DIYAPASON-L Digest #285 - Wednesday, March 21, 2001
 
Re: Forming small-scale copper pipes (long)
  by "David Doerschuk" <d.doerschuk@worldnet.att.net>
 

(back) Subject: Re: Forming small-scale copper pipes (long) From: "David Doerschuk" <d.doerschuk@worldnet.att.net> Date: Wed, 21 Mar 2001 23:27:19 -0600   DIYapason,   Thanks very much for all the responses! Several people responded = privately, and I thought I'd try and do a summary of all the comments, while slipping in a few opinions and further questions.   To recap, I'm interested in building a rank of small-scale 16' open diapasons out of copper (or brass, actually). I want to build them with French mouths, using tin/lead for the mouth and languid, low cutups, = minute nicking, and 2.5" wind. I prefer cone tuning over scrolls or sleeves on diapasons, so I plan to either anneal the top ends, or grind them to a lesser thickness to lessen the force needed to tune (tin/lead is very plastic compared to copper or brass).   Mandrels: 1. It was pointed out that builders use not more than 2 dozen metal mandrels across the entire compass. The mandrel is used to shape the = metal, but it is not used as a wrapped interior mold, so it is not necessary to have 1 mandrel per pipe diameter. 2. Maple dowels and other hardwood rounds have been used successfully by one list member as wooden mandrels to form copper pipes. He was very clever: He would choose an under-sized dowel, wrap it with newspaper = until it was exactly the right size, then use one block of wood to secure the copper sheet against the mandrel while wrapping the copper around the mandrel with a second block. 3. No one thought running out and machining 100 mandrels was a good idea :-) whew! 4. No one had anything bad to say about large slip roller machines, although the cost of building one with a 16.5' span is fairly expensive.   Soldering / Joining: 1. A sectionalized pipe has been done before: a WurliTzer 16' Tuba that = had been flattened was repaired by cutting it into sections, re-shaping the cylinders, and then re-soldering! I should have known better than to = make jokes! 2. Several people pointed out the relative difficulty of soldering copper versus soldering tin/lead pipe metal. One person noted that the thermal conductivity of copper was so high that soldering one end of the pipe frequently UN-soldered previously completed joints. He suggested silver solder or brazing to reduce the problem. I agree, and now plan to use a 1500 degree F brazing stick on the longitudinal seams of both the pipe = body and the foot. 3. The mouth assembly, since it is of tin/lead, must be soldered into the pipe body and this doesn't seem to be a problem. However, if the languid = is made of tin/lead, an order-of-assembly problem comes up: the languid must be installed before the foot is attached to the body. All brazing must be complete before any soldering can start on the mouth or languid. = Therefore the pipe foot, which can't be joined to the body until the languid is installed, *must* be soldered to the body instead of brazed. I would = rather braze it for strength (and color matching), so my question is: does = anyone see anything obviously wrong with making the languid out of copper (or brass)? I imagine that the languid would still be sufficiently ductile = to allow reasonable manipulation during voicing, but I am far from sure. 4. Regarding the longitudinal seam of the pipe body and the foot: = assuming that the copper wall thickness is 0.040" or less, does anyone see any advantage to a particular joint over a simple lap joint?   Sanity Check: Several people wanted to know why I was interested in using copper since it's harder to work with than tin/lead. Several other people noted bad musical experiences with copper ranks, including hardness of tone and an unpleasant harshness. Two people noted that with reasonable used ranks starting at $200-$300, or free if you've got well-honed scrounging capabilities (a surprisingly common denominator between the folks on this list!), why would you ever want to roll your own (OK, that's a tiny joke). Well, here's my thoughts: 1. Copper can be "flamed" with a torch, producing beautiful blue/green colors. 2. Copper itself is kind of pretty, and very different from tin/lead -- it's also fairly unusual. 3. Copper and brass both have structural advantages over tin/lead, and can be made with thinner walls and lower finished weights. 4. Frankly, and I don't mean to be alarmist here, lead gives me the willies. I use gloves when handling tin/lead pipes, and worry about absorbing lead from molten metal, planing sheets, cutting, etc. Call me a fool, but heavy metal poisoning is a singularly unpleasant way to check = out. 5. I think the copper pipes would look fabulous with high tin content tin/lead French mouths, carefully burnished. 6. I am extremely curious about whether, in a rigid round tube pipe, it makes the slightest bit of musical difference what metal is used. This subject was addressed with near-religious fervor by George Audsley in his seminal work "The Art of Organ Building". He opined widely and variously = on different ratios of tin/lead, and abused organ builders who used zinc, too much lead, or other strange inventions. He never produced any supporting physics, nor does he do any blind testing. He certainly knows much more than I ever will about organ building, but I disagree with him on this point.   I am gradually talking myself into building a pipe body that, above the mouth, has several interchangeable cylinders for the upper body. I'm open to suggestions here, but what about a C pipe with several body-above-the-mouth portions made of: 1. 70% tin / 30% lead 2. A hard copper 3. A hard brass 4. A T6 aluminum 5. A carbon steel body with a wall thickness of 1/2", just to have a test case with reflective walls! With identical room conditions, one at a time we install the various upper bodies and record a .wav file of the pipe sounding. Then, put the 5 (or more?) .wav file on the web and invite everyone to listen. All the pipes would have identical voicing since they share a common foot and mouth assembly. Maybe differences could be reliably heard, I don't know, but it would be quite interesting to find out!   Please forgive me for running on so long. Thank you all for your help, = and I wish you the best of luck with your own projects.   David Doerschuk