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Tubing Schmatic
Tubing Schematic for Welte-Mignon Licensee
by John Grant (120707 MMDigest)

When it rains it pours.  A week or so ago I took some previously mentioned [120703 MMDigest] large format drawings of Welte (Licensee) drawings from an original service manual to my local graphic production house to have them digitized in anticipation of being able to take orders for copies at the upcoming AMICA convention.  Imagine my surprise when I went to pick up the digital files and a few "proof" copies to discover in with the mix there was an actual blueprint (white on blue) of a drawing bearing the date 1921 which shows not one, but two "Transforming Bars" of the type being recently discussed.

The original drawing itself, which I had not realized was in the package containing the other drawings is very faint, fragile, and will probably have to be entirely re-created, however, here are some initial details.  The drawing title block shows the following information:

  Welte Mignon
  Reproducing Piano
  Outlined by George A. Abeel (or possibly Abgel)
  Drawn and Traced for the
  Danquard Player Action School
  By J.H.G. Miller 1921

Although it is not specifically labeled as a grand or upright configuration, the placement of the various components suggest an upright lay-out.  The tracker bar(s) shown are of the type having a vertically oriented slot below and between the first and second tracker bar holes which is used to trip the re-play pneumatic.  Also, the "Pressure Regulating" pneumatics shown (last point of control before entering the stack) are of the type having a hinged pallet valve serving as the regulating or "choking" device.

Now it starts to get a little confusing.  Prominent in the center of the drawing is a depiction of the so-called "transforming bar" shown schematically as a long rectangle with curved ends, sort of like a racetrack except the end lines are only about a 90 degree segment of a circle, not 180 degrees.  Whether this is an accurate representation of the actual part is unknown.  This feature is clearly captioned as "(Former Type)".  It is probable that the "1921" date in the title block refers only to the vintage of the drawing itself and not to the vintage of the component design or lay-out.

In another part of the drawing, a somewhat simplified alternate configuration is shown.  It is depicted as having a true rectangular design with 90 degree corners.  Oddly, its caption labels it as "Transforming Bar Later Type (1920)"

Pending further analysis, I will associate the "Former Type transforming bar" with the pallet valve style regulator and the "Later Type transforming bar" with either late production of the pallet valve style regulator or early production of the knife valve style regulator.  At some point, the "transforming" function was reduced to the relatively simple rotating switch shown in the "Auto Pneumatic Action Co." drawings which also show the knife valve regulator.

This still leaves open to question what style of "transforming bar" would have been used with the even earlier "tapered plug" style regulators.

I am sending Robbie two files showing the salient sections of the blueprint.  They are a little difficult to read but should suffice until some pixel editing can be performed on them.  I will have a slightly reduced size copy of the entire blueprint, as well as the Auto Pneumatic Co. drawings (grand and upright) available for inspection, with me at the AMICA convention in Pittsburgh next week.

John Grant [delete ".geentroep" to reply]
7 Jul 2012 11:11:02 -0400 (EDT)

jgrant01.jpg (1,003 kb)

jgrant02.jpg (251 kb)

jgrant00.jpg (17 kb)
Rear view of "transforming bar".  Photo courtesy Tim Gautreaux.

08 July 2012

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