I don't understand how some planes ended up being so fast

[Koopernic]

Readers interested in the friction a sleeve valve might produce might be interested in this patent which asserts that a rotating sleeve in a poppet valve engine will eliminate engine wear through friction and increase efficiency.

Note also, I believe if used in a two stroke the sleeve only requires to rotate rather than to travel in an orbiting motion. Furthermore it can uncover intake and exhaust ports bottom and top of cylinder of to ensure purging.

Patent US6289872 - Rotating sleeve engine

Rotating sleeve engine
US 6289872 B1
ABSTRACT
An internal combustion engine is provided including at least one cylinder having a conventional valvetrain. The valvetrain consists of at least one camshaft, at least one intake poppet valve per cylinder activated by the camshaft and at least one exhaust valve per cylinder activated by the camshaft as well. Rotably disposed within the engine block is a rotatable cylinder liner which is supported from the block with at least two journal bearings. A piston is mounted in each liner for reciprocating movement therein. A connecting rod connects each piston to a crankshaft converting the reciprocating motion to crank rotation. The sleeve rotates with the objective of improving the lubrication conditions of the piston rings and piston. The reduction in friction coefficient between the piston rings and liner at certain portions of the cycle will result in significant frictional benefits. The motion of the liner will result in continuous fluid lubrication which results in severe reduction of piston ring and liner wear.

 

[Zipper730]

Post #203

Diverging by single digit percents, especially very low single digits makes very little difference in some aspects aircraft performance.

True enough, but I was just trying to make a point, and explain what I was trying to say.

You could vary the weight of a clean Mustang for example by hundreds of pounds (source claims 1000) and only vary the top speed at altitude by 3mph.

Didn't know that, but I'm surprised it'd be so little...

Difference between a good paint job and a poor one is more than that.

I could believe that, after all the whole premise of laminar flow was reducing drag through smooth airflow over the skin...

It did but they still weren't using all the volume. ANd there were a number of restrictions on how the plane was to be loaded,flown and even taxied at those high weights. A biggie was that at high weights you HAD to fill the outer wing tanks (they didn't exist on the early planes) to spread out the span loading, you couldn't fill the bombbay with AP bombs, hang a pair of 4000lbs under the plane and just fill the inner wing tanks, you had a good chance of bending/breaking the wing even if the gross weights were the same.

Didn't know that...

If you are referring to the B-15 I am sure some bright spark thought of it. It just wasn't worth the effort.

I'm not so sure, just as a basic estimate using the k-constant formula, bumping the horsepower up from 1000 (T/O), 850 (Normal) to 1500 (T/O) 1350 (Normal) seems to show an increase in speed to 233 mph; if one was to add a turbocharger (or a twin-stage supercharger) to the design and increase the critical altitude to 25000 feet (or 21500 feet), that seems to suggest a considerable top-speed if the weight stayed the same.

There was only one plane, they were never going to build anymore.

Actually, if I recall the primary goal was experimentation, but they did consider potentially ordering up to 200 if I recall right.

Look at the B-19, took so long to build (Douglas didn't even want to finish it) that it was obsolete on the day it first flew. Army wanted it for analyzing/evaluating structural design. Not because they thought it was a viable warplane.

Seems quite a strange reason to build a plane, but who knows, maybe something good came out of it.

 

[Shortround6]

Post #203
True enough, but I was just trying to make a point, and explain what I was trying to say.

you can find all kinds of interesting, but somewhat useless statistics, like the output of an engine per square inch of valve area. Interesting to a designer bu of no practical value to the users. Fuel fraction is somewhat the same, It may show how clever the designer was but doesn't actually tell you anything about the actual performance of the aircraft as too many other things are different.

I could believe that, after all the whole premise of laminar flow was reducing drag through smooth airflow over the skin...

You could find differences of 5-10mph due to paint (or higher)on non laminar (so called) flow aircraft

I'm not so sure, just as a basic estimate using the k-constant formula, bumping the horsepower up from 1000 (T/O), 850 (Normal) to 1500 (T/O) 1350 (Normal) seems to show an increase in speed to 233 mph; if one was to add a turbocharger (or a twin-stage supercharger) to the design and increase the critical altitude to 25000 feet (or 21500 feet), that seems to suggest a considerable top-speed if the weight stayed the same.

Trouble is the weight either won't stay the same or the difference in power plant weight comes out of the payload. AN R-2600 is roughly 500lbs heavier than an R-1830 so four of them add a ton to the empty weight of the aircraft, and this is without the larger, heavier propellers and any trick superchargers. BTW before the war P &W had the patents on two stage supercharging so Wright would be starting from scratch to to try to get around them. For some reason the R-2600 never took to turbo charging very well, the R-1820 did pretty well in the B-17s but the R-3350 (used R-2600 cylinders) had a multitude of problems, but this is all well after the decision or not proceed with the XB-15 was made. If the Army decided to go with B-18s instead of B-17s because of price the chances of large scale (even by 1930s standards) of the B-15 was basically non-existent.

Seems quite a strange reason to build a plane, but who knows, maybe something good came out of it.

In the 1930s and 40s IF the Army (or Navy) paid for a design study or prototype aircraft then the Army or Navy became not only the owner of the aircraft but the owner of the data used to design and build the aircraft and was free to share such data with whatever companies and agencies they saw fit to share with. How much of the design data the Army got from the B-19 was shared with Boeing, Consolidated, Martin, Lockheed and others I don't know but please remember that designing and building very large aircraft was much more complicated than just scaling up smaller aircraft.

 

[Zipper730]

you can find all kinds of interesting, but somewhat useless statistics, like the output of an engine per square inch of valve area.

In the old days there was a tendency to try and maximize horsepower by displacement (hence the hyper-engine).

Fuel fraction is somewhat the same, It may show how clever the designer was but doesn't actually tell you anything about the actual performance of the aircraft as too many other things are different.

It does tend to show a consistent benefit to range though...

You could find differences of 5-10mph due to paint (or higher)on non laminar (so called) flow aircraft

That's rather significant...

Trouble is the weight either won't stay the same or the difference in power plant weight comes out of the payload. AN R-2600 is roughly 500lbs heavier than an R-1830 so four of them add a ton to the empty weight of the aircraft, and this is without the larger, heavier propellers and any trick superchargers.

What size propeller was used on the XB-15, and what was used on the B-314?

BTW before the war P &W had the patents on two stage supercharging so Wright would be starting from scratch to to try to get around them.

They'd have to re-invent something that somebody else already had mastered, and if the patent is still in force, they'd have to pay royalties...

I suggest twin-stage supercharging because the XB-15 had a rather poor climb rate and from what I remember based on the B-29: If the climb rate is sufficiently slow, you burn up so much fuel climbing to altitude that the energy saved while cruising up there stops being practical unless you can fly halfway around the world... climbing to 21,500 would be less fuel consuming than climbing to 25,200 (the B-17E/F's figures).

For some reason the R-2600 never took to turbo charging very well

I know this might sound silly to ask, but do you have any idea why?

If the Army decided to go with B-18s instead of B-17s because of price the chances of large scale (even by 1930s standards) of the B-15 was basically non-existent.

So the cost was the reason for some favoring the B-18? (I'm honestly surprised nobody considered issuing specifications for a four-engined bomber earlier... since the V/1500 and XNBL-1, the US or UK didn't seem to develop anything with 4 engines until the mid/late-1930's).

In the 1930s and 40s IF the Army (or Navy) paid for a design study or prototype aircraft then the Army or Navy became not only the owner of the aircraft but the owner of the data used to design and build the aircraft and was free to share such data with whatever companies and agencies they saw fit to share with.

When did that change?

How much of the design data the Army got from the B-19 was shared with Boeing, Consolidated, Martin, Lockheed and others I don't know

I would imagine it would be a lot. While I'm not fully aware of the effects of scaling factors, I am aware that they are significant.

 

[Deleted member 68059]

The Jumo 213J was supposed to reach 2750 RPM. .

3700... not 2750. Sure you just made a typo....

If you want to read the original report - you can find it at Udvar-Hazy - if you dont mind
trawling through microfilm all day....haha

NASM-HAZY-MF-8184-1361_001 (_001 is my designation, meaning page number)

 

[tomo pauk]

<snip>

BTW, Calum - when we can expect the book?

 

[Deleted member 68059]

Hi Tomo !

I have set a printing date of August 2018. I hit 275 pages (US letter/A4) last week and expect to hit something close to 400 when its ready. A lot depends on the final copyright bill to the various archives. A full page print of photos costs an absolute fortune in rights-usage....this will determine the page count really.

I`ve just finished reviewing all of the Ernest Hives (@ Rolls-Royce) letters to the Ministry of Aircraft Production, so got that to write up next. He really spoke his mind I can tell you !!! Some of his letters would have caused an international diplomatic incident, if they had got out at the time. I think you need a man like that calling the shots to be successful in times like that.

I`m trying to raise about $35,000 USD to have the surviving UK collection of German and Japanese captured docs. microfilms digitised (4000 reels of 35mm film). Thats my long-term project to safeguard all this data. So if you know any rich aviation philanthropists, do let me know !

If we were clever - could maybe organize it such that all this data could be got to online one day...and not need a plane ticket to England and 6months of spare time to rifle through 50,000 index cards....

C.

 

[tomo pauk]

Paul Allen might be your man...

 

[drgondog]

Would you say it created less drag than any wing before it?

Same airfoil from NA-73X through P-51B/C/D/K. Same manufacturing processes for NAA at both Inglewood and Dallas. The Parasite Drag for the Mustang airframe from NA-73X through P-51K Essentially the same. That said, the Meredith system drag recovery was better in the Merlin Mustang for high temp/high speed envelope.

For same Hp ratings, the P-51A with V-1710-81 was slightly faster than P-51B/D at same GW though 10,000 ft with crossover between 11-15K in low blower for 1650-3 and-7. Ditto for climb.

 

[Peter Gunn]

I think people forget or never really knew how fast (and capable) an Allison powered Mustang really was. Too much literature has it overshadowed by it's Merlin powered "big" brother and dismisses it as only a stopgap until the "real" Mustang arrives.

If only someone would write a definitive book regarding the development of the Mustangs early marques. "Sigh"... one can hope.