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Unit Valve Varian
Ampico "A" Unit Valve Variant Discovered
by John Grant (120724 MMDigest)

A short time ago, while looking through my "boneyard" of reproducer parts, something strange about an Ampico stack caught my eye.  At first glance it looked to be a Type 5 or 6, as defined in the Howe/Morgan article, "The Evolution of the Ampico", originally published in the 1991 AMICA Bulletin and subsequently updated by Morgan:

It is a push-rod style stack with two hammer breaks.  (I am currently away on vacation and did not record where the breaks occur, but I can provide that information later if will aid in the analysis.)  I am used to seeing the troublesome upside-down unit valves with wooden covers in these stacks, but suddenly I realized I was looking at valves that still had wooden covers but were right-side up!  This would appear then to be an earlier use of a right-side up valve design, in contrast to the Howe/Morgan Type 7 variant which states, "First right-side-up unit valves in stack, metal top-seats flared, limiting adjustment."

This design must have been in production for a very short time as I have seen no other examples of it.  I obtained it in a collection of similar parts, so it was not associated with a specific piano brand, size or vintage that I can identify.  Perhaps the breaks can help narrow down the list of possible candidate brands and years of manufacture.  The only other possibly helpful information is two sets of numbers stamped into the bass-end wooden end of the stack reading "FA28" and "14271".

Evolutionarily, in keeping with the Howe/Morgan numbering scheme, I suppose this variant could be considered either a Type 6B (accompanied by a re-designation of the present Type 6 design as Type 6A) or a Type 7A (accompanied by a re-designation of the present Type 7 design as Type 7B) depending on which attribute (wooden valve cover or right-side up orientation) is considered its most defining feature.

The stack is missing one of these secondary valves, so on the outside chance I find a stripped piano with compatible hammer breaks which qualifies for restoration, or someone out there can use the stack (call me!), a replacement valve will need to be found or fabricated.  It _may_ be possible to substitute a normal right-side up, metal top-seat valve, but I have not yet tried the "fit" of such a substitution.  Modifying an existing upside-down valve to work _may_ also be feasible, but tricky.

Has anyone else seen one of these variants and can you provide more information about its employment?

John Grant [delete ".geentroep" to reply]
24 Jul 2012 12:15:33 -0400 (EDT)

Ampico_A_Valve_Variant.jpg (98 kb)

Ampico_A_Stack_Variant.jpg (119 kb)

25 July 2012

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