Advantages to radial engines?
Frank Stutzman
town, sniff) and was talking about the the Wilga that was there. The question
came up as to what the advantages are to a radial engine. I have no idea. Are
there any? Anybody know?
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Steve Pennypacker
> Somebody at work here made it down to the Salinas airshow (I had to stay in
> town, sniff) and was talking about the the Wilga that was there. The question
> came up as to what the advantages are to a radial engine. I have no idea. Are
> there any? Anybody know?
They sound better :-)
--
Steve Pennypacker PP-ASEL
Dennis McCurdy
: In article <1992Oct5.1...@netnews.synoptics.com>, fra...@synoptics.com (Frank Stutzman) writes:
: > Somebody at work here made it down to the Salinas airshow (I had to stay in
: > town, sniff) and was talking about the the Wilga that was there. The question
: > came up as to what the advantages are to a radial engine.
: They sound better :-)
:
: --
: Steve Pennypacker PP-ASEL
As I remember it (this is really going back) cooling is better on a radial
engine and you get a power burst every 40 degrees of prop travel. On opposed
engines you get a power burst every 60 degrees. One of the disadvantages
of radials is they use copius quantities of oil and are rather expensive to
overhaul. I'm sure there are others.
Actually, their sound is the only advantage I care about! :-)
--
Dennis L. McCurdy |
PP-ASEL A&P |
dlm@unislc |
d...@unislc.slc.unisys.com |
Brad Leftwich
fra...@synoptics.com (Frank Stutzman) wrote:
>
> ...The question
> came up as to what the advantages are to a radial engine.
In early days there were at least two advantages to radials (and rotaries,
too)
1. Shorter crankshaft, hence lighter weight
2. All cylinders are exposed for better cooling
Unfortunately, the correlary to better cooling in this case is a larger
frontal area with higher drag, which I think is the main reason for the
radial's demise in these aerodynamically conscious times.
But doesn't this discussion belong in rec.aviation.misc?
--Brad Leftwich
Ross Oliver
|> As I remember it (this is really going back) cooling is better on a radial
|> engine and you get a power burst every 40 degrees of prop travel. On opposed
|> engines you get a power burst every 60 degrees. One of the disadvantages
|> of radials is they use copius quantities of oil and are rather expensive to
|> overhaul. I'm sure there are others.
Is high oil consumption an artifact of a radial configuration, or caused by
the fact that the design and materials are 50+ years old? Would it be possible
to build a modern radial engine that did not have high oil consumption?
Just curious,
Ross Oliver
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Cthulu for President. Why choose a lesser evil?
Dennis McCurdy
: Is high oil consumption an artifact of a radial configuration, or caused by
: the fact that the design and materials are 50+ years old? Would it be possible
: to build a modern radial engine that did not have high oil consumption?
The main problem (with a "good" engine) is one of gravity. When the engine is
just sitting there oil seeps past the rings and into the combustion chamber
of the lower cylinders. This is why when you start a radial it belches lots
of smoke and the amount of smoke gradually lessens as it burns away the excess
oil in the lower jugs. This is why you see guys "pull it through" before they
start a radial (or at least one reason). They want as much of the oil to get
pumped out the valves as possible before starting. I was always told 6 turns
of the prop was sufficient.
Personally, I would enjoy seeing some radials used in homebuilts. Anyone seen
something like this? Yow!
: Ross Oliver
Charlie Stone 4915162
>town, sniff) and was talking about the the Wilga that was there. The question
>came up as to what the advantages are to a radial engine. I have no idea. Are
I think that they are lighter for a given cubic capacity than an inline
engine and at the expense of frontal area there is more even cooling for
the cylinders than is possible with an aircooled inline or opposed engine.
Charlie Stone
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For my next (and possibly last) manoevre !!
C. Stone.
Perth, Australia.
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Steve Pennypacker
>
> Personally, I would enjoy seeing some radials used in homebuilts. Anyone seen
> something like this? Yow!
The Hatz which won Grand Champion- Plans Built at Oshkosh this year (and
which I've camped next to for the last 2 years :) is powered by a Kinner
radial. There are also lots of WWI replicas which are powered by radials
and rotaries. I seem to remember a picture of a radial powered
Starduster (??) in KITPLANES earlier this year. So yes, they do exist.
I don't think I've seen a radial powered Lancair yet ;-)
--
Steve Pennypacker PP-ASEL
Laird P. Broadfield
>Somebody at work here made it down to the Salinas airshow (I had to stay in
>town, sniff) and was talking about the the Wilga that was there. The question
>came up as to what the advantages are to a radial engine. I have no idea. Are
>there any? Anybody know?
Based solely on thinkology (i.e. I haven't a clue, but I've got a couple of
good guesses) two things leap to mind: easy to make a non-counterbalanced
engine (opposed cylinders/pistons balance each other's motion), and more
easily designed to be air-cooled.
--
Laird P. Broadfield lai...@crash.cts.com ...{ucsd, nosc}!crash!lairdb
Hi! I'm a shareware signature! Send $5 if you use me, send $10 for manual!
Lar Kaufman
not necessarily bad, but I can make some comments from the perspective
of a (US) FAA-Licensed Airframe and Powerplant mechanic with some
experience in radial engine maintenance.
Radial engines deliver their power at low RPM. This is their chief
advantage. You quickly run into some physical limits in trying to
deliver horsepower at high RPM; the power must be transmitted through
the propeller blades to move air mass, and the higher the RPM the shorter
the propeller blades must be to prevent their tips from moving at
trans-sonic speeds, which ruins propeller efficiency.
You could design radial engines with smaller frontal area, especially if
you used a liquid coolant design, but then you would lose your power
benefits, which derive largely from the long piston stroke.
The main reason that radial engines are not being developed much anymore
(I know of a guy in Texas who markets 3- and 6-cylinder radial homebuild
engines) is a circumstance of machine tool technology development. It is
very expensive to machine radial engines, which use cam plates for valve
actuation that require very large grinding equipment and high precision
in grinding the cam plates. An automotive cam can be ground with high
precision on much smaller and more common equipment. Because no other
form of machinery has the need to worry about passing power through the
limiting factor of propeller blades with the added concern of weight
control, the machining equipment for radial engines has a very limited
market. (Other applications are happy to add a heavy transmission to
gear the engine rpm to output needs.)
Don't think radial engine technology is obsolete, either. Radial engines
represent some of the most sophisticated of all engine designs. For
example, there were 28 cylinder (4 banks of 7 cylinders) turbo-compound
radials that used a mechanical supercharger and then scavenged exhaust
gas velocity by driving a spur gear that input the power directly to the
crankshaft. Perhaps the most interesting design was the Bristol Centaurus
engine (used in the Hawker Sea Fury, at the end of WWII) which was a
sleeve-valve design. Instead of using pushrods and poppet valves, in the
Centaurus, the piston sleeve rotated, opening and closing intake and
exhaust ports in a sliding action. (If I mis-describe the Centaurus
design, I apologize - I've only read about it and that was long ago.)
Still, I think the radial engine might make a comeback using modern
computer technology and improved hydraulic technology. The technique
I would use is to use direct hydraulic actuation of the valves under
computer control, eliminating the mechanical valve actuation mechanism.
-lar
--
Lar Kaufman, Chair, Committee for Common Man work: 617-893-6562
personal account: la...@world.std.com
occasional weekend system: la...@whooper.austin.tx.us