Theory of Machines: Unit II: Gears and Gear Trains

non-standard gears

Gears and Gear Trains - Theory of Machines

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The gear teeth obtained by modifying the standard proportions of gear teeth parameters is known as non-standard gear teeth.

NON-STANDARD GEARS

• As discussed in Section 4.9, the standard proportions for the various gear systems should have standard values of gear teeth parameters such as tooth depth, addendum, tooth thickness, minimum clearance, etc.

• The gear teeth obtained by modifying the standard proportions of gear teeth parameters is known as non-standard gear teeth.

• Non-standard gears, also known as profile shifted gears, are primarily used for avoiding interference and hence undercutting by having unequal addendum, longer addendum for the pinion and shorter addendum for the gear.

• The important reasons for employing non-standard gears are:

(1) To prevent interference.

(ii) To eliminate undercutting.

(iii) To maintain a reasonable contact ratio.

(iv) To attain a predetermined centre distance.

(v) To increase the strength at the root and flank of the teeth.

(vi) To improve sliding and contact relation.

• The two main non-standard gear systems are:

1. Long and short addendum system, and

2. Extended centre distance system.

Theory of Machines: Unit II: Gears and Gear Trains : Tag: : Gears and Gear Trains - Theory of Machines - non-standard gears

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