Mechanical & control system

1. MECHANICAL SYSTEM
& CONTROL
Levers & Gear
Systems
By MR S SIBANDE

2. LESSON OBJECTIVES
LEARNERS SHOULD BE ABLE:
 To define lever and gears
 To identify the three types of levers.
 To label the parts of lever system.
 Determine the mechanical advantage of various lever
systems.
 To identify all types of gears & ratio.

3. LEVERS
 Lever - is a rigid bar resting on a pivot, used to move a heavy or firmly fixed load
with one end when pressure is applied to the other.
 The three lever system parts:
Fulcrum, effort & load(resistance)
Fulcrum(pivot) -the central point, pin, or shaft on which a mechanism turns.
Effort -The force applied to a machine to cause motion of an object. (Newton)
Load(resistance) -The force exerted by an object due to gravity or friction.(Newton)
Mechanical Advantage – The number of times a machine multiplies the effort force.
MA= Ed/Ld
 three classes of levers:
1st, 2nd and 3rd class.

4. TYPES OF LEVERS

5. EXAMPLES OF CLASS LEVERS

6. PARTS OF LEVER
SYSTEM
A= LEVER B=FULCRUM C=LOAD DISTANCE D=LOAD FORCE
E=EFFORT ARM F=EFFORT FORCE G=EFFORT DISTANCE H=LOAD ARM

7. MECHANICAL ADVANTAGE
OF LEVERS
MA= Ed/Ld(Rd) Lf = Ef x MA Ef = Lf / MA
LOAD= RESISTANCE (L= R)

8. TYPES OF GEARS
 A gear is a component within a transmission device that transmits rotational
force to another gear or device. A gear is a wheel with teeth that mesh together
with other gears.
1. SPUR GEAR.- Teeth is parallel to axis of rotation, it transmit power from one
shaft to another parallel shaft and it uses in Electric screwdriver, oscillating
sprinkler, windup alarm clock, washing machine and
clothes dryer

9. GEARS CONT’
 BEVEL GEAR-Are useful when the direction of a shaft's rotation needs to be changed and are
usually mounted on shafts that are 90 degrees apart, but can be designed to work at other
angles as well. The teeth on bevel gears can be straight, spiral or hypoid locomotives,
marine applications, automobiles, printing presses, cooling towers, power plants, steel
plants, railway track inspection machines, etc.
 WORM GEAR-are used when
large gear reductions are
needed. Also in widely in
material handling and
transportation machinery,
machine tools,
automobiles etc.

10. GEARS CONT & RATIOS
 IDLER GEAR BELT AND PULLY
Gear ratio is the ratio of the number of teeth on one
gear to the number of teeth on the
other gear.
Velocity ratio (V.R.=Ed/Ld)