Something Interesting

[Greybeard]

One of the problems with radial engines is the habit they have of wet sumping, but in this case oil seeps down to fill the lowest cylinder head. When you try to turn the engine over you can get a hydraulic lock which will gently force the cylinder head and barrel off the crankcase or bend the con rod.

Yikes! Surely, if that's a known thing the engineers would drain the heads before attempting to rotate the engine.

There was a case of a Piston Provost a few years ago where this happened. The seriously weakened engine blew up in flight and the pilot burned to death before the plane hit the ground.
I had a look in my log book and it was one that I had flown. Rather relieved I wasn't flying it on that trip.

WTF! Didn't know you were a flyer.

[ellis]

Or is that a fly by night   

ELLIS

[Black Sheep]

It's a few years since I hung up my flying suit. The problem with that particular radial was that in private hands it was only being flown occasionally, giving it plenty of time for oil to seep gently past guides and rings. Whoever was flying it would hand pull the prop through for a couple of revs to check for a hydraulic lock. So far so good. But this particular pilot if he encountered a lock would turn the prop backwards and forwards until it was free to turn and then go for a start. This didn't clear all the oil and so over time the master con rod became over stressed and eventually failed. In its RAF time, there were very strict rules about having to run the engine up 3 times a week for 20 mins or remove the spark plugs to get any oil out. Getting slightly back on topic, all our wet sumping problems would be solved by running up our engines for 20 minutes 3 times a week. But would the neighbours appreciate it?   

[RichardL]

A few things:

I thought the caption saying "only three" was referring to production models, but maybe that's also wrong.

When you think about it, the term "radial" is not the same as saying "symetrically radial". Would not this mean that every V-twin is a "radial" engine?

And last, when I went to John's third link, it hung the Safari browser on my iPad (not the whole pad). Had to reboot to get out of it. Don't know why. Maybe it has something to do with Apple not supporting ActiveX.

Richard

[RichardL]

...and BMW, for that matter. Is there something fundamental in the meaning of "radial" that I'm missing?

Richard L.

[bsa-bill]

Is there something fundamental in the meaning of "radial" that I'm missing?

not as far as I'm concerned, perhaps a degree pedanitism (new word , I haven't heard it used before, I have some great words, wonderful words, actually the very best words in the world)

No I regard a radial engine as one having a complete set of cylinders equally spaced around 360 degrees of the crank or a Wankel type engine could also be termed radial.

[duTch]

 

......perhaps a degree pedanitism (new word , I haven't heard it used before, ...

 Me neither(either)- but it sounds good.. though I'd pedantically go with 'pedanticism' (not in my dictionary, and spell unchecker suggestion was 'pediatrician'.... sorry for tube pedantry, it's my OCD.

 **there's an Aussie band called 'Tism' ...
 I'm no expert,  but always considered a radial engine to have a fixed crank/bang sticks assembly, and the barrels all integral with  the prop... , whereas a Wankel has an internal rotor (rotary).....also 

  **Just edited 'wake' to ' Wankel"...stoopid phone spell unchecker again

[RichardL]

I regard a radial engine as one having a complete set of cylinders equally spaced around 360 degrees of the crank...

Well, BMW fits that description. Not sure I understand Dutch's description.

Richard L.

[duTch]

 

Not sure I understand Dutch's description.

 I fixed this bit in case that's what you mean; '  **Just edited 'wake' to ' Wankel"...stoopid phone spell unchecker again


 
 So this bit;

'm no expert,  but always considered a radial engine to have a fixed crank/bang sticks assembly, and the barrels all integral with  the prop...

 ......can be explained here;

https://en.wikipedia.org/wiki/Rotary_engine

 I obviously was deludedly wrong

 as compared to this;

https://en.wikipedia.org/wiki/Radial_engine

....

 and this;

 

, whereas a Wankel has an internal rotor (rotary).....also 

...can best be explained here;

 

https://en.wikipedia.org/wiki/Wankel_engine

 ...by my understanding what powers the RX series Mazdas , and the RE Suzukis from the '70s, and the ?? Noturn prototype....

 NB ***edit 20:53: ish; last quote erroneously said 'https://en.wikipedia.org/wiki/Radial_engine'...now replaced with ;
   https://en.wikipedia.org/wiki/Wankel_engine

[RichardL]

Dutch,

Even the Wiki article (https://en.wikipedia.org/wiki/Radial_engine) explained it wrong (as I read it). They say the top cylinder has the master rod attached to the cranshaft and I don't see that. I see a 5-position journal block where each rod has its own "sub-journal" (my term), then that block is attached to the main  crank's main journal. I realize all this is Radial 101 to Sluggo, but I've never thought of the how-to on these amusing engines.

Richard L.

[duTch]

 

....(as I read it). .....

   

 I only looked at the pictures go round and round

[cyclobutch]

Though BMW have had a hand in a few radials of course.

https://en.wikipedia.org/wiki/BMW_801

[chaterlea25]

Hi Richard,
One conrod has to be a "Master" or the engine would not work,  without the master rod any cylinder firing or on comression would want to "twist" the big end block

If you study the maths the stroke of the master versus the slave cylinders is a little different as each slave big end
is moving relative to the master rod and big end centre 

Further on the Wiki page this photo shows the assembly better

John

[RichardL]

THAT is clear, showing the master rod as integral with the carrier for the other rods. Having seen this, I took a closer look at the animation and see that the master rod is not pivoting on what looks like its journal, while the other rods are pivoting.

Thanks, John.

Richard L.

[jachenbach]

Well I had to do some more research and it seems that what appears to be a radial engine but with a stationary crankshaft was called a rotary engine, though not in any way similar to a Wankel. Apparently used in WWI and pictures I've found in Wikipedia are a Le Rhone. So Black Sheep, now I've figured out what you meant. Seems odd to me they did it this way, but I'm sure they had what they thought were good reasons.