Presentación sobre mecanismos para 2º ESO en inglés.

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(MECHANISMS 2(MECHANISMS 2ndnd
E.S.OE.S.O.).)
TechnologyTechnology
Transmission ofTransmission of
circular movement.circular movement.
Jesús Prieto Fuentes
P.A.L.E. 2008

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PreviousPrevious
►22ndnd
year ESOyear ESO
►Thematic Block VII: MechanismsThematic Block VII: Mechanisms
►Students: two years in the bilingualStudents: two years in the bilingual
section, first year with Technology.section, first year with Technology.

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GoalsGoals
►To approach to the technicalTo approach to the technical
vocabulary.vocabulary.
►To identify the main mechanisms inTo identify the main mechanisms in
usual things.usual things.
►To know the main applications ofTo know the main applications of
the different mechanisms.the different mechanisms.

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Circular movement.Circular movement.
► Circular or rotary movement is the most usual inCircular or rotary movement is the most usual in
machines.machines.
► Generally this movement is produced by anyGenerally this movement is produced by any
kind of engine.kind of engine.
► The rotary movement is transmitted between twoThe rotary movement is transmitted between two
shafts:shafts:
► In order to transmit this movement we needIn order to transmit this movement we need
different mechanisms.different mechanisms.

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MECHANISMS

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Types of transmission ofTypes of transmission of
the circular movement andthe circular movement and
mechanismsmechanisms
Between parallel shaftsBetween parallel shafts
Toothed wheels and chainsToothed wheels and chains
Pulleys and beltPulleys and belt
Spur gear system.Spur gear system.
Between perpendicular shaftsBetween perpendicular shafts
Bevel gearsBevel gears
Spur Gear-worm gearSpur Gear-worm gear

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ROTARY SPEED
AND VELOCITY
RATIO

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Rotary speeds.Rotary speeds.
 The rotary speed depends on the
diameter of the wheel and, in case of
the gears, also on the number of teeth.
 The rpm (revolutions per minute) of a
large wheel will be less than a smaller
one.

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Velocity ratio (i)Velocity ratio (i)
 The relationship between the speeds isThe relationship between the speeds is
inverse to the diameters´ one, that isinverse to the diameters´ one, that is
known asknown as velocity ratiovelocity ratio ..
 If the driver wheel is larger than the drivenIf the driver wheel is larger than the driven
one, then i>1 so the transmissionone, then i>1 so the transmission
multipliesmultiplies the speed.the speed.
 If the driver wheel is smaller than theIf the driver wheel is smaller than the
driven one, then i<1 so the transmissiondriven one, then i<1 so the transmission
reducesreduces the speed.the speed.

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ExampleExample
In this case; the
diameter of the driven
wheel (400mm.) is
twice the diameter of
the driver wheel
(200mm.), so the speed
must be the half.
Diameter of the driver wheel
Diameter of the driven wheel
200
400
1
2
i = = =
Which is the velocity ratio?

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GlossaryGlossary
►ShaftShaft
►PulleyPulley
►Gear / Spur gear / Bevel gearGear / Spur gear / Bevel gear
►Worm gear / endless screwWorm gear / endless screw
►Rotary speed / rpmRotary speed / rpm
►Velocity ratioVelocity ratio

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ACTIVITIES

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Activity 1 (Test)Activity 1 (Test)
1. Which of the following assemblies transmit the
rotary movement between parallel shafts in the
same direction?

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Activity 2Activity 2
2. Driven pulley
Diameter = 300mm.
1. Driver pulley
Diameter = 100mm.
Speed: 1500 r.p.m.
CALCULATE:
Speed of the driven pulley:
Velocity ratio:

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Questions areQuestions are
welcome.welcome.
Plenary
Investigate at home and
try to discover this
mechanisms in some
machine that you use.
Do you want to
comment something
about this subject?

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Thank you very muchThank you very much
for your attention!for your attention!

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Toothed wheels and chainsToothed wheels and chains

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Pulleys and beltPulleys and belt

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Spur gear system.Spur gear system.

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Bevel gearsBevel gears

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Spur Gear-worm gearSpur Gear-worm gear

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Circular movement.Circular movement.
►Circular or rotary movement is the mostCircular or rotary movement is the most
usual in machines.usual in machines.
►Generally this movement is produced byGenerally this movement is produced by
any kind of engine.any kind of engine.
►The rotary movement is transmittedThe rotary movement is transmitted
between two shafts:between two shafts:
►In order to transmit this movement we needIn order to transmit this movement we need
different mechanisms.different mechanisms.

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Velocity ratio (i)Velocity ratio (i)
 The relationship between the speeds isThe relationship between the speeds is
inverse to the diameters´ one, that isinverse to the diameters´ one, that is
calledcalled velocity ratiovelocity ratio ..
 If the driver wheel is larger than the drivenIf the driver wheel is larger than the driven
one, then i>1 so the transmissionone, then i>1 so the transmission
multipliesmultiplies the speed.the speed.
 If the driver wheel is smaller than theIf the driver wheel is smaller than the
driven one, then i<1 so the transmissiondriven one, then i<1 so the transmission
reducesreduces the speed.the speed.

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Activity 1 (Test)Activity 1 (Test)
1.1. Which of the following assemblies transmit theWhich of the following assemblies transmit the
rotary movement between parallel shafts in therotary movement between parallel shafts in the
same direction?same direction?
3. In the following arrangements. Which one
multiplies the speed?
2. One of the following gear systems
transmit the movement between parallel
shafts. Which one?