Flashcards
What is a structure that relies of the weight of the material for their strength and support. Typically made with stone, brick, soil and concrete blocks?
Mass structures
What are the key features of a mass structure?
They rely on the weight of the material for their strength and support.
What are mass structures usually made of?
Stone, brick, soil and concrete blocks
What are framed structures?
A structure that is made by connecting individual parts called members of material.
What structure is made by connecting individual parts called members?
Framed structures
Examples of framed structures
Bridges, roof truss
Examples of mass structures
Pyramids, igloos, water dams
What structure is made from thin materials to create a hollow structure?
Shell structures
What is a shell structure?
A structure made from thin materials that create a hollow structure
What are shell structures typically made of?
Sheet steel or plastic
Examples of shell structures
A car body, aircraft fuse cage.
What structure is naturally formed and grow and erode over time?
Natural structures
What are natural structures?
Naturally formed structures that grow and erode over time
Examples of natural structures
Skeletons, trees and Grand Canyon.
What linkage forms a Z shape
Reverse motion linkages
What linkage forms a /-/ shape
Parallel linkages
What linkage forms a quarter circle shape
Bell crank linkage
Do materials react better when being crushed or being pulled apart?
Crushed
What is the rise in a cam?
The part of the cam that causes the follower to rise
What is a dwell in a cam?
When the cam rotates but the follower does not rise or fall
What is the fall in a cam?
The part of the cam that causes the follower to fall
What is one cycle in a cam?
One rotation or revolution of the cam.
Does an ellipse cam ever dwell
No
Main characteristics of a snail cam
It has a very sharp fall and if put on the wrong way it will break.
What are the 4 types of rotation?
Rotary, linear, oscillating, reciprocating
What does a displacement diagram show.
It shows the displacement of the cam at different points of rotation.
If a driver and driven goes from small to big what happens to the speed and torque
Less speed and more torque.
If a driver and driven go from big to small then what happens to the speed and torque
It will have more speed and less torque
Velocity ratio diameter
Diameter of driven pulley/diameter of driver pulley
Velocity ratio torque
Output torque/input torque
Velocity ratio speed
Input speed/ output speed
What is the formula for torque
Torque = Force(F) x Distance(M)
What are spur gears?
Spur gears are gears that push together when rotating and have teeth .
What are the advantages of spur gears?
Slipping doesn’t happen because of the positive drive, less parts required because there is no need for a belt or chain, low cost to get.
What are the disadvantages of spur gears?
Suited to low speeds, the gear teeth experience a lot of stress, can’t transfer power between non parallel shafts, make a lot of noise when operating at high speeds.
What are gear trains?
A gear train is made up of more than 2 gears.
What are idler gears?
An idler gear makes it so that the driver and the driven are rotating the same way.
What are compound gears?
A number of gears that are fixed together and rotate at the same speed and share the same shaft.
What are bevel gears?
Used to change direction of the drive in the gear system 90 degrees.
What is torque in gears?
The turning force when the load F is applied at distance L away from the centre of rotation.
What is the equation for torque in gears?
Torque = Force x Distance
T = N x mm
What measurement is torque expressed in?
Torque is measured in Newton millimetres (Nmm).
What is torque determined by
It is determined by the Distance and the Load
What is a worm gear?
It is another way of changing the direction of the drive in a gear system 90 degrees. It is powered by a motor.
