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I was visiting with one of my loyal fans this evening, and we were discussing the differences between two-stroke and four-stroke engines. I really didn't (and don't) have a fast explanation as to why they're different.
So I did some googling to find a web page with an explanation of the differences. I found a couple that were adiquate, but not very illustrative. Then I ran across keveney.com. Mr. Keveney has a site that has wonderful animations of different types of engines. I like the site even more because the html is simple and the animations are animated gif files, not flash or some other dumb thing. Here is their illustrations of a two-stroke engine and a four-stroke engine.
The explanation at the bottom of the two-stroke page mentions that they are have more power per weight of engine then four-stroke engines, but they pollute more. Another difference between the two is that in the four-stroke engine, the fuel-air and combustion all takes place at the top part of the piston. The bottom of the piston (where the crankshaft lives) has lots of oil in it, so it can be very effectively lubricated. The bottom of the piston in a two-stroke engine also is used to push the fuel and air around, so there's no dedicated oil bath. You have to mix oil with the gas so that the crankshaft gets some lubrication. This arrangement means that two-stroke engines wear much faster than four-stroke, and must be overhauled much more often.
It was also pointed out to me this evening that comments are set to only be registered users. I hadn't realized that meant that people had to register with blogger and have a blog to comment, which wasn't at all my intention. So comments are opened up now. I've heard of popular blogs being spammed in their comments; I guess I'll cross that bridge when I come to it.
Have a good weekend...