian Rupnow:
Here is a picture of the Setting Tool in place. The cylinder fits over it and locates into the counterbore in top of the crankcase. I have made it and installed it and the results are about what I expected. Although the design calls for a 1/16" thick spacer on each side of the crankshaft to prevent endplay, in reality there is virtually no endplay in the driving side of the crankshaft, but it is still free to rotate. The other end of the crankshaft, the "follower" end will require a 1/32" spacer. Why the big difference from the design.--Well, mainly because of "stack up" of tolerances. There are a lot of pieces fitting together to give this theoretical 1/16" spacer on each side. Although I could have held all of my tolerances much closer when machining the parts, I doubt that I could ever had everything come out as a perfect match for the drawing. The 0.531" wide setting master will allow for a 1/2" wide connecting rod and a 1/64" brass or teflon spacer on each side of it between the webs.

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