DIYAPASON-L Digest #283 - Monday, March 19, 2001
 
Slip rollers for long, small scale pipes?
  by <d.doerschuk@att.net>
 

(back) Subject: Slip rollers for long, small scale pipes? From: <d.doerschuk@att.net> Date: Tue, 20 Mar 2001 04:20:00 +0000   Hello everyone,   I've been lurking for some months, reading about all your interesting projects, and since the list is a bit quiet now I thought I'd say hello.   My name is David Doerschuk, and I've been interested in organs since I first convinced my parents to let me try organ lessons as a teenager. Really, since before then; I remember being fascinated with the Casavant at St. Elizabeth's in Ridgewood N.J. from the time I joined the choir there in the 2nd grade. Wonderful, resonant music that must be like God's voice. Plus, a nifty control system. Boy, do I like control systems. I ended up with a master's in electrical engineering, in the control systems track. I work for a petrochemical company as a control systems engineer. Knobs, switches and buttons to wavelets, DFFTs and wacky filters...I like it all. What could be a happier combination than my favorite music with my favorite engineering topic?   The question I'd like to ask today deals with forming sheet copper into long tubes to form pipes. All the references I've found describe shaping tin/lead alloy sheet around mandrels, usually with a hook-shaped wrap- forming tool having a specific name that I can't recall right now. Especially considering the small scales typical in residential organs (long pipe, small diameter), I cannot imagine this method being successful with hard copper sheet. Furthermore, the traditional mandrel-based fabrication assumes that the builder has a large series of mandrels, one per pipe diameter: carrying that from 16' up to 3" with reasonable variations in the scale/halving yields quite a few mandrels, probably almost 100...that's a lot of lathe time not to mention a few bucks in steel. (On the positive side, they could double as a set of untuned chimes.....nah.)   So mandrels don't seem practical for a single organ application, although I don't doubt that they're the hot ticket for a full-time builder using tin/lead instead of hard copper. Sheet metal workers have long used a clever device called a slip roll that uses a pair of lower, usually steady, driven rollers opposing a upper centered moveable roller to create cylinders of sheet metal. The lower horizontal tangent of the upper roller can be positioned at various distances beneath the (identical) upper horizontal tangents of the lower rollers; the greater the distance, the smaller the radius of the finished cylinder I've finished a 16' design that uses 2.25" solid rollers, a pillar block at either end, and 3 intermediate lower bearings, but am balking at the cost of building it.   Basically, I think there's probably a better way, probably known to every 6-year-old out there with the exception of yours truly. I'm scratching my head, running through the following reasoning:   1. Dom Bedos made metal pipes. 2. His were up to 32' long. 3. I don't think South Bend existed in the 18th century. (their loss :-) 4. Wood swells; in particular, wood swells radially, not axially. Not the hot ticket for long, semi- precision (0.010"?)mandrels. 5. I've never read anthing about building pipes by making the precision rolls in small sections and then soldering them together: a 16' pipe out of 8 2' long rolls, so I'm going to can that idea instantly out of fear of total derision from the list. 6. I'm out of reasoning.   Any help will be very much appreciated.   Very best of luck with all your projects!   David Doerschuk