Cabaret mechanical movement pdf


 

Feb 22, Automata Resources. Videos. Poultry in Motion · Killer Tomato · How to Make Automata. Books. Cabaret Mechanical Movement (PDF). download Cabaret Mechanical Movement: Understanding Movement and Making Automata: Read 15 Books Reviews - terney.info Cabaret Mechanical Movement and millions of other books are available for site Kindle. Cabaret Mechanical Movement: Understanding Movement and Making Automata Paperback – April, Making other sorts of three dimensional objects can also be hard, but he extra dimension of.

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Cabaret Mechanical Movement Pdf

Cabaret Mechanical Movement - Download as PDF File .pdf) or read online. TOYS IN WOOD. method for learning about mechanisms while constructing the kits. Our book, Cabaret Mechanical Movement is aimed at students and teachers alike. It clearly . “I wanted to say how much I enjoyed the Cabaret Mechanical Movement book – it explained some complex ideas around Newtonian mechanics in an erudite.

As well as being a globally accessible alternative, the web site supplements parts of the book and will have details of current shows. Photography by Heini Schneebeli. Colophon 2. Contents 3. Who, What, Why? Some Principles 5. Levers 6. Shafts 7. Cranks 8. Cams 9. Springs Linkages Ratchets

If this chapter gets too heavy, try skipping on to something more practical. The history of automata usually begins around B.

They use the same mechanisms that are used in the simplest piece of automata or mechanical sculpture. Observation Just look around Everything you see is moving. Electrons are moving in atoms. You and the things you see are rotating with the Earth. The birds just rotate so their mechanism is simpler. If you want to make things move be sure to spend some time studying how other things move. The observation of movement all around you will provide lots of inspiration for your own ideas.

But before you create something with mechanical movement it will help you to understand a little about those mechanical principles. The Barecats by Paul Spooner Who is winding-up whom? When the small cat points the big cat looks up. When you look at mechanisms try to work out which part is driving and which part is driven. For example, a unicycle is a machine.

So, legs pushing the pedals Input , produce a rotating wheel Output. The motions and forces that occur between Input and Output are described by the science of Mechanics. Mechanics The science of mechanics has been studied for a very long time. The origins can be traced back to the early dynasties of ancient Egypt. The first recorded scientific foundations for mechanics were developed in the 3rd century BC by a Greek mathematician called Archimedes. He worked out formulae for the equilibrium of simple levers and centres of gravity.

Levers—chapter 2 Another important historical development was recorded almost two thousand years later by Galileo Galilei born He studied the theories of Archimedes and in particular, the use of mathematics to solve physical problems.

In the year that Galileo died , Isaac Newton was born. He introduced the concepts of force and mass. From this he formulated his Three Laws of Motion. Newton discovered that motion does not require force. Force is only required to accelerate or decelerate motion.

Basically, any moving object will continue in a straight line and at a constant speed indefinitely unless some force interferes with its motion. In reality, a moving object usually slows to a stop because friction or air resistance drain its energy. Therefore, a force acting on a moving object will speed it up, slow it down, or change the direction in which it is moving.

A force acting on a stationary object may start it moving. Running Men by Peter Markey The front foot of each of the runners is attached to a crank. The cranks are offset from each other so that each runner moves forward at a different time.

A principle that can be demonstrated by the case of a rocket launch. The downward expulsion of gases causes a reactive force that drives the rocket upward. So, if an object is pushed or pulled, it will push or pull equally in the opposite direction. These laws of classical mechanics—or Newtonian Mechanics, as they are sometimes known—play an important part in understanding mechanical principles.

Whether or not they are any help when it comes to making things is debatable. All mechanical systems are made from combining the same basic mechanisms. It can be shown that there are really only 5 basic mechanisms. These are; 1. The Inclined Plane, or a slope 2. The Wedge 3.

The Screw 4. The Lever 5. The Wheel However, the wedge is like an inclined plane, or two inclined planes joined together, and the screw is like an inclined plane wrapped around a shaft. The wheel is like a lever which rotates through o. This means that there are really only two basic mechanisms—the lever and the inclined plane—and all other mechanisms are based on them.

Levers All machines, including automata, will almost certainly employ at least one lever. Of course, if a machine only had a single lever it would be quite a simple thing and most machines will use a combination of levers and other mechanisms. A lever is a very simple device. It consists of a rigid bar which pivots turns on a fixed point. This pivot point is called the Fulcrum.

Archimedes wrote lots of books on mechanical principles. Also, to gain this super mechanical advantage the load, in this case, the Earth, would need to be close to the fulcrum and the lever would need to be very, very long.

As with the opening chapter, you might want to skip some of this theory. However, levers are key to understanding mechanisms and there are real world examples of each type to help you through. Archimedes divided levers into three separate types or orders. Each one has the fulcrum, load and effort arranged differently.

A Lever of the First Order By moving the fulcrum closer to, or further away from the load, you change the distance the lever must travel and the amount of effort required to move the load. A pair of scissors is an example of a lever of the first order. The effort is applied to the ends held in the hand. The load is at the cutting edges.

The fulcrum is the rivet or screw which holds the two halves together. A lever of the first order always has the fulcrum located between the load and the effort.

Sheep Shearing Man by Ron Fuller The man goes up and down and on every twelfth turn of the handle he stays up long enough to have his head chopped off by the scissors. The leverage is the ratio of the distances of the effort and load to the fulcrum A and B below. When we look at these ratios we can tell how the lever will work.

In this example, the leverage is the ratio of A and B, which is , or On the left, four tins of cat food are two units away from the fulcrum. On the right, four tins of cat food are two units away from the fulcrum. Because the distance to the fulcrum is the same on both sides it should be obvious that the tins will balance. In the next example the fulcrum is off centre.

This means we have some leverage and a mechanical advantage. On the left, one tin of cat food is eight units away from the fulcrum. A Lever of the Second Order Here the load lies between the fulcrum and the effort. This kind of lever can be described as a force magnifier, having very good mechanical advantage. The wheelbarrow is an example of a lever of the second order. It is used to overcome the resistance of a heavy load by using a small force.

To achieve this mechanical advantage, the wheelbarrow obeys a rule that applies to all force magnifiers: The effort must move a greater distance than the load. Lifting the handles using a relatively small effort raises a heavy load. The fulcrum is the axle of the wheel. Nutcrackers are another example of a class two lever. Because a class two lever is a powerful force magnifier, the toughest of nuts can be cracked with a relatively small effort.

A Lever of the Third Order In a class three lever the effort is applied between the fulcrum and the load. This kind of lever can be described as a force reducer since the effort will always be greater than the load. This may not sound very useful but in certain cases it may be the only possible arrangement.

It also has the advantage that the load moves faster than the effort. So you could call it a movement amplifier. Your arm is an example of a class three lever, with your elbow as the fulcrum. The effort comes from the bicep muscle which attaches to your forearm just below the elbow.

The load, held in your hand, requires effort from the muscles to pull up against the fulcrum. The ladder below is a class three lever. The effort to lift the ladder, or hold it in place has to be applied between the load and the fulcrum.

So the higher up the ladder the fireman goes, the greater the effort needed to support him. A fishing rod is another class three lever. One hand acts as the fulcrum while the other applies the effort to move the rod up and down. The load is the weight of the tackle, bait and perhaps, a fish—which is raised a long distance by a short movement of the hand.

For example, a pair of tweezers 3rd Order are easier to control than a pair of pliers 2nd Order because the effort is applied closer to the load. An Allegory of Love by Paul Spooner The man keeps trying to hit the nail on the head but always misses on either side. This is mainly because the nail moves as well!

Practical When designing a mechanism which uses any of these three classes of lever remember that the movement of a lever will always be through the arc of a circle and not in a straight line.

Get some cardboard and 2 pins. Cut out a long straight piece your lever and a circle. Experiment by pinning them down onto another piece of card as shown on the next page.

Pin the circle down off-centre. Rotate the circle and notice how it moves the lever. Try changing the pivot point fulcrum of the lever. You should see that positioning the circle close to the fulcrum is equivalent to trying to push a door open near its hinges. Make pencil marks on the backing card to indicate how much the lever moves in different arrangements. This combination of cam and lever is one of the most common mechanisms in automata making. It allows you to test ideas very quickly and cheaply.

The method shown above could be used to decide on the size, shape and position of a cam when you know how much movement you need from the lever.

You might want to consider how you could use the cam and lever mechanism in your own design. Shafts can be anything from a piece of stiff wire or a wooden dowel to an accurately engineered steel rod. The part with the hole that supports the shaft is called the bearing. Shafts should be strong enough to support the mechanisms they carry and the right size to fit the bearings that they run in. Not too tight and not too loose. Bearings To keep the rotating shaft stable and to help it to run smoothly it is supported by a bearing.

The bearing and shaft need to be chosen together. That is, friction will wear out the bearing. Sometimes the bearing is made by simply drilling a hole but if better support or less friction is needed something more substantial might be called for.

This is because they have good quality bearings. The simplified illustration below shows how they are put together. The outer race is fixed and the inner race rotates with the shaft. Because the balls can roll with a small area of contact with the races, the friction is very low. They are made very accurately from hardened, polished steel which also helps to reduce friction. Sit-up Anubis by Paul Spooner A simple wire shaft is bent at one end to make a handle. A thin shaft works because the moving parts are so light.

You should try to constrain the movement of shafts so that they only move in the way that you want them to.

In this simple example the shaft passes through a single bearing. You could copy this with two pieces of cardboard and a drinking straw. Try it and see what problems you have. Make the hole in the disc off-centre and see how much weight you can lift up and down. Here, a second bearing has been added to provide better support to the shaft. The discs, or collars, at each end of the shaft stop it from moving from side to side.

The snail cam shown here pushes a shaft upwards. This shaft also needs the support of a bearing. If the bearing in this case, just a hole is too big, the shaft could easily move off-centre causing extra friction or jamming. By adding thickness to the bearing the up and down movement of the cam follower is much more predictable. The diameter of the hole which forms the bearing should be just big enough to allow free up and down movement.

The additional u-shaped bracket shown here is a way to position a bearing as close as possible to the end of the shaft where the cam is pushing up. Whenever bearings are working in pairs you need to take care that they are properly aligned. For example, if the bearings are holes at each end of a box, you could design the box so that the ends could be drilled at the same time.

You will find that the diameter of the dowelling can vary. A couple of test drillings with a sharp bit! Fixing You also need to think about how you will fix your cams and other mechanisms to the shaft. Below are three practical methods for avoiding the problem of the cam slipping on the shaft. A pin is pushed through a pre-drilled hole into the cam and the shaft.

The hub is part of the cam or glued to it. A screw passes through the hub and into the shaft. This keeps the fixing away from the radial surface of the cam. This is similar to 2, but easier to make. A wire, or split-pin passes through the shaft only. A screw in the cam holds it in position. Yet another way is to have a square shaft. You also have to make the square shaft round at the ends if you want it to rotate smoothly. Cranks A crank is a lever attached to a rotating shaft. Sometimes the crank is used to turn a shaft—for instance, when it is used as a handle, and sometimes the crank is driven by the rotating shaft.

In this case the crank will change the type of motion. The circular disc, with the pin, forms a crank on the end of the shaft. The pin connects to the vertical rod it has to be loose enough to allow the crank to rotate. The movement of the vertical rod is constrained by the guides. When the shaft rotates the vertical rod moves up and down like a piston.

This up and down movement is called reciprocating motion. So the crank is converting the circular motion of the rotating shaft into the up and down motion of the rod. The diagrams below show the crank in four different positions. Diagram One shows the vertical rod at its highest position.

Diagram Three shows the rod at its lowest position. The lines indicate the amount of vertical movement created by the crank. The rotating shaft will often need to be supported by bearings on both sides of the crank. In this case, the crank will look more like the illustration above.

The throw of a crank is the diameter of the path it travels. In this sequence it can be seen that the crank pin black is simply repeating the motion of the handle. You can add as many cranks to a shaft as you want but you will probably need extra bearings to support the shaft.

You can also offset the cranks from each other so that they are in different positions at different times. In the example above, when one crank is up, the other is down. Here the crank will lift the lever through a small arc as the shaft rotates. Gravity will tend to keep the lever in contact with the crank pin. Gravity Gravity is the force that attracts bodies to the centre of the Earth.

This happens because objects are attracted to each other with a force which is proportional to their mass. The Earth has a lot of mass so it pulls all the smaller objects towards its centre.

Here a lever is raised and lowered because it is resting on the rotating crank pin. Number 1 shows the lever in its lowest position and 3 shows it in its highest position. If the shaft rotates at high speed it is possible that the lever will not stay in contact with the crankshaft.

If the lever is struck hard it may bounce up higher than expected. Also, It may not have time to fall back while the crank shaft is at the lowest position.

The next design overcomes these problems. In this design the crankshaft passes through a slot in the lever. This means that the lever is driven up and down by the crank. The bead on the handle can rotate. This makes the crank handle easier to turn. Dancing Girls by Peter Markey The handle rotates a crank at the back which is connected to a crank at the front.

You can see that the connecting piece has two slots which allow the cranks to rotate. Can you work out how the front crank will move? Practical Although cranks seem simpler than cams they can be harder to make. A cam on a shaft has only one fixing point but if you make a crank from parts there are four points to fix.

However, wire is quite easy to change, so see what you can do with a pair of pliers and a coathanger welding rod may be easier if you happen to have some.

You will learn much more about the practicalities by playing with materials and mechanisms than by reading. If the string pulls down the lever, how will it go back up? How can you stop the string from slipping off the crank?

If you find it easy, attach something to the lever. How about a jointed leg and foot? Cams Like cranks, cams can also turn a rotary motion into an upward and downward motion. But they can also do lots of other more complicated things. Cranks are useful but you can have some real fun with cams.

Cams come in many shapes. The two on this page are called lobed cams because they have lobes. A lobe is just an addition to the circular shape. As with cranks, the throw of a cam and the amount of movement it creates, is the distance between the maximum and minimum radii.

One complete revolution of the cam is called a cycle. For the four-lobed cam there will be four distinct events per revolution. The timing of the events in a cycle depends on the speed of rotation.

This cam will produce one event per revolution. These lobed cams will produce two, three and five events per revolution.

You can probably guess that to produce a very long sequence of events you need more space on the cam profile.

That means you need a bigger cam. Who are you calling eccentric? It is also possible to make a cam from a circle.

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This type of cam is known as an eccentric cam and The part that the cam moves is called the follower. This is because it follows, or tracks, the profile of the cam. This produces a very smooth movement which makes it good for lifting heavier loads. Be careful not to make the eccentricity too extreme though. This cam has a raised and a dipped radius.

At the points where the profile returns to the constant radius no movement will occur in the follower. This part of the profile is known as a pause or dwell angle. You can see this more clearly in the sequence below.

Firstly, remember the previous advice about bearings. A smooth and true running shaft is always a good starting point. Think of the cam as a lever—more leverage will make the work of the cam easier. So a bigger cam will produce small movements relatively easily. You need to consider how it will follow the profile of the cam.

A sharper point on the follower will be more able to track intricate variations 1, below. You also need to consider the direction of rotation. Some cams, like the snail cam, will jam against the follower if they rotate in the wrong direction. A lot of the simpler machines that are sold in Cabaret Mechanical Theatre use cams to rotate a follower and produce rotation in a different plane. Strictly speaking, this sort of mechanism is a friction drive chapter 9. The cam and follower are working like a pair of gear wheels at right angles to each other.

In the diagrams you can see how it works. Dragon by Peter Markey The cam on the left lifts and rotates the follower clockwise if viewed from above.

Cabaret Mechanical Movement

Then the second cam, on the right, lifts and rotates the follower anti- clockwise. So, a single mechanism is acting as a cam and a friction drive. The small pins on either side of the follower stop it from rotating too far. It should be clear that using cams this way is not terribly efficient. However, these mechanisms work well enough for use in simple wooden toys. In more serious applications, you might use bevel gears to achieve the same result.

Cams for Memory and Switching Unlike cranks, cams have the ability to store information. So another way to look at cams is as the mechanical version of a computer program.

The information is stored in the shape of the cam. As the cam rotates, this information is retrieved by a cam follower. A series of cams on a single shaft can carry out quite complex programs. This is the way a lot of industrial processes were controlled before microprocessors took over and you might still find older washing machines with cam timers to control their various functions.

In these sorts of examples the cams operate switches which then operate relays, motors or other electrical devices. This is a way of simplifying, or replacing, the mechanisms in a machine.

Two Different Approaches Springs Springs have the ability to return to their original shape after stretching or compressing. This means they can be used to keep other components together or apart. Springs come in lots of different shapes and they can be used in a number of different ways. These are the four basic types: 1.

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Compress push , 2. Extension pull , 3. Torsion and 4. The definitions of spring types can be a little confusing. For instance, an elastic band can be used as an extension spring firing pieces of paper across the classroom , a radial spring stopping a rolled up poster from unrolling or a torsion spring driving the propellor in a model aeroplane. The laminated leaf spring above left is a special type of compression spring that is used in the suspension system of some cars.

The coiled, or clock spring right is a type of torsion spring. In a clockwork toy, winding it up tightens it and the winding energy is stored in the spring. As it unwinds slowly the energy drives the mechanism which operates the toy. A common example of spring usage would be when you need to keep a lever against a cam so that it follows its profile correctly.

In the previous diagram, the lever or cam follower should follow the shape of the cam through the action of gravity but if the cam rotates quickly the lever may tend to skip over some of the low points. The spring helps to ensure that it tracks the shape correctly. Of course, there is always a downside and in this case the spring will also increase the friction between the cam and the follower.

For this reason, springs are often arranged so that their tension can be adjusted. Most door handles have springs inside. In the cam example, a weight would give a constant load, whereas the load would vary with the spring.

It may also be easier to adjust a weight. If you do use springs, you may find yourself making your own from spring steel wire piano wire because all the springs you can find are either too strong or too weak. Old typewriters and small domestic appliances can be a good source for light springs. Linkages A linkage is a connection that transfers motion from one mechanical component to another.

Sometimes a linkage is a lever. This exploded diagram shows a linkage connecting a crank to a lever. As the crank rotates, the linkage transfers motion to the lever. The length of the linkage will not affect the distance travelled. This mechanism is known as a crank slider. Crank Slider with high bearing As the crank turns it pushes the linkage up and down and from side to side.

The amount of sideways movement can be altered by moving the bearing up or down. Crank Slider with low bearing The closer the bearing is to the crank, the more sideways movement there will be.

The high and low points remains the same. Additional movement in the wings and legs is gained by the clever use of linkages. The wings and legs are levers.

They are pushed or pulled by the linkages strings and wires which are attached to the base. When the body of the horse is pushed up and down the linkages give movement to the wings and legs. This exploded diagram shows a three-bar linkage. It transfers the rotating motion of the crank via bar 1 and bar 3 to a side-to-side motion of bar 2.

The pegs beside bar 1 limits its movement and stop it rotating too far with the crank. The sequence on the next page makes the action clearer. The crank-slider arrangement makes the top of bar 1 describe the shape of an ellipse A.

Bar two is a lever with a fixed pivot point at the bottom. Bar 3 connects the other two bars so that the top of bar 2 B approximates a straight line movement. The rotary action of the crank, is turned into an ellipse and then an arc by constraining levers at different points. Going Another Way—The Bell Crank A bell crank linkage is useful for changing an up-down movement to a side-to- side movement or vice-versa.

The diagram shows a crank which pushes the vertical rod up and down. The bell crank rotates around its pivot point and moves the horizontal rod from side to side.

The bell crank is really just another type of lever so the amount of movement can be increased by making it bigger or smaller.

You can also make one end of the bell crank longer or shorter to change the amount of leverage. It would be possible to devote a whole book to linkages but we only have space to cover a few. The ratchet is a mechanism which gives a motion that is not continuous.

This is known as stepped or intermittent motion. The ratchet is a wheel with notches cut into it. download on site. Some Principles, 2. Levers, 3. Shafts, 4. Cranks 5. Cams, 6. Springs, 7. Linkages, 8. Ratchets, 9. Control, The Checklist. The link for making pin wheel templates is here. Follow on Instagram! You are here:

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