Tyfon horns are of a very simple construction. There is the bell, diaphragm, and back cap, and that's about it. The bell also is the same unit as the mounting foot, diaphragm housing, and nozzle. The back cap is adjustable, and screws into place, very similar to a Wabco E-2 or Nathan M horn. All A-75s (I believe), most A-125s, and some A-200s were made of bronze. Some A-125s and a lot of the A-200s were also made of aluminum. There are even some rare A-200s which are cast iron!

To assemble the horn, place the diaphragm into the diaphragm housing, and screw on the back cap. Once the horn has been voiced and the back cap is in place, tighten the locking bolt on the top of the diaphragm housing. So as to not bend the housing too far, place a washer or two in between the two ears for the locking bolt. Prototypically, the lock bolt is a square head bolt, and the nut locks in place with a cotter pin.

tips

The first thing to be careful of when working with a Tyfon is the disassembly. To disassemble the horn, loosen the lock nut on the diaphragm housing. Then, apply air to the horn, and while the horn is blowing, unscrew the back cap. Now that you have it apart, check the internal seat and nozzle to be sure they are level with no low spots. These two surfaces should be in the same plane with each other.

If you are working with metal diaphragms, you may notice that the diaphragms are slightly convex to one side if you place a straightedge over them. This is normal. When assembling a horn using metal diaphragms, make sure the convex side is facing the nozzle, and the leaf with least wear is against the nozzle. This aids pressure against the nozzle, forming the seal necessary to allow the diaphragm to start oscillating. Typically, three disks are used in these horns. If working with a plastic or rubber-coated plastic diaphragm, there will be a step on one side of the diaphragm. This step should be facing the nozzle. Just like the convex side of the metal diaphragms, the step aids in forming a seal against the nozzle. Also, no matter what diaphragm you are working with, if it's cracked, severely deformed, or bowed out in the wrong direction (common with rubber-coated diaphragms), it will need to be replaced.

Now that the diaphragm and nozzle have been checked, the horn needs to be assembled and voiced. Take out the diaphragm and run the back cap in all the way. If it doesn't go all the way and rather gets stuck part way, the threads may need to be corrected. Once this is done, reinsert the diaphragm and apply anti-seize to the threads. Put the back cap on and tighten it to just hand tight. Now, with air applied that is 10-25 pounds BELOW operating pressure, tighten the back cap until the desired sound is blown. Tighten the lock nut and test the horn at full pressure. If it doesn't sound correctly from low to high pressure, the back cap will need to be readjusted.