Editing Radial engine (section)

==Engine operation==
[[File:Radial engine.gif|thumb|Another example of the engine operation]]
[[File:TwinWaspConRods.jpg|thumb|Master rod (upright) and slaved connecting rods from a two-row, fourteen-cylinder [[Pratt & Whitney R-1535 Twin Wasp Junior]] ]]Since the axes of the cylinders are coplanar, the [[connecting rod]]s cannot all be directly attached to the [[crankshaft]] unless mechanically complex forked connecting rods are used, none of which have been successful. Instead, the [[piston]]s are connected to the crankshaft with a master-and-articulating-rod assembly. One piston, the uppermost one in the animation, has a master rod with a direct attachment to the crankshaft. The remaining pistons pin their [[connecting rod]]s' attachments to rings around the edge of the master rod. Extra "rows" of radial cylinders can be added in order to increase the capacity of the engine without adding to its diameter.

[[Four-stroke cycle|Four-stroke]] radials have an odd number of cylinders per row, so that a consistent every-other-piston [[firing order]] can be maintained, providing smooth operation. For example, on a five-cylinder engine the firing order is 1, 3, 5, 2, 4, and back to cylinder 1. Moreover, this always leaves a one-piston gap between the piston on its combustion stroke and the piston on compression. The active stroke directly helps compress the next cylinder to fire, making the motion more uniform. If an even number of cylinders were used, an equally timed firing cycle would not be feasible.

As with most four-strokes, the crankshaft takes two revolutions to complete the four strokes of each piston (intake, compression, combustion, exhaust). The camshaft ring is geared to spin slower and in the opposite direction to the crankshaft. Its cam lobes are placed in two rows; one for the intake valves and one for the exhaust valves. The radial engine normally uses fewer cam lobes than other types. For example, in the engine in the animated illustration, four cam lobes serve all 10 valves across the five cylinders, whereas 10 would be required for a typical inline engine with the same number of cylinders and valves.

Most radial engines use overhead [[poppet valve]]s driven by [[pushrod]]s and [[Tappet|lifter]]s on a cam plate which is concentric with the crankshaft, with a few smaller radials, like the [[Kinner B-5]] and Russian [[Shvetsov M-11]], using individual camshafts within the crankcase for each cylinder. A few engines use [[sleeve valve]]s such as the 14-cylinder [[Bristol Hercules]] and the 18-cylinder [[Bristol Centaurus]], which are quieter and smoother running but require much tighter [[manufacturing tolerance]]s.{{Citation needed|date=October 2014}}