Rolls Royce Griffon

[capney]

A little history for you..
My first flight ever was in an Avro Shackleton powered by Rolls Royce Griffon engines and flying out of Ballykelly in N Ireland many a year ago.
The flight was of several hours flying mostly very, very low patrolling the Irish sea and dropping bombs on buoys. I was hooked from that point on.
I was prompted to pick up the pace of this thread when I saw this picture of mine of the Rolls Royce Griffon engine on a mobile trolley and in running condition.
On this day there was a Rolls Royce Merlin alongside it and both were run together....Wonderful for us lovers of all things mechanical.



I have found some info on the www and acknowledged sources below.

Rolls-Royce Griffon

Although the Griffon entered service long after the Merlin, in many ways it is an older design, being based on the Buzzard which first ran in 1928 and which itself was a scaled up version of the Kestrel. The big Buzzard ran at only 2,000 rpm and was mostly used to power flying boats, but  was developed into the "R" engine that ran at 3,400rpm for short periods. The "R" powered the Supermarine S6 to its Schneider wins in 1929 and 31. A derated version of the "R" was being developed in 1933 but this was dropped so that Rolls Royce could concentrate on the Merlin. It is perhaps surprising that work on the Griffon did not start again in earnest until 1939, 10 years after the "R" engine flew. However, once restarted, work on the Griffon proceeded at a fantastic rate and the new engine was put to good use in the Spitfire. The Griffon ran at 2,750 rpm, a remarkably high speed for such a big engine.
The first Griffons had single-stage superchargers, and were fitted to the Spitfire MK XII. These aircraft arrived just in time to take on the Focke-Wulf 190 "Tip and Run" fighter bombers that were attacking England's South Coast. Their impressive low-level performance was used to good effect.
For high altitude a two-stage supercharger was needed and these arrived in the Spitfire XIV and XVIII. This enabled the Spitfire to stay in the forefront of fighter performance until the end of the war.
freespace.virgin.net

Avro Shackleton

Designed and built as the RAF’s first dedicated four-engine long-range maritime patrol aircraft, the Avro Shackleton was the final expression of Avro’s classic heavy bombers, the Lancaster and Lincoln. Retaining the wing and landing gear of the Lincoln, the Shackleton had a larger, rounder and shorter fuselage, which provided space for a crew of 10. Armament included two 20mm cannon in the nose, two in a dorsal turret, and two machine guns in the tail plus bombs or depth charges, depending on the mission.

warbirdalley.com

If you wish to see and hear both these engines running then please visit my U tube Channel via this link.

www.youtube.com/user/capney?feature=mhum#p/a/u/1/r2-OIJM8uKQ

You will notice the propellers are seriously cut down to size for obvious reasons.
You should also spot the contrarotating blades on the griffon engine There were two propellors on each engine with one going clockwise and the other anti. With four engines and eight props this machine could stay airbourne for hour after hour and cruise on three of its four engines.

[DAG]

Thank you for the history lesson and info. Robert, very interesting and much appreciated!

[kedigato]

I noticed the odd propellers right away and was going to ask you about them, Robert. But I still can't get my head around one going clockwise and the other anticlockwise. For me, it seems that the one would defeat the effort of the other? Wouldn't the front one disturb the motion of the second one? Obviously not, or they wouldn't have flown. When they were all running, did one run at a faster speed than the other?

I think I am saying all this muddled up, which it is in my head trying to understand this. Perhaps it has nothing to do with the forward speed / "push" from the propellers, but only the uplift from the wind under the wings?

I am very likely making a fool of myself, but I would like to have it explained. Thanks Robert!

So, now I am going to look at your link.

[capney]

Grrrrrr... I have just spent the last hour or so putting together an article on contra-rotating propellers.
I saved it several times and now its gone... somewhere.
If I find it I shall post it. I`m upset now....

[kedigato]

I'll go "grrrrr-grrrrr" with you, Robert.

I'm sure all of us have lost things, whole pages of it sometimes, and then remember to SAVE every now and then. It all goes well for a while (me even saving every paragraph and overdoing it ;D), then we either get lazy or too sure of ourselves and - WHOOSH, it all goes sailing off somewhere or other.

However, since you saved it, several times, it can't have gone far. It has found a nice little hidey-hole and is peeking out and having a laugh at you searching for it. But I don't doubt that you will find the little devil, and then I can get to read, and hopefully, understand it.

Thanks in advance for all the trouble you've had on my account. xx

[capney]

Manage to recover a small section of it.
I`ve learnt a little myself in researching this subject, Always a good thing.
This picture is of The Avro Shackleton. This first aircrafty type I flew in.
Spot the two sets of props, The twist in the blades and the tapereing.


Contra-rotating propellers, also referred to as coaxial contra-rotating propellers, apply the maximum power of usually a single piston or turboprop engine to drive two propellers in opposite rotation.
When airspeed is low the mass of the air flowing through the propeller disk (thrust ) causes a significant amount of tangential or rotational air flow to be created by the spinning blades. The energy of this tangential air flow is wasted in a single-propeller design. To use this wasted effort the placement of a second propeller behind the first takes advantage of the disturbed airflow. The tangential air flow also causes handling problems at low speed as the air strikes the vertical stabilizer, causing the aircraft to yaw left or right, depending of the direction of propeller rotation.
If it is well designed, a contra-rotating propeller will have no rotational air flow, pushing a maximum amount of air uniformly through the propeller disk, resulting in high performance and low induced energy loss. It also serves to counter the asymmetrical torque effect of a conventional single propeller. Some contra-rotating systems were designed to be used at take off for maximum power and efficiency under such conditions, and allowing one of the propellers to be disabled during cruise to extend flight time.
Contra-rotating propellers have been found to be between 6% and 16% more efficient than normal propellers.

[kedigato]

I've been doing a bit of reading up myself, Robert.

First off, from what you've said and what I've read, my original thought of the front propeller "disturbing" the action of the second one is completely wrong, the opposite being the case.

I've also learnt that some propellers turn left and others right, some planes tend to have left ones and others right, there is even the "British" and "American" ones - like steering wheels on cars, ;D ;D. Then some turn clockwise on one wing and anti-clockwise on the other, ie, inward and outwards.

All sorts of weird, wonderful and interesting facts!

I also learned that it is the same with boats motors. Many years ago, Peter and I, took courses for motor boat drivers licenses and both of us passed both exams and so are the proud owners of each having a license for the German inland waterways and also for the coastal waters and adjoining high-sea waters. However, although we learned all sorts of things re navigation, how to tie the proper knot for whatever use, "parking" boats, saving people fallen overboard, ....................., I can't remember ever learning that the propellers turned either the one way or the other! I just now read that if a boat is set up for having, say, a left-turning propeller, and you mount a right-turning one on, then you would drive backwards in the forward gear.

Oh, I couldn't even say which way the motor on our boat turned. Just that it was a great 85PS Evenrude, and actually too powerful for the boat. But they came together.

Anyway. I got offtrack but I have enjoyed reading about all this and I thank you, Robert.