The Poppin
I built a flame licker engine before and was never able to get it to run. This will be an attempt at another design.
As always I start with what looks to be the toughest part to make. The plans call for the main frame to be milled as one piece. Since my lathe is broke down at the moment I decided to do it first.
I was able to get a piece of brass the right size that could be milled to the overall dimensions of the frame. (Thank You Larry) To save a little hammering on the mini mill I used a drill bit to drill most of the stock away. All of the critical holes were drilled and reamed before milling. That should keep the bearing bores and holes in line. After about 4 hours I ended up with this.
The ball bearings are 5/16" OD and 5/32" ID purchased from a local hobby shop. The 2-56 bolts that secure the bearings are from the same hobby shop.
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The new drive belt for the lathe still hasn't arrived so I decided to make the crankshaft next. It is a four piece fabrication.
The shaft sections are 5/32" I had 3/16" steel rod that I'd intended to turn them from, but with the lathe being down I found a couple of 5/32" welding rods that were exactly .156" Chip the flux off and you have ready made shafts. The 7/32" connections were milled from a piece of 1/4" key stock. The hole were drilled .002" undersize for a press fit and Locktite was used to keep them tight to the shaft. To keep everything straight and in line the main shaft is made one long piece. After the Locktite sets the center is cut away and polished flat to the connections.
It fits the bearing perfectly and turns freely.
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Next part made was the cylinder.
The cylinder was turned from 1" O.D. cast iron rod. One end was faced flat then center drilled to accept the live center in the lathe. That made the set up a little more rigid for turning the grooves in the O.D. The 15 grooves are .045" wide and .125" deep. The fins are .033" wide. It was then drilled 1/2" and parted off the rod allowing .030" on the back face for finishing. It was then chucked up in the lathe, finished to length and bored to .625" leaving the wall thickness .062" from the bore to the bottom of the O.D. grooves. Four holes were drilled and tapped 2-56 for the screws that secure it to the frame on one end and for the cylinder head on the other end.
The piston was also to be cast iron. It has a thin wall to make it lighter.
It was turned from the same piece of cast iron rod. A pretty straight forward piece. The O.D. was turned to .625" and I used a 1/2" end mill to drill the center out. A small boring bar finished the I.D. to give it a .040" wall thickness. The screw hole in the center was drilled and it was parted off the bar to it's finished length.
After a little polishing and lapping the piston has a very close but smooth sliding fit to the cylinder.
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The connecting rod is a rather complicated fabrication.
The rod end is made up of two little interlocking blocks of brass milled for a snug fit. They are held together with a close fitting 1.6MM screw. The rod was made from a section of 3/32 welding rod. One end was soldered into the rod end and the other end is drill 3/64" for the piston wrist pin. The piston yoke is made from 3/16" diameter brass, drilled and tapped on the outboard end for a short screw that will secure it to the piston. The opposite end is drilled 3/64" for the wrist pin, then slotted for clearance on the rod.
It went together without a problem. Mounted to the crankshaft, everything turns freely. It's starting to look like an engine.
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The flywheels are made up of two parts.
The flywheels were turned from 2"O.D. brass stock. The turning and drilling is pretty straight machining so I won't detail the work. Hubs are machined to fit the flywheel bore. They are threaded 5/16-24 on the inboard ends. A thin 5/16-24 nut will be made to tighten the hubs to the flywheels. The hubs are drilled and tapped for a 4-40 set screw that will hold them to the crankshaft.
If it never runs, at least it's going to be a pretty little engine.
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Next I tackled the cam.
It was made by drilling and reaming a 5/16" hole in the end of a piece of 1" cold roll steel, then parting it off .047" thick. The rest of the shaping was done on the bench grinder. The 1/16" thick cam washer was basic turning.
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I decided to take a shortcut with the flywheel nuts. Instead of making them I turned two 5/16-24 nuts down to 3/32 thick.
Seemed like a great idea but as the assembled picture shows, the nut is slightly bigger than the lower throw of the cam. It will still work but I'll have to take it back off and grind the high points off the nut so the cam roller won't hit them.
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Now for some small parts.
The valve rod is another two piece assembly. The cross shaft is 1/8" diameter turned on both ends for 2.5MM thread. A hole is drilled in the center of it and tapped 1.6MM to accept the rod. The rod is 1/16" diameter threaded 1.6MM on both ends. One end screws into the cross shaft and the other end will attach to the valve reed
It's a little difficult to see the threads on the rod, in fact I can't without my cheaters. By the way, if you ever need a 1/6" diameter shaft and have an old bicycle wheel laying around, the spokes just might be .059" The one I found in the back of the garage was.
The bushings that will support the valve rod in the frame were made from 3/16" brass rod.
They are turned for a light press fit into the frame and reamed 1/8" I.D. for a free running fit on the valve cross shaft. The second picture above shows all the valve rod parts fit into the frame.
Two more parts to the valve system are the roller and it's pivot.
They will be attached to one end of the rocker arm shown in the second picture. The other end of the arm will be attached to the cam side of the valve rod cross shaft.
The assembled rocker can be seen in the first picture above. The roller can be seen on the high lobe of the cam through the lower hole in the flywheel. The return spring is simply a piece of steel guitar string captured between two nuts on the other end of the cross shaft.
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Just two more parts to make.
With the completion of the cylinder head and valve reed it's finished.
The alcohol burner I had made for a previous attempt at a flame licker is a little too high for this model, so I had to set the engine up on a 1" board to get the flame to the correct level. After a little tinkering it RUNS!!
If you'd like to try this model you can download the plans here.
More to come