What exactly are mechanisms?

© 2011 Project Lead The Way, Inc.Automation and Robotics VEX

Step #1: Use the next “6” slides in order to complete the step “1” exercise

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

Mechanisms - Change Direction

• Meshed gears in a gear train always turn in opposite directions…..PLEASE MAKE SURE YOU UNDERSTAND THE DIFFERENCE BETWEEN THE INPUT AND OUTPUT!!!

The “driver” is always the input or where the force/energy starts

The “follower” is also referred to as the “output” or the “driven”. This is where the energy is transferred to

The flow of power is reversible only if you can make the input shaft turn by turning the output shaft

Mechanisms - Change Direction….continued

The Input power is reversible only if the input can be turned in both directions….. Clockwise or counterclockwise.

Mechanisms - Change MovementRotary Linear

Reciprocating Oscillating

Around in a circle

Back and forth in an arc

Straight in one directionBack and forth in a straight line

Mechanisms - Change Speed

• Gear ratios compare the output (or driven gear) to the input (or drive gear)

• Gear Ratios can be determined using number (n) of teeth on the gear or diameter (d) of the gear

• If the output gear is larger than the

input gear the speed will decrease

• If the output gear is smaller than the

input gear the speed will increase.

Mechanisms –Change Force or Torque

A force is a push or pull in a straight line.

Torque is a push or pull in a circular direction.

What are the mechanisms

that robots may use?

© 2011 Project Lead The Way, Inc.Automation and Robotics VEX

There are pictures and videos of each of the “12” mechanisms that you must build

Step #2:

Use the remaining slides in order to complete “Simple Mechanisms” checklist…..AFTER EACH BUILD PLEASE HAVE ME INITIAL YOUR WORK

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

THESE FOUR BULLETS ARE SUPER IMPORTANT TO LEARN OVER THE NEXT 10 CLASS PERIODS…..FOR ALL OF YOUR PROJECTS WILL REQUIRE YOU TO PERFORM ONE OR MORE OF EACH OF THESE!!!!

1. Simple Gear TrainA simple gear train is used to transmit rotary motion…THESE GEARS WILL MOVE IN OPPOSITE DIRECTIONS

Watch the Mechanism in ACTION!!!!

2. Simple Gear Train with IdlerA simple gear train is used to transmit rotary motion……THE MIDDLE GEAR CAUSED THE TWO OUTSIDE GEARS TO MOVE IN THE SAME DIRECTION!!!

Watch the Mechanism in ACTION!!!!

3. Bevel Geara gear working another gear at an angle to it by means of bevel wheels

Watch the Mechanism in ACTION!!!!

4. Differential Geara set of gears allowing a vehicle's driven wheels to revolve at different speeds when going around corners.

Watch the Mechanism in ACTION!!!!

How a differential gear works in a car

5. Worm and WheelA worm gear (or worm drive) is a specific gear composition in which a screw (worm) meshes with a gear/wheel similar to a spur gear. The set-up allows the user to determine rotational speed and also allows for higher torque to be transmitted

Watch the Mechanism in ACTION!!!!

6. LeadscrewA leadscrew (or lead screw), also known as a power screw or translation screw, is a screw used as a linkage in a machine, to translate turning motion into linear motion

Watch the Mechanism in ACTION!!!!

7. Rack and Piniona type of linear actuator that comprises a pair of gears which convert rotational motion into linear motion.

Watch the Mechanism in ACTION!!!!

8. Universal JointA universal joint, (universal coupling, U-joint, Cardan joint, Hardy-Spicer joint, or Hooke's joint) is a joint or coupling in a rigid rod that allows the rod to 'bend' in any direction, and is commonly used in shafts that transmit rotary motion

Watch the Mechanism in ACTION!!!!

9. Chain Drivea way of transmitting mechanical power from one place to another. It is often used to convey power to the wheels of a vehicle, particularly bicycles and motorcycles.

Watch the Mechanism in ACTION!!!!

10. Belt Drive

a loop of flexible material used to mechanically link two or more rotating shafts, most often parallel.

11.Crank and SliderA crank and slider mechanism changes rotary to reciprocal motion or vice versa. In the car engine (illustrated) the reciprocating motion of the piston caused by exploding fuel is converted into rotary motion as the con-rod moves the crankshaft around.

Watch the Mechanism in ACTION!!!!

12. Cam and Follower

A cam is a shaped piece of metal or plastic fixed to a rotating shaft. A cammechanism has three parts: cam, slide and follower. The cam shaft rotates continually, turning the cam. The follower is a rod that rests on the edge of the turning cam.

Watch the Mechanism in ACTION!!!!