Criteria S.I. Engine (Petrol or Spark Ignition Engine) C.I. Engine (Diesel or Compression Ignition Engine) Working Cycle Works on Otto Cycle or Constant Volume Cycle. Works on Diesel Cycle. Mixture During Suction Stroke Takes a mixture of air and petrol during the suction stroke. Takes only air during the suction stroke. Fuel Used Uses petrol as fuel. Uses diesel as fuel. Compression Ratio Has a compression ratio that varies from 6 to 10. Has a compression ratio that varies from 16 to 20. Engine Weight and Cost S.I. engines are lighter and cheaper. C.I. engines are heavier and costlier. Initial Cost Initial cost is lower compared to C.I. engines. Initial cost is high due to high compression ratio. Starting Starting is easy. Starting is difficult, especially in cold conditions. ...
GEAR BOX - It is Mechanism which provides variation in speed and torque.
FUNCTION OF GEAR BOX
• it provides variation in speed and torque.
• it help the vehicle to run in reverse direction.
• increase or decrease speed
Types Of Gear Box:-
* Sliding mesh gear box
* Constant mesh gear box
* Synchromesh gear box
1.) SLIDING MESH GEAR BOX
• CONSTRUCTION - In this the clutch gear which mounted on the clutch shaft. This gear box shaft is attached to the Clutch.
The clutch gear A meshed with lay shaft gear D .
Lay shaft is a intermediate shaft.
There are 3 gear on lay shaft E,F and G. There is also an idle shaft on which a small idle gear H is mounted. This idle gear used for reversing the direction of vehicles.
There is a main shaft which is aligned to the Clutch shaft. The two gear B & C mounted on main shaft in such a way they can slide on main - shaft.
SPLINED SHAFT IS ALSO CALLED Main shaft.
• WORKING - The gear A is always rotating when clutch is engaged. The gear D, E ,F ,G and H is also rotate with gear A. Because gear D is always meshed with A. But gear B and C is not meshed with any gear. When drivers need high and low speed the gear B and C is used.
FIRST GEAR - In this , the main shaft is slides on which gear B ,C is mounted. The gear C slides and it is meshed with gear F. Because of this Gear C and Gear F conection the main shaft is rotating.
The power is transmitted from clutch shaft through A,D,F and C to main shaft.
SECOND GEAR - The main shaft slides again and this time gear B is meshed with Gear E. This time power is transmitted through A,D,E and B to main shaft.
HIGH OR TOP GEAR - For high gear , the gear B is slides on main shaft in such a way that's it is directly engaged to gear A through splines. It mean the clutch shaft is connected to main shaft.
It means the all power from clutch shaft is transfer to main shaft thats why is called high gear.
REVERSE GEAR - The gear C is slides on main shaft and it is meshed with idle gear H. It reverse the direction of rotation.
The power is transmitted from clutch shaft through Gear A,D,G,H and C to main shaft.
2.) CONSTANT MESH GEAR BOX -
• CONSTRUCTION:- The gear A mounted on the clutch shaft. The gear E , F , G and H are mounted on on the lay shaft. In this type , the gear E is always meshed with gear A. There is splined main shaft which is in alignment with gear box - shaft.
The gear B, C and D rotate freely on the main shaft. There is an idle shaft Gear I is mounted on it.
The gear B is always mesh with gear F and gear C is always mesh with gear G. The gear D is called reverse gear is always mesh with gear I which is mesh with gear H. There are two dog clutch D1 & D2 is mounted on main shaft which help in gear shifting.
WORKING:- In this the gear C is called a First gear , and Gear B is called a second gear and gear D is called a reverse gear.
FIRST GEAR - In this , the dog clutch D2 is slided on main shaft in such a way that the teeth of dog clutch are in contact with gear C. That means dog clutch D2 is engaged with gear C. The power of engine is transmitted through dog clutch D2 with gears A,E,G,C to main shaft.
SECOND GEAR -In this the dog Clutch D¹ is slided on main Shaft toword right such that the teeth of dog Clutch are - engaged with the teeth of gear B.
Top Gear - in this, the dog Clutch if slided toward left are such that its teeth are engaged with the teeth of gear A.
Reverse Gear - in this, the dog Clutch D2 is slided on the main shaft and it's teeth are engaged with of gear D. Then idler gear I reverse the direction of rotation of main shaft.
3.) SYNCHROMESH GEAR BOX - It is a modified version of constant mesh gear box. In this gear box all the gear on main shaft remain constant mesh with gears on lay shaft. In place of DOG CLUTCH we use synchronising devices. There two synchronising devices.(like two dog clutch used in constant mesh gear box).
This device make frictional contact with gear for engagement.
CONSTRUCTION:- The Gear A is mounted on clutch shaft. The gear A is always mesh with gear D which mounted on lay shaft. Gear B and Gear C are mounted on main shaft. Gear B is always mesh with Gear E but Gear C is sliding mesh type. Gear C is meshed with Gear F or Reverse Gear H by sliding. Gear is H is mounted on ildler shaft. Gear H is always mesh with gear G.
Between Gear A and Gear B synchromesh device is mounted.
CONSTRUCTION OF SYNCHRONISING DEVICE- It has various parts ( I, J ,S , K ,F). It is fitted on splined shaft and free to slide on it. Part I has teeth on outer surface and mesh with Gear J which has internal teeth. Sleeve S which helps in sliding the device and also part J. There two gear K on Gear A and Gear B which has external teeth. The Gear J is meshed with gear K when it slided. There are also two frictional surface F1 and F2 on part I and also on Gear A and Gear B.
WORKING OF SYNCHROMESH GEARBOX:-
NEUTRAL POSITION:- In this case Gear A and Gear D , Gear B and Gear E are in meshed and due to this they are rotating. The power is transmitted to Gear A to Gear D and also Gear E and Gear B.
FIRST GEAR :- In this , The Gear C is slided toward left to mesh with gear F. The Gear B is rotating freely on main shaft.The power is transmitted from Gear A to Lay shaft gears D and F and Gear F to Gear C.
SECOND GEAR:- In This, The Gear F and SYNCHRONISING device is slided toward right. The synchronising device is engaged with the teeth K of the Gear B. The power is transmitted from clutch shaft through Gear A to Lay shaft gear D and E. Gear E is mesh with B so the Gear B is also rotating.
HIGH OR TOP GEAR:- In this, the synchronising device is shifted away from the Gear B and slided toward left with Gear A. Now Gear A is engaged with Synchronising device . The power is transmitted from clutch shaft gear A to synchroniser and to main shaft.
REVERSE GEAR- In this , the synchronising device is neutral but Gear C is slided on main shaft and mesh with idler Gear H. The gear H is meshed with Gear G and mounted on ildler shaft. The power is transmitted from the Gear A to Lay shaft Gears D,G, H to main shaft Gear C.