Basics f Mechanics By V . Nitin (2/4)

Basic Definitions: Mass: The quantity of MATTER present in an object. It is always constant. Force: The mass multiplied by the acceleration the body posses or exerts. F=m*a.

What will I show?? Weight: The mass multiplied by “Acceleration due to GRAVITY” at that particular point is known as weight. It changes from place to place. W=m*g. What will I show??

Angular velocity: The rate of change of “angular displacement” is known as angular velocity. W= d(ɸ)/dt . Torque: Torque is a measure of how much a force acting on an object causes the object to rotate. T =r X f

Work: Work is said to be done on a body when there is a displacement of the point of application. Power: The rate at which work or energy is spent. Power=d(w)/dt . Power= w x T .

Link: Every part that moves relatively to some other part is known as kinematic link (or link). Group of Links Structure Machine

Structure: Structure is a group of resistive bodies having no relative bodies between them. Usually used for carrying loads. Machine: A machine is a device that converts the input work given to it into an useful work.

Types of links:

Power Transmission: Transmitting power from one point to another point by using various means is known power transmission. Ex: 1.Gear transmission. 2.Belt transmission. 3.Wire transmission. 4.Wireless transmission.

Belt transmission: A belt is a loop of flexible material used to mechanically link two or more rotating shafts. Belts may be used as a source of motion, to transmit power efficiently.

Types of belts: 1.Flat belt: These are the first type of belts developed. They run with the help of friction and tension. The wheels are produced slightly with a concave circumference so that the belt doesn't slip.

2. Round belt: These belts are similar to ropes 2.Round belt: These belts are similar to ropes . They are used for low torque power transmission. They are designed to run in a pulley with 60 degree groove.

3. V-Belt: Its the basic belt for power transmission 3.V-Belt: Its the basic belt for power transmission. The belt is in the shape of trapezoidal hence it is called v-belt. They provide the best combination of speed, torque, and friction. When higher power is to be transmitted two or more v-belts can be joined side by side in arrangement resulting into a “multiple v-belt drive”.

4.Timing belt: These are best belt available to transmit power to any distance. They contain teeth which can be used to track relative moment. They provide an efficiency up to 98%.

Gear Transmission: A gear is a rotating part having cut teeth, or cogs, which mesh with another toothed part in order to transmit torque. A gear transmission of torque and speed depends upon its gear ratio.

Gear Terminology: 1.Pitch circle 2.no. of teeth 3.Teeth profile 4.Addendum 5.Dedendum 6.Whole depth 7.Working depth

Basic Formulae’s: Wmotorr1=W2r2 1.n1W1=n2W1 2.W1T1=W2T2 For Compound gears r1T1=r2T2 Wmotorr1=W2r2

Types of Gears: 1.Internal and External gears: As name implies a gear having teeth on the external surface is known as external gear and similarly gear having teeth on the internal surface is known as internal gear.

2.Spur gear: Spur gears are the most commonly used gears due to their simplicity and the fact that they have the highest possible efficiency of all gear types. They cannot withstand higher loads.

2.Helical gear: They are further developed spur gear whose teeth are cut at an angle making them capable to sustain higher loads. Helical gears can also be operated at right angles.

3.Double helical gear: A Herringbone gear, also known as a Double helical gear is a special type of gear which is a side to side combination of two helical gears of opposite hands

4.Bevel gear: Bevel Gear are used exclusively to transmit rotary motion between intersecting shafts. Through commonly seen in right angle drives, bevel gears can be cut to drive any angle.

5.Crown gear: A crown gear (or a contrate gear) is a gear which has teeth that project at right angles to the face of the wheel.

How many gears are present?

6. Worm gear: Worm gears resemble screws 6.Worm gear: Worm gears resemble screws. A worm gear is usually meshed with a spur gear or a helical gear, which is called the gear, wheel, or worm wheel. Its is the best gear to attain high torque and low speed. Its also acts as a brake to reverse spin.

7.Rack and Pinion: Rack is a gear of infinite radius The smallest of the mating gear is known as pinion.

Steering mechanisms: Steering gear mechanism is used to change the course of direction of two or more wheels with reference to chassis to move in a desired path. There are two fundamental steering gear mechanisms 1.Davis steering gear 2.Akerman steering gear

1.Davis steering gear mechanism: It is the “PERFECT” steering gear mechanism. Due to presence of many number of sliding pairs it is not preferred for general purpose.

2.Ackerman steering gear mechanism: Ackerman steering gear mechanism is a modified form of four bar mechanism and also occupies less space compared to davis steering gear mechanism. Since it consists of turning pairs it is preferred over