Mechanical Devises Flashcards
What is motion
• Motion is the action of something being moved
• Motionless is something at rest
• There are different types of motion which can be added together and even changed from one to another
What are all the different types of motion
- Linear motion
(movement in one direction along a straight line) - Reciprocating motion
(A repetitive back-and-forth or up-and-down linear action) - Oscillating motion
(A repetitive back-and-forth motion along a curved path) - Rotary motion
(Objects moving in a circular motion usually around a fixed axis)
What are levers
They have two parts – a bar and a pivot also known as the fulcrum
What is mechanical advantage
- Levers help provide mechanical advantage (MA)
What is the equation for mechanical advantage (MA)
MA = Load/Effort
It can also be made into a ratio Load : Effort
What is a First order lever (Class 1)
• Class 1 levers act in a seesaw or scissor action
• The load and effort are at opposite sides with the fulcrum positioned at any point between
What is a Second order lever (Class 2)
• Class 2 levers act in a wheelbarrow action or that similar to a nutcracker
• The effort is at the opposite end to the fulcrum, with the load positioned between
What is a Third order lever (Class 3)
• Class 3 levers have a pincer-like action seen with tweezers and tongs
• The load is at the opposite end to the fulcrum, with the effort positioned between
What does equilibrium mean
• When the effort and the load are equal, equilibrium can be created in a mechanism
What are linkages
Linkages are mechanisms that use rigid parts to:
• Change the magnitude of a force
• Change the direction of a force, or
• Transform it into a different motion
What is a reverse motion linkage
• This changes the direction of the input motion
• If the input is pulled, the output will push
• The linkage uses a fixed central pivot
What is a Parallel motion linkage
• Also known as push / pull linkage as it keeps the direction of the output the same as the input
What is a Bell crank linkage
• Input direction is converted through 90 degrees
• It changes horizontal motion to vertical and vice versa
• Often found in steering and throttle mechanisms on vehicles
What is a crank and slider
• Crank and sliders convert rotary motion into reciprocating motion and vice versa
• A linkage commonly found in engines to transfer the energy from pistons
• The slider is guided along a set path
What is a treadle linkage
• Treadle linkages convert rotary motion into
oscillating motion and vice versa
What are rotary systems
• Rotary systems drive mechanisms in machinery and equipment
• A rotating axle called a camshaft is used to drive, or is driven by, other mechanical components
How are cams used in rotary sytems
• Cams are shaped pieces of material that are attached to the camshaft
• Cams change rotary motion into reciprocating motion through a follower
How are followers used in rotary systems
• Followers rest on a cam and track its rise and fall
There are:
- flat followers
- knife-edged followers
- roller followers
What are gear trains
• Cog wheels are meshed to create gear trains
• A simple gear train has a drive cog or ‘drive gear’ which rotates the ‘driven gear’
How can gear ratios be calculated
• Gear ratios can be worked out by comparing the number of teeth on each gear
• If the drive gear has 20 teeth and the driven gear has 10, then the driven gear will rotate twice for each turn of the drive gear
What is an idler gear
• An idler gear ensures that the direction of the drive gear and the driven gear are the same
• The idler gear sits between the two gears and directly transfers the drive
What are pulleys and belts
• Drive belts are used to transfer drive from one pulley to another
• Belts rely on friction to grip the pully and are often made from rubber but also many other materials
• A pulley is often grooved to help increase the friction on the belt
What are ‘block and tackle’ systems
• Block and tackle systems combine pulleys to liftheavy weights
• A rope is looped around pulleys in a block to form a tackle, to reduce the effort needed to lift
• As more pulleys are added, the lighter it becomes, although more rope needs to be pulled through
