Wheels and Gears
Gears are generally used for one of the ff. Reasons
1.
Transmit torque from one axle to another
2.
To increase/decrease speed of rotation
3.
To reverse the direction of rotation
4.
To move rotational motion to a different axis
5.
To change rotary motion to linear motion
6.
To keep the rotation of 2 axles synchronized
Types of Gear
1.
External vs Internal
2.
Spur
3.
Helical
4.
Double Helical
5.
Bevel
6.
Crown
7.
Hypoid
8.
Worm
9.
Rack and Pinion
10.
Cam
11.
Chains and belts
12.
Ratchet
TYPES
1.
A. Internal Gear
- opposite of external Gear
- the teeth point towards the center
- addendum and dededdum take reverse
positions
- provide a compact parallel shaft transmission
drive with large speed reduction
- eliminates the use of an idler gear
B. External Gear
- the teeth are formed on the outer surface
of a cylinder or cone
2. Spur Gear
-
“straight-cut”
gears
-
Simplest and most common type
-
Whine at high speed
-
Cannot take as much torque
-
For low speed applications
3. Helical Gears
-
Offer refinement over spur gears
-
The leading edges of the teeth are set as an angle
-
Very similar
to spur gears except teeth are not perpendicular to the face
-
Can be used on non-parallel shafts to transmit
motion
-
Run quieter and smoother
4. Double Helical
Gears
-
“Herringbone
gears”
-
Resemble 2 helical gears that have been placed
side by side
-
Help to avoid issues related to side thrust created
with the use of helical gears
5. Bevel Gears/Miter
Gears
-
Axes of the 2 shafts intersect
-
Tooth bearing faces of gears are conically shaped
-
Most often mounted on shafts that are 90 degrees
apart
-
The pitch surface is a cone
6. Crown Gear
-
“contrate
gear”
-
Teeth project at right angles to the plane of the wheel
-
Teeth resemble the points of the crown
-
Can mesh accurately with a bevel gear
-
Can mesh sometimes with a spur gear
7. Hypoid Gear
-
Similar in general form to bevel gears
-
Operate on non-intersecting axes
-
Have spiral teeth that are curved & oblique
-
Axes may be at right angles or otherwise
8. Worm Gears
-
Used to transmit power at 90 degrees
-
High reductions are required
-
Resembles a thread that rides in concaved or
helical teeth
9. Rack and Pinion
-
Rack –
straight gear that transmits power and motion in a linear movement
-
Pinion
– single gear that meshes with a sliding toothed rack
-
Converts rotary motion to back and forth
10. Cam
-
Gear not centered on the shaft
-
Used where discontinuous action is required
-
Wheel with shaped bumps on it
-
Connected to rods, levers, or springs
-
Increases horsepower and torque
-
Ideal for heavily modified engines
11. Chains and
Belts
-
Connect two separated wheels so that one turns,
the other will turn in the same direction
-
“timing
belt”
-
Part of an internal combustion engine
12. Ratchet
-
Allows a wheel to turn in only one direction
-
Has specially shaped teeth
-
Pawl –
bar on a pivot; fixed above the ratchet wheel. Slides over the ratchet in one
direction, but blocks the motion of the teeth.
