Question for all you motor engineers and mechanics?

Question

Many years ago I sat a test for mech. eng. Royal Navy, One of the questions was as follows>>> WHAT IS A CRANKSHAFT FOR.>>> p.s. I do know the answer, top points for 1st correct answer.

P.S. answer in the shortest poss way 7 words

Dave A Do leave it out. Incidently, the pistons "drive" the crankshaft, NOT VICE-VERSA Oh and thats a clue!!!

Note to The mecanic. Torque is NOT spelt toque, as a "mecanic" you should know that.

Lofty 76>>> The pistons DO drive the crankshaft, there is ALWAYS 1 piston under "FIRE" to drive the other idle pistons, also the weight of the flywheel/clutch/ torque converter keeps the whole mechanism rotating.

To all who said coverting MOTION to MOTION. You can't CONVERT one thing to the SAME thing, The very act of converting something IS to CHANGE it to something else.

Answer 1

Hi. from your question it sounds like you served the same course, in the same service (R.N.) as I did many years ago. The numerous questions asked in tests>> Whats a crankshaft for?, Whats a camshaft for? Whats a piston for? Whats a valve for? They ALL have a specific answer,sadly not much taught or learned now -days.
Now your question, what is a crankshaft for in seven words (just like the exam paper).
***To convert reciprocating FORCE to rotary POWER***.
(The FORCE is the fuel/air explosion in the cylinder that drives the piston down.)
(The POWER is what drives the vehicle/boat/plane/whatever.)
***So the Crankshafts job, is to do as described above***
As you noted you can't covert/change one thing to the same thing, that goes against the meaning of "Convert or Change".
I rest my case.

Answer 2

Respect to Dave A, the pistons only drive the crankshaft during the power strokes, the rest of the time the crankshaft drives the pistons.

Incidentally :

"Translates reciprocating linear piston motion into rotation"

Answer 3

To give rotary motion from longitudinal motion.

What were their other questions? "Is the bow the pointy end or the blunt end?" and similar?

EDIT:
Actually, Dave A is correct most of the time - on the induction, compression and exhaust stroke, the motion of the crank is driving the motion of the piston, not the other way round. The piston only drives the crank on the power stroke.

Answer 4

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Answer 5

What For ?? the crankshaft is to crank engine it has rods with bearings that raises the pistons up and down which gives the engine compression (along with the valves) to fire and power the engine,, intake , compression ,, power and exhaust

Answer 6

the crankshaft is in the lower part of the engine it has the connecting rods and pistons attached to it by the connecting rods when they move up and down the cylinders the crankshaft spins and turns the transmission gears

Answer 7

convert recipricating motion in to rotory

technically apart from the power stroke it is the inertia in the flywheel that turns the engine unless it is a mutlicylinder engine

Answer 8

translates reciprocating linear piston motion into rotation

Answer 9

To turn reciprocating motion into rotary motion

Answer 10

Motion powered by twists and turns.