The Duo-Art steamboat pump has the reputation of being the quietest ever devised, since there are no connecting-rod bearings to loosen and knock.  The stroke is comparatively short, compared with other designs, but it can go quite fast without noise.  The wooden rollers are covered with leather, for even more noise reduction.  See http://www.mmdigest.com/Pictures/tuttle02.html

Although this was a fine design, and many collectors prize it, it was so big and thick that it was soon replaced.  After that, they briefly went to a similar arrangement with four bellows and short connecting rods instead of eccentrics.  You can see one on Sam Harris' website: http://www.geocities.com/Heartland/Ranch/9374/stroud/page09.html

By the 1920s Duo-Art had gone to the standard box pump, just like Ampico.

Richard Vance
Date: Tue, 11 Sep 2001 10:07:43 -0400