ktmrfs wrote:
monkey44 wrote:
When I read these 'loudness' threads it reminds me of a generator I bought used from my local dealer once - used it for building homes when no power was available at the site.
It fired up off a battery (with jumpers), and ran at 1800 rpm, then you put a load on it, and it still ran at 1800 rpm and carried all the load of saws, compressor, etc on my jobs. It was VERY QUIET although I never measured it.
At the time, numerous Honda and Yamaha generator were advertised at 1800 rpm at idle, but even if you put a light bulb on it, let alone a saw load, it jumped to 3600 rpm and was very loud.
Brand name Kohler. The dealer told me it was out of a Motor Home ... It was pretty large and heavy (But I could pick it up and put in my PU), but ran on gas or propane, and put out 110v and 220v - so I imagine that was some of its weight and size.
Where am I going with this - AM curious why a mfgr can't build a quiet, idle constant 1800 rpm generator today. This one I had was used and in 1980s ... Am sure technology has improved significantly since then, with electronics and methods to create the power needed. Ran on a carb, not FI.
I'm not sure how the rpm factors into power production, I know we could run all our equipment at once (all with motors - table saw and compressor for example were half-horse each) and it never did anything but idle along quietly at 1800 rpm.
they can and some do. However, it isn't "free" HP= torque x rpm so in general it will take a bigger engine to develop the same HP at 1800rpm as one running at 3600rpm. And it takes roughly 1HP/500 watt of output power. 1HP=750 watts, but then there is conversion efficiency.
so, it's a tradeoff of engine size, weight and cost vs. longevity, noise, etc.
I suppose one could add in the ergonomics of the situation, who wants to pack a 200 lb. generator? The open frame generator (Kohler) that was mentioned probably had enough copper and HP in it so there was ample power available. Hence, no RPM increase and sound didn't rise. I have an open frame generator (have used many) and not one can I say was "quiet". The one I have now is miserable with noise but will power my house or a job site.