Squeaking Horn?

Hello all,

I know you guys are probably more experts with train horns, but I have an air horn from an old truck (not sure where… Grandpa just got it for me from an Antique Shop). It’s a Hadley model 11670. It has a 16 and a 14.5 inch horn.

When I first hooked it up (about 45 PSI, since I didn’t know if this thing was a pipe bomb or not), only air and some dust came out of it. I increased to about 60 to no change.

I took everything apart. Used some rubbing alcohol to clean some old grime off of the diaphragm (they weren’t bent at all), cleaned the chamber on the inside, and the bowl that goes on the adjuster screw. Put everything back together. The 16 inch horn worked! However… the 14.5 horn did not.

I took everything back apart on that side of the horn. I noticed that the main cap doesn’t appear to be the right one… There is empty space to the left of it. The bolt holes still line up, and the diaphragm appears to cover the right area, with the same bolt holes.

I figured I’d mess with the adjustment screw. I read this thread talking about how in the event of squeaking, one should tighten the adjustment screw.

I kept tightening it, and the squeaking has been getting louder. Unfortunately I’ve tightened the screw all the way and it’s still squeaking!

I know you guys are experts on train horns, but I figured this would be a good place to ask about my horn. I also apologize for probably not using the terminology you guys commonly use. This is only my second horn and the first problem I’ve encountered!

Here is a link to a picture of the cap and the gap I am talking about. I couldn’t get it to upload to here correctly (camera doesn’t go to that low of a resolution). https://goo.gl/photos/HgZ3cykBQWFmqrxWA

Thank you guys in advance, that is, if you don’t kick me out for only playing with sissy Truck horns.

Blow through the horn just with your mouth. If you get air leaking past the diaphragm you will need to find out where it’s leaking and seal it.

It could be worn seal on the cap, damaged diaphragm, worn out nozzle etc.

If you have difficulty seeing where the leak is you could try putting the back of the horn into a shallow water bath and then run some air through it. If you see bubbles coming out from under the rim of the cap you would fix that first and then move onto troubleshooting leaks internally.

On the inside the diaphragm needs to seal against the face of the nozzle (the inner ring of the trumpet). The adjuster screw should just be tight enough to allow for that seal but not overly tight so that the diaphragm cannot oscillate. Note that over tightening the screw will bend the diaphragm and most likely render it useless.

Good luck - if all else fails, get onto Hornblasters and buy a set of Shockers :slight_smile:

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Don’t just tighten it all the way! you could bend and over stretch the diaphragm if it is plastic.

Loosen it all the way then run air through it. You’ll just hear air rush out the horn and then gradually tighten it until it sounds right. Too loose or too tight and it won’t sound right at all, there is just a sweet spot for the operating pressure you’ll run the horn.