In weeks 5 and 6, we focus on the material quality of physical objects by building a Rube-Goldberg Machine (RGM). MEDA202’s tutorial classes will divide into 10 groups of 4 students, each create a component of the machine (in a chain reaction). The first group will determine how the machine gets started. The last group will decide the function of machine.
Look the following machines:
Consider , present your research that answers the following questions:
- Describe the machines: what do they do? what are their components?
- What do they have in common?
- Does the audience participate physically? If so, how?
Machines and Mechanics:
1. What is a machine?
A machine does work (or helps you do work).
Examples: a hammer, a skateboard, a ramp, a pair of chopsticks etc.
‘Machines employ power to achieve desired forces and movement.’ (wikipedia)
Machines increase the usefulness of forces e.g. transmit or magnify the force.
- Wheels and axle
- Inclined planes/ wedge/ screw
‘A simple machine is a mechanical device that changes the direction or magnitude of a force. In general, a simple machine can be defined as one of the simplest mechanisms that provide mechanical advantage (also called leverage)’
‘A simple machine is an elementary device that has a specific movement (often called a mechanism), which can be combined with other devices and movements to form a machine. Thus simple machines are considered to be the “building blocks” of more complicated machines.’
From wikipedia: http://en.wikipedia.org/wiki/Simple_machines
Watch: This advertisement by Honda (‘inspired’ by Fishel and Weiss)
What are some of the simple mechanisms and machines? What are the complext ones?
2. What laws of Physics concern us?
(You don’t need to do the maths, you just need to be aware of them.)
- Extra energy is needed to overcome friction.
- Friction transforms kinetic energy into heat and sound.
- Friction can be used to stop a moving object.
e.g. A rolling marble won’t roll for ever, it will stop eventually because of friction with the surface it is rolling on.
Inertia (Newton’s First Law)
- the tendency of an object to remain stationary, or a moving object to move in a straight line at constant speed.
- Extra energy is needed to overcome inertia to move a stationary object, or change the direction and/ or speed of a moving object.
e.g. A marble rolls down a slope hitting a stationary marble causing it to move a short distance.
- Types of energy: kinetic, potential, light, heat, sound, chemical etc.
- Kinetic energy: energy of a moving object. A moving object has maximum kinetic energy at greatest speed.
- Potential energy: energy of a raised weight. A stationary object has maximum potential energy at maximum height.
e.g. A marble is on top of ramp. The higher the ramp, the greater the potential energy of the marble. The greater the kinetic energy when the marble rolls down the ramp.
Like in this advertisement for Touchwood:
Work = Force x Distance/ W = Fd
e.g. Going up the steps: you are doing work is calculated by your weight (in Newton) multiplied by the distance of the stairs. You do the same work walking up a ramp and a flight of stairs to reach the same place.
Marbles that fall down need to do extra work to get back up. Like in this machine:
Force = Mass x Acceleration/ F = Ma (Newton’s second law)
The greater mass of the object, the greater the force is needed to accelerate the movement of the object.
The Law of Conservation of Energy: energy cannot be destroyed or created. It transforms.
e.g. A speeding marble hits a stationary marble. Some kinetic energy is transferred to the stationary marble causing it to move, some energy is transformed into heat (friction) and sound (what we here when the marbles collide).
Law of Conservation of momentum: when objects collide, their total momentum is unchanged (provided there are no acting other forces e.g. friction).
Collision between moving objects (or a moving object and stationary objects) transfer energy. Momentum has size and direction. Linear momentum increases with speed and mass.
e.g. When a snooker ball (a bigger mass) collides with a marble (smaller mass), the marble will move away at greater speed.
Angular momentum describe forces in circular motion/rotation. It also increases with speed and mass. It also depends on the shape of the object.
The greater the diameter of the object, the greater the angular momentum.
When the rotating object changes in shape (e.g. diameter), it changes in speed.
e.g. The spinning balloon (in The Ways Things Go) spins in decreasing orbits and speed as the balloon looses air.
3. Open and closed systems
Power (in) = Power (out)?
There is no free lunch.
Are the inputs/ outputs within the system?
Conservation of energy: in reality total energy is seldom conserved because of friction.
e.g. In your chain reaction, energy will be ‘lost’ (transformed into heat and sound). Will your system need an energy boost? What form can this energy boost take?
Watch: Student’s RGM from 2011
Exercise: Build a Rube-Goldberg
- Divide into groups of 4 (tell your tutor who you are and your group will be given a number).
- Head to the DMC Gallery and you will be allocated a space.
- Each member contribute to their part by building 1 simple machine (i.e. have at least three simple machines in your RGM component).
- Begin to build your component with the materials provided – you can also bring in your own machines.
- remember to discuss with the group preceding and/or succeeding your component how you would connect your parts together.
Materials and construction:
In week 2, we continue to work with materials, focusing on how to get them to work in a predictable way reliably (i.e. every single time). In continuing to build the RGM, we will look at the types of materials we are working with and how to make them work for us.
Here are some common materials you may be using in constructing a work and their qualities:
- Pure or alloys
- Conductor (heat and electricity)
- Strong by also malleable
- Common e.g. Steel, aluminium, copper, silver, brass
- Hard but brittle
- Insulator (heat and electricity)
- Common e.g. Clay, glass, gemstones
- Light, low density
- Some can be moulded with heat
- Common e.g. Acrylic, Nylon, PVC, styrene, rubber, foam
- Mixtures of materials
- Wood — mixture of cellulose fibres held together by lignin
- Natural wood: balsa
- Composite wood: plywood, MDF, masonite, bamboo ply, chipboard
- Paper and cardboard
- Foam core
Methods of joining:
One of the most important part of the RGM construction is how you join different parts together to ensure that the ‘machine’ function as you intend for it to. The method of joining needs to suit the materials you are bringing together.
As you continually test the functions of your RGM components, things that are not fasten down appropriately will start to move over time e.g. tape may slacken, pins may bend, bluetack may harden etc. You need to ensure the joints are durable so that they will not fall apart after a couple of tests.
Conversely, some parts that serve as triggers need to rest in the sweet spot, it needs to be secured enough not to start moving on its own, but not so secured that it can’t be triggered. Remember that anything may move due to the floor’s vibration.
Your aim: is to have the components work every single time.
Below are some constructions from previous workshops. What materials are used in these simple machines? What is joining the parts together (or helping them stay in place)? Is there a more effective way of joining these materials?
Some non-permanent fastening methods:
- Nuts and bolts
- Rubber bands
Some permanent fastening methods:
- Glues (wood glues, epoxies, plastic glues, super glue, hot glue, tape)
- Welding and soldering
- Needles and thread
Demonstration: fastening and joining:
- Making a pivot/ lever
- Making a pulley system
- Making a t-joint using dissimilar materials
Work on component of RGM in DMC Gallery
In building your machine component, you will use a variety of materials and different joining and fastening methods.
- What are the characteristics of your materials?
- What methods can you use to join the materials together?
- Join your pieces together and test the effectiveness of your joint.
- Take photos.
Discuss with the preceding and succeeding groups on the methods of ‘joining’ your components – test.
Post photos of your class’s exercises and findings onto your personal blog, and post a link to them on this blog.
How does Ian Burn take advantage of the materials he used in this work? View documentation here?