Gear Train

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Gears Trains 06/14/22 A gear train is two or more gear working together by meshing their teeth and turning each other in a system to generate power and speed. It reduces speed and increases torque. To create large gear ratio, gears are connected together to form gear trains. They often consist of multiple gears in the train ( Idler gear ) GEAR 'C' GEAR 'B' GEAR 'A' v v C B A

Transcript of Gear Train

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Gears Trains

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A gear train is two or more gear working together by meshing their teeth and turning each other in a system to generate power and speed. It reduces speed and increases torque. To create large gear ratio, gears are connected together to form gear trains. They often consist of multiple gears in the train

(Idler gear)GEAR 'C'GEAR 'B'GEAR 'A'

v

v

CBA

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GEAR 'C'GEAR 'B'GEAR 'A'

v

v

CBASIMPLE GEAR

TRAIN

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. module

module

mesh would notrwise theygears othe all e same formust be th

and

tD =m =

in rpmN = speed meter,circle diaD = Pitch r,on the gea of teeth t = number

r= Dcle. v = on the cir velocity v = linear

.r velocity = angula = m tDand = m tD; = m tD

tD =

tD =

tDm =

CCBBAA

C

C

B

B

A

A

2

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CCBBAA

CCBBAA

CCBBAA

CCBBAA

CC

BB

AA

tNtNtNrevoftermsinor

ttttmtmtm

DDD

DDDv

min/

222

The velocity v of any point on the circle must be the same for all the gears, otherwise they would be slipping.

Application:a) to connect gears where a large center distance is requiredb) to obtain desired direction of motion of the driven gear ( CW or CCW)c) to obtain high speed ratio

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COMPOUND GEAR TRAIN

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GEAR 'A'

GEAR 'B'

GEAR 'C'

GEAR 'D'

Compound Gears

A

C

BD

Output

Input

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Compound gears are simply a chain of simple gear trains with the input of the second being the output of the first. A chain of two pairs is shown below. Gear B is the output of the first pair and gear C is the input of the second pair. Gears B and C are locked to the same shaft and revolve at the same speed.

For large velocities ratios, compound gear train arrangement is preferred.

The velocity of each tooth on A and B are the same so: A tA = B tB -as they are simple gears.

Likewise for C and D, C tC = D tD.

C

D

A

B

DB

CA

C

DD

A

BBCA

C

DDC

A

BBA

C

D

D

C

A

B

B

A

tt

tt

tt

tt

Ttand

tt

ttand

tt

GR

tt

tt

OutNInN

aswrittenbemayratiogearThe

NSince

GRtt

tt

shaftsametheonareCandBgearSince

C

D

A

B

C

D

A

B

D

A

CB

:

2

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Reverted gear train

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EPICYCLIC GEAR TRAIN

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Epicyclic means one gear revolving upon and around another. The design involves planet and sun gears as one orbits the other like a planet around the sun

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• Any object orbiting around a center must rotate once. Now consider that B is free to rotate on its shaft and meshes with C. Suppose the arm is held stationary and gear C is rotated once. B spins about its own center and the number of revolutions it makes is the ratio . B will rotate by this number for every complete revolution of C.

• Now consider that C is unable to rotate and the arm A is revolved once. Gear B will revolve because of the orbit. It is this extra rotation that causes confusion. One way to get round this is to imagine that the whole system is revolved once

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Arm 'A'

B

C

Planet wheel

Sun wheel

Arm

B

C

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In an epicyclic gear train, an arm carries two gears A and B having 36 and 45 teeth respectively. If the arm rotates at 150 r.p.m. in the anticlockwise direction about the centre of the gear A which is fixed, determine the speed of gear B. If the gear A instead of being fixed, makes 300 r.p.m. in the clockwise direction, what will be the speed of gear B ?

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An epicyclic gear consists of three gears A, B and C as shown in Fig. The gear A has 72 internal teeth and gear C has 32 external teeth. The gear B meshes with both A and C and is carried on an arm EF which rotates about the centre of A at 18 r.p.m.. If the gear A is fixed, determine the speed of gears B and C.

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In an epicyclic gear train, the internal wheels A and B and compound wheels C and D rotate independently about axis O. The wheels E and F rotate on pins fixed to the arm G. E gears with A and C and F gears with B and D. All the wheels have the same module and the number of teeth are : TC = 28; TD = 26; TE = TF = 18.1.Sketch the arrangement ; 2.Find the number of teeth on A and B ; 3. If the arm G makes 100 r.p.m. clockwise and A is fixed, find the speed of B ; 4.If the arm G makes 100 r.p.m. clockwise and wheel A makes 10 r.p.m. counter clockwise ; find the speed of wheel B.

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