Toybox – EPICS

Students

Oliver Schwartz
Computer Science, 2021

Hadley Irwin
Philosophy, 2020

David Bewicke-Copley
Anthropology, 2020

Seb Benzecry
English, 2020

Project Description

In this semester of EPICS, we constructed an automaton toy mimicking the running motion of a tiger. The project was constructed primarily from plywood and brass. Our intention with this project was for the automaton element to take the form of a wooden tiger, attached to cogs in such a manner that turning said cogs through an externally attached handle causes the legs to move, imitating a tiger’s gait.

We were inspired to create this project as we think that, through the course of its production, we would engage a plethora of the core skills central to the EPICS course, and gain experience using the equivalently important machinery and equipment in the EPICS lab. In addition to the personal challenge we looked forward to with this project, we hope that our design will facilitate an educational element through its capacity to teach mechanics and motor skills to young children. In fact, one of our team members, Oliver, has organized to donate the toy to a childcare center in Sydney, Australia. This will address the “Community Service” element of the course description.

The design that we produced encapsulates the spirit of modern engineering. The project is a sophisticated system of mechanical and functional units, contained and constructed in such a manner that (without understanding the work behind the finished product) the final form of the unit appears sleek and efficient.

Technical Background

Mechanical toys are the most interesting category of toys because of their capacity to entertain humans of all ages. This is achieved through the remarkable capacity of mechanical toys to replicate – quite accurately – complex motion observed in real life. Mechanical automata are any forms of mechanical objects that are “relatively self-operating after they have been set in motion” (Encyclopedia Brittanica). The term ‘automaton is derived from the Ancient Greek αὐτόματος (automatos) meaning “acting of one’s own will”, or “self acting” in other words (Tufts University Greek Dictionary).

Creating such automata is more complicated than it may appear: there is a well-defined design approach to crafting such mechanical toys. Automata can be created using a wide variety of materials, from wood and metal to 3D-printed plastic. However, it is essential that the designer considers which materials will be best suited for the particular design that he or she is attempting to develop. The design process itself consists of two steps: 1) motion approximation and 2) layout stage. The first step is called motion approximation where the motion of the object is stipulated, and all the requisite working parts are determined. Motion approximation involves developing mathematical models to represent the motions of interdependent components (Ceylan, Li, Mitra, M, and Pauly – this paper highlights some of the mathematics involved in developing a movement model for a mechanical toy). The second stage is called the layout stage, where the dimensions are decided for the toy (Ceylan, Li, Mitra, M, and Pauly).

Typical mechanical elements involved in automata include gears, pulleys, and hinges (Ceylan, Li, Mitra, M, and Pauly). These components serve to convert a driving force into the specific motion of the toy (Ceylan, Li, Mitra, M, and Pauly). The design process for an automaton is quite extensive and is the domain of a select few experts who are intimately familiar with the set of components available, and how these can be assembled to work in tandem.

Britannica, The Editors of Encyclopaedia. “Automaton.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 18 Sept. 2013, ww.britannica.com/technology/automaton.

Greek Dictionary Headword Search Results, www.perseus.tufts.edu/hopper/resolveform?type=exact&lookup=automatos&lang=greek.

D. Ceylan, W. Li, N. J. Mitra, Agrawala M., and M. Pauly. Designing and fabricating mechanical automata from mocap sequences. ACM Transactions on Graphics Article 186, 32(6), 2013.

Design Drawings

Fabrication Process

Our fabrication process involved several steps: constructing the box framework to house the automata; piecing together the mechanism to drive the automata; putting these components together to form the final product. Of course there were several intermediary steps which involved extensive sanding, gluing, testing, and painting.

First of all, we constructed our box to house the automata. This consisted of four faces of ½ inch thick plywood. We decided to omit two of the faces (four instead of six) to ensure the automata mechanism was visible – the most complex part of the design. We used the jig-saw to cut the wood into two five-inch by five-inch pieces, and two five-inch by six-inch pieces. Following this, we used the belt sander to smoothen the edges and corners. We used PVA glue to stick these faces together – as they are not bearing any significant load, we decided screws/nails were not necessary. We used Irwin clamps to secure the wood while the glue dried. After the PVA glue dried, we used a sander machine to sand down the dried glue for a more polished look. Following this, we used 150-grit followed by 300-grit sandpaper in order to leave our box with a gentle, delicate finish. Finally, we applied dark-brown wood stain to give the plywood an authentic, natural look.

Following this, we constructed the driving mechanism for the automata. Once we had constructed the box, we were able to calculate the dimensions for the mechanism accordingly. These consisted of: a handle, a camshaft (made of a wooden dowel), and three small wooden blocks to convert the rotational motion of the camshaft to an up/down motion of a dowel protruding through the top face of the box. We used the Carvey machine to cut these pieces – see the diagrams for more information on this section. We also drilled a hole (with a hand drill) in the top face of the box to allow the dowel piece to oscillate up and down as necessary. We used a trial-by-error method when widening the hole, starting out with a very narrow hole, and gradually widening we reached the appropriate width.

The next step was to construct the body and limbs of our tiger automata. We decided to use hardwood to give the tiger some weight. After sketching (roughly) the dimensions of the tiger torso, we used the jig-saw to cut a rough shape. Following this, we used the belt sander to smoothen the edges. To refine the torso shape, we used the Dremel tool to add contours to the torso, giving the tiger a more authentic appearance. We followed an identical process to cut out the limbs (front and back legs). Then, we drilled holes through the torso and limbs, attaching each set of legs on a freely-rotating dowel, allowing the legs to oscillate back and forth. We drilled another hole part-way through the tiger’s belly, and proceeded to mount the torso on the dowel protruding from the box.

After having completed the tiger, we constructed 2 hinge pieces for the two leg supports using the jig-saw and Dremel tools. These hinges attached via brass skewers to the legs, so when the torso oscillates up and down, the legs in turn move back and forth, mimicking a running motion.

To conclude our project, we used orange, black, and white paint to paint the tiger’s stripes. This was a critical and complex step and involved several revisions.

Students

Project Description

Technical Background

Design Drawings

Fabrication Process

Final Result