jim's poppin engine video!!!!!

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mklotz:
I've built both Poppin and that engine...

My Poppin is a much better runner. To get the Duclos engine to run, I have to preheat the cylinder quite a bit and then apply some heavyish oil to the piston to enhance the seal.

However, once started, the thing runs like a banshee - so fast, in fact, that I have difficulty understanding how the hot gas can quench as fast as it apparently does.

Keep at it. The design is solid but the engine is tempermental at best.

madjackghengis:
Hi Marv, thanks for chiming in on this, I appreciate it. I've been studying my non-runner, and the design in the magazine, and I think I've found the original problem. I didn't have or use a milling machine for the cam, but set the blank off in a four jaw, expecting it to come out the same. I could tell right away from the looks of my cam, and that in the picture things didn't turn out the same. It took a couple of hours, but I figured out I'd have to offset the blank a whole lot different to get the same cam configuration. In the end, my timing is off on both opening and closing. I have to either use the rotary table as is shown, or calculate the offset from the figures given.
I can see by the looks of your engine, it's a runner, and I think I've got the knowledge I need to make mine run, but you're statement regarding "poppin'" has me set on building it, even if I get this one running. Too many engines, not enough time. Thanks for showing that one of these will run, Phil did say his was turning about three thousand rpm when up to speed. Funny you should have to use oil to seal the piston when he cautions against getting any oil in at all, on account of getting the piston gummy. I reckon I can get this cam thing straightened out this afternoon, after everything else is done. Again, thanks much for showing your engine, it adds some confidence after a lot of years spent staring at the thing. :lol: mad jack

madjackghengis:
At the risk of taking over Jim's log, I think I found the problem with my flame sucker! After studying the build in the magazine, and studying all my parts laid out on the bench, I found my cam just doesn't have the same profile as the one in the plans. I used a different method of generating it, as I didn't have a mill at the time, so I used a four jaw chuck, and used Mr. Duclos' figures for my offset. I did it again, and came out with the same shape and form of cam profile, the wrong one. There is a difference between milling the cam on a rotary table after offsetting it, and offsetting it in a four jaw chuck and turning it, with the four jaw chuck you have to use the diameter of the cut for the offset, rather than the radius, so I set up the four jaw with a fresh piece of aluminum, and did it again, using new numbers this time.

Note the substantial difference in the cam curves from the old on the left, to the new on the right. I think I will finally get this old project actually running, once that cam and crank are finished and put in place. If so, I will finally get the only engine I ever didn't get running, operational and finally close that book after giving it to some worthy soul I hardly see, so I won't be haunted by it any more. :lol: mad jack

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