I’m currently trying to take the backing plates off my train horns because 3 of the trumpets stopped working. I can not for the life of me get the screws out. Any tips or tricks? I’m trying to avoid drilling the screws out. I can get like 1-2 screws per horn but I can’t get them all out, before the head starts stripping. I soaked in pb-blaster and Freeze off, and screw loose.
what kind of horns?
I’ll upload a picture in a second. I bought the horns about a year ago. Don’t remember what brand
Okay so this is going to be an ugly project. Steel screws that are in aluminium means they’re gonna be tighter than a bull’s oven in fly season.
Use a drill bit small enough to get into the rounded out screw heads, but large enough to use the drill to chew the head off the screw without going deep. Slightly larger than the screw diameter should be fine.
The caps will come off without damage, and then there’s enough of the screw left to put some Vise Grips on them and turn them out.
I’ve had to use this technique and it does work, but take your time and be patient. If you have a workbench vise, it’ll help.
-Kris
Okay thanks for the reply. I’m get to work tonight
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Finally got around to drilling the screw heads off, all of these plastic covers in the horns have rips in them. Is that why they don’t make sound?
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Those plastic pieces look like your diaphragm 
If you know the name brand and model, you might be able to get some new ones.
If not, then it’s the perfect time to upgrade.
-Kris
The amount of oxidation that horn has faced is pretty nasty. The back caps look like an absolute nightmare, and I’m sure that also was not helping. Plus the nozzle rust on that one chamber will probably screw with the frequency it’s supposed to blow at. I don’t think it would be worth your money trying to repair that horn. Even Shockers are an upgrade from that. Despite the plastic castings, it’s the steel diaphragms they use that count.
If you run the horn under your vehicle, you definitely do not want an aluminum horn if you get snow in the winter.
Yea that looks pretty ordinary. Personally I would support the above statements - just cut your losses and buy something fresh, however the good news is that if you want to try and resurrect them there’s probably nothing more than some elbow grease and ingenuity required. The point being, don’t go spending money on them.
You’ve probably figured out how the horns work. The diaphragm needs to seat/seal against that front facing ring (which is the nozzle/seat), The pressure applied to that seating comes from those inner parts of the back caps. If you can get the circular surfaces all nice and clean and uniformly flat again, then the remaining challenge would be to find something suitable as a diaphragm replacement. Tracking down some similar gauge plastic or even a thin sheet of metal wouldn’t be all that difficult. Make a gasket or put some silicone sealant on the back caps and make sure air doesn’t leak out of anywhere when you try and blow through them (i.e. using lung pressure). If you can get them to that stage they should start working again.