Gears The Transmitters of Mechanical Power Essay Example for Free

Gears The Transmitters of Mechanical Power EssayA body under net burden is under tranlational trend and a body under net torque is under rotational motion but they both baffle something in common and that is both pass kinetic energy. This energy stick out be exploited to do some useful work. The mechanistic energy of an aspi dimensionn throw out be apply to move some otherwise object. Some examples rear be a rotating shaft of a motor, which throw out be used to move a vehicle for public transport. But for this to happen the force, the torque, the mehanical energy or the mechanically skillful power needs to be transmitted from bingle moving or rotating body to some other body. How mechanical force or torque or energy or power is transmitted from whiz body to a nonher body? There be many ways, many mechanisms like pulley, chain, cogwheelings etc. So what is a Gear? Gear is a device, a mechanism through which mechanical force, torque, energy or power is transmitte d from hotshot object to another. To draw an analogy appurtenance has same role for mechanical energy that electrical wire has for electrical energy. No not just that role of gear is oft more(prenominal) than that. Gears act to increase or decrease the velocity from one moving element to another moving element. This way they has analogy with transformers in electrical domain.A gear is a circular object with a large number of odontiasis on it and two gears physically engage with individually other to transmit mechanical power. This is illustrated in the following picture (http//www. osha. gov/SLTC/etools/machineguarding/animations/gears. html). paradigm 1 Two gears sedulous with each other In the subsequent sections we will briefly talk virtually diametrical terminology or so gears and about different types of gears In the most coomon configuproportionn a gear is engaged with another gear. However, it arsehole engage with any other device which has compatible teath.One in teresting arrangement is a analog object with teath, which is as well as termed as Rack. If a gear is engaged with a rack then forms what is cognise a Rack and a Pinion. It should however, be noted that a rack can be seen as a segment of a gear with infinite radius. Now let us talk about two gears of un check size engages with each other as in figure 1, above. This combination produces mechanical advantage i. e. angular spee and torque of the second gear is different from that of the first gear. Let us research this important concept about gears. Mchanical advantageThe physical interlocking of the teeth in a twain of gears ensures that circumference of these gears move at the same linear speed. As the angualr speed is circumferential speed sh atomic number 18d by its radius the bigger gear moves at smaller angular speed than the smaller gear engaged with it. Let us look at it from the number of teath consideration. Because the teeth of two good-natured gears are locked one to one, by the time all the teeth of the smaller gear have passed the gunpoint of conform to only a fraction of the teath of the bigger gear has done that. In other words he smaller gear rotates faster than the bigger gear.This results in the following formula (Angular Speed A) x (Number of teeth A) = (Angular Speed B) x (Number of teeth B) or, (Angular Speed A)/ (Angular Speed B) = (Number of Teath B) / (Number of Teath B) This ratio is nothing but Gear Ratio. Similarly, one can dertermine torque ratio. The bigger gear experiences larger torque and vice versa. The torque ratio is equal to the ratio of the radii of the two gears and is inverse of the velocity ratio. Larger torque implies smaller velocity and vice versa. This accompaniment is in confirmity with the law of conservation of energy.In this discussion we have ignored the friction, which dissipates the energy. Velocity ratio universe a geometrical term remain unaffected by friction, however in that location is loss in t orque ratio cod to friction and thus actual torque ratio is always slight than inverse of the velocity ratio. Because, gear is not perfectly circular due to presence of teath on the circumference, there is something called pitch radius, which is some sort of average between the radius at the root of the teath and at the outer of the teath and is used for these calculations for velocity ratio.Torque ratio etc. The pitch radius depends on the point of contact of the two gears. Also this point of contact keeps changing over time. Due to this the velocity ratio and torque ratio is not constant and instead keeps changing over the period of engagement. These ratios (velocity and torque ratios) that we have discussed so far are gross values and changes from point to point on the gear teath. However, the blueprint of the tooth can be made such that the velocity ratio remains constant with time on short and long term basis.This is done in good quality gears, because fluctuations in the ve locity ratio causes undue vibration, put extra stress on the teeth, which can in turn break as the laod and the speed are many times very high. Keeping the velocity ratio constant is also desired from the precision considerations in devices like delicate instruments, eatches, clocks etc. Now let us compare gears with other mechanisms of mechanical power transmission. Gears and other Means of Power Transmission There are other mechanisms for mechanical power transmission such as chains, belts, pulleys etc.Each of these has its own advantages and limitations. However, no(prenominal) is as diverse as gears. The problem of slippage is often encountered with these devices and the gears have edge over othe mechanisms. Similarly gears have constant velocity ratio, which is not the case with other devices. However, gears are generally more costly, but this high cost is initial investment only and is paid back many more times due to very high life of gears than other devices. In the subseq uent sections we will talk about different types of gears. Spur gearThese are the most simple common gear. This is nothing but a plough with teath projecting radially and the leading edges of the teeth are aligned latitude to the axis of rotation. These gears are used for power transmission between parallel shafts. Such a gear is shown in figur 1, above. Helical gear This is a refinement over promote gear. In this gear the leading edge of the teeth is fit(p) at an agle to the axis of rotation and not not parallel to the axis of rotation as in case of spur gear. Because the gear is curved, this makes the tooth to be a segment of a helix.Such a tooth engages more gradually than do spur gear teeth. Therefore, this gear runs smoothly and produces much lesser noise than the spur gear. Besides, volute gear can tranmit power between non-parallel shafts as well. A pair of helical gears can be engage in two ways the shafts can be oriented at at either the sum or the difference of the h elix angles of the gears. These configurations of the shafts are know as parallel or cut through, respectively. The parallel configuration is the mechanically more sound than the crossed configuration.In this configuration, the helices of a pair of engaging teeth meet at a common tangent, and therefore, the contact between the tooth surfaces will, is a curve, which extends some aloofness across their face widths. On the other hand, the helices do not meet tangentially in the crossed configuration, and between tooth surfaces only point contact is achieved. Because of this (the small area of contact), crossed helical gears are and can be used with light loads only. Generally, helical gears come in pairs.The helix angle of one is the negative of the helix angle of the other in this pair and this pair is termed as having a office handed helix and a left handed helix of equal angles. When engaged in the parallel mode, these equal and opposite angles add to zero i. e. the angle between shafts is zero or the the shafts are parallel. When engaged in the crossed configuration, the angle between shafts is twice the helix angle of individual gears. However, it should be borne in mind that parallel configuration of gears and paralles shafts are two different things i. e. parallel configuration of axes may not always lead to parallel shafts.The helical gear is shown in figure 2, below (http//en. wikipedia. org/wiki/ImageHelical_Gears. jpg). Figure 2 Helical gears in parallel and crossed configurations Double Helical Gear This gear is known as herringbone gear as well. This was invented to overcome the problem of axial thrust caused by helical gear. Here teath are of V shape. In this, each gear can be visualized as two standard and mirror image, helical gears stacked. This configuration cancels out the thrust because each half of the gear thrusts in the opposite direction. These can be interchanged with spur gears without changing the bearings.