The Crecy Engine

[Gondor]

I subscribe to the Curious Droid YouTube channel and today he published the following video.

https://youtu.be/cxK_zWgw6gY

I found it very interesting and it helped me to understand how a Sleeve Valve engine works as well 

Gondor

[kitnut617]

Also, see if you can get hold of a copy of the Rolls Royce Heritage Trust book, 'The Rolls Royce Crecy'. An excellent book with hundreds of photos and diagrams. I've based a couple of my models on what I read in it.

However Alastair, the Centaurus, Sabre and Eagle all had very much different mechanisms to operate the sleeve, lots of shafts and gears used. The Crecy is a very simple system.

[Gondor]

Also, see if you can get hold of a copy of the Rolls Royce Heritage Trust book, 'The Rolls Royce Crecy'. An excellent book with hundreds of photos and diagrams. I've based a couple of my models on what I read in it.

However Alastair, the Centaurus, Sabre and Eagle all had very much different mechanisms to operate the sleeve, lots of shafts and gears used. The Crecy is a very simple system.

The sleeve valve used with the Crecy probably is a simple version, which helps me understand how the basics work and from there I can extrapolate.....

Gondor

[zenrat]

Two stroke V12.  I wonder what that would have sounded like when on song.

[kitnut617]

I found this on SPF in their Rolls Royce Crecy thread (not sure who to credit but you can always go there and thanks him yourselves). I'm not sure if it will work on this forum but it's an animation of how the engine works.



OK, it did so here's the other one.

[kitnut617]

Two stroke V12.  I wonder what that would have sounded like when on song.

It is a 2-Stroke but it doesn't operate like modern motorcycle engine 2-Strokes. For starters, there's no under the piston compression, the crank has it's own oil system just like a 4-Stroke. The engine has a large supercharger which then pumps just compressed air into the combustion chamber where the fuel injectors squirts the fuel in from the top. The RRHT book describes that whenever the testers had to swap a test engine over from the Crecy to either a Merlin or Griffon, they were always amazed at how clean the crank oil was in the Crecy after it had been run for a while on the test stand, whereas the Merlin or Griffon oil always came out black and dirty.

[PR19_Kit]

Two stroke V12.  I wonder what that would have sounded like when on song.

LOUD!

The vid says people could hear it 15 miles away!

[Rheged]

Two stroke V12.  I wonder what that would have sounded like when on song.

LOUD!

The vid says people could hear it 15 miles away!

I'm sorry, could you speak up a little?  There's a Crecy animation running and I can't hear a thing





     Cracking animations!!

[PR19_Kit]

The animations work well, and explain sleeve valves very well, but..........

While they show how the valve sleeves are timed relative to the pistons, they don't show how they are twisted as they rise and fall. That's got to be a pretty clever device that does that but I'd love to know how they do it.

[Later] Hmmm, on second thoughts they DO show that. The sleeve around the outside of the eccentric imparts a sideways motion to the drive peg of the sleeve and twists it as it rises and falls.

[kitnut617]

The animations work well, and explain sleeve valves very well, but..........

[Later] Hmmm, on second thoughts they DO show that. The sleeve around the outside of the eccentric imparts a sideways motion to the drive peg of the sleeve and twists it as it rises and falls.

Yes that's right, the little piston at the top of the plate that the sleeves are attached to, is an important part of the operation too, as it keeps the top of the plate pointing upwards, but also allows the plate to rock which is the mechanism for the sleeves twisting motion.

Not shown in the animation is how the incoming compressed air and then the exhaust works. The engine doesn't have manifolds as such, intake or exhaust. The natural Vee of the engine block is used instead, about half way up the Vee a plate is bolted to both of the block sides, the compressed air passes through the underside of this plate. There's another plate attached the same way but at the top of the Vee, and the exhaust exists between the two plated to the rear of the engine. The exhaust then goes through an exhaust augmenter which was slaved to the crankshaft. This was to offset the power needed to run the supercharger which was attached to the front of the engine. The exhaust pressure from the exhaust augmenter still had enough thrust to help push the aircraft forward at higher altitudes.

When you look at the whole engine, supercharger and augmenter put together, it looks just like an early turbine engine. 

[PR19_Kit]

I can't help feeling that my fave aeroplane engine, the Napier Nomad, owed quite a bit to the Crecy.

It had sleeve valves, a BIG supercharger and exhaust augmentation too, but it was a flat engine, and a DIESEL too! 

[kitnut617]

The sleeve valve was being pushed by the Air Ministry, a guy called ? Riccardo was the guy who had done the initial development. Bristol, Napier and RR took it from there. The initial design was as a diesel, only converting to petrol at the beginning of the war, IIRC to keep the fuel supply as common as possible.

[Hobbes]

yep, Harry Ricardo, of Ricardo Engineering