Ch01

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Unformatted text preview: Solutions to Chapter 1 Exercise Problems Problem 1.1 Find a mechanism as an isolated device or in a machine and make a realistic sketch of the mechanism. Then make a freehand sketch of the kinematic schematics for the mechanism chosen. Typical examples of solutions for this problem are given in the problem definitions of Chapter 3. Some examples are: 201˚ A B 2 ω2 1.88" 1.64" 3 C 4 2.22" 1 D 1.55" Bicycle suspension 2ω 3 B 3 C 2 4 θ A D Oscillating fan ω2 Y A 6˚ 2 Door C B 3 X D 4 Door closing linkage -1- Problem 1.2 Cabinet hinges use various types of linkages for the folding mechanism. Identify three types of cabinet hinges and make a freehand sketch of the kinematic mechanism used. There are a large number of mechanisms that are used to obtain various types of hinge motions. Below are three of them. The first is a 6-bar Watt’s linkage used for chest lids. The hinge guides the chest lid such that no part of the lid crosses the plane of the back of the chest. The second example is a four bar linkage that guides the door from the open to closed position. The hinge is basically hidden when the door is closed. The third uses a 6-bar Watt’s linkage with a slider. The lid glides about the back corner of the box. -2- Problem 1.3 The drawings shown below are pictorial representations of real mechanisms that are commonly encountered. Make a freehand sketch of the kinematic schematic representation of each mechanism. A Pin in a slot (pin attached to seat) B 4 2 3 Water Pump Folding Chair C 1 Casement window mechanism -3- Solution A B 2 3 4 1 C Water Pump 1 2 3 Folding Chair 4 3 5 2 1 6 Casement window mechanism -4- Problem 1.4 Linkages are often used to guide devices such as computer keyboards in and out of cabinets. Find three such devices, and make a freehand sketch of the kinematic mechanisms used for the devices. Typewriter desk linkage Under drawer swing up mechanism Overhead bin hinge Problem 1.5 Fourbar linkages are used in common devices around the home and businesses. Locate six such devices and make a freehand sketch of each device and describe its function. Solution: Sample examples are given in the following: -5- Brake for wheelchair. The mechanism exhibits a toggle motion Walking toy. The fourbar linkage moves the leg and wing. Door closer. The fourbar linkage is connected to a damper mechanism Kickback protector on table saw. The fourbar linkage is a parallelogram linkage. -6- Tree trimmer. The fourbar linkage is a double lever mechanism used to increase the mechanical advantage Vicegrips. The fourba...
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