THEORY OF MACHINES ME5401
AGENDA- GEAR BOX IN TRANMISSION SYSTEM
FUNCTIONS
• TO PROVIDE VARIATION IN SPEED AND
TORQUE
•TO PROVIDE NEUTRAL CONDITION TO THE
VEHICLE
•TO PROVIDE REVERSE MOVEMENT OF
VEHICLE WITHOUT CHANGING IN DIRECTION
OF ROTATION OF CRANKSHAFT
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PRINCIPLE
• A Gear box is a mechanical method of
transferring energy or motion from one
device to another and is used to increase
torque while reducing speed.
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CLASSIFICATION
• MANUAL OPERATED
•SEMIAUTOMATIC
•FULL AUTOMATIC TRANSMISSION
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SLIDINGMESH GEAR BOX
•In this type of gear box,
gears are engaged and
disengaged by sliding of
the gear wheels.
•Gear wheels on the
splined main shaft engage
with gear wheels on the
lay shaft or counter shaft
by sliding themselves.
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Sliding mesh type Gearbox Gear position
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CONSTANT MESH GEAR BOX
• In this case, Gear
wheels on the main shaft
and the lay shafts are
constantly engaged and
the rotary motion is
transmitted to the main
shaft by engaging dog
clutches
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ADVANTAGES OF CONSTANT MESH GEAR
BOX
• USE OF HEICAL OR DOUBLE HELICAL GEAR TEETH
•BY SYNCHRONIZING DEVICES – SMOOTH ENGAGEMENT
•ANY DAMAGE TO DOG CLUTCH TEETH AND NOT TO THE TEETH
OF THE GEAR WHEEL
• DAMAGED GEAR WHEEL WILL RESULT IMPERFACT MOTION AND
NOISE
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Synchromesh Gear Box
• Similar to constant mesh type, because all the gears on the main
shaft are in constant mesh with corresponding gears on the
layshaft.
• The gears on the main shaft are free to rotate on it and that on
the layshaft are fixed to it.
• Avoids the necessity of double declutching.
• The parts which ultimately are to be engaged are first brought
into frictional contact which equalizes their speed, after which
these may be engaged smoothly.
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Line Diagram of Synchromesh Gear Box
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Selector Mechanism with gear lever on
top of the transmision
• There are forks mounted on the
sleeves on three separate selector
rods which are supported in the
gearbox casing.
• Each selector sleeve can slide on
its rod.
• There are slots on the selector
rods and the sleeves are provided
with spring loaded balls to avoid
unwanted engagement of the
gears.
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Selector Mechanism with gear lever on
top of the transmission
• These balls resist the movement of the forks
until some force is applied to the gear lever to
overcome their resistance.
• Grooves are provided on the gear bosses
where the selector forks can fit in.
• Transverse motion of the gear lever selects
the forks which is to be engaged and the
longitudinal movement then slides the forks
and its gear to engage the selected gear.
• Various gear position are marked on the gear
lever knob itself.
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Selector Mechanism
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Interlock Mechanism
• Prevents two gears
engaging
simultaneously
• If this occurs the
gearbox will lock up and
shaft rotation will be
impossible.
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The table below shows some example gear ratio
for a 5 – speed manual gear box.
RPM of Gear Output Shaft
GEAR RATIO when the Engine is at 3000
RPM
1st 3.166:1 947
2nd 1.882:1 1594
3rd 1.296:1 2314
4th 0.972:1 3086
5th 0.738:1 4065
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LUBRICATION OF GEAR BOX
• DIP AND SPLASH SYSTEM
• CORRECT GRADE OF OIL
•CORRECT QUANTITY OF OIL
•VENTILATION
•REGULAR INTERVAL
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TROUBLE SHOOTING OF GEAR BOX
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Problems Causes Remedy
1. Overload Decrease load or use a larger model
2. Insufficient or excessive lubricating Adjust oil level so it aligns with mark
oil on oil gauge
3. Contaminated oil Flush interior and replace oil
Change oil with one having the proper
4. Oil viscosity is improper
Gear case becomes viscosity
unusually hot Reassemble and tighten properly
5. Bearing are improperly mounted
(Consult dealer)
6. Shaft is connected improperly Align properly
7. Air vent port is closed Remove rubber plug from oil cap
Install cooling fan or move to cooler
8. Ambient temperature is too high
area
1. Improper meshing Adjust properly (Consult dealer)
2. Bearings are damaged or worn Replace bearings (Consult dealer)
3. Overloaded Decrease load or use a larger model
4. Insufficient oil Add oil so level aligns with oil gauge
Unusual or excessive 5. Oil seal is not wet with oil Lubricate
noise 6. Improper installation or connection Tighten loose bolts and align correctly
7. Bearing are improperly mounted Adjust (Consult dealer)
8. Input rpm is too high Reduce
Remove foreign particles and replace
9. Foreign particles are mixed in oil oil after flushing interior. (Consult
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dealer)
Problems Causes Remedy
1. Gear teeth are worn Replace wheel (Consult dealer)
Remove foreign particles and
2. Foreign particles are mixed in oil replace oil after flushing interior.
(Consult dealer)
Vibration is excessive
3. Bearings are worn or damaged Replace bearings (Consult dealer)
4. Mounting bolts are loose Tighten
5. Wheel is improperly aligned Replace wheel (Consult dealer)
Replace worm and wheel (Consult
1. Teeth seizure
dealer)
Input/output shafts do not 2. Bearings are worn or damaged Replace bearings (Consult dealer)
rotate at all Remove foreign particles and
3. Foreign particles are mixed in oil replace oil after flushing interior.
(Consult dealer)
1. Wheel teeth is worn Replace wheel (Consult dealer)
2. Wheel boss or shaft key are Replace wheel or key (Consult
Input/output shafts rotates damaged dealer)
in idle condition and output 3. Input shaft or worm teeth are Replace shaft or worm (Consult
shaft is not driven damaged dealer)
4. Input shaft is broken Replace shaft (Consult dealer)
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Problems Causes Remedy
1. Overload Reduced load
2. Contaminated oil Replace oil after flushing interior
3. Insufficient oil Add oil
Replace oil with one having the
4. Oil viscosity is too low
proper viscosity
Teeth are worn Install cooling fan or move to
5. Ambient temperature is too high
cooler area
Remove foreign particles, clean
6. Foreign particles are mixed in oil
interior and replace oil
Reducer rpm or use a different
7. Excessive rpm
model
8. Backlash is improper Reassemble and adjust
1. Overload Reduce load or use a larger model
2. Impact load is greater than rated Reduce impact load or use a larger
Main body has cracks or load. model
shaft is broken
3. Connection is improper Align properly
4. Gear case has partial thickness
Replace gear case (Consult dealer)
or cavities
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Problems Causes Remedy
1. Oil seal is defective Replace oil seal
2. Cover mounting bolts are loose Tighten bolts
3. Air does not escape Check oil cap
4. Input and output shafts are
Replace shafts (Consult dealer)
marred
Adjust oil level so it aligns with
5. Excessive oil
mark on oil gauge
Oil leaks
6. Gear case has cavities Replace gear case (Consult dealer)
7. Gear case has fissures Replace gear case (Consult dealer)
8. Other than normal installation
directions (horizontal oblique, Const dealer about installation
upside-down etc)
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