Construction and Designations of the P Train Horns by AirChime
The P horn has similar appearance with the K horn series. The diaphragm and bell housings are constructed as one piece and the back caps bolts on the housing of the diaphragm. These units were held into place with bolts upon a universal manifold. Unlike the M series horns, the housings for the diaphragms are also of the same sizes. P horns also are longer, have smaller diaphragm housings and have a throat more narrow compared to the K series horns. The cast "Nathan AirChime" inside a raised rectangle can also be seen on each of the sides of the P horn bell.
The construction inside the P horn is totally different from that of the K series. The P horn does not have a diffuser that evenly distributes the inward bound air stream. Also, the air orifice of the P horn opens up at the bottom of the inside chamber of the horn. It also utilizes a lone stainless diaphragm.
Mostly on the newer P series horn uses a dual diaphragm although it is not necessary. Unlike the M series, the housing made of aluminum and the caps will not devalue as time goes by. This is due to the rubber gaskets that cushioned the outer edges of the diaphragm. A rubber gasket which is held by a spring in its place is covering the nozzle as well so it also will not wear out with use.
The P horns are usable for many years due to the physical assembly of the horns. The only required maintenance for this type of horn is to replace the rubber gaskets and diaphragms when worn out by usage. The working life of the P horn is extensive that several of these horns have been in continuous usage for more than 30 years and still have not experienced maintenance since first used. The still sound precisely as what they are expected to sound.
The P horns were normally sold along with restrictors placed on the base. These restrictors are plugs with hexagonal sockets drilled to a certain diameter. Different "chokes" can be used to the P horn depending on the diameter of the drilled hole, making the tone mellower. The restrictors are normally utilized to The P horns though they were also available for the M and K series.
The P horn is categorized by the character P which is preceded by the amount of bells that were utilized in the horn. An R will precede the bell if the bell is reversed. The P5 is not actually a horn with five chimes. It is a P horn using the 5 bell and it is a single-note horn. An actual P5 is properly assigned as P12345 and a P5A is rightfully classified to as a P1234A5. A common reversal, which is having bell 2 and bell 4 reversed, will respectively have the P134R24 and P134R24A classification.
The P124 horn is normally classified to as P3. It is available in a five-chime design manifold with "blanks" placed on the embrasures that has no bells and on a specialized three-chime design manifold as well. The single-bell type P horn comes on a single-bell designed manifold.
The five-chime design manifold is also referred to as s "gull-wing" manifold due to its shape. The typical design has 2 bells affixed above one another on both sides of the center bell. The placement set up of the bells is not vital. You will find a P12345L or P5L for short occasionally. This pertains to the P12345 on the newer design of low-profile manifolds which was introduced in the year 1976. This is not an official designation though.
Originally, the low-profile design manifold comprised of the three-chime design manifold with 2 "extenders". These extenders were utilized to attach the extra two bells. The two last locations and the center location are approximately an inch to the front from the two last horn position just to keep the horn as compact as possible. These allow nearer arrangement to the bells yet not having the housing of the diaphragms to touch each the other housings. Newer P12345L horns comprise of a low-profile one-piece manifold which looks similar to the initial low-profile three-piece manifolds.
The 0 bell plays a low A, which is an octave lower than the 4 bell. It has remained as it is after Nathan had changed foundries, with the exclusion of the "Pat. Pend." now cast replacing the previous "Pat. Pending". Nathan proposed the P01345 design which was tuned to the tone A major 7th. Only a small number of railroads were noted to have acquired this horn.
Don Tead and Nathan worked together in 1976 to deal out the P01235 horn for use on Amtrak's E60CH locomotives. This type of horn has a very admirable tone as it was tuned to A major 7th too. It also boasts a range of higher than an octave which makes a very effective warning, just like the P01345. It was unfortunate that only the E60CH locomotives of Amtrak were the known users of P01235 horns.
