Show at Historic Camden
Currently (today is 11 Nov. 2021) I have work on display at Historic Camden Broad St. Camden, SC. On display are turnings, furniture, sculpture and a working model of an 18th century water powered sash sawmill. Please check out Historic Camden’s website here.
This is a working model of a water powered sash sawmill. These sawmills were constructed throughout the colonies and then the States in the 17th, 18th, and 19th centuries. The 6th US Census in 1840 recorded that there were 31,650 water powered sawmills. Sawmills outnumbered every other mill including grist mills. In this model water is introduced at the top of the wheel by way of the head race, captured in “buckets” and the weight of the water turns the wheel. This is known as an overshot wheel. The wheel is connected to a large shaft which turns a large diameter wooden toothed wheel (bull gear). The teeth of this wheel engage a much smaller wheel (trundle gear) which is on another shaft that runs to a spot directly under the saw itself. By means of a cam, the rotary motion of the wheel is then converted into a reciprocating motion and the connecting rod (the pitman) pushes the saw frame up and down. It is necessary to advance the log riding on the carriage to contact the saw blade. This is done by means of a rack (part of the underside of the carriage) and corresponding pinion gear connected by shaft to a small wheel (rag wheel) with teeth set at small increments. On the up stroke of the saw, when the blade is not cutting, a lever moves an arm hooked to those teeth and advances the wheel just a little – as little as 1/8”. The down stroke then cuts the wood that was advanced. The process is repeated until a lever near the tail block disengages the advancement mechanism and the carriage with the log no longer moves. The carriage is then manually hauled back to the beginning and the log is adjusted for the next cut or is replaced with the next log. The logs are held in place by “dogs” which looked like large staples or heavy tent stakes. At this time iron was precious and its use was limited to those applications where it was absolutely needed such as gudgeons (bearings) on either end of the main shaft, the bands that secured them and the afore mentioned dogs. Steel was more expensive than silver and therefore only used for the saw blade. The rest of the sawmill workings were fashioned from wood.
Once the Millwright has completed the sawmill, the Sawyer can begin to cut wood. The Millwright himself may become the Sawyer.
Regular maintenance was a necessity for a reasonable output. The teeth of the bull gear had to be waxed with tallow or bees wax. The gudgeons had to be greased with tallow or lard. The saw blade had to be sharpened and set to keep the blade running true.
The sawmill required large amounts of water to operate. The time and duration of operation was dependent upon the weather. Springtime was typically when water flow was abundant. Sawmills located next to streams and rivers operated best at this time. The logs harvested in the winter when sap flow was at a minimum were milled at this time. Sawmills that were fed from a pond had more flexibility in duration of operation.
Logs were dragged onto the floor of the sawmill by various mechanical means. The sawmill may have a capstan that was powered by the waterwheel to aid in moving the logs. Block and tackle may have been used. Once on the floor, the log was rolled onto the carriage and positioned by means of cant hooks. The log was kept in place by large iron pins through the head and tail block and by “dogs” which look like large iron staples.
With the log in place, the sawyer would open the sluice gate allowing water to flow down the headrace and onto the wheel. The more the sluice was opened the greater the water flow and the faster the wheel would turn. Speeds ranged from 6 – 12 revolutions a minute. At 6 RPM the saw blade would move up and down 60 times.
Once the log had advanced far enough to trip the stop, the sawyer closed the sluice gate stopping the movement of the saw blade. He then pulled the carriage back to the starting position, repositioned the log, reset the log advancement mechanism and opened the sluice gate again. The rate at which a log was advanced was adjustable, slower for hard woods and large logs and faster for soft wood and smaller logs.
Once all the cuts were made, the boards (or beam) were removed from the carriage and a new log was rolled into place to begin the process all over again.
Here is a video I took when the model was almost complete.