Nathan AirChime M3 Train Horn

Описание: My now fully restored scalloped base Nathan M3 locomotive horn.

I acquired this horn in early 2023. Whilst it did function, the 1 and 2 bells sounded considerably weaker, and the horn consumed a huge amount of air. Initially I assumed it was due to lack of back cap tightness, so I attempted to re-voice the horn. Unfortunately this was impossible due to the sheer amount of internal wear the power chambers had experienced from in-service usage.

The horn was disassembled and I consulted horn specialist and machinist Mike Muha. He advised me to conduct some measurements and we realised the back cap clamping rings were severely worn down which meant the diaphragms would not receive adequate clamping force regardless of how tight the back caps were.

The heads and back caps were posted to Mike’s shop where he then re-machined every interface back to factory original specification. His work is absolutely stellar and I would recommend his services to any horn collector.

To refresh the appearance, I repainted the horn in a red exterior with yellow bell throats.

I then voiced and assembled the horn with the assistance of an air gauge so I could monitor the speaking pressures.

It is mandatory practise to blow the horn for at least 2-3 minutes after initial voicing to let it ‘break-in’ for the diaphragms to settle. If this step is skipped, the horn will fall out of voicing after a short period.

This video is the break in process. The horn did require some minor adjustments in back cap tightness after break in, but now it is working flawlessly and each bell is speaking at the exact factory designated pressure. Bells 1, 2, 4 are now speaking at 13, 16, 19psi respectively.

The excessive quilling / feathering of the horn in this video was so that I could listen to how each bell would step-in, and that would indicate if it required any further adjustments.

Very happy with this horn, and thanks to Mike Muha for his incredible work.

Huge thank you to ‪@m3nathan‬ for letting me borrow the air setup for this break in procedure. It was excellent to catch up again and I enjoyed the day very much.