﻿ DTOTW - Mechansims for use in mechanical toys and automata. Velocity ratios and levers introduced as a background to the theory behind simple mechanisms. Mechanical toys and Automata project - Guidance, Help and Research starting points - Resources fro students and teachers of Design & Technology at KS3, KS4 and KS5 - and beyond. Gear ratios - Velocity ratios - Driven velocity - Input speed - Output Speed - Simple Gearing example
Year 9 ~ Thinking about projects ....
~ CAMS ~ Making things move ‘up and down’
or from ‘side to side’.
Look around at the links, levers, cams, pulleys and gears that are used in everyday situations and try to think of new ideas for mechanical toys.  Look at the web-sites that show ‘automata’ and analyse why these toys work as they do.
Start by looking at the three ‘orders’ of levers.  The first class ~  Number 1 is a simple see-saw or scissors.  Notice how the effort needed to move the load is reversed in the direction it acts on the load.  Look at the other two classes and see if the same happens with those. Class 2 is seen in the example of the wheelbarrow and the class 3 lever is seen in things such as tweezers and fishing rods. This last class is an inefficient system as the load is further from the fulcrum than the effort.
Class 1                                Class   2                                 Class 3
The two illustrations shown here demonstrate how  two dimensional movement can be produced from either a simple circular cam that has an offset central
axle, or from a more complex pear shaped cam (See the ‘cats’ model above).  Still more complex movements  can be produced from a wavy line cut into a cylinder (see the dog’s head shown above)  or from a specially shaped cam.

With odd shaped CAMS a prototype should be
made from  card and the output movement