Manual transmission final

MANUAL TRANSMISSION

PRESENTED BY.

• AHIRE SATISH B.

BASIC LAYOUT OF TRANSMISSION SYSTEM

INTRODUCTION1> Also known as Manual gearbox or Standard Transmission.

2> It generally uses a driver-operated clutch, typically operated by a foot pedal(car) or hand lever(motorcycle).

3> Clutch is used for regulating torque transfer from the internal combustion engine to the transmission.

4> Gear stick, either operated by foot (as on a motorcycle) or by hand (as in a car) is used for shifting to the lower or higher gears.

BASIC LAYOUT OF A 5-SPEED TRANSMISSION

CUT SECTION OF A MANUAL GEARBOX

Parts of a Gearbox

• Shifter Lever• Input Shaft or Clutch Shaft• Counter Shaft• Main Shaft or Output Shaft• Gears (Helical/Spur)• Synchronizer unit or Dog Clutch Unit• Shifter Forks• Transmission Casing

Shifter Lever

• It is a lever that facilitates the driver to change the gear arrangement according to his driving conditions.

• The bottom end of the shift lever is connected to the shifter shaft in the gearbox.

Input Shaft or Clutch Shaft

• It is also called as Clutch Shaft because it is driven by the clutch plate.

• It Has external splines so as to mesh with the internally splined clutch plate.

• It transmits power from the engine to the counter shaft via the clutch.

• It helps in rotating the gears inside the gearbox.

Input Shaft

Counter Shaft

• It holds the counter shaft gears which mesh with the main shaft gears.

• It is a shaft that receives power from the Clutch Shaft or the Input Shaft and transmits it to the Main Shaft.

• It helps in achieving the desired torque ratios by meshing with the corresponding gears when required.

Counter Shaft or Lay Shaft

Main Shaft

• This shaft is also called the output shaft.• It receives the power from the Countershaft

and transmits it to the final drive like the differential.

TYPES OF GEARS USED IN GEARBOX• Spur Gears :- Used in Sliding mesh and some types of

Constant mesh gearboxes. In this type the teeth are straight cut. Angle of cut is 90 degrees.

• Helical Gears :- Used in most types of constant mesh and all synchromesh gearboxes.In this type the teeth are cut at a certain angle. Angle of cut is 17-20 degrees.

DIFFERENCE BETWEEN SPUR AND HELICALSPUR GEARS HELICAL GEARS

These are more efficient because less teeth touching when two gears are connected.

These are less efficient because they have more teeth touching when two gears are connected, leading to increased friction.

Spur gears cost less to manufacture than helical gears.

More costlier due to higher design costs.

Due to less teeth touching when two gears are connected load capacity is less.

Because the load distributes across more teeth the load capacity is high.

Are less durable due to teeth bearing excessive load.

These are more durable due to the reason of uniform load distribution.

Shifter Fork

• It is the unit for moving the gears into the desired arrangement.

• The Shifter fork slides the corresponding sliding sleeve or synchronizer sleeve according to the driver input.

Shifter Fork

MATERIAL USED IN GEARBOX• Numerous nonferrous alloys, cast irons, powder-metallurgy

and plastics are used in the manufacture of gears.

• However steels are most commonly used because of their high strength to weight ratio and low cost.

• Gearbox housings are made up of Aluminum alloys, cast iron

FUNCTION OF GEARBOXES

• It is used to increase/decrease the engine torque.

• To enable a neutral position of the gearbox while in rest position.

• To be able to move the vehicle in reverse direction

• It is used as a housing for gears and also the gearbox oil and other components

FUNCTION OF GEARBOXES

Reversing in GearboxesThe reversing in gearboxes is achieved by using an Idler Gear.

TYPES OF GEARBOXES

Unsynchronized Type of Gearboxes1> Sliding mesh gearbox

Synchronized Type of Gearboxes 1> Constant mesh gearbox

2> Synchromesh gearbox

EVOLUTION OF GEARBOXES

SLIDING MESH GEARBOX• Known as sliding mesh gearbox or Crash Box.• “Gears are slid to mesh with each other to transmit

power”.• No synchronizer unit hence crashing of gears occurs

due to variable speeds of the different gears.• Double Declutching required to shift to lower or

higher gears without crashing of gears.

LAYOUT OF SLIDING MESH GEARBOX

EVOLUTION OF GEARBOXES CONSTANT MESH GEARBOX

1> In this type gears are always in mesh and rotating, but gears on one shaft can freely rotate or be locked to the shaft. “The gears are fixed to the shaft and cannot slide sideways”.

2> The locking mechanism for a gear consists of a collar (or dog collar) on the shaft which is able to slide sideways so that teeth (or dogs) on its inner surface bridge two circular rings with teeth on their outer circumference: one attached to the gear, one to the shaft

3> When the rings are bridged by the collar, that particular gear is rotationally locked to the shaft and determines the output speed of the transmission.

DOG CLUTCH/DOG GEAR

CONSTANT MESH GEARBOX

EVOLUTION OF GEARBOXES

SYNCHROMESH GEARBOX

• Synchromesh gearboxes are similar like constant mesh gearboxes except that these type of gearboxes use a Synchronizer unit to match the speed of the gear to that of the shaft.

• Synchronizer unit avoids the necessity of double declutching while shifting gears.

LAYOUT OF SYNCHROMESH GEARBOX

FUNCTION OF SYNCHRONISER UNIT• An automobile has a synchronizer mechanism or synchromesh,

which consists of a cone clutch and blocking ring.• Before the teeth can engage, the cone clutch engages first

which brings the selector and gear to the same speed using friction.

• until synchronization occurs, the teeth are prevented from making contact, because further motion of the selector is prevented by a blocker (or baulk) ring.

• When synchronization occurs, further passage of the selector which brings the teeth together.

• The synchronizer has to overcome the momentum of the entire input shaft and clutch disk when it is changing shaft rpm to match the new gear ratio.

COMPONENTS OF A SYNCHRONIZER UNIT