Wheel-and-Axle and Pulley - Dulaney High School Home Page by wanghonghx

VIEWS: 55 PAGES: 33

									  Wheels and Pulleys

Introduction to Engineering and
Technology Concepts
                  Mindjog

1. How much effort will be needed to lift a
   100 pound load if distance to effort is
   five feet and distance to resistance is
   one foot?
2. How much effort will be needed to lift a
   48 pound load if distance to effort is
   two feet and distance to resistance is
   8 feet?
Wheel & Axle
          Wheel and Axle

The Wheel and Axle work off the same
principle as the lever.

              Wheel diameter = 8
              Axle diameter = 1
              Produce an 8/1 MA
             Wheel and Axle
If the effort (input) is applied to the wheel, the axle
is the resistance (output).
 – This will produce a mechanical advantage
    equal to the size ratio of the wheel as
    compared to the axle.

                  Wheel diameter = 8
       R     E    Axle diameter = 1
                  Produces an MA of 8
What class lever is this wheel configuration?
              Wheel and Axle
If the effort (input) is applied to the axle, the
wheel is the resistance (output).
 – This will create an increase in output
    distance but it will take more effort to turn.

                   Wheel diameter = 8
       E     R
                   Axle diameter = 1
                   Produces an MA of 1/8

What class lever is this wheel configuration?
  IDENTIFY ITEMS THAT
 APPLY THE PRINCIPLE OF
 THE WHEEL AND AXLE IN
THEIR OPERATION. GIVE AT
LEAST TWO EXAMPLES FOR
      EACH CLASS.
    Wheel Examples (2nd Class)

Doorknob           Car Jack
Screwdriver        Telescope/
Car Climate        Microscope Knobs
Controls           Windmill/Wind
Dimmer Switch      Turbines
Pencil Sharpener   Waterwheel
Lamp Switch        Wheel of Fortune
Hamster Wheel      The Price is Right
Pottery Wheel
    Wheel Examples (3rd Class)

Ferris Wheel      Carousel/Merry-Go-
Wheelbarrow       Round
Clock Hands       Pizza Cutter
Band Saw          Paint Roller
Circular Saw      Fan Blade
Blender/Grinder   Boat or Airplane
Bike/Car Tires    Propeller
Fishing Reel      Helicopter Rotor
                  Big Wheel™
   Mechanical Transmission

A device which accomplishes one, or
more, of the following:
– Transfer motion from one point to another
– Increase output speed OR force
– Change direction of motion
– Change type of motion
               Motion

Four types of motion:
– LINEAR – Straight line, one direction
– RECIPROCATING – straight line, back
  and forth
– ROTATIONAL – Circular
– OSCILLATING - Swinging
                    Pulleys

 A pulley is basically a wheel with a groove in
 the circumference of the wheel, with a belt or
 cable being fed around the groove.
 Pulleys create a mechanical advantage by
 connecting a small input drive pulley to a
 larger follower with a belt.

 Driver                                Follower
(Effort)                              (Resistance)
         Mechanical Advantage
         MA = FOLLOWER ÷ DRIVER

Driver                                Follower
1mm                                    4mm

  The Pulley Drive Train above produces an
  MA of 4. This means 10 lbs of input torque
  will create 40 lbs output, but the driver must
  rotate 4 times to rotate output 1 time. Speed
  is reduced by 4.
         Mechanical Advantage
         MA = FOLLOWER ÷ DRIVER

Driver                        Follower
3mm                            9mm


Driver                            Follower
2mm                                14mm
         Increasing Speed

Increase the speed of the output by
using a larger driver gear and a smaller
follower gear. Speed increases and
power decreases.


Driver                            Follower
4mm                                1mm
   Compound Drive Pulley Trains
• A Compound Drive Pulley Train has pairs of
  pulleys working in combination, with the
  follower of one pulley sharing the same axle
  as the driver of the next sequential pulley
  train.
  Compound Drive Pulley Trains
MA = (FOLLOWER 1 X FOLLOWER 2) ÷
        (DRIVER 1 x DRIVER 2)

 – Driver 1 = 2mm   Follower 1 = 8mm
 – Driver 2 = 3mm   Follower 2 = 9mm
 Compound Drive Pulley Trains
MA = (FOLLOWER 1 X FOLLOWER 2) ÷
        (DRIVER 1 x DRIVER 2)

– Driver 1 = 3mm   Follower 1 = 9mm
– Driver 2 = 2mm   Follower 2 = 14mm
               Problem

Sketch the following two pulley
trains:
– A: Simple pulley train with belt
  wrapped so both pulleys rotate in
  same direction.
– B. Simple pulley train with belt
  wrapped so both pulleys rotate in
  opposite direction.
                Solution

A: Simple pulley train with belt wrapped
so both pulleys rotate in same direction.
                Solution

B. Simple pulley train with belt wrapped
so both pulleys rotate in opposite
direction.
              Problem

Calculate the mechanical
advantage of the compound pulley
drive train model.
– Show your work.
– Small Pulley Diameter = 25mm
– Large Pulley Diameter = 100mm
Pulleys
           Lifting Pulleys

Lifting Pulleys in transmission
systems
– Single pulley
– Moveable pulley
– Block and Tackle
          Single Pulley

Provides change of
motion, but no
mechanical
advantage       100 ft
                         100 lbs       100 lbs




                                                 100 lbs



                             100 lbs
          Single Pulley

The resistance arm
and the effort arm are
both the radius of the
pulley. Since they are
equal, there is no
mechanical advantage.
          Moveable pulley
Provides change of direction and a
mechanical advantage of 1:2 (at the
expense of having to increase the amount
of line to pull)

                    50 lbs        50 lbs

                                           50 lbs



                                                50 lbs
                              100 lbs
                    100 lbs
Moveable pulley

     A moveable pulley is
     a second-class
     pulley.
     The effort arm is the
     diameter and the
     resistance arm is the
     radius.
     MA = dE ÷ dR
     MA = 2 ÷ 1 = 2
         Block and Tackle
Multiple pulleys providing a greater
mechanical advantage.
MA is determined by the number of pulleys.


                 25 lbs
                          25 lbs       25 lbs

                                                25 lbs



                                                     25 lbs
                                   100 lbs
                     100 lbs
         Block and Tackle

Gun Tackle        Luff Tackle
Block and Tackle
Block and Tackle
                 Review

Give real-world example of each of the
following pulleys.
– Force Multiplier
– Speed Multiplier
– Direction Changer
Give one example of a simple machine
or transmission that changes output
motion. Identify both input and output
motions.

								
To top