Piston engine design

Question 1

What factors determine engine power

Answer 1

Greater mass of mixture combusted greater the power

Question 2

Engine Characteristics

Answer 2

Number of Cylinders, arrangements,
method of cooling, type of fuel,
Propellor driven arrangement

Question 3

Types of Engine design.

Answer 3

Radial(+Dual),

In-line, V-line, Horizontally opposed. Most common design for modern light aircraft.

Question 4

What is the need for 2 spark plugs

Answer 4

Redundancy measure. Increases safety.

Also more efficient combustion as mixture ignited from both sides of cylinder.

Question 5

What is the crankthrow

Answer 5

Distance between crank pin and crank journal. Amount the piston moves.
2 throw equals 1 stroke.

Question 6

Firing order for 4 cylinder engine.

Answer 6

1,3,4,2. Alternating firing order reduces stress on crankshaft.

Question 7

What is a crank assembly

Answer 7

Crankshaft, connecting rods and pistons collectively

Question 8

What is the camshaft

Answer 8

Operates the valves via push rods. Rotates half the speed of crankshaft.

Question 9

Valves characteristics

Answer 9

Inlet valve bigger than exhaust. Close under spring pressure. 2 springs on each valve wound in different directions.

Question 10

Tappet clearance

Answer 10

Allows for thermal expansion. Correct tappet clearance ensures valves close properly at all operating temperatures. Large clearance will prevent valve from opening properly. Small= Not closing properly at high temperatures,