Article on how to make a simple ratchet mechanism out of wood

The latest installment of my quarterly column on automaton-making techniques is now live! Dug’s Automata Tips, Techniques and Tricks No. 11 shows a step-by-step procedure for making a simple ratchet mechanism out of wood. The ratchet is advanced on tooth at a time by a driving pawl which is powered by a hand-crank. This can be an easy way to extend the duration of an automaton's performance. Simply attach some of the automaton's actions to the axle that is being slowly advanced, one step at a time. Meanwhile, a more fast paced set of actions can be driven off of the same axle to which the driving pawl is attached.

Need an example? Imagine that the figure of a man with a car jack is driven by a mechanism (probably a cam) attached to the driving pawl. Every time the hand of the automaton makes a rotation, the man could raise and lower the handle on the jack. Next, imaging that a car jack is connected to the same axle as the ratchet that is being driven. It would rise a fixed increment for every rotation of the automaton handle. It's not an exciting example, but it should give you an idea for how the two axles, while operating simultaneously, have a different pace and type of motion. One is continuous complete rotary motion. The other is partial intermittent motion.

The rest is up to you! I hope you enjoy the article on how to make a simple ratchet out of wood.

-Dug North

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How to glue something to a wooden axle without gluing the thing next to it!

The folks at the Timberkits Workshop have taken a bit of time to share this helpful hint for gluing collars to a wooden axle. In this case, the collars of the Drummer Timberkit need to be located as close as possible to both sides of a lever. The collars must be glued in place to keep the lever from shifting, but the lever must NOT be glued. How do you glue the two collars without gluing the lever? The answer is shown in the video!

Timberkits wooden automata kits can be ordered online:
For the United States visit: http://www.timberkitsus.com/store/
For the UK and Europe http: xhttp://www.timberkits.com/Home/

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Reciprocating motion from an axle rotating on same axis

One reader of The Automata / Automaton Blog wrote to me with an interesting question. He wrote: "I'm looking for a simple mechanism to convert rotational motion to reciprocal motion along the SAME axis as the rotation, not perpendicular."

I decided to investigate potential solutions in one of my favorite books on mechanisms, Five Hundred and Seven Mechanical Movements. Below are some of the solutions I found listed by the numbers that appear in my copy of the book (Astragal Press, 1995).

• 95. Oblique disc imparting rectilinear motion to rod resting upon its surface
• 106. & 107. Uniform reciprocating rectilinear motion produced by rotary motion of grooved cams
• 136. Crown tooth gear with rod pressed against rim
• 143. Sliding worm screw and toothed wheel
• 165. Circular to rectilinear motion via waved-wheel (or cam)
• 167. Drum or cylinder with endless groove and follower
• 237. Crown-ratchet (driven by crown, not pawl)
• 272. Beveled disc with follower on its circumference.
• 351. Partially toothed pinion and rack with return mechanism

I have probably missed a few in the book, and there are certainly many more possible solutions.

Order your own copy of Five Hundred and Seven Mechanical Movements: Embracing All Those Which Are Most Important in Dynamics, Hydraulics, Hydrostatics, Pneumatics, Steam Engines...

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