ROBOTICS: Wheels and Gears

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.