high torque is required at the driving wheels when a vehicle is starting from rest, climbing a hill or accelerating.
Gear set - permit the engine crankshaft to revolve at a relatively high speed while the wheels turn at slower speeds
The driving force or tractive effort used must be equal to the total resistance of the forces opposing the motion of a vehicle and keeping it moving along a road at uniform speed [Air or wind resistance, gradient resistance, and Rolling resistance]. Type of gear box
1. Sliding mesh type
2. Constant mesh type
3. Synchromesh type
Gear Ratio=[Speed of driving shaft]/[speed of driven shaft] Sliding Gear Box
Meshing of gears takes place by sliding of gears on each other
The driving shaft of the gear box is known as the primary shaft or clutch shaft.
The clutch gear rigidly fixed to the clutch shaft always remains connected to the driven gear of the countershaft or the lay shaft.
Three other gears are also fixed on the lay shaft.
Two gears are mounted on the splined main shaft which can be slide or moved axially to mesh with the corresponding gears on the lay shaft.
A reverse idler gear mounted on another shaft always remains connected to the reverse gear of the lay shaft. Constant mesh Gear Box
All the gears mesh with each other all the time.
The primary shaft which carries the clutch is splined and carries a gear that meshes with the largest lay shaft gear.
The main shaft has a number of gears that mesh with the gears on the lay shaft, However, these gears being on bushes or ball/roller bearings are free to move on the main shaft without transmitting any torque.
All the gears on the lay shaft are rigidly fixed with it.
When the left-hand dog clutch is made to slide to the left by means of the gearshift lever, it meshes with the clutch gear and the top speed gear is obtained
For smooth engagement of the dog clutches it is necessary that the speed of mainshaft gear and the sliding...
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