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GEAR TRAINS NPTEL PDF

1) How do you identify a planetary gear? A gear whose axis itself is revolving is called a planetary gear. In some epicyclic gear trains, we may find two or more. described a number of gear applications, typical ones are shown in Figs. used in high speed and high load application in all types of trains and a wide range. The velocity ratio of an epicyclic gear train is determined by the following methods: (a) Tabulation method; (b) Formula method; and (c) Instant centre method or.

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Their most common and highest-volume applications can be found in front and rear axles of rear-wheel-drive or all-wheel-drive vehicles. Smaller gear is known as pinion and larger mating gear is npte gear. This means mild wear is bound to occur in gear operations.

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Therefore, contact stress is. For high speed reduction, nprel stage or three stage construction are preferred, otherwise gear wheel size increases, which increases the gearbox gwar. Generally tooth profile is designed so that velocity ratio does not change due to inaccuracies in center distance. Higher entraining velocity increase “spin losses”. Gear surface with adsorbed gases. In normal atmospheric conditions, all engineering metallic surfaces are primarily coated with some adsorbed gas Fig. Recommended oil viscosity [2].

An efficient method of achieving high reduction ratios in minimum space is the use of planetary gearing.

So N-S is prefferable. As contact moves towards or away from pitch point, sliding occurs. In helical angle greater than 15 degrees, the tooth bending capacity generally begins to drop off due to the fact that the tooth thickness decreases rapidly. In practice, sliding comes along rolling action.

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Chapter 1. Introduction to Mechanisms

Sliding at point I. Worm gears have crossed axes Fig. Pressure angle at base circle is zero. These types of geometrics are known as external gears. Sliding and rolling friction losses at the loaded gear meshes and at the bearings largely define the load-dependent mechanical power losses. Loss due to load and loss due to speed. The internal gears eliminates the use of an idler gear, where it is necessary to have two parallel shafts rotate in the same direction.

These dimensions are determined on the basis of tooth stresses, which are imposed by the transmitted tooth load. Ideally, rolling gears are required.

By using parameters shown in Table 6. But sometime failure of lubrication pump failure, filter chocking, excessive leakage occurs and gear materials must be able to handle such extreme situations. Insufficient backlash is sometimes the cause of excessive heat and wear.

Epicyclic gear train nptel pdf merge

This friction process is characterized by solid-body friction as well as by fluid friction Fig. Too much or too less lubricant is harmful for gear operation.

In a geared system, the total power loss is comprised of two groups of losses: Friction losses can be divided into two major categories: With increase in pitch line velocity, lubricant used should be less viscous in order to min.

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In addition, lower loads are imposed on the support bearings because of a decrease radial load component. Normal gear load W n for a given application depends on pitch diameter and face width. In high speed units, the churning losses may exceed the friction losses; therefore, the type and amount of lubricant are critical. Helical crossed axis gears.

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Using AGMA pitting equation formula, determine the maximum contact stress. It prevents jamming of teeth and compensates for thermal expansion of teeth. There is no limit to the speed reduction ratio that can be achieved using gearing; but larger ratio must be obtained using multi-stage reduction.

Hypoid gears are widely used in many power trains to transfer power between two non-intersecting crossed axes. Composite roughness depends on gear manufaturing process as given in Table 6. Usually, following two types of lubrication mechanisms are commonly used for gear lubrication. On changing center distance, line of action still remains tangent to both base circles but slope changes.

The sliding friction losses are related to the coefficient of friction, normal load and sliding velocity on the contact surfaces, while the rolling friction losses occur due to the formation of an elastohydrodynamic EHL film. To estimate the working life of gears, it is essential to analyze the destructive forces at work, and knowledge of the ability of chosen gear materials to withstand those forces. Higher value of T f cause scuffing failure of gears.

In simple gear mesh, a maximum ratio in order of 7: Gear life depends on effective lubrication, which can be quatified by minimum film thickness to R compositeas shown in Fig.