Levers and Linkages 1 To understand the difference

Levers and Linkages

1. To understand the difference between levers and linkages. 2. To understand how levers and linkages can be used to change motion (changing magnitude)

Write the date in your book: Add the following title to your page and underline: Levers and Linkages

Levers are possibly the oldest type of mechanism. A lever is a simple machine that allows you to gain a mechanical advantage in moving an object or in applying a force to an object. Levers help us lift loads with lesser effort. A lever changes an (input) movement and force (effort) into an output movement and force (load). A lever moves around a fixed point which is called a pivot. https: //www. youtube. com/watch? v=E 8 RA 9 Kw_Ia. E

§ The LOAD is the object to be moved § The EFFORT is the force applied to move the load (object) § The FULCRUM is the point where the load is pivoted

First order levers have a pivot in the middle This is the most common type of lever. With a class 1 lever the fulcrum is in the middle. The effort is on one side and the load is on the other. A see saw is an example of a class one lever. Other examples are a crowbar, scissors, claw hammer, tin snips, weight scales.

Second order levers have the load in the middle With a class 2 lever, the fulcrum is at one end, the effort is at the other end and the load is in the middle. A wheelbarrow is an example of a class 2 lever. Other examples include bottle openers, nut crackers and foot pumps.

Third order levers have the effort in the middle With a class 3 lever, the pivot is at one end, the load is at the other and the effort is in the middle. A shovel is an example of a class 3 lever. Other examples are a pair of tweezers, a fishing rod. Arms and legs are also examples of class 3 levers.

First order lever Third order lever Second order lever Copy the diagrams into your workbooks and make sure your label them first, second and third order levers.

More LEVERS… Find LEVERS in your body? Put your hands on both sides of your face. Move your jaw up and down. • Lots of LEVERS joined together are called LINKAGES. LEVERS join at a moving or fixed PIVOT.

Linkages are widely used in mechanisms to transfer force and can change the direction of movement. They are simply an assembly of levers to transmit motion and force. Different linkages can be designed to transmit motion and force. The number and shapes of the linkage can change the direction of the force, and the position of the pivots can change the size or magnitude of the force. The closer the pivot is to the output end of the lever the larger the force is at the output. http: //www. technologystudent. com/cams/link 1. htm

REVERSE MOTION LINKAGE https: //www. youtube. com/watch? v=osf. Sm. G 9 tfck As the top rod moves to the left the bottom rod moves to the right. The bars move in opposite directions. Another way of describing this linkage is the direction of movement in one rod is reversed in the other rod. The fixed pivot is the centre of rotation.

PUSH PULL LINKAGE If you want the output to move in the same direction as the input, then you would use the push-pull linkage. This consists of levers connected with two fixed pivot points.

PARALLEL MOTION LINKAGE https: //www. youtube. com/watch? v=MN 9 Uh. HINXDw As the large rod at the top of the diagram moves to the left the two small rods at the bottom move to the right. All the rods are parallel to each other.

BELL CRANK LINKAGE https: //www. youtube. com/watch? v=-nu. Ah. MMAb. Xw A bell crank linkage changes direction of a force through 90 oc. The magnitude of the output force can be changed by moving the fixed pivot so its not an equal distance between the two moving points.

A lever is a very simple device it's basically a rigid bar that pivots on a fixed point. Linkages are mechanisms which allow force or motion to be directed where it is needed. Linkages can be used to change: • The direction of motion • The type of motion • The size of a force

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