1.5 Mechanical Devices Flashcards
What are the types of motion?
- Linear
- Rotary
- Reciprocating
- Oscillating
What is linear motion?
movement in a straight line, such as on a paper trimmer.
What is rotary motion?
movement round in a circle, such as a wheel turning
What is reciprocating motion?
movement backwards and forwards in a straight line, such as the movement of the needle on a sewing machine
What is oscillating motion?
movement swinging from side to side, such as a pendulum in a clock
What is a lever?
a mechanism that moves around a fixed point (a pivot)
What is a load?
the object to be moved
What is the effort?
the force applied to move the load
What is the fulcrum?
the point where the load is pivoted
What is a class 1 lever?
a lever where the fulcrum is located between the load and the effort, e.g., a seesaw
What is a class 2 lever?
the load is between the effort (force) and the fulcrum, e.g., a wheelbarrow
What is a class 3 lever?
the fulcrum is at one end and the force is applied in the middle and the weight is on the other end, e.g., cooking tongs
What are linkages?
mechanisms that transfer force and can change the direction of movement
What are the properties of a simple linkage?
- change the direction of motion and force
- change the size of the output motion compared to the size of the input motion
- create parallel motion
- change one type of motion into another type of motion
What are the properties of a simple linkage with the pivot closer to the output end of the level?
- change the direction of motion and force
- change the size of the output motion compared to the size of the input motion
- change the size of the output force compared to the size of the input force
What is a bell-crank mechanism?
- The direction of motion is turned through 90 degrees
- The magnitude of the output force is greater than that of the input force when the fixed pivot is closer to the output lever
What is a parallel motion linkage?
In a parallel motion linkage, often referred to as a push-pull linkage, the direction of motion and magnitude of the forces are the same but are used when the force cannot be transferred directly in a straight line.
What is a cam?
A mechanism with a cam, slide and follower. When the cam rotates the follower moves up and down.
What are the three things a cam can do?
- Go up (rise)
- Go down (fall)
- Stay still (dwell)
What are the different shaped cams?
- Round
- Egg-shaped
- Ellipse
- Eccentric
- Hexagon
- Snail
What is a gear train?
a mechanism for transmitting rotary motion and torque
What is a torque?
The turning force that causes rotation
How do you find the velocity ratio of a simple gear train?
Number of teeth on the driven gear ÷ number of teeth on the driver gear
What is friction?
The resistance of motion when one object rubs against another
What is Co-efficient of friction?
The amount of friction a material has
How do you find the velocity ratio of a sprocket and chain system?
Number of teeth on the driven sprocket ÷ number of teeth on the driver sprocket
How do you find the velocity ratio of two pulleys?
Diameter of the driven pulley ÷ diameter of the driver pulley
