I need a cheap APU


Why is it that they can make a car engine so quiet you can barely tell it's running, but they can't make a quiet generator?

I'm sure you can gear up a 4 cylinder car engine to spin an 8000 watt generator (requires about 10-13 hp) under full load while the car engine is just a hair above idle. It would be quiet and probably use less gas than you'd think. It would be too heavy for a truck APU but for providing power at a hunting cabin type of thing it would be almost perfect.
 
Why is it that they can make a car engine so quiet you can barely tell it's running, but they can't make a quiet generator?

I'm sure you can gear up a 4 cylinder car engine to spin an 8000 watt generator (requires about 10-13 hp) under full load while the car engine is just a hair above idle. It would be quiet and probably use less gas than you'd think. It would be too heavy for a truck APU but for providing power at a hunting cabin type of thing it would be almost perfect.

You could with no problem at all and yes, it would be very quiet. I'm sure people have done it. If your near a stream and on a hill you can power it with the strip mining approach. Doesn't even have to be a steep hill. My science teacher in high school did it. He stuck maybe an 8" pipe up stream then down to 6" then 4" then into a concrete box that he made with a squirrel cage inside. He used it mostly during the winter to power an oven heating element inside his forced hot air furnace.
 
You could with no problem at all and yes, it would be very quiet. I'm sure people have done it.
Only problem I can think of is that you'd need some kind of a clutch, or a belt drive that can be removed easily so you can rev up the engine every now & then to blow out the carbon. If the drive ratio is set up to spin the generator head at 3600 RPM when the engine is at 900 or so, the generator head would probably fly apart if you open the throttle on the engine. Mechanically, ... I won't even mention what would happen electrically if it was under load when you did that.
 
You can use the clutch off an AC system to drive and disable the generator. The clutch comes in 2 parts. The electromagnet inside which does not turn and the actual pulley that drives the compressor or generator. When 12 volts is applied to the electromagnet it engages the compressor or generator.
 

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