On 3/4/2021 5:00 PM, Martin Gregorie wrote:
On Thu, 04 Mar 2021 14:27:53 -0700, Dan Marotta wrote:

9,000 RPM makes quite a racket, no matter the muffler. Have a good
noise canceling headset...

Yeah, I know - the engine I took weight and power numbers was a 20cc RC
aircraft engine, while I was iriginally thinking of thre 20cc petrol
engines you used to see on small chainsaws and big drills.

But, add a bit of weight and bulk for water cooling and put it in a sound-
absorbing box with the motor/generator combo sat on rubber mounts and I
think you cound reduce the sound level quite a lot.

But, the main poing of my piece was to show just how light and relatively
fuel efficient such a small generator set would be compared with an
battery of equivalent capacity.

A litre of gas or diesel fuel weighs 800g and has an energy capacity of
9.7 kWh.

Totally OTT: As an ex-free flight model flyer, I think the finest engine
sound I've ever heard was a 1cc Cyclon-06 glow motor with an open exhaust
spinning a 7" x 4" prop at 30,500 rpm on 25% nitro fuel mix.



I'd prefer a quiet engine, like the ones on small Honda generators.
Presumably 4-stroke, so a bit heavier, but very efficient (for a small ICE).

I'll leave it to the IGC folks to tear their hair out on how to deal
with the engine noise no longer being an indicator of (simultaneous)
propulsion.

Perhaps for a "sustainer" model you could run the engine only when you
decide you need propulsion, and have an engine large enough to supply as
much power to the batteries as the electric motor is using, or a bit more.