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

Spring Fundraising Drive In Progress. Please visit out home page to see this and other announcements:     Thank you. --Jody

MMD > Archives > January 2016 > 2016.01.07 > 08Prev  Next

Suction Box Check Valve Problem
By David Dewey

Stan Morton wrote: "I recently removed the evacuator assembly from my
piano, with reservoir intact, and blocked off all ports, and the system
held vacuum for approximately 15 seconds before the reservoir was
depleted.  When reinstalled with all hoses reconnected, the reservoir
vacuum only lasts 4 to 5 seconds."

Stan, 15 seconds isn't very long (and 4 to 5 seconds is intolerable!),
and while it will pump a player, it will rapidly fatigue the pumper!
I would be much happier with something close to a minute.

If you have the ability, I would recover the exhauster reservoir (at
least) and make certain the flap valves are working properly.  You can
reconnect one hose at a time and measure the change in holding time to
find your "main" leak, although it does appear that the vacuum motor
check valve is very suspect.

As to the felt, it seems everyone had their own idea of what would keep
the box quieter.  If you have to tear the felt, you can replace it, but
you might want to try to use a putty knife to separate it from the
bottom board of the piano, instead of tearing it.

I've not had to repair a vacuum box flap valve yet, but I did run into
one player that had no check valve!  I over-thought the problem and made
a check valve out of some PVC fittings, a ping-pong ball and a piano
wire spring.  It works, but it's way over-built and takes up too much
space.  Good luck!  One does wonder how much work was done 22 years
ago, though.

I have had one instance of hearing that a player I rebuilt needs it
again.  In thinking it through, I rebuilt it in 1977, so the repair is
now 39 years old and the original build was about 55 years old, so maybe
it is time?!  Hmmm, this year is going to be our 40th anniversary;
I wonder what I'm going to have to repair!

David Dewey

(Message sent Thu 7 Jan 2016, 19:51:35 GMT, from time zone GMT-0800.)

Key Words in Subject:  Box, Check, Problem, Suction, Valve

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 1995-2019 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

Pay via PayPal

No PayPal account required

Translate This Page

. .