A high tech leak finder! Pass the salmon please.

By: frugalhorn

Jul 23 2012

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Category: Uncategorized


Focal Length:6mm
Shutter:1/0 sec

In my last post we discussed the flow or water from leaks when the horn was filled with water and observed the dripping. As with plumbing the drip may have migrated somewhat from the point of the leak and can be misleading….

Now ! !  The GAS method!!!…..Years ago I used a large two-inch tapered rubber lab bottle stopper to check for leaks in non-screwbell horn. The other end of the system was a trimmed Schrader valve from an old dead bicycle tube, trimmed carefully and inserted into the leadpipe. Put the horn under water, pump up the horn with a bike pump and watch for bubbles. go slowly so that you can see where the leaks are, (Often the tuning slides are leaky. I keep a little paper pad nearby to note where I’m seeing leaks. If you use one of the large black lab stoppers, make sure you attach a “puller” on the outside large end to remove the stopper. (I inserted a sturdy eye bolt into the stopper) The stopper needs to be firmly pushed in place or it will be the point of “the big leak”. and the bike pump may not be able to push the big stopper out without the having the leadpipe stopper popping out first.

I think I’ve just discovered how to put more than one pix in a single blog. Hmm, what an IT whizzz!

So an upgrade was needed, new technology! Many of the horns I work up are screwbelled, for various reasons. One reason is the usual,  portability, using a cut bell tail,  and the other is to salvage a bell tail or flare that is other wise trashed. (It may take two bell tails to make one good screwbell tail)  Generally I use an Alexander compatible ringset. It is the standard and many players want the ability to swap bell flares.

The screwbell detachable  “GAS” system requires a rubber gasket (Old rubber roofing) a tin can top ( canned salmon) that just fits inside the female side of the ring set and a donor or unused male side to pinch the rubber gasket and tin panel in place to seal up the horn at the ring set. Then Place the leadpipe bike valve in place, put the horn corpus underwater (uses much less water than having to submerge the whole horn with a fixed bell), attaching the bike pump to the bike valve, pump gently, and observe. Don’t pump too hard or you may get so many bubbles that you’ll have a hard time determining where the leaks are…

If you remove the valve covers, you may be able to determine if the bearings are leaking or if the bubbles are coming out from under the top plate at the outer edge, it may be leaking around the valve within the casing.  Needless to say if you have a bad ferrule joint you’ll see it. Once I did an NiSi Olds Geyer wrap horn and determined that there were several hair-line cracks in the branch tubing which were difficult to see with the naked eye, but they sure did leak air…

I’m sure the engineers out there could attach a pressure valve and determine how much air a horn could hold prior to a tuning slide being pushed out or ‘whatever’ other event that could be used to entertain one’s self. Great fun! Less pressure than two pix up….All this is very easy to do, and you may learn something about your horn…


2 comments on “A high tech leak finder! Pass the salmon please.”

  1. Your “low tech” method described here is still vastly more sophisticated than what I did. no pump other than human lungs. and the cut bell seal is elegant but requires that extra threaded ringset piece. I used wide vinyl tape.across the throat opening with a strapping tape collar below the ring. Really like the EPDM roofing idea, though. the schrader /leadpipe fitting is brilliant. I needed a spotter to look for bubbles while pressurizing the corpus.

    are the specs for ringset threads publicly available anywhere? seems they might be similar to large camera or telescope lens mount thread specs. with the right numbers and access to a metal lathe, a sealing blank with space for an epdm or canning jar gasket could be fashioned from a piece of large brass rod stock.
    …assuming there comes a shortage of canned salmon.


    • If you have a detachable flare you can always use it for the male side of the ring set, but it will require a deeper tub to put the horn in. As to threads, The Alex thread is sort of the standard in the industry, The newer Conns, Durks, Hoyers, and many custom horns use an Alex compatible ringset. The Holton sets are compatible with Holton, and the Jupiter ring set is likewise a mono match. The Yamaha 567/667 match but the Yamaha 668 match 668’s. I don’t know about the custom level Yamaha’s. Then there are the bayonet ringsets The large lens idea is interesting, but I know nothing of them. My older Nikon Cameras were all bayonet . Another match for the metal plate is a standard cat food can. I’ve have a whole collection of tin plates cut from can tops…I also use them in many ringset soldering applications, to separate the upper and lower sets when soldering on the upper ring.


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