K Train Horns Maintenance

The kettle drum principle is the basis for the K train horn. The diaphragm assembly of the K horn is made of a pair of disks that are kept apart by a silicone ring. Other components of a K Horn are the diffuser ring, back cap and bell. On the same piece as the bell are cast the mounting foot, orifice, diaphragm housing and nozzle, the bell is cast in aluminium. The early models of K series air horns were sand cast and since 1977 they are die-cast. To attach the diffuser you use three cap screws and to complete the horn assembly of the horn you place the diaphragm assembly into the back of the cap then the back cap is attached to the bell using six bolts.

As easy as the assembly, you can also disassemble a K series air horn. The only problem you can encounter while disassembling a K train horn is the diaphragm being stuck in the back cap which can be easily solved by using an air gun, blowing in the relief hole should free the diaphragm assembly. Once the K horn has been disassembled you should check the nozzle for corrosion. You should also check that the nozzle and outer seat on the bell are flat and in the same plane. If that is not the case, they can be remachined.

The diaphragm should also be checked, unless it is cracked you can just flip the diaphragm assembly. If any cracks are visible on any component of the diaphragm you can try to replace only that component or the whole diaphragm assembly. One other problem that can occur with the diaphragm is the disk being concave towards the inside. You can solve this by just reversing the diaphragm or you can remove and reverse just disk creating the problem, this should be carefully done in order to preserve the silicone ring that seals the air between the diaphragm disks.

These are the main components on a K series train horn that get worn. The diffuser might get cracked but can easily be replaced. Another problem that might be encountered is with the base gasket between the bell and manifold, this can be either rebuild or replaced.

Some people like to get involved more in the way their K series train horns sound so they try to fine-tune them. This can be done by changing the diaphragms between bells and sometimes by changing the back caps.