Basic mechanisms for beginners.

1. Mechanisms

2. What is a Mechanism?
A mechanism is the part of a machine
which contains two or more pieces
arranged so that the motion of one
compels the motion of the others.
Generally used to:
– Change the direction of movement
– Change the type of movement
– Change the speed of movement
– Change the amount of torque or force
available to do work

3. Mechanism Movement
Rotary
Linear
Reciprocating
Oscillating

4. Universal Joint
• Angular Range
> 90˚ and < 270˚
• Speed and Torque
constant
• Ratio 1:1
• Flow of Power
reversible
• Input & Output Shafts
same direction

5. Where Can You Find a
Universal Joint?
• Drive shaft of
vehicles
• Power take-off
www.rqriley.com/imagespln/pattersn_ujoint.jpg
Universal joints are
used to transmit rotary
movement at an angle
that is not 90°.

6. Bevel Gear
• 90˚ Angle
• Speed and Torque
constant
• Gear Ratio 1:1
• Flow of Power
reversible

7. Where Can You Find a
Bevel Gear?
• The bevel gear is
used to change
rotational motion at a
90˚ angle.
• Using gears with
differing numbers of
teeth will change the
speed and torque.
• Hand drill
• Car differential
• Shaft-driven bicycle

8. Simple Gear Train with Idler
• Input and Output Shafts
parallel
• Speed is decreased
• Torque is increased
• Ratio 4:1
• Flow of Power
reversible
• Input and Output Gears
same direction
• Without Idler Gear
different direction
IDLER GEAR

9. Where Do You Find a
Simple Gear Train with Idler?
Two meshed gears will rotate
in opposite directions.
An Idler Gear allows the
drive and driven gears to
rotate in the same direction.
Paper Transport Rollers

10. Worm and Wheel
• 90˚ Angle
• Speed is decreased
• Torque is increased
• Gear Ratio 20:1
• Flow of Power
NOT reversible
• Direction of Travel
reversible

11. Where Do You Find a
Worm and Wheel?
• A worm is used to
reduce speed and
increase torque.
• The motion is not
reversible; a gear
cannot drive a worm.
• Tuning mechanism on
string instruments
• Electric motors
• Winch

12. Crown and Pinion
• 90˚ Angle
• Speed is decreased
• Torque is increased
• Gear Ratio 3.2:1
• Flow of Power
reversible
• Direction of Travel
reversible

13. Where Do You Find
a Crown and Pinion?
• Watches
• Carousel
• DVD player
How many crown
and pinion gears do
you see in this
pendulum clock?

14. Rack and Pinion
• Input Movement
rotary
• Output Movement
linear
• Distance is
2 in.
• With a Larger Pinion Gear -
the rack will move a longer
distance
• Flow of Power
reversible
• Direction of Travel
reversible

15. Where Do You Find a
Rack and Pinion?
• Used to convert
between rotary
and linear
motion.
• Provides gear
reduction to
make it easier to
turn the wheels.
• Used in steering systems
of cars to convert rotary
motion of steering wheel
to the side to side motion
in the wheels.
• Rack and pinion
steering
Rack
Pinion

16. Lead Screw
• Input Movement
rotary
• Output Movement
linear
• 6 Revolutions = 1 in.
• Flow of Power
NOT reversible
• Force is Increased
• Direction of Travel
reversible

17. Where Do You Find a
Lead Screw?
• Jack
• Vice
• Changes rotary
movement into linear
movement
• Significantly
increases force
• A person can put a
little force into
turning the handle to
move a heavy car.

18. Pulley and Belt
• Input and Output Shaft
parallel
• Speed is increased
• Torque is decreased
• Ratio 1:2.5
• Flow of Power is reversible
• Open Belt wheels turn in
same direction
• Crossed Belt wheels turn
in opposite direction

19. Where Do You Find a
Pulley and Belt?
• Lawn mower
• Car engine
BELTS

20. Cam and Follower
• Input Movement
rotary
• Output Movement
reciprocating
• Follower moves up and
down 1 time for every
revolution of the crank
• Flow of Power
Not reversible
• Direction of Travel
reversible
FOLLOWER
CAM

21. Where Do You Find a
Cam and Follower?
• As a cam rotates,
the flat follower is
raised and lowered,
converting rotary
motion to
reciprocating (back
and forth) motion.
• Cam shaft

22. Crank and Slider
• Input Movement
rotary
• Output Movement
reciprocating
• Slider Moves
1 in. - diameter of
crank
• Increased Crank
increased
distance slider
moves
• Flow of Power
not reversible

23. Where Do You Find a
Crank and Slider?
• Steam train
• Internal combustion
engine

24. Image Resources
Microsoft, Inc. (2008). Clip Art. Retrieved November 25, 2008, from
http://office.microsoft.com/en-us/clipart/default.aspx