AIR HORNS....no blow!!

I recently purchased a set of GABRIELO TRUMPET air horns, solid brass trumpets and cast bronze bodies. The smaller is +_ 17" and the larger +_22".

Can't get them to 'trumpet'. Disassembled to find two circular brass shims with large hole in the center. Freed the adjusting screw but no matter the volume of air or set of the screw, no sound.
Tried a Google search for parts, diagrams, anything...no luck.
Any of you folks have suggestions, ideas?
 
Those brass shims you mention are actually diaphragms which vibrate to make the trumpet sound you mention. I repaired an old set years ago that would not blow. I opened them to find some pitting in the base below the diaphragms in the base. I filed that down with a flat file, to remove the pitting, making sure I maintained a flat surface as if I was using a milling machine. After cleaning the rest of the parts, re-assembling them, I had to adjust the set screws to get the diaphragms to vibrate properly to make the trumpet sound. Take a look at what you see and tell us more. Are they new or used? I'm sure you just don't have an adjustment right or there is an air leak that won't get the diaphragms started vibrating properly. Let us know!
 
87...
I have flat filed the trumpet side flange, lapped it to the cast base side flange.
The diaphragms are used. I do have air leaks at the parting joints.
It there supposed to be gaskets on the flanges and/or between the two diaphragms?
What air pressure should set the horns off?

Thanks. Ed
 
Seems like the ones I did did use gaskets on the outer circumference. It really doesn't take a lot of pressure to get them going. Once you get the diaphragm going it will sound off. If you have air leaks, that's where your problem is. If you want do do a quick fix, RTV should seal the outer edges.
 
87.....

Just threw another log in the shop stove. Quit for the night with all this freezing rain....lotta strange cracking sounds from the woods tonight!

Will try the RTV thing in the warmer A.M..

And, I'm probably pushing too much pressure anyway.

Thanks, again.
 
I used to work where we had a ton of air horns that HAD to work, each truck had two horns in case one quit. The trick is to get the diaphragm to viberate . It is a mater of adjustment. My horns had threads and a lock nut to change the spring pressure on the diapharms. Most horns will work from about 40psi to max truck pressure, around 125 psi Nnone of our air horns diaphragms had a hole in them,in fact if they did the wouldn't work. That was the most common repair. Diaphragms are available at any truck shop. That's the way it was with my horns. Your horn ma be different. Hope this helps, Steve
 
Steve,
Thank you for your interest.
My horns, once the base has been removed from the trumpet, reveal two shim stock-thin diaphragms with approximately a 1" machined hole in the center. Within the base is a spring loaded, screw adjustable poppet which appears to seat on the diaphragms. I have eliminated air leaks from the mating flange yet regardless of spring pressure nor air pressure, the units will not blow.
As an observation, I have noticed that as soon as I admit pressure to the unit, I can hear the poppet seat over the opening of the diaphragms but I can't seem to get them to vibrate. I'm stumped!!!
Thanks, Ed
 

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