Background: Designs of basic treadle lathes have been around for centuries. In these designs, a foot pedal is used to turn a flywheel that is attached to the workpiece to be "turned".
In most of these designs, the foot pedal (or treadle) is directly connected to the flywheel via a "crank rod" or "crank link" There are two problems associated with this approach. 1.) There is no clutch (i.e., the ability for the flywheel to "coast" without the flywheal driving the flywheel mechanism. 2.) The moment that the crank arm exerts on the wheel depends on its angular position. Sometimes the crank arm is perpendicular to the link arm (max moment). Sometimes the crank arm is parallel to the link arm (zero moment or "deadspot").
Recently, descriptions of treadle lathes that use modern, mass-produced, reliable, commodity, off-the shelf, low cost mechanical components, such as antifriction bearings and freewheels. (Note that a "freewheel" is the device on a multi-speed bicycle that incorporates a coaster (i.e., one directional) clutch and multiple sprockets. Figure 3 depicts such a bicycle freewheel.)
The use of modern ball bearings has obvious advantages. The use of a bicycle freewheel has the advantage of removing the two problems outlined above (i.e., the no-clutch problem, and the variable moment (and deadspot) problem.
If one were to take advantage of modern commodity, off-the-shelf mechanical marvels such as ball bearings and freewheels, one could "re-visit" the concept of the treadle lathe. It should be rather straigntforward to design a "human-powered" lathe that could exhibit the features listed below.
Opportunity (Need) Statement: It would be great if a low cost, treadle lathe with the features listed above could be designed that was targeted to be made by woodworkers themselves, with materials, off-the-shelf components and tools commonly abailible to them This system would also create significantly less noise than electrically powered units.
A group could design one-of-a-kind devices, but perhaps a better outcome would be to design devices that could be easily (i.e., inexpensively) used throughout the woodworking arena in the form of kit plans.
Secondary (Educational) Need Statement: In Clarkson’s Capstone Integrated Design Course Sequence, it is required to present mechanical engineering students with an appropriate design project challenge. Such a challenge should provide students with 1) a real opportunity to apply contemporary design methodology and their engineering science knowledge and skills 2) in a way that balances and moderates fabrication effort, 3) producing a physical artifact (i.e., prototype proof-of-concept) that can be subsequently evaluated 4) in the two-semester-timeframe. The design of a treadle lathe with the added requirement of being "woodworker made" will require numerous decisions based on engineering mechanics, and thus is thought to satisfy this educational need.