Wheels and PulleysIntroduction to Engineering and Technology Concepts

MindjogHow 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?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 AxleThe Wheel and Axle work off the same principle as the lever.Wheel diameter = 8Axle diameter = 1Produce an 8/1 MA

Wheel and AxleIf 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.

What class lever is this wheel configuration?REWheel diameter = 8Axle diameter = 1Produces an MA of 8

Wheel and AxleIf 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.

What class lever is this wheel configuration?ERWheel diameter = 8Axle diameter = 1Produces an MA of 1/8

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)DoorknobScrewdriverCar Climate ControlsDimmer SwitchPencil SharpenerLamp SwitchHamster WheelPottery WheelCar JackTelescope/ Microscope KnobsWindmill/Wind TurbinesWaterwheelWheel of FortuneThe Price is Right

Wheel Examples (3rd Class)Ferris WheelWheelbarrowClock HandsBand SawCircular SawBlender/GrinderBike/Car TiresFishing ReelCarousel/Merry-Go-RoundPizza CutterPaint RollerFan BladeBoat or Airplane PropellerHelicopter RotorBig Wheel

Mechanical TransmissionA device which accomplishes one, or more, of the following:Transfer motion from one point to anotherIncrease output speed OR forceChange direction of motionChange type of motion

MotionFour types of motion:LINEAR Straight line, one directionRECIPROCATING straight line, back and forthROTATIONAL CircularOSCILLATING - Swinging

PulleysA 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(Effort)Follower(Resistance)

Mechanical AdvantageMA = FOLLOWER DRIVER

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.Driver1mmFollower4mm

Mechanical AdvantageMA = FOLLOWER DRIVERDriver3mmFollower9mmDriver2mmFollower14mm

Increasing SpeedIncrease the speed of the output by using a larger driver gear and a smaller follower gear. Speed increases and power decreases.Driver4mmFollower1mm

Compound Drive Pulley TrainsA 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 TrainsMA = (FOLLOWER 1 X FOLLOWER 2) (DRIVER 1 x DRIVER 2)

Driver 1 = 2mmFollower 1 = 8mmDriver 2 = 3mmFollower 2 = 9mm

Compound Drive Pulley TrainsMA = (FOLLOWER 1 X FOLLOWER 2) (DRIVER 1 x DRIVER 2)

Driver 1 = 3mmFollower 1 = 9mmDriver 2 = 2mmFollower 2 = 14mm

ProblemSketch 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.

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

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

ProblemCalculate the mechanical advantage of the compound pulley drive train model.Show your work.Small Pulley Diameter = 25mmLarge Pulley Diameter = 100mm

Pulleys

Lifting PulleysLifting Pulleys in transmission systemsSingle pulleyMoveable pulleyBlock and Tackle

Single PulleyProvides change of motion, but no mechanical advantage

Single PulleyThe resistance arm and the effort arm are both the radius of the pulley. Since they are equal, there is no mechanical advantage.

Moveable pulleyProvides change of direction and a mechanical advantage of 1:2 (at the expense of having to increase the amount of line to pull)

Moveable pulleyA moveable pulley is a second-class pulley.The effort arm is the diameter and the resistance arm is the radius.MA = dE dRMA = 2 1 = 2

Block and TackleMultiple pulleys providing a greater mechanical advantage.MA is determined by the number of pulleys.

Block and TackleGun TackleLuff Tackle

Block and Tackle

Block and Tackle

ReviewGive real-world example of each of the following pulleys.Force MultiplierSpeed MultiplierDirection ChangerGive one example of a simple machine or transmission that changes output motion. Identify both input and output motions.