Mechanical Music Digest  Archives
You Are Not Logged In Login/Get New Account
Please Log In. Accounts are free!
Logged In users are granted additional features including a more current version of the Archives and a simplified process for submitting articles.
Home Archives Calendar Gallery Store Links Info
MMD > Archives > November 2001 > 2001.11.01 > 09Prev  Next


Ampico B Rewind Problems
By Craig Brougher

Robbie, you wrote a caveat to explain what you meant by an unstable
"valve."  However I think you are still laboring under the misconception
that someone at the factory occasionally placed a solid, airtight
cardboard cover into the Ampico valve's top seat and shellacked it in.
You wrote:

>[ Sorry, I used a poor expression.  The valve is stable but the
>[ pneumatics it controls aren't.  If only one bleed is used, such
>[ as at the valve seat, then equal suction is applied to both the
>[ reroll pneumatic and to the shutoff pneumatic.  Therefore the
>[ bleed aperture is a compromise, and the one or the other pneumatic
>[ suffers.  -- Robbie

Actually, your comment or its caveat doesn't apply in the Ampico B
case, anyway.  It's fully stable and will never float between bleeds
or fail to seat tightly because the cardboard bleed hole isn't really
a "bleed hole."  That was D.L. Bullock's implication, that some
cardboards didn't even have holes.  If either were the case, it
wouldn't work at all.  And if the actual factory hole in the card
was close to a bleed hole size, the system would not work either.
It's larger than a bleed.  If the factory in some cases just pressed
in a cardboard blank, the leakage around the card would be plenty, too.

It should be obvious that something is wrong with the "unstable valve
system," theory here, because "C" valve is used only as the vacuum
supply for "D" valve.  If C valve was inherently unstable, it would be
so whether it was controlling a pneumatic directly or through another
valve.  Rest assured that the system never gives a moments' trouble.

You are referring to a pressure divider in which two equally sized
bleeds (or bleeds relatively close to the same cross sectional area)
will partition the pump pressure accordingly.  And if the outside valve
hole is actually closed off airtight, there would be no valve action at
all.  The poppet would float, not having enough air pressure above it
to seal it down.  That doesn't happen here.

Craig Brougher


(Message sent Thu 1 Nov 2001, 15:29:53 GMT, from time zone GMT-0800.)

Key Words in Subject:  Ampico, B, Problems, Rewind

Home    Archives    Calendar    Gallery    Store    Links    Info   


Enter text below to search the MMD Website with Google



CONTACT FORM: Click HERE to write to the editor, or to post a message about Mechanical Musical Instruments to the MMD

Unless otherwise noted, all opinions are those of the individual authors and may not represent those of the editors. Compilation copyright 1995-2024 by Jody Kravitz.

Please read our Republication Policy before copying information from or creating links to this web site.

Click HERE to contact the webmaster regarding problems with the website.

Please support publication of the MMD by donating online

Please Support Publication of the MMD with your Generous Donation

Pay via PayPal

No PayPal account required

                                     
Translate This Page