It looks very nice, George. I am looking forward to watching it run.
I had an out of town house guest here for the last week. He is a model engineer, but not normally into IC engines. He and I have worked on joint projects from time to time for many years and get together once or twice a year for a week of toy building. He does not do much machining, but is a wizard with a file and sheet metal. So, while he was here I machined parts for our current project for a few days and he became intrigued with TINY. He played with it for hours and I would occasionally make up a new part for it to try and he would install it and test run. This is a summary of some of the findings plus a little bit of things after he left.
I had been running on naphtha plus 5 percent WD40. We continued with this mix for the first day. On a whim, we mixed up regular gasoline with 5 percent WD40. The first thing noticed was that starting was much easier. Once fuel had filled the fuel line, one revolution with finger over the air intake to choke it and starting routinely became one twist of the hand starting knob. With With naphtha 4 to 5 twists were the norm. The needle valve also became less sensitive. On naphtha full rich to lean was a half turn. On gasoline it went to 3/4 turn. In addition the cylinder fin temperature dropped about 15 degrees. Fuel consumption dropped a little bit from about 7 minutes per ml on naphtha to 6 minutes on gasoline.
The biggest down side is the smell of gasoline, but the improvement in performance makes this OK for me.
Looking for further improvement on ease of adjustment, a series of mixer bodies was made up, identical except for the bore. I had been running with the 0.093 hole as specified by Arv. Tubes were tried with holes from 0.073 to 0.098. Performance was definitely degraded at each end of the range, with a slight improvement with 0.082 and 0.086 holes. I settled on a 0.082 hole. All these tests were run on gasoline. Before anyone decides that this is gospel truth for Tiny, keep in mind that I live at almost 6000 feet of elevation and mixers act different up here than at low elevations.
Early in our playing, we did a sustained wide open throttle test. It cooked the Viton o-ring in about 20 minutes. The cylinder fin temperature was reading about 165-170 degrees F as measured with an IR thermometer.
We repeated the test now that the cylinder fin temperatures were lower, about 150-155 deg F. It cooked the o-ring in about 20 minutes the same as before. The o-ring showed no sign of wear in either test, but became hard and would not seal. On low speed running the o-ring holds up fine.
That's about the point we were at when Jim packed up and hit the road for a 10 hour drive home. All told, we used about 30 ml of naphtha based fuel and 120 ml of gasoline based fuel through TINY. That's about 14 to 15 hours of running bringing the total at that time to about 45 hours running time on TINY. Except for the first 10 or so hours using a PTFE insulated plug, a Corian insulated plug has been used. Thanks to George for getting me to try it is this small a size. Still looks good and works well. I have pulled it a couple of times for inspection and other than cleaning off the oil and soot build up from running rich no maintenance has been needed on it. It was not needed then, but since it was out it was cleaned. I used a 0.020 gap most of the time, but increased it to 0.025 the last time I had it out.
The saga continues with what has been done since Jim left. That's for another post.
Gail in NM
