Bell Crank: Difference between revisions

Latest revision as of 09:04, 5 February 2018

Description

If an ‘L’-shaped lever is pivoted at its centre, the direction of the input movement or force would be turned through 90° at the output. This linkage is known as a Bell Crank (so called because it was used in Victorian times in linkages used to operate doorbells and servants' bells). They can be used to change the angle of motion through any angle but 90° is common.

Features and Uses

The Brake Caliper on a bicycle is a common device which uses the principle of this mechanism. Here the force from the handlebar lever is turned through 90° to squeeze the brake block against the wheel rim.

If the fulcrum or pivot is at an equal distance from the input and output then the movement of the output will be equal to the movement of the input. Otherwise the movement will be different and the system will have some degree of Mechanical Advantage.

Animations

Examples from Nguyen Duc Thang's YouTube Channel 2100 Animated Mechanical Mechanisms

90° Bell Crank

Robot Gripper - a hydraulic or pneumatic cylinder opens and closes the jaws, permitting it to grasp and release objects. The blue jaw is a Bell Crank which, together with the green con-rod and pink slider, creates a slider crank mechanism.

Toggle Clamp - the adjustable clamp head is held on a Bell Crank which, together with green con-rod and violet lever, form a four bar linkage coming into toggle as the green handle of the con-rod is pushed down.

DT Online Buyers' Guide

Simple Frames and Linkages can be explored using Construction Kits such as those listed below.

More varied models can be constructed using the materials listed at Truss Bridge Models or Stripwood Technology Materials and tools described in Stripwood Technology Tools.

Click top left to enlarge


Viga Wooden Construction Set	Straws and Connectors	Construction Engineering Blocks	K'Nex Education Group Set	Engino STEM Construction Set	Lego Duplo Tech Machines Set	Lego Education Core Set	Meccano Easy Construction Box	Fischertechnik Universal Building Kit

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-[[File:MechanismsBellCrank.jpg|250px|right]]
+[[File:MechanismsBellCrank.jpg|300px|right]]
+__TOC__
-If an ‘L’-shaped [[Class of Lever|lever]] is pivoted at its centre, the direction of the input movement or force would be turned through 90° at the output. This [[linkage]] is known as a [https://en.wikipedia.org/wiki/Bellcrank '''Bell Crank'''] ''(so called because it was used in Victorian times in linkages used to operate doorbells and servants' bells)''. They can be used to change the angle of motion through any angle but 90° is common.
-A common device which uses this mechanism is the brake caliper on a bicycle. Here the force from the handlebar lever is turned through 90° to squeeze the brake block against the wheel rim.
+=====Description=====
+If an ‘L’-shaped '''[[Class of Lever|lever]]''' is pivoted at its centre, the direction of the input movement or force would be turned through 90° at the output. This '''[[:Category:Linkages|linkage]]''' is known as a [https://en.wikipedia.org/wiki/Bellcrank '''Bell Crank'''] ''(so called because it was used in Victorian times in linkages used to operate doorbells and servants' bells)''. They can be used to change the angle of motion through any angle but 90° is common.
+[[File:Campagnolo Record brake caliper.jpg|200px|right|Campagnolo Record brake caliper|link=https://en.wikipedia.org/wiki/Bicycle_brake#Side-pull_caliper_brakes]]
+=====Features and Uses=====
+The [https://en.wikipedia.org/wiki/Bicycle_brake#Side-pull_caliper_brakes '''Brake Caliper'''] on a bicycle is a common device which uses the principle of this mechanism. Here the force from the handlebar lever is turned through 90° to squeeze the brake block against the wheel rim.
 If the fulcrum or pivot is at an equal distance from the input and output then the movement of the output will be equal to the movement of the input. Otherwise the movement will be different and the system will have some degree of '''[[Mechanical Advantage]]'''.
+=====Animations=====
+* Examples from '''[[2100 Animated Mechanical Mechanisms|Nguyen Duc Thang's]]''' YouTube Channel '''[[2100 Animated Mechanical Mechanisms]]'''
+{|
+|-
+| [https://youtu.be/e51sMAdGS40 '''90° Bell Crank''']
+| {{#ev:youtube|e51sMAdGS40|150x150|right||frame|loop=1&autoplay=0&playlist=e51sMAdGS40}}
+| [https://youtu.be/YGlT0LtRzMw '''Robot Gripper'''] - a hydraulic or pneumatic cylinder opens and closes the jaws, permitting it to grasp and release objects. The blue jaw is a Bell Crank which, together with the green con-rod and pink slider, creates a slider crank mechanism.
+| {{#ev:youtube|YGlT0LtRzMw|150x150|right||frame|loop=1&autoplay=0&playlist=YGlT0LtRzMw}}
+| [https://youtu.be/lrL2_5tj1IE '''Toggle Clamp'''] - the adjustable clamp head is held on a Bell Crank which, together with green con-rod and violet lever, form a four bar linkage coming into toggle as the green handle of the con-rod is pushed down.
+| {{#ev:youtube|lrL2_5tj1IE|150x150|right||frame|loop=1&autoplay=0&playlist=lrL2_5tj1IE}}
+|}
+{{Construction Kits Buyers Guide}}