Dash8King
Topic Author
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Joined: Wed Nov 21, 2001 8:45 am

Radial Engines

Sat Aug 24, 2002 2:34 pm

Are Radial engines the same as Piston? What are the differences? I know that the DC-3 uses a piston but then people refer to them as Radial engines can anyone help me?

Thanks a lot for putting up with my dumb questions.
 
tulsarefueler
Posts: 41
Joined: Thu Aug 22, 2002 10:17 am

RE: Radial Engines

Sat Aug 24, 2002 2:59 pm

Radial engine are piston engines. The main difference is the cylinders are in
a circular pattern instead of horizontally opposed or in a V pattern.
 
L-188
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RE: Radial Engines

Sat Aug 24, 2002 4:30 pm

A radial engine has radial symmetry in it's layout, just like a starfish.

The other two typically are bilaterally symmetric, like humans. One side matches the other.


Seriously though.

looking from the front or the back, the pistons are mounted around the crankshaft in the middle. The engine case is bolted to the airframe and the crank turns the prop.

This is not to be confused with the similar rotary engine. Same basic layout but the crankshaft is bolted to the airplane and the engine case and pistons all spin with the airframe.

The rotary engine was widely used on WWI fighters. It the reason why the Sopwith Camel had a wicked left turn, or was it right? I can't remember.
OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.
 
timz
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Piston Engines

Sun Aug 25, 2002 8:49 am

This may not be quite right, but close enough: a piston engine has pistons. You know what they are, right?

But there are lots of different arrangements of piston engines. Your car might have four pistons (in four cylinders) in a row along the crankshaft, with the axes of the cylinders parallel; some aircraft engines used to use that arrangement, but it's fairly rare now. V-6's and V-8's are common in cars but rare in aircraft. Radial engines are just another possible cylinder arrangement of a piston engine.

Maybe 98% (?) of piston engines flying today are air-cooled, unlike your car (probably). That's one reason for the radial arrangement.
 
LZ-TLT
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RE: Radial Engines

Sun Aug 25, 2002 9:22 am

To add to Timz's comment:

The Junkers Ju-88 has 18-cylinder Y-form engines(3 banks a 6 cylinders arranged in an Y form around the crankshaft)

While building the Tu-4(B-29 clone), the russians considered the use of their own developed, 48-cylinder X-form engines(4 12-cylinder banks arranged in an X-form around the crankshaft). However, the intention was cancelled due to unreliability and maintenance problems of these experimental engines.

The french pre-WWII Caudron racing aircraft were equipped with straight(not V) Renault 6 or 8-cylinder engines(common in cars, but not that common in aircraft, even in those years)

ALL WWII watercooled engines - the DB series(powering the Me-109), VK-105PF and VK-107PF (all Yak fighters), RR Gryphon/Merlin(Hurricane/Spitfire/Mustang), Allison(Curtiss Kittyhawk), just to mention the most popular ones were V-12's mounted inverted
 
PPGMD
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RE: Radial Engines

Sun Aug 25, 2002 10:12 am

Well that I know of there is one one readily made radial engine that is the Russian M-14, its gear backwards, so the prop spins the other way, which I think is couter clockwise from the pilots seat. They are used in the Sukoi series of aerobatic airplanes (SU-29 and SU-31), and in the Pitts Model 12 made by home builders. Its a rather fine engine that is much cleaner than the old radials thanks to the clean kit. Oh one intresting thing the starter is powered by air pressure so its not uncommon to see Dive tanks in the hanger. I know that I spent several hours starting one as it neared time to do the certification flights.
At worst, you screw up and die.
 
L-188
Posts: 29881
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RE: Radial Engines

Sun Aug 25, 2002 11:32 am

Check that

I wasn't aware that the RR Merlin and Griphon, and Allison 1710 where inverted mounted. I was under the impression the where mounted right side up.
OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.
 
LZ-TLT
Posts: 427
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RE: Radial Engines

Sun Aug 25, 2002 3:05 pm

checked it, you're right, L-188.
My fault, pls excuse me
 
timz
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Couple More Clarifications, Maybe

Mon Aug 26, 2002 7:27 am

No expert on Ju88s, but I assume 99.9% (or maybe 100%) of them had either BMW 14-cylinder two-row radials or Junkers Jumo inverted V-12s. I think the Jumo 222 that appeared in a few prototypes was a 24-cyl-- 6 banks of 4-in-line.

I'll try another spelling: Griffon?

I guess all Rolls-Royce and Allison V-12s were right-side-up, weren't they? By which we mean the crankshaft was at the bottom of the engine with the cylinder banks forming a 60-degree vee above it-- the usual arrangement, in other words. But German WWII V-12s were all? inverted.
 
Dash8King
Topic Author
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RE: Couple More Clarifications, Maybe

Mon Aug 26, 2002 11:40 am

Ok thanks a lot, I now have another question how can you tell by looking at it if it is a piston or a radial engine. Like a C150 is Piston but a DC-3 is Radial so how can you tell by looking at it. BTW, yes I did know what a piston was.
 
PPGMD
Posts: 2398
Joined: Sun Sep 30, 2001 5:39 am

RE: Radial Engines

Mon Aug 26, 2002 12:51 pm

If you are looking at the engine itself the engine is like this

The cylinders will be surrounding the the crankshat. If you are looking at the cowling often they are circular with a round vent that is almost unobsructed.

Oh that picture was from a T-28 F or H model has about 1425hp.

Now a piston is well like your car engine. Take a look under the hood of almost any GA plane and you will see it.
At worst, you screw up and die.
 
Dash8King
Topic Author
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RE: Radial Engines

Mon Aug 26, 2002 3:25 pm

Wow ok thanks a lot PPGMD I have all the answers to all the questions I asked so I thank you all for responding and passing on information to me which I am sure I will be able to pass on to someone too.

Thanks Again.
 
broke
Posts: 1299
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RE: Radial Engines

Mon Aug 26, 2002 9:26 pm

A few notes on radial engines that you may not know.
U.S. radials are designated with the letter "R", the number following the "R" is the approximate displacement in cubic inches.
Pratt & Whitney radials generally have 7 cylinders in each row.
Wright Aeronautical radials generally have 9 cylinders in each row.
There are very few radials with an even number of cylinders in a row; the reason is vibration and resonance problems.
Radial engines are turned over on the starter a couple of times before turning the fuel and ignition "on" to pump any oil that has accumulated in the bottom cylinder(s) out of that cylinder(s). Trying to compress oil on the start is a good way to blow the bottom cylinder (As known as a "Jug") right off the engine.
Oil in the bottom cylinder(s) is also the reason why radials tend to smoke badly during the start.
 
timz
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Joined: Fri Sep 17, 1999 7:43 am

Odd # Of Cyl Per Row

Tue Aug 27, 2002 1:35 am

Assuming the radial engine is a four-stroke cycle (as most are, right?), then if you think about it you'll see that a single-row radial pretty well has to have an odd number of cylinders. Otherwise you can't arrange the power strokes and intake strokes.
 
IMissPiedmont
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RE: Radial Engines

Tue Aug 27, 2002 1:20 pm

And then you can add rotary engines. They are, of course also piston engines. The difference being that a radial has a fixed engine with a moving crankshaft while the rotary has a fixed crankshaft with a moving engine. Confused yet?
The day you stop learning is the day you should die.
 
Guest

RE: Radial Engines

Wed Aug 28, 2002 5:22 am

Radial engines are in many ways like piston engines, but radial engines have symmetry.

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