Taylor Sawmill: a technical explanation

Page outline

The rebuilt Taylor Sawmill in Derry, New Hampshire, located on Ballard State Forest, is one of very few still-functional "up and down" sawmills. It remains capable of cutting logs into boards and timbers 60 years after being reconstructed in the 1940's, and uses the same concepts as sawmills dating back to the early 1700's, harnessing water to replace manual labor.

Even though the mill is open to the public during cutting demonstrations, it can be difficult to puzzle out exactly what's happening while looking at a collection of worn greasy parts. Especially when, as at Taylor mill, you can't see all the parts working together due to floors or walls; and also, certain areas are inaccessible due to safety concerns. This series of computer renders and text will explain the mechanical workings of the sawmill in what is hoped to be a simple and easy to grasp manner.

The part of the dam that brings water out to the wheel is called the 'sluice' or 'sluiceway' (1). When the mill is not running, a heavy wooden gate (2) seals the end of the sluice and keeps the water contained. To start the water, a wheel is turned on the first floor (3); this is connected by chain drive to a shaft that runs out along the top of the sluiceway. On this shaft are small gears (the 'pinion') that fit into a long strip of gear teeth (the 'rack') attached to the gate. As the wheel is turned, the gate is raised, allowing water to flow under. The water fills the buckets on the water wheel (4), and the off-centered weight makes it spin. On the same shaft as the water wheel, inside the mill, is a huge (about 10 feet) gear called the 'bull gear' (5). This drives a smaller gear; because the smaller gear has fewer teeth, it needs to spin faster. On the same shaft as the smaller gear, there is a drum with a loose belt around it (6). Because this belt is loose, it doesn't get any traction, and the power from the water wheel does not get to the rest of the mill.

---

To bring to the water's power to the rest of the mill, the loose belt must be tensioned. This is done by turning a four-handled wheel on the first floor (1). A rope wound around the wheel is attached to the first part of a pair of levers arms (2) that go down to the third floor. The lower lever controls a smaller 'idler' wheel that is bolted to a sliding framework in rails (3). As the control wheel upstairs is turned, the rope pulls up on the levers, which pulls the idler wheel and its framework up against the bottom of the clutch belt (4). This increases the tension of the belt, so that it can get traction and start moving. When the belt is tight enough, a set of wheels and belt (5) brings the water's power to the second floor.

---

Once the clutch is engaged, power is transmitted from the third floor upward to the second. A horizontal 'jack shaft' (1) delivers the power to two different parts. The first part is the reversing mechanism (2); more on that later. On the end of the jack shaft is the heavy, counterweighted 'pitman wheel' (3). Attached to the rim of the pitman wheel is a jointed timber that connects it to the bottom of the 'saw sash' (4). The sash is trapped by several iron slides, so that it can only go up and down on its guides (hence the name "up and down sawmill"). As the pitman wheel rotates, the sash is pushed upward and pulled down. Each full revolution of the pitman wheel equals on complete motion of down then up: each cycle is one 'stroke'.The blade (5) is attached to the top and bottom of the sash and tensioned to keep it straight. The saw is designed to cut when the sash is going down, so the heavy weight of the sash itself can help the cutting action.

---

The log is spiked in position on the 'log carriage' (1), between the 'head' (upper left) and the 'tail' (lower right). The carriage itself rides on metal rails, alot like small railroad tracks. On the bottom of the carriage are metal plates that are grooved down the middle to stay on the rail, and have gear teeth on both sides of each rail so that it can be moved. As the saw sash moves, a small piece attached to its side (2) transmits some of its power to a lever overhead. Near where that lever pivots, the 'advance arm' (3) hangs down. It moves a rocker that changes the direction of the movement from up/down to forward/backward. The 'advance finger' (4) is attached to this rocker, and rests on the 'advance wheel' (5), on a large ring of ratchet teeth around its rim. Each time the sash goes up, the advance finger is pulled back a little bit, slipping backward on the ratchet teeth. When the saw comes down, the finger gets a grip in one of the teeth and pushes the wheel forward slightly. The large advance wheel is attached to a shaft that crosses both sides of the carriage (6), and has small pinion gears that mesh with the teeth on the bottom of the carriage. The carriage moves roughly 1/4" per stroke.

---

When the mill is first started, the carriage is in neutral: even though the saw is moving, the carriage is not being advanced forward. This is because the advance finger (1) is not being allowed to rest on the advance wheel. When everything is set to start cutting, a lever (2) is pegged in the up/on position, which lets the advance finger engage the wheel since the end of the lever is chained to the advance finger. The carriage advance can be stopped at any point by lowering the lever, which lifts the finger clear. The mill also has an automatic stop at the end of a log. A small ramp (3) bolted to the side of the carriage will push upward on a rod (4) when the carriage gets near the end, which lifts the advance finger and stops the carriage's movement.

---

When the saw has cut all the way to the end of the log, the carriage must be returned to its original position so that the saw blade is out of the way while positioning the log for the next cut. First, the carriage advance is disabled. A belt (1) coming off the main jack shaft on the second floor provides power for moving the carriage backward. This belt is twisted into a figure-8 shape: normally, a straight belt means that the two wheels at the ends are rotating in the same direction. Because this belt is twisted, the second wheel is rotating opposite the first. Another shaft (2), wheel, and belt bring power to the reverse drive itself (3). The reverse drive is mounted on a sliding frame, very similar to that of the clutch idler wheel. This reverse drive sits directly below the wide, flat leather portion of the advance wheel (4), but seperated by a short distance. To engage reverse, a pedal through the floor is stepped on (5), which levers up the reverse drive in its framework, and presses it against the advance wheel. Because the direction of movement has been reversed by the twisted belt, the advance wheel is rolled backward instead of forward.

---

Old Sturbridge Village also has a functioning up-and-down sawmill. More so than the Taylor mill, Sturbridge puts great effort into historical accuracy relating to both mechanics and operation. The rest of the village is interesting as well.
http://www.osv.org/

Ledyard, Connecticut has another mill. Theirs uses a turbine rather than a wheel. The Ledyard mill is original, unlike Taylor or Sturbridge. Not much info on the web, just an address and schedule.
http://www.town.ledyard.ct.us/culture.htm

Society for the Preservation of Old Mills (SPOOM) is a group interested in raising interst in historic mills and even buying, running, or building them.
http://www.spoom.org/

The Timberframer's Guild builds, rebuilds, and modifies timber-framed buildings, along with teaching the skills and concepts associated. When up-and-down sawmills were the way to get lumber, this was the way buildings were done.
http://www.tfguild.org/

Last modified 3rd August 2004 / Edward Spoerl
\graphics\taylor mill\html\