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Radial Engines

1) Radial engines connect pistons to the crankshaft via a master connecting rod and articulating rods attached to rings on the master rod, since the coplanar cylinder axes prevent direct attachment otherwise. 2) Radial engines have an odd number of cylinders per row to maintain a consistent firing order for smooth operation, with the power stroke of one piston helping compress the next. 3) Radial engines use fewer cam lobes than other engine types due to the radial arrangement, requiring fewer lobes to operate the valves of multiple cylinders.

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94 views4 pages

Radial Engines

1) Radial engines connect pistons to the crankshaft via a master connecting rod and articulating rods attached to rings on the master rod, since the coplanar cylinder axes prevent direct attachment otherwise. 2) Radial engines have an odd number of cylinders per row to maintain a consistent firing order for smooth operation, with the power stroke of one piston helping compress the next. 3) Radial engines use fewer cam lobes than other engine types due to the radial arrangement, requiring fewer lobes to operate the valves of multiple cylinders.

Uploaded by

Aashik Aashik
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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Engine operation

Since the axes of the cylinders are


coplanar, the connecting rods cannot all
be directly attached to the crankshaft
unless mechanically complex forked
connecting rods are used, none of which
have been successful. Instead, the
pistons 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
rods' 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 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.[1] The prototype radial Zoche
aero-diesels (below) have an even
number of cylinders, either four or eight;
but this is not problematic, because they
are two-stroke engines, with twice the
number of power strokes as a four-
stroke engine per crankshaft rotation.[2]
The radial engine normally uses fewer
cam lobes than other types. 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. The cam lobes are placed in
two rows for the intake and exhaust. For
example, four cam lobes serve all five
cylinders, whereas 10 would be required
for a typical inline engine with the same
number of cylinders and valves.

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