Re: Whistle Notes

Whistles are just manufactured to length, but the design may have aimed at a particular chord. Most five chime whistles seem to have a very pleasing sound, but many six chime whistles have an edge to them. This may have been deliberate in order to get your attention, since six chime whistles were frequently found on passenger engines, which would have been moving at high speeds when approaching a crossing.

I've heard of individual engineers tuning their whistles by hammering wood blocks into the various chambers in order to shorten them and raise the pitch. I watched the fireman on a D&S charter change the whistle from sounding obnoxious to sounding really good, simply by rotating it on the bowl. My guess is the annular slot in the bowl wasn't uniform in width and the short chambers were over blowing when the slot under them was too wide.

The people at Horn and Whistle have all sorts of equations and they maintain that pressure has no effect on the note sounded, but then how to account for being able to quill the whistle? Boiler pressure clearly does seem to have an effect, as my IC steamboat whistle sounds great at Cass on 200 psi but sounds sort of flat on 150 psi on the sawmill boiler at Crossroads Village. Lower pressure steam is cooler and the speed of sound is affected by both temperature and density, so these variables may be playing into how a whistle sounds. Higher pressure seems to raise the tone, which also happens when the speed of sound increases at higher temperatures.

The cut up, which is the distance from the bowl to the lip of the bell also has an effect. Generally 2" is used on most five chime and six chime locomotive whistles, but the shorter Reading six chimes are set at about 1 1/2". The nice sounding Powell 3 chime at the Nevada Northern has had the lip cut away to raise the cut up on one of the chambers, but since it is a dome top whistle, I don't know which chamber was affected. The 3 chime Powell that Earl used to have on the C&TS and later on the #18 at Alamosa was reportedly off the Weyerhaeuser #120. It sounded great at all three locations, but did sound different as well, probably due to differences in boiler pressure.

Michael Allen