Friday, April 18, 2014


Time to add a new engine to the collection, and this one is a Non Compression gas engine. As I understand it was a concept being experimented with 100 or so years ago. The engines run on 2 cycle. A fuel charge is drawn in for part of a stroke, then the spark plug fires, igniting the fuel and driving the piston the rest of the stroke. The return stroke of the piston is exhaust, and the cycle starts over again.
The engines start and run fairly well, but simply do not develop any amount of usable power. That is why you never see anything but a replica model of one now days.
As with most any engine, a cylinder, crank, and flywheels, etc. were needed, and to expedite the job I poured castings, using some other castings that I had on hand a foundry patterns. Extras were poured in case there were defects I would not have to do it all over again. There were a couple minor defects, but I was easily able to pick out a set of good castings and proceed. (In a pinch I could have used all of them)
Machining proceeded, the engine was fitted with a cast iron sleeve in the cylinder and ball bearings for the crankshaft
The piston and piston ring were machined out of a hunk of automobile cam shaft. That is a high quality cast iron.
I elected to make a roller cam follower to operate the exhaust valve. Those 1/32" diameter cotter pins used to hold the pivot pins were a little delicate, but that is all part of the hobby.
The cylinder head was machined out of 416 stainless steel, and it is fitted with one of my homemade spark plugs. The valves look very much like automotive valves, but heads are only slightly larger than 1/4".      The intake is atmospherically aspirated, similar to most any old single cylinder engine.

Finally on April 15th it was ready for testing to see if it would run. Here is the video. Take a look for yourself.
During the initial testing the engine was running on propane using the demand regulator that I built last year. It will also run on gasoline using a vapor carburetor. And the ignition buzz coil is also one shown in a previous posting.