Pennsylvania Trolley Museum has acquired a 1953 GE 25 tonner that will eventually become our broad gauge shop switcher and rescue loco. We'd like to equip it with a Hancock 4700N whistle--the type popular on the NH, Clinchfield, and a few others. I'm told they are very scarce and thus we're unlikely to find one for sale. OK, let's try the alternate: Make one ourselves. Does anyone have the drawing for this device? Or does anyone have one they'd be willing to loan to PTM to be (carefully) dismantled for production of a drawing? We'd then make the drawing available to anyone who wanted it. It's the sound that counts most to us, owning the real thing isn't that important.

An awful lot of the trouble has already been done on your behalf by whistle and horn hobbyists. No need to reinvent the wheel.

Check out the Yahoo Groups "Steam-Whistles"
http://groups.yahoo.com/group/steam-whistles/

and "Horn and Whistle":
http://groups.yahoo.com/group/Horn_Whistle/

The former group is largely concerned with restoration, engineering, replication, and sound physics, while the latter is a bit more geared toward both horn mechanics/dynamics and collecting. The former's file archives are loaded to the gills with engineering spreadsheets, designs, etc.

The odds are better than 50-50 that someone has already undertaken attempts to replicate the Hancock 4700, with or without reflector. The odds are about 100% that members of both groups will point out everything Hancock did wrong with that air whistle design and offer you a vastly improved design with better efficiency, better dynamic and audio qualities, and easier construction.