In "Shop Shed & Road" LBSC seems to use nothing bigger than 1/8" dia. for his whistles so 1/4" should be plenty.

Incidentally, he tells that he used his 5-pint blow-lamp as a compressed-air source for testing the notes.

You will not get the same results on air as on steam

Roy

I read somewhere that unnecessary whistling was strongly discouraged during the steam-age because it's so wasteful. How much steam does a whistle use? Does anyone have any figures for full-size or model locomotives?

More usefully perhaps, the diameter needed to achieve a given flow depends on length too – 10 metres of ⌀3mm pipe offers much more resistance than 0.1m of ⌀3mm, and heat loss from long pipes makes them even worse. In practice, driving a big whistle calls for largest shortest pipe that can be managed: a long small diameter pipe is likely to throttle the whistle. I vote for the biggest diameter that looks OK on the engine.

Dave

Whistles sound muck better on steam than on air.

SOD. " Does anyone have any figures for full-size or model locomotives? ". This is data from the Lunkenheimer catalogue published in 1912

From the table, for a 2" whistle with a 1/2" pipe fitting it requires 0.24 cu.ft of air per second at 40 psi to blow it. (An air compressor that can deliver 14 cfm. )

Paul