Reciprocating Engine Flashcards
What is the main advantage of a horizontally opposed engine over a radial engine for powering modern aircraft?
The horizontally opposed engine has a much smaller frontal area and is easier to streamline than a radial engine
How many throws are there in the crankshaft of a six-cylinder horizontally opposed engine?
Six
What kind of connecting rod arrangement is used in a radial engine?
Master rod connects single throw of the crankshaft with a piston. All of the other pistons are connected to the master rod with link rods (Master and articulating)
Of what material are most piston rings made?
Gray cast Iron
What is the reason for using hydraulic valve lifters in an aircraft engine?
Hydraulic valve lifters keep all of the clearance out of the valve operating mechanism. This decreases the wear of the valve train components
At what speed does the camshaft turn, relative to the crankshaft speed in an opposed engine?
About one half the crankshaft speed
What kind of main bearings are used in a horizontally opposed engine?
Steel backed, lead alloy bearing inserts
On what stroke is the piston of a reciprocating engine when the intake valve begins to open?
On the exhaust stroke
On what stroke is the piston of a reciprocating engine when the exhaust valve begins to open?
On the power stroke
Why are both hot and cold clearances given for most radial engines?
The hot clearance is given for valve timing purposes. The timing is adjusted with the valves in the cylinder number 1, set with the hot clearance. When the timing is set, ALL valves are adjusted to their cold clearance.
What is meant by a cam ground piston?
A piston that is not perfectly round. The dimension parallel with the wrist pin is several thousandths of an inch less than its dimension perpendicular to the wrist pin. When the piston reaches operating temperature, the metal in the piston pin boss expands enough that the piston becomes perfectly round
Where is the piston in a recip engine when the ignition spark occurs?
About 30 degree of crankshaft rotation before TDC on the compression stroke
What is meant by a full-floating wrist pin?
A wrist pin that is not clamped in either the connecting rod or the piston. Full-floating wrist pins are kept from scoring the cylinder walls by soft metal plugs in their ends
Why do most aircraft recip engines use more than one spring on each valve?
By using more than one spring and having the wires diameter and pitch of the springs different, valve float is minimalized. The springs have different resonant frequencies, so at least one spring will always be exerting a force on the valve.
Would excessive valve clearance cause the valves to open early or late?
Excessive clearance will cause the valves to open late and close early
