A. Mechanical Devices Flashcards
Linear Motion
Movement in one direction along a straight line
Reciprocating motion
Repetitive linear movement (up and down / side to side)
Rotary motion
Movement on or around an axis
Oscillating motion
Movement backwards and forwards along a curved path
What is a lever?
A simple way to gain mechanical advantage, making lifting or moving something easier
What is a fulcrum?
A pivot point around which a lever turns
What is an effort?
An input force
What is a load?
An output force
How do you calculate mechanical advantage?
MA = Load / Effort
Where is the fulcrum, load and effort in a First Order Lever?
The fulcrum is between the force and the load
E.g. Pliers
Where is the fulcrum, load and effort in a Second Order Lever?
The fulcrum is at one end with the effort at the opposite end
E.g. a wheelbarrow
Where is the fulcrum, load and effort in a Third Order Lever?
The fulcrum is at one end and the load is at the opposite end. The effort is applied in the middle.
E.g. tweezers
What are rotary systems?
Drive mechanisms in equipment and machinery. Transfer the direction force along different paths and through changes of angle and direction
What type of movement does a circular/eccentric cam have?
Steady rise and fall
What type of movement does a pear cam have?
Rapid rise and fall followed by a long dwell (rest)
What type of movement does a snail cam have?
Long dwell (rest) followed by a steady rise and sudden fall.
(Can only turn in one direction)
What type of movement does a heart shaped cam have?
Slight rise and fall with no dwell period
What is a drive gear?
The drive gear (input) turns the driven gear (output).
The gears turn in opposite directions and the toothed wheels interlock to prevent slipping.
What is an idler gear?
Used to change the direction of rotation so that the driven gear turns in the same direction as the drive gear.
How do you calculate gear ratio?
Driven gear / Drive gear
How do you calculate velocity ratio (gears)
Drive gear / Driven gear
To achieve maximum speed: Larger drive gear paired with a smaller driven gear
A gear system of a simple toy train has a driver gear with 15 teeth and a driven gear with 30 teeth. What is the gear ratio?
Driven / Drive = 30/15
= 2:1 or 2
What is a fixed pulley?
Uses a wheel with a groove in it and a rope that sits on the groove. Can change the direction of the force needed, which makes lifting easier.
Weight will feel the same
What is a block and tackle pulley?
Uses two or more pulleys, one fixed and one movable, to help reduce the amount of effort needed to lift a load. Provides a mechanical advantage, making the load easier to lift.
