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- Jul 16, 2007
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Well it's not a model engine but it's part of a model engine. This is a 2 inch scale Pickering flyball governor that I just finished. I have been getting my engines ready for the NAMES show next week and while I was doing that I decided I needed a quick, simple project, by that I mean no camshafts and multiple valves etc. You get the idea. Many years ago at an antique engine show a fellow had this governor for sale. It was complete but one of the small iron pieces had a crack in it. I have always liked the looks of governors for their mechanical bits and pieces so with the price being right I bought it. While walking by it a month or so ago I thought "that would make a neat model" so I disassembled it, measured it and made a drawing of all the parts. I then scaled it down and figured out how to make a model out of it (shaft sizes, gear tooth shapes, set screw sizes etc.) I wanted to make it as a workable governor with a balanced valve as I have a small 1 inch on my Case engine that isn't balanced and it doesn't work like it should. After working out most of the obvious problems I started chopping away at brass, 12L and stainless. I wanted to copy the mounting setup for the flyballs so I set up my plan to attack this situation. The orginals were made in 2 pieces so I figured this would be the way to go. I first drilled the end of some .438 dia. brass, one end .062 dia and the other end was tapped 0-80. I then set up my ball turning attachment on my 6" Atlas lathe and made a little more than a hemisphere on each end of the stock. After this I put the stock in the mill and sliced off the hemisphere at the centerline. I then made up a holding fixture by turning a concave radius in the end of a piece of stock with a 0-80 tapped hole in the center. The threaded hemisphere was then mounted on a stud and screwed into the fixture bar. With a small endmill I put a .010 deep slot through the hemisphere. I started out with some .010 spring steel that I had but once bolted together with the ball halves found that it was way too rigid so I had to come up with something else for the springs. Having nothing thinner I came up with the idea of cutting some strips (.156 wide) out of some .006 feeler gauge stock. I used my Dremel with an abrasive disc to cut them out and then cleaned them up on my bench grinder. I ground the center hole with a small mounted stone. I reassemble the balls with the new stock and gave it the spring test. It seemed like it would work so I tightened down the 0-80 bolts and filed and polished them off flush with the balls. No turning back now! The next obstacle was how to mount the ends of the flat springs into the end discs. On the full sized governor they cast slots in the discs, located the springs and then filled the slot with lead. I used a similar approach. I cut the slots with a .062 endmill tilted at 4 degrees in both discs. I then made brass packing pieces to fit into the slots and then slowly filed one side until it would just fit tight enough to hold the flat spring in place. After everything was assembed and trued up I fluxed it up and put a small piece of soft solder at each slot and heated it up till the solder just sweated into place. All of the remaining parts were made, cleaned up and polished with 800 grit paper. Upon assembling I then found out that the .006 stock was still way too stiff, oh well! I have 2 options available, remake the balls, end discs and and some new springs out of ???? stock or grind the existing springs narrower, say to .125 wide, and give that a try. I learned many years ago that scaling parts and pieces down isn't just a matter of machining them, it's trying to make the physics part work. Right now I have an exact copy of a Pickering governor that the balls won't fly out on. Anyway enough of the chatter. I'm sure you would like to see some pictures so here goes.
gbritnell
gbritnell
