The Serpent Forum

Russ Kaiser · Joined: 02 Mar 2007 Posts: 29 Location: Winston-Salem, NC

Hey guys. I have a couple of instruments completed so it is time to get rid of one. I am interested in what you think of the new finish. I think it looks more natural. Let me know.

eBay auction link

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J.c. Sherman · Joined: 05 Mar 2007 Posts: 22 Location: Cleveland, USA

Definitely like the finish!

Are you making your own bocal?

J.c.S.

Russ Kaiser · Joined: 02 Mar 2007 Posts: 29 Location: Winston-Salem, NC

I sort of make my own bocal...(trade secret about to be revealed)

I cheat by starting with a pre-tapered lead pipe. From a construction point of view having a tapered pipe is about 99% of the battle. At one point I considered drawing my own pipe, but it would literally take me half a day with the tools on hand to make the pipe and I would probably ruin the first 10 I tried. Then of course I would have to fill it and then bend it.

I start with a tuba lead pipe that comes pre-filled with pitch. I don't really like working with the pitch, I would much rather use Cerrobend, but I don't have a choice in the matter. Anyway, I bend it to the shape you see and make a receiver for the small end to accept a mouthpiece.

At some point, I would like to get an instrument manufacturer with tube drawing equipment to make me a more purpose-built pipe. Slightly smaller on the small end and slightly bigger on the big end. I am sure I would have to deal with one of the German firms or perhaps Kanstul. The big guys wouldn't want to deal with me. Even then, I am sure I would have to commit to buying 30 to 50 at a time to make it cost effective for both of us. This is not something I am willing to do at this time.

paulschmidt · Joined: 04 Mar 2007 Posts: 44

It might be less expensive to have a tapered steel mandrel made by a machine shop, then roll your own bocals. This would be simple and easy, and no need to draw anything. Looking at a Monk bocal, I can see that they use this method. You would need a patteren to cut the brass sheet so that it consistently comes out right when wrapped around the mandrel, but this pattern could be made quickly with paper wrapped on the mandrel and marked with pencil.
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Russ Kaiser · Joined: 02 Mar 2007 Posts: 29 Location: Winston-Salem, NC

Paul,

This is a good idea, but in the back of my mind it has the ring of one of those things that is easier said than done. I look at the dovetail joint on my besson and I am amazed at the artistry in this type of work.

Am I wrong in thinking that you took the natural trumpet building class? Something like that would prepare me to make a bocal in the method you describe. One thing that would be mandatory would be a small forge for annealing.

What do you think of this idea. I used to work in a shop where we used large spin forming lathes to make light fixture reflectors (big stadium lights). In spin forming we always started with flat stock and worked it "up" the chuck. Do you think it would be possible to start with a pipe chucked over a tapered mandrel at the large end and work the pipe down the mandrel with something like a two handed burnisher? This is something that in theory I could do on my wood lathe. I would still have to get the brass dead soft first, but in the end I would have a seamless bocal. Of course, getting the mandrel out of the bocal at the end of the spin would be a trick.

What does everyone think?

paulschmidt · Joined: 04 Mar 2007 Posts: 44

No need for anything more elaborate than a simple butt seam on the bocal. It would not need to be tabbed like the seams on bells. I think it would be difficult to spin form the bocal, if I understand your proposed method. But you are correct in assuming that I took the Barclay trumpet making class...one of the most interesting, useful, educational, and satisfying things I have ever done. You also do not need a forge, just a propane torch such as any hardware store carries (there are also somewhat hotter burning gasses available that you can experiment with). You anneal the brass trapezoid with the propane torch and water quench to make it nice and soft. Then wrap it around the mandrel and burnish with a smooth steel rod (even a screwdriver shaft would work) of some sort until the edges meet up in a butt joint. Then slide the brass off of the mandrel, and gently squeeze to a slightly smaller diameter so that one edge slides slightly under the other. Then slide back onto the mandrel just enough to pop the edges back into alignment, and remove again. Now the edges are held together with some spring compression. Drag a sharp edged steel object, such as a utility knife blade or steel ruler, up and down inside the seam to clean up the butted edges and remove any tiny burrs, and simultaneously clean oxidation from the edges. Then you lay the brass tube on some bricks, preferably at a slightly downhill angle, apply suitable flux to the seam, and use the propane torch to melt some silver solder into the uphill edge of the seam. The heat will slightly open the seam at the heated point, and by moving the torch downhill, you can get the solder to wick into the slightly widened spot as it moves downhill. Allow to cool. If needed in subsequent work, the bocal can now be heated a bit without popping the seam by using lower heat. Put the bocal back on the mandrel and burnish smooth. Make a form for the bend out of wood, and fill the bocal with bending alloy (plug the bottom with a cork, prefill with boiling water while held vertically, then pour in the molten alloy to displace the water - this prevents air bubbles. Run under cool water to harden, then bend around the wooden form, making sure that the seam is oriented along the side of the bend, so that it is neither stretched nor compressed in the process. Burnish out any small wrinkles. Melt out the alloy and inspect for any flaws in the seam, which can be touched up if necessary. Trim ends and polish. Voila! Parts and tools are simple and inexpensive. Only the mandrel will cost some. If adding some fittings or ferrules to the end(s), use softer solder (NOT silver solder) for those.
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Richard_Cane · Posted: Tue Jun 26, 2007 9:24 am Post subject:

Maybe you should consider subcontracting the bocal production to Paul...
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Russ Kaiser · Joined: 02 Mar 2007 Posts: 29 Location: Winston-Salem, NC

paulschmidt · Joined: 04 Mar 2007 Posts: 44

If you are only playing that small amount for ready-made bocals and they suit you, then there is no need to roll you own.

I listed lots of steps in my previous posting, so it sounds like lots of work. Once you get good at it, I estimate an hour to make a bocal; the first few would of course take longer. Bob Barclay can crank out a bocal in the time it takes us to read how to do it. But don't think that I am pressing to have you make your own!
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Russ Kaiser · Joined: 02 Mar 2007 Posts: 29 Location: Winston-Salem, NC

Paul,

As so often happens when I read back something I have written on a user group like this I realize the actual tone that I intended wasn't clear. I value your input tremendously and I want you to know that I had a smile on my face the entire time I was writing that last response.

I know the bounderies of my personal skill set and I have no doubt I would make a mess out of trying to produce my own bocals; at least the first twenty or so. I just recently learned that soldering in sandles is not a good idea.

Russ