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 > January 1997 > 1997.01.23 > 20Prev  Next

Proportional Solodant
By Robbie Rhodes

Dan Wilson pointed out the drawback of strict proportioning of pressure: at soft volume the Accompaniment notes will fail completely. My earlier definition of my goal is better: I want the Accomp intensity suppressed a constant decibel value lower than the Theme. 3 db is 70% hammer velocity (and the result of 50% accelerating force), therefore the _working_ Accomp pressure will be 50% of the working Theme pressure. "Working pressure" (for the hammer-accelerating force) is defined as the actual stack pressure minus the pressure needed to overcome the dead weight of the hammer and damper. (Or, in a vertical piano, it's mostly the force of the damper spring.)

Craig is right, the Hickman regulator _will_ do the task, in conjunction with an adaptation of the Ampico B "voltage divider". The trick is that the First Intensity Adjuster is replaced by a fixed reference vacuum of about 4 inches; this is the effective "dead weight" force. The reference regulator would be similar to a pump spill, like on the Ampico B pump.

This scheme nicely solves the problem Dan Wilson raises. As the pedaling (Theme) vacuum diminishes the Accompaniment vacuum must also diminish, but both are proportioned with respect to the 4-inches vacuum "floor". Thus the proportioning is referenced about the "dead weight" force, and so both Theme and Accomp notes will ultimately fail together as the Theme (pumping) pressure is diminished toward zero.

I'll provide the physics and math discussion privately to anyone who's interested -- but "the real proof is in the pumping!"

Robbie Rhodes

(Message sent Fri 24 Jan 1997, 02:50:29 GMT, from time zone GMT-0800.)

Key Words in Subject:  Proportional, Solodant

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