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. ...
OVERDRIVE :-The purpose of overdrive is to rotate the propeller shaft faster than the speed the engine crankshaft. It is fitted between gear box and propeller shaft.
Construction: It is basically an epicyclic or planetary Gear. In this 3 types of gear mounted on different shaft.These are sun gear, ring gear & Planet The sun gear mounted on the inherma Shaft which it at Centre.
The Planet geart are attached with Planet Carrier. The planet gear in mesh with sun gear and can revolve around at earth revolve around sun.
when Planet gears are revolving, Planet Carrier Shaft is also rotating.There if also a ring gear surrounding the planit gear. It has internal teeth which are in mesh with the Planet gear teeth.
Working → For overdrive, the planet Carrier is attached to the gear box shaft and sun gear attached yo Propeller shaft Thus the Planet Carrier is the driving memeberand sun gear shaft is a driven member. The ring gear is locked with the help of brake shoe. The speed of the sun gear is more the the speed of planet Carrier in r.p.m. For overdrive we lock the ring gear and overdrive is engaged.