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DIFFERENCE BETWEEN S.I AND C.I ENGINES

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. ...

SYNCHROMESH GEAR BOX

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.



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DIFFERENCE BETWEEN S.I AND C.I ENGINES

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. ...
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