⇒TRANSFORMATION OF MOTION⇐

ROTARY-LINEAR TRANSFORMATION

WHEEL

Wheels reduce contact with the ground and decrease friction. If there isn't enough friction, they can slide out of control. We need less force to move vehicles with larger wheels and they move more quickly.

RACK AND PINION

This mechanism has two parts: the rack is a bar with many theeth and the pinion is a gear with theeth that interlock with the rack. It transforms rotary motion into linear motion.

NUT AND BOLT

This mechanism transforms rotary motion into linear motion. It has two parts: a bolt with a spiral groove and a nut that turns around it.

WINCH AND CRANK
It is a cylinder that rotates around a horizontal axis. We turn the crank to rotate the winch. The crank increases the force and the winch transforms rotary motion into linear motion. This mechanism has the Law of the Lever.

RECIPROCATING ROTARY-LINEAR TRANSFORMATION

CRANKSHAFT

We can conect multiple rods to one shaft. The rods are connected to cranks, and the cranks are connected to the crankshaft. It can synchronise the movements of various parts.

CAM

A cam is a irregulary device that rotates on a shaft. When the cam rotates, it pushes a special bar called follower. This follower can move other parts or it can turn a switch on and off.

When we put multiple cams on a shaft, it's called a camshaft. We can use it to synchronise the movements of various parts.

ROTARY TRANSMISSION

Rotary transmission systems put two rotating elements into contact. These mechanisms have two purposes:
⇒Transferring rotary force to an input location to another location.
⇒Changing the rotary speed by using rotating elements of different sizes.
There are various mechanisms:

    

Pulleys with belts

Friction wheels

Interlocking gears

Sprockets with chains

 

Here, the most reliable mechanism is the interlocking gears, because they don't slip easily.

CHANGES IN SPEED

We can increase, decrease and make constant the speed with these systems:

  

Decreasing and  Increasing speed system

Cosntant speed system

SPEED RATIOS

The relationship between the speeds of the two wheels is inversely proportional to their sizes. 

                                      

                         N2/N1=D1/D2

The relationship is called the ratio of transmission, where N is the speed of relation and D is the diameter of the wheel. 

BELT DRIVES AND GEAR TRAINS  

-Wheel 1 turns wheel 2, wich moves faster because it is smaller. If wheel 1 makes 1 rotation, wheel 2 makes 1.5 rotations.

-Wheel 2 and wheel 3 are connected to the same axis, so they turn together.

-Wheel 3 turns wheel 4, wich moves faster because it is smaller. If wheel 3 makes 1.5 rotations, wheel 4 makes 3 rotations (1.5x2=3)

                      N4/N1=D1XD3/D2XD4

CHANGES IN DIRECTION AND ROTATIONS

We can change the direction of the rotation by using belts in different possicions or different axis.

Parallel axes

Perpendicular axes

Different posicion of the belts

Crossed axes

 








WORM DRIVE
A worm drive reduces the speed of rotary system very well. It has two parts: a worm shaft and a worm gear. The shaft has more than one groove. Each groove interlocks with one of the worm gear. This mechanism is not reversible.