Steam era Hancock was well known to the railroads during the days of
steam. The company produced many appliances, one of which was the popular long-bell three-chime
steam whistle. When railroads began
dieselizing, Hancock, along with other manufacturers of railroad equipment, adjusted their offerings in order to remain competitive. And so Hancock modified their whistle design so they could be used on diesel locomotives.
Diesel era Hancock already had vast experience with steam whistles, and practically none with air horns. Also, diesel locomotives were an emerging technology, and most early models were equipped with single-note 'honkers'. These horns were anything but appealing to the general public. Therefore, Hancock developed their line of air whistles in an attempt to
romanticize the diesel locomotives. Production of these air whistles spanned from the late 1950s until the late 1960s.
Users The
New York, New Haven and Hartford Railroad was the largest user of these whistles, and every
FL9 purchased by the New Haven came from the factory equipped with a Hancock 4700 air whistle on the roof in the front, and an H4700 whistle (no reflector dish) on the rear. Additionally, the NH's 40 Budd RDCs had two Hancock 4700 whistles, plus their Mack FCD-1 & FCD-2 railbuses, 30 GP9s, 15 RS-11s, 15 H-16-44s, 20 SW1200s & their fleet of Pullman-Westinghouse stainless steel MUs. One DL-109 was also retrofitted with a pair. Other railroads occasionally used them, notably the New York Central on some RS-3s, the Seaboard Air Line on their SDP-35s, the Cambria & Indiana on its SW9s, and the Minneapolis, Northfield & Southern. Unfortunately, it was found that at high speeds, the whistles were difficult to hear. Class I railroads eventually replaced their Hancock whistles with horns, namely for safety reasons. Short line users were generally steel mill railroads, where it was found that the whistle was easier to hear than a horn within the mill. == Types of air whistles ==