Building a continues duty 18 watt generator

[Andy-7300]

I have an old Ryobi 4cycle(Aprox 20-30 CC) string trimmer engine I would like to direct drive to a generator like this http://www.windstreampower.com/443540_PMDCG.php to run at about 2000 rpm. Because the engine is designed to operate at 6-8,000 RPM I would have to put on a larger flywheel. The big unknown is because this engine is designed to run at such higher speeds would it last very long running like this ?

[harryn]

Most commerical long life engines are designed to run with piston speeds in the 10 - 30 meters per second velocity range. I am pretty sure your engine is way past that. Still, might last a while.

Have you estimated your fuel consumption ? I was pretty surprised when I ran the numbers for commerical gas and diesel engine driven generators in the 5 - 50 hp range. The bottom line, believe it or not, is that fuel costs dominate everything, and the engine costs after 2 - months are not significant.

It is useful to keep in mind that the really large generators used by the power companies are 2X + the efficiency of consumer engines.