Pros and cons of engine types?

[earl1937]

This has been a very interesting and informative thread.  Thank you Shida for your research and insights.

What I haven't seen discussed yet is the differences in torque and power curves among the various engine types and how that plays into aircraft design.

From a very high level both are affected by displacement which is a combination of piston size (diameter) and stroke.  Inline engines typically produce maximum torque at very low RPM where V types typically produce torque at much higher RPMs.  The reason is that an inline engine can, by it's design, allow fo a much longer piston stroke.  I suspect though am not sure that both flat and radial engines would also produce torque at higher RPMs due to stroke limitations.

That makes an inline engine an odd choice for an aircraft where it would seem moving the torque curve up the rpm spectrum would be a better choice.

I've also not seen any discusson of valve design and am curious what types of valving were used in the various aircraft engines of WWII.  I suspect it was kept very simple in the radial engines but am curious as the v types were introduced.

In the radial engines of the 40's and 50's, the valve stems were filled with "sodium" to better cool the valve. Not sure if they are still doing that now are not. Interesting quote about the in line and torque out put. I had always thought the radial engine produced more torque because of the ability to carry a larger prop. Not sure though, but other considerations had to be taken into account. Wonder how the F6F would have fared with the same engine as the P-51? Might have been faster than with the radial, but the fuseledge would have to be lengthen and I suspect that overall size played a part in using the radial because of deck space on carriers. I would think also that exposing the whole radial engine by removing all the cowling had some bearing on design, as they were a lot easier to work on from what I have been told, than in line engines. Working from carriers, I would think that acceleration created by different engine designs also played a part in it.

[B3YT]

It would very much change the centre of gravity quite a bit . I wouldn't thnk it would change the length of the F4u though . 

[SIK1]

It would very much change the centre of gravity quite a bit . I wouldn't thnk it would change the length of the F4u though . 

It probably would change the F4U quite a bit. Much of the noses length is taken up by the main fuel tank which is in front of the cockpit. Just look at how long the nose is in the super corsair with the R-4360, which I believe is shorter than a Merlin.

[B3YT]

ahhh  I thought the tank was behind the pilot .

[bozon]

Excellent posts nrshida! thanks.

You made some nerds very happy. 

[kvuo75]

valve stems were filled with "sodium" to better cool the valve. Not sure if they are still doing that now are not.

my car's engine has sodium filled valves. so at least in cars they still do it.  (it is a flat 4 btw)

[LCADolby]

   


I'm fairly sure that one was also a 180° V12 Dolby. Take a look at the small offset between the banks. With a boxer the centreline of one cylinder usually aligns exactly with the gap between two on the opposing bank. This is the problem when people (not necessarily you Dolby) see a flat engine and automatically think it's a boxer. Another interesting flat 12 was the Mercedes-Benz C291 engine. They put the induction system between the cams and the exhaust out of the top allowing the engine to sit very low in the car (normally the exhaust system needs a lot of clearance).

Boxers and flat 12s are pretty wide. When the aerodynamics became a big thing in F1 it was more advantageous you use narrower Vs.

Was working from memory

[nrshida]

Was working from memory

No disrespect intended Mr. Dolbeh 

[GScholz]

What was the advantage to having an inverted V design?

It allows the reduction gear to be placed lower on the engine, which in turn lowers the thrust line. This is considered aerodynamically preferable in single-engined low-wing monoplanes.

Junkers Jumo 213



Rolls-Royce Merlin

[Ardy123]

It allows the reduction gear to be placed lower on the engine, which in turn lowers the thrust line. This is considered aerodynamically preferable in single-engined low-wing monoplanes.

Junkers Jumo 213
(Image removed from quote.)


Rolls-Royce Merlin
(Image removed from quote.)

ahh make sense... thanks for the info 

[GScholz]

NP

[earl1937]

NP

I just wanted you to know that I appreciate your posts and information concerning German Aircraft and engines! Each time, it generates interest on my part and I always have to go research on the subject and I always learn something! 

[morfiend]

 IIRC JUMO made a diesel areo engine that used 2 pistons per cylinder! 1 piston at the top of the bore and another at the bottom,each had it's own crank.  I think the JUMO 222 but I could be mistaken.

  There's also the 24 cylinder double opposed  180 degree V 12,not sure if it was successful or not but I think the Tiffie/tempest was supposed to be fitted with them.



   

[Babalonian]

Going to school for my FAA certificate and though I know the basics I still have the "gotta know it all" feeling. SO! pros and cons of the following

opposed
V block
In-line
reciprocating

*facepalm* 

I started my own pursuit of an AMT certificate last year (advanced to AMT16/powerplants so I didn't have to sit around until this year), congrats.  I've been staying after class til' 1am and helping all my classmates with questions lately in 19/20 (recips OH, IO-540s), and if I can pull a new/good carb (or a mixture needle and seat) for a R985 outa my arse I can get into it with the one in the test cells.  Im in Reno this week, my current prof (new one I haven't had before) asked if I'd at least work 20hrs on engines....  25hr maint alone on the stang on Saturday before I left town on Sunday stuck that fork.

Work, school and volunteering kill all my AH time lately.

[GScholz]

I just wanted you to know that I appreciate your posts and information concerning German Aircraft and engines! Each time, it generates interest on my part and I always have to go research on the subject and I always learn something! 

You're welcome. I thoroughly enjoy your posts on aircraft here in this small corner of the bbs.