crankshaft

Lets learn all about CRANKSHAFT- an important engine component.

INTRODUCTION:

• The working of other components of the engine, such as camshaft for fuel timing, firing order of each unit, opening of inlet valve and exhaust valve, operation of air start distributer etc depends on correct rotation of the crank shaft.
• Failure of crankshaft can stall the engine/ship.
• The parts forming a crankshaft are : journals( crankshaft), crank webs and the crankpins.
• They are too big to make a single unit and so they are constructed by joining together individual forgings.(will be discussed below how it is done).

MATERIAL:
  1. For slow speed marine diesel engines:
      steel castings or forgings
  2. For medium and high speed M.D.E
      Alloy steel

WEIGHT:
For 2-stroke crosshead engines- over 300 tonns.

CLASSIFICATON:
 They are divided into four depending upon the methods of construction-
(a) Fully built
(b) Semi-built
(c) Welded crankshaft
(d) Solid single piece used in very small engines.

Now we will know the above mentioned classifications one by one in a simple way.

(A) FULLY BUILT

• As already mentioned above the parts which forms a crankshaft: journal, webs,      crankpins.
• Journals and crankpins are made from forgings, and the webs may be forged or cast.They are made separately.
• These parts are shrink-fitted.
• Webs were heated up and the crank pin and journals fitted into the holes.The holes gets expanded due to heating.
• Were used on older engines. 

  Let's see the diagram: