# An Introduction to Mechanisms

### 1. Cam Profiles

• Name the following cam profiles and explain how it controls the movement of the follower.

### 2. Pulley Calculations

For each of the problems below - draw a diagram of the pulleys described and then calculate the answer.

• a) A driver pulley has a diameter of 150mm and rotates with a speed of 30rpm. Calculate the speed of a driven pulley with a diameter of 50mm.
• b) A driver pulley has a diameter of 70mm and rotates with a speed of 200rpm. Calculate the speed of a driven pulley with a diameter of 350mm.
• c) A driver pulley has a diameter of 100mm and rotates with a speed of 60rpm. Calculate the required diameter of a driven pulley if we want it to rotate at 150rpm.
• d) We have a driver pulley with a diameter of 80mm. And a driven pulley with a diameter of 40mm. What speed will the driver pulley need if the driven pulley must rotate at a speed of 90rpm?
• e) A driven pulley has a diameter of 10mm and must rotate at a speed of 200rpm. What diameter will the driver pulley need if it can only rotate at 50rpm?

### 3. DC Motors

Define the following DC motor terms:

• a) Magnetic field
• b) Armature
• c) Commutator
• d) Brushes

### 4. Glues

Describe the main uses for the following glues:

• a) PVA glue
• b) Epoxy Resin Glue
• c) Super Glue
• d) Spray glues
• e) Clear model glue

### 5. C.A.D. usage

• a) What is the meaning of the term C.A.D?
• b) How does making a 3D model of a product help a design team develop the product?
• c) Do you thing there is no need to use an expensive piece of equipment such as a laser cutter to make a model? Explain your answer.

### 6. Mechanism Design

A local florist has asked you to design a model to be placed next to the checkout. The mechanism (shown Below) is nearly complete but a simple mechanism needs adding. The mechanism must make the characters arm move up and down in a fairly smooth movement.

• a) Complete the drawing by adding the mechanism.
• b) Explain how it works?

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