ROLLS-ROYCE CRECY

[matt]

Re: ROLLS-ROYCE CRECY

i've heard that once a two stroke reaches a certain size in cu. in.'s it's ability to prduce more power than a four stroke dies, is this true?

if so, how did the crecy produce 5000 hp?

[AirDOGGe]

Re: ROLLS-ROYCE CRECY

it would have only 60 to 70% of the mechanical stress of a four stroke with the same power.

The Napier Nomad was another impressive 2-stroker:

A 12-cylinder two-stroke turbo-compounded Diesel, the Nomad was one of the most complex and fuel-effecient engines ever built.

There's several large photos of the Napier on the NASM engines webpages...Check out the 36 cylinder Lycoming XR-7755 while you are there....what a beast!

http://www.enginehistory.org/nasm2.htm

.

[First time Juke]

Re: ROLLS-ROYCE CRECY

Model engines are 90 % twostrokes. Some of them can do 28 000 rpm. Italian Rossi for example can put out ca. 2.5 hp with 3.6 ccm ( .20 cuin ) displacement. Fuel contains the lubricant ( 20 % ) and fuel is methanol + 10 to 20 % nitromethanol.
I did put an 1.4 hp producing engine on 900 gram ( flyweight ) model and it flew so fast that I was experiencing very unfamiliar feelings ( like will I survive this ordeal ). That was over 1 hp / kilo power to weight ratio...I have become a lot better flyer since that, but never dared to put that powerful engine again on my small models ( no flaps etc. ).

Well this is far away from the topic.

Re: ROLLS-ROYCE CRECY

<< THE TWO STROKE CYCLE WAS CAUSING SEVERE PISTON

OVERHEATING PROBLEMS DURING THE TEST PROGRAM.>>

This engine set the absolute thermodynamic record for several decades for piston engines at over 20 HP/sq. in. of piston area. RPM, BMEP, and all other factors not withstanding, This figure represents a SEVERE thermodynamic load (heat flux) to and through the piston. This is independant of the cycle (two vs. four stroke) and more dependant on the obscene amount of power and heat.

Difficulties existed in sufficient cooling oil spray to the piston back side and top ring welding due to very high maximum combustion pressures. The sleave valve also inhibits piston heat transfer to the cylinder. However, it is a fascinating architecture and may have possibilities with the application of modern materials and methods. As a two stroke, it would have only 60 to 70% of the mechanical stress of a four stroke with the same power. This would lead to a 5000 HP engine suffering the same physical stresses as the latest Thorn Merlins at ~3400 HP.

Cooling those pistons would be a real -itch though...

Eric Ahlstrom

[Peashooter]

Here's more on the Crecy and other famous RR Aero engines. Peas

http://www.stobbe.dk/industrial-products/technical-literature/combustion-engines/rolls-royce/Rolls-aircraft.html

[52eme]

nope, not the good fred, sorry..
actually i'm the fred from paris, and Don B must have talked to you about me.. i hope you'll be able to join us for the SARH symposium next month..

fred

[THE DOCTOR]

IS THIS THE FRED THAT OWNS THE ROLLS-ROYCE KESTREL

THAT WAS TAKEN TO PECIES AT THE HOLLISTER AIRPORT ????

REGUARDING HOTTING UP THE CRECY, SIR STANLEY HOOKER

RELATES IN HIS BOOK "NOT MUCH OF AN ENGINEER"

THE TWO STROKE CYCLE WAS CAUSING SEVERE PISTON

OVERHEATING PROBLEMS DURING THE TEST PROGRAM.

OF COURSE TODAY WE COULD MAKE A CERAMIC/XXXX

PISTON!!!!!

IF WE ONLY HAD DA MONEY; WE COULD GO REALLY FAST.........


DA DOC

[52eme]

the RR Crecy was indeed a beautiful piece of engineering.
V-12, 26.1Litre and.. 5000hp

it aparently had avery distinctive noise because the valves were set as to let the exhaust gaz exit the cylinder very rapidly and give additional thrust.

Click Here For Image

RR produced some pretty amazing engines in the 30s and 40s, the Exe and Pennine X-6 and Eagle H-24...

now Doc, what kind of power do you think you could get out of that Crecy ?


Regards
fred

(admin note *edited message to link to image rather than display image, which is a copyright violation*)

[THE DOCTOR]

according to the RRHT book No. 21, the 2 stroke, V-12,

direct injection, sleeve valve CRECY. had an amazing exhaust

note!!!

That right; 2-stroke!!!!


Da Doc