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Technology

Grade 9

Mechanisms and motion

Module 3

Pulleys and gears

  • Pulleys and gears are used to transfer rotary motion from one place to another. Both are wheels. Pulleys are wheels with grooves in the rims, in which a belt or rope can run. Pulleys can transfer rotary motion from one shaft to another or can be used to lift heavy loads.
  • Gears are wheels with teeth evenly spaced around the rims. Several gears can be placed, so that their teeth interlock, or mesh. When two or more gears are used together, they form what is called a gear train. Gears can be used to change the speed and direction in which something rotates. When chains are used to connect the “gears”, a chain and sprocket system is formed, for example on bicycles and motorcycles.Simple pulley
    Twisted pulley
    Compound pulley
    Two gears
    A Gear train

Compound gears

Rack&Pinion

Worm and wheel

Bevel gears

Gear Systems

  • The illustration shows gears fixed to parallel shafts, forming a simple gear train. The gear fixed on the drive shaft is called the driver gear and is connected to the driven gear. The shafts will turn in opposite directions and, because the gears have different sizes, they will turn at different speeds. The difference in their speeds (velocity ratio) can be calculated from the number of teeth on each gear.
  • This means that in this case the driver shaft must turn twice for the driven shaft to complete one turn.

Pulley Systems

  • Pulley systems use a belt to transmit motion and force from the driver shaft to the driven shaft. Cars use a pulley system with V-belts running in grooves on the pulley wheels. Speed changes are made by using different sizes of pulleys on the driver and driven shafts respectively. By comparing the sizes of the two pulleys you can calculate the velocity ratio (VR) of the system.
  • If the diameter of the driver pulley in a pulley system is 100 mm and that of the driven pulley 25 mm,
  • This means that one turn of the driver shaft will give four turns of the driven shaft. The speed of the driven shaft can be calculated as follows:
  • If the input speed is 2000rpm and the VR 1:4 the output speed is 8000 rpm.

Activity 1

1. Add arrows to the sketches to indicate the output direction.

  1. Sketch the cross-section of a V-belt and pulley.
  2. Give two examples of the use of pulley systems.
  1. The figure shows two gears in mesh:

4.1 If the input speed is 1 250 rpm what is the output speed?

4.2 How could the driver and driven gears be made to rotate in the same direction?

  1. What are the advantages and disadvantages of chain and sprocket systems compared to pulley systems?
Advantages Disadvantages
Chain and sprocket systems
Pulley systems
LO 2.3

Assessment

LO 2
TECHNOLOGICAL KNOWLEDGE AND UNDERSTANDING The learner will be able to understand and apply relevant technological knowledge ethically and responsibly.
We know this when the learner:
systems and control:2.3 demonstrates knowledge and understanding of interacting mechanical systems and sub-systems by practical analysis and represents them using system diagrams:
  • gear systems;
  • belt drive pulley systems with more than one stage;
  • mechanical control mechanism (e.g. ratchet and pawl, cleats);
  • pneumatic or hydraulic systems that use restrictors;
  • one-way valves;
  • systems where mechanical, electrical or pneumatic or hydraulic systems are combined;

Memorandum

ACTIVITY 1

1.

2.

  1. Drilling machine, Block and tackle
  • 80 4 × 1250 1 size 12{ { {"80"} over {4} } times { {"1250"} over {1} } } {} = 250 ohm
  • Insert idling gear

4. Advantages of tooth gears and chains

  • Greater forces can be transferred
  • Chains do not slip/slide
  • Chains can be disassembled for removal

5.Advantages of pulleys and belts

  • Belts are not noisy
  • Belts can be stretched for fitting and for removal
  • Crossed belts can change the direction of rotation

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Google
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
Privacy Information Security Software Version 1.1a
Good
are your images copyright or can i use them freely in education
Stephanie Reply

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Source:  OpenStax, Technology grade 9. OpenStax CNX. Sep 15, 2009 Download for free at http://cnx.org/content/col11071/1.1
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