Popular Woodworking 2007-08 № 163, страница 57
Fancy footwork. I press the foot pedal down to the floor and that pulls the chain down with it ...
User's perspective. The chain runs around this bicycle-gear sprocket spinning it (the flywheel behind helps keep the momentum up) ...
Power enough. And that gives me enough rpm to turn end grain on this bowl.
Trial run. One of the Honduran artisans takes the new lathe for a spin.
to make chair parts. These lathes were built like the chairmaker's lathes from Britain - they turn backward and then forward with each stroke. What I wanted to introduce was a unidirectional lathe. A lathe like this could be used for turning bowls (as well as spindles), and so we decided to teach them to make mortars and pestles that the artisans could sell. The challenge was that I had to come up with a lathe that could be built using parts that could be found in any hardware store in the world.
The solution was a bicycle gear-driven lathe from the drawings by Richard Starr in his book "Woodworking with Kids" (Taunton Press). I modified the plans to use some hardware that I knew I could get in Honduras. Then I tested the idea by making a lathe in my shop in Paint Lick, Ky.
The Bicycle-chain Lathe
As I mentioned, a spring-pole lathe moves in two directions: toward the user as he or she
presses the foot pedal, and away from the user as the pedal returns to the up position.
The new lathe still has the foot pedal. But the foot pedal is attached to a bicycle chain (instead ofthe usual rope and springy bit of branch). The bicycle chain runs around the bicycle sprocket and back down where it attaches to the heavy spring, which is bolted to the wooden frame of the lathe.
When you push down on the pedal, the chain makes the shaft of the bicycle sprocket spin in one direction only. When the chain moves back, the shaft continues to spin in one direction. This is much like when you are riding a geared bicycle. When you pedal forward the bike moves forward. When you idle or pedal backward, the bike doesn't go backward - it continues to move forward.
The metal shaft that runs through the bicycle sprocket is attached to a large wooden flywheel on one end (the flywheel keeps the momentum of the shaft going) and to the faceplate of the lathe on the other where the turning occurs.
I used hardware store pillow blocks as bearings and to attach the shaft to the lathe. And I used plumber's floor flanges to mount the flywheel to the shaft.
Learning the Lathe
After arriving in Honduras there was - as usual - a lot of waiting involved in locating a truck, arranging to get to the hardware stores and getting the timber cut for the flywheel. But we eventually got there, and were underway. The artisans took to the idea of the new machine with great vigor.
The flywheel had to be made in two parts to have enough mass to turn large pieces of wood into bowls. This created a problem in boring the hole in the center of the flywheel, so we turned to ancient technology again for help. In an old book on blacksmithing, I found drawings of a beam drill (see photo at right) that solved the problem, even in the most remote villages.
The solution was a brace and bit held down with a piece of timber like the lever on a drill press.
We also managed to upgrade the old hand-cranked grinder on the premises by modifying a grinding wheel so it could be mounted on the lathe as well.
We had the new lathe up and running, the artisans and new apprentices had bowl blanks cut out with their new chain saw, and in no time they were turning the green wood into their first bowls. The hook tools I'd brought with me gave them some trouble so they stayed mostly with a
66 ■ Popular Woodworking August 2007