Early American sash sawmills were typically powered with an undershot water wheel called a flutter wheel. These wooden wheels were relatively small diameter and wide. The small diameter enabled appropriately fast rotation speeds necessary for efficient sawing - about 100-140 rpm. Presumably the sight and sound of the rapidly rotating motion of the small diameter wheel inspired the name.
The paddles were referred to as "floats" and were fixed into place either by wood pieces inserted into the shaft as seen in the photo are right, or attached to a rim on each end of the wheel as shown below in the figure below from Oliver Evans' 1795 volume on mills.
Sawmills used reciprocating straight blades mounted in a wood frame, or sash, for hundreds of years, so a key part of the power train was conversion of the rotary motion of the water wheel to reciprocating motion. Flutter wheel-driven sawmills accomplished this by using a a simple configuration of a crank attached directly to the wheel shaft. The "pitman" which was attached to a crank on the flutter wheel shaft. The upper end of the pitman was connected to the saw frame.
The entire mechanism could readily be constructed by any competent millwright and used mostly wood. Iron or steel pins (gudgeons) were often used on the ends of the flutter wheel shaft and the crank was iron. These few iron parts could be re-used when damage or rot required replacement or repair of the wooden wheel.
By the mid-19th century, flutter wheels were mostly obsolete because of the advent of new water wheel designs, turbines, and the increasing use of circular saws in mills. By 1870, millwright and author David Craik felt no need to discuss flutter wheels in his tome on millwrighting, but simply dismissed them as something that was once "common in old saw-mills" (p. 95).
A rare photo of an original flutter wheel. Photo from Hamilton (1964) is captioned "Ruins of a flutter wheel, Ledyard, Conn."
Date of photo and location in Ledyard is unknown, but this is not from the Ledyard Up-Down Sawmill which was configured for a water turbine in the 1870s. The turbine at the Ledyard Up-Down Sawmill was still in place in 1964.
Hamilton, E. P. (1964). The Village Mill in Early New England. Old Sturbridge Village, Sturbridge, Massachusetts. Accessed 8/14/2011 http://www.osv.org/explore_learn.
The single most-referenced source for late 18th century American mills. First published by inventor and millwright Oliver Evans in 1795 with 15 editions to 1860. The main part of the book relates to flour mills and was written by Evans with no information on sawmills. However, as Evans book was nearly finished, he received a manuscript from a Pennsylvania millwright named Thomas Ellicott.
Ellicott’s material was included in the Evans book as Part the Fifth, The Practical Millwright. Article 39 (Of Sawmills – Their Utility) of Part V by Ellicott contains the classic and frequently cited primary text and diagram (Plate XI) of a sash sawmill.
Plate XI shows the position of the flutter wheel directly under the saw, with a crank on the flutter wheel shaft connected directly to the pitman arm that drives the saw sash up and down. Note that the axle of the flutter wheel is at right angle to the saw carriage.
Plate XI also superimposes elevation views of two different configurations of flutter wheels in the lower left and right corners.
Ellicott also helpfully included recommended dimensions of flutter wheels for mill sites with different height falls (or head) of water. All the wheel diameters were small (2 1/2 to 3 feet). The width of the wheels ranged from 5 feet for a 12 foot head to 9 feet for a 5 foot head.