An Explanation Of The Rolls Royce Griffon Counter Rotating Propeller Gearbox
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- เผยแพร่เมื่อ 13 ก.พ. 2021
- Four of these Rolls-Royce Griffon 57 / 58 engines powered the Avro Shackleton maritime patrol aircraft from the early 1950`s through to 1991. Counter-rotating (now referred to as contra-rotating) pairs of 13ft diameter propellers were used to give more efficient low speed cruising at low altitude whilst submarine hunting. This video shows the operation of the gears in the engine which split the 2490 BHP into two, opposite rotation concentric shafts each transmitting 5300 lb ft of torque...yes, you read that figure right!
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This is what TH-cam is for....Thank you for this clear demonstration of how these counter rotating propellers function.
Contra rotating*
Counter rotating propellers are propellers that rotate in opposing directions on different engines, like the P38 or the Airbus A400M.
that is an impressive piece of kit, it's amazing how easily it spins considering the horsepower that it handles.
Great engineering, for me Griffon engine is an extraordinary machine. Thank you Peter!
It really is proof of humanity’s connection to the divine that such insightful inventiveness arose. It’s a marvel. Yet what is more miraculous is the physics quirk that allows access to the contra-rotating efficiencies which add up to an extra 20% of power for free to the whole equation, plus helps negate the torque effect of a high powered piston engine etc.
I have always wondered how the engineering for it worked and now I know and I am gobsmacked at how simple it is, truly amazing. So glad I stumbled across it. 👏👏😁
What a fantastically beautiful piece of engineering and inventive brilliance. Total respect for the engineers and people of the UK who: commissioned, designed and built that.
This is awesome! So cool to see the internals of the gearbox. I always wondered what the insides looked like.
Designed before computers too. That's what amazes me.
Thank you for this demonstration. I've seen illustrations before but had difficulty sorting things out. I can now see why the air racers using these units had problems.
Smart. The extra gear is reversing the rotation. Thanks for explaining
Terrific. Finally a real mechanic showing how gearing gives rotation power from one engine, on one shaft, to both propellers to produce contra rotation. On quibble, some sources say counter-rotating is defined as a propeller on one wing going one way and the other way on the other wing rather than two propellers on one shaft. Thank you.
Thanks for your kind words! You are correct, the term generally means two separate engines. I used the term counter-rotating because this is what the manufacturer, de Havilland Propellers, called it at the time of manufacture in the 1950`s, we would now refer to this as contra-rotating.
@@FlightEngineering1 When referring to two separate engines they are correctly termed handed engines. The idea being to eliminate having a critical engine in case of a single engine failure.
It's interesting that rather than trying to arrange the same reduction ratio with different tooth counts (due to the smaller gears required for the reversing drive), they used the same number of smaller teeth.
Thanks for posting !. Now I understand the mechanism of counter rotation !👍
I've always wanted to know they worked. This as explained it really well
Perfect video to explain how it works. Nicely done, thank you!
Thanks for this, quite fascinating seeing how it works.
Thank you for this practical explanation of an extraordinary engineering design.
thanks for showing us the insides. very interesting
That is so clever looks so simple but is very complex with the counter rotation just amazing
Bless you for sharing this with us.
Interesting to see - thanks for videoing it!
My right ear enjoyed this
Smooth engineering
Perfect explanation.
Great video, well done.
Magnificient ! Thank you.
Thanks for this, wondered how it was done, v clever!
Very interesting,I love the contrarotating propeller planes.
the worlds fastest turbo prop airplane actually has contra-rotating propellers ,, the russian TU-95 Bear bomber
It's all so simple once you've seen it 😁 thanks for your time sir , brilliant 👌
Great stuff. Thanks for this.
Thanks,I have 57 years and for long time ago,had this question,thanks
Our infinitely variable FrictionLess gear tech enables >10X gear box reduction!
Very cool, thanks for making this video.
You`re welcome, thanks for watching!
Beautiful! It's amazing that those seemingly small teeth can transfer 2500hp to two 13ft props.
Simple, elegant engineering...
Thanks. That was brilliant
Yes yes... now i see... I've wondered all my life how that worked... :)
Beautiful
Great video! Extremely informative. Thank you for sharing this.
Thank you sir wonderfull
Such a beauty.
If only Reginald Mitchell could have seen that. I can't imagine the staggering amount of machining required just for that reduction/counter-rotating gear mechanism and housing.
It's not as complex as it looks. The whole gearbox body is either a casting, or more likely a forging for strength. The only real machining needed would be the mating surfaces and bearing journals. As for the spur gears, gear cutting machines had existed for decades by the 1940s, being invented in Germany in the late 1890s. So most of the process could be automated and didn't require a huge amount of labor once the production line got going.
The staggering amount of work would be done on the prototype engines and the processes for making serialized production parts, because those were hand made. You had to make the template for the casting/forging, the tooling and machinery to make the parts. It's why engineers tried to reuse as many existing parts as possible.
Thanks for displaying this gearbox. I’m amazed at how slender the shaft is that connects to the engine’s crankshaft. I suppose, that unlike a car where road friction and grip is high that there is much less with a propeller biting at the air. - great video
Nope, it's just exceedingly strong forged steel, or some steel alloy. Using the Merlin as an example, each power stroke puts something like 9 tons of rotational torque on the crankshaft per piston power stroke, which is increased with the gear reduction drive on the front of the engine to double or more. The Griffon was an even bigger engine with higher horsepower.
But this makes it easy to see why contra rotating gearboxes were subject to high failure rates with its spur gears. You have 2,000HP+ on just a couple of gear teeth at any given time, which is a tremendous strain on even the strongest steel. One tooth cracking and snapping off will wreck everything. Ideally, they should have used helical cut gears, but such precision in the 1940s would have been hideously expensive, far above what even a spur gear coaxial gear box had cost.
As for the air friction, you're not thinking in the correct terms of fluid dynamics. A propeller doesn't require much to turn it by hand, but at the speeds it turns, it may as well be going through a dense liquid like water. The propeller tips have a huge amount of drag at high speeds, which is why engine designers did everything they could to keep the whole length of the propeller sub sonic, hence reduction gears.
Thanks GGigabyteM for the explanation- makes sense
@@steven4737 Except the engineers already thought of that, because they had 6,000+ pound aircraft hanging off of the engine and nose casing that could experience G forces in excess of 6 and in extremes 9 or 10 for short durations in dog fights. Not to mention the vibration from the engine and propeller.
There's plenty of strength in the engine casing to use helical gears. But if you wanted to eliminate the side loading, double cut helical gears with opposing teeth would eliminate that problem.
Torque is simply power divided by speed. In this case, if the input power is 2,220 horsepower (1,655 kilowatts) at 2,750 RPM (specs from Wikipedia article, for the version of Griffon in another application), that's 4,202 pound-feet (5,700 Nm) of torque... or ten times what any car engine produces.
Keep in mind that between the engine of a car and the wheels there is transmission system which has a much higher reduction ratio (so much higher torque multiplication) in first gear than this gearbox has.
Excelllent... So That is how they do it. :))
aThing of Beauty
Wow!
I believe that what you are describing is a CONTRA rotating propeller gearbox. Contra, because the propellers are on a single engine. If you have two engines with the props rotating in opposite directions then you would have COUNTER rotation.
Yes, that’s correct. I am using the term which de Havilland used when they manufactured it, but we now refer to them as contra👍
Thats fantastic! I thought only a turbine engine could do that!
Before reading the description in it's full length, I did the calculation for the torque, and arrived at nearly 6000Nm, but I didn't know the RPM, just guessed at 2600. From the description's stated 5300 lb ft, I must have been close. That mean if the pinion gear diameter is around 25cm, the force on the teeth is close to 5 tons 😵 - or maybe half per pinion, if the load is evenly split.
There are multiple output specification for the Griffon in the Wikipedia page for that engine, with the highest (for the version of Griffon in another application) being 2,220 horsepower (1,655 kilowatts) at 2,750 RPM... corresponding to 4,202 pound-feet (5,700 Nm) of torque at that speed. The same Wikipedia article lists 2,345 hp (1,749 kW) for the Griffon 57A in the Shackleton, but with no speed specified.
That was great, thank you ! At which weight are we looking at for the whole ting ?
I`ll have to guess, but I can lift it, so between 60 and 80kg.
Great video, how much does it weigh, and do you know of any other counter-rotating gearboxes in the 1000-1500 hp class?
Contra rotating*
The Griffon engine is in the 1700-2500 hp class, not the 1000-1500 hp class.
There was really no need for a coaxial propeller setup in 1000-1500 hp engines. While coaxial propellers are more efficient than a single propeller, they add weight, complexity and cost and were rare outside experimental aircraft. You needed to be in the 2000 HP+ category to have the benefits of a coaxial propeller outweigh the problems. At some point, you need exceedingly impractically sized propellers to absorb the power of the engine, as seen with the F4U Corsair with the gull wings to provide clearance for the huge propeller. It definitely could have benefited from a coaxial propeller setup, but I don't think Pratt&Whitney ever had an R-2800 with the required gearbox for it to work.
But coaxial propellers were nothing new by the time of WWII, engineers had been experimenting with them as far back as the teens and twenties on biplanes. But they had the same problems back then with complex gearing being so unreliable that the propellers often parted company from the engine when a failure happened.
There will always be an England.
I enjoyed this vid, thank you very much.
I guess the torpedo used this type of counter roto system?
These propellers are contra-rotating, as they are on the same axis. Counter-rotating is when two engines with propellers turn clockwise on one engine, anti-clockwise on the second engine.
That is correct. I use the term counter-rotating because that is what the manufacturer, de Havilland called them at the time. I suspect the usage has changed since then maybe?
where those reduction gears dependable or did they have failures?
Was the face width on the second set smaller than the rear set? This in order to save power loss. Lubrication? That’s some grunt going through that set of gears, did the Russians copy the concept for The Bear’s contra rotation props? I note deep machining of the hubs to minimise weight but no radial slots.
Theres no wonder it whines. Do they both counter rotate at the same number of revs? I couldn't quiet see? Great video, thank-you.
Yes, the gear ratios (ratios of tooth counts or effective diameters) are the same for each propeller, so they turn at the same speeds but opposite directions.
Do both output shafts rotate at the same rpm ?
The rear prop receives skewed air from the front prop so has more work to do.
They do, but as this system is typically more efficient than a single propeller, I guess that any losses caused by that are cancelled out. Also, the pitch of the front and rear props is not necessarily the same.
👍
Now that's a piece of gear that lol xx
Very interesting! Just so I got it right. Gear in the back (facing the output shafts) has smaller gears - but the same number of teeth?
The gears should be the same diameter (otherwise there would be a difference in torque) but the teeth are a diferent size so they don't touch.
Same number of teeth, but smaller pitch. So the gears end up smaller.
In fact,@@vinny142, both the input (smaller) and output (larger) gears of the reversing set are smaller in diameter than the corresponding gears of the other set, to keep them from meshing. The teeth are smaller because they have the same counts on smaller gear diameters.
What needs to match between the two propellers is the drive ratio, which is the same because the ratios of gear teeth (and effective diameters) are the same.
Sorry just watched it again, I can now see the differing diameters of the forward and back gears, with the idler simply acting as a lever, one gear turning and reversing the other. Is that correct? cheers
Yes that is correct
I always wondered how they got the prop to counter rotate. I also curious why they had so many problems with the props on the XB-35's.
I`m not sure how the XB-35 gearbox worked, I know it was remote from the engines. Rolls-Royce kept with what they knew, and just doubled up on it, but in fairness, any new gearbox handling this kind of torque can give trouble without a doubt.
I'm amazed how simple this is actually.
Omfg it's one os the most interesting thigs i've ever seen on youtube
What really interests me is that Instead of having a gearbox made up by 3 extra gears, why don’t the engineers give a try of a single spider gear, just like the differential setting for the cars??
Isn’t that much lighter and easier to maintain?
An input bevel gear, bevel idler gear, and output bevel gear would be the same gear count as this small input ger, idler gear, and large output gear... and bevel gears would have been both more expensive to manufacturer and more difficult to locate (because axial position is critical for bevel gears but not for parallel gears).
Is the second smaller set of teeth the same ratio as the big teeth or are there really the same number of small and big teeth?
Same numbers of teeth, but smaller, ie one pair of gears is scaled down from the other. which leaves a gap for the idler gear.
@@FlightEngineering1 Thank you.
1:00 you can see a fair amount of wear on the gear teeth. The straight cut must have been noisy to boot!
The teeth are not really worn, they needed cleaning though. What can you see that indicates wear? Yes, straight-cut gears are noisy for sure, and you can hear these from close-up on some of our other videos, however, once the engine gets on load, the exhaust drowns out everything else (for miles around!)
@@FlightEngineering1 if you look at 1:08, the gear on the lower right, the upper side of the tooth at 7 o’clock, it’s easy to see the depth of wear on that side. Being on the crankshaft it show clockwise rotation wear. And yes, I’m sure it could be heard for miles.
Where to find numbers of gear teeth? In the video it's clearly seen only 25-teeth gear and a big 53-teeth gear.
I didn't see a view which allowed accurate counting of any gear other than the idler (and the idler tooth count doesn't matter). The drive ratio is given as 0.4423 so if the large (driven) gears have 53 teeth the small (driving) gears must have 23.44 teeth... so someone has miscounted or mis-calculated. I'm guessing it's 52 teeth (large) and 23 teeth (small).
A little bit unrelated to this video perhaps: Why does the Griffon sound so different than the Merlin and other V12's of that era? Is it due to the different firing order ?
Yes it is the firing order. The crankshaft is arranged differently. It still fires alternately between each bank, and all cylinders fire at equal spacings but I suspect there are exhaust ports close to each other firing in quick succession one one engine but not the other which would cause that irregular firing effect you hear from the Griffon.
@@FlightEngineering1 Thanks for clearing that up. It has puzzled med for quite some time
@@FlightEngineering1 Different firing order necessitated by the placement of the magnetos at the front of the engine, or ... ?
i'm surprised the gears where not cross cut to keep gear whine down.
That's called "helical". Helical would be quieter, but would cause axial thrust (the gears push each other along their shafts), which makes bearings more difficult.
Is this similar to an 87/88?
I haven`t seen one, or read the manuals, but I suspect yes, they are the same.
Uhh...how did they have the same speed if the gear at the front has less teeth/size???
The numbers of teeth are the same, but they are smaller teeth on one pair of gears, making the gears a smaller diameter, leaving a gap between the gears, allowing for an idler gear to mesh with them and therefore reverse the rotation.
hello gentlemen, it came in my hands a Rolls Royce Griffon in immaculate condition, the engine is rotating easily I can say.
i need to install the magneto, connect the petrol, and oil hoses, but I don't have any experience n these engines.
i am wondering if any one of you could help me with some information.
i am willing to pay the cost, even if someone could come to Cyprus and help me to start this engine.
Hi. If you are on Facebook, put a post on “Historic Aero Engines Group” there are lots of people there who can help you.
@@FlightEngineering1 thanks a lot my friend
One German bullet that is wedged in the gearbox will do a lot of damage.
…slid rules
If one looks carefully, there are only about two teeth meshing at any one time , so that means that 1000 Horse Power are being transmitted through two teeth,
The logic and rational thinking of engineering in the last 200 years, have taken over from the emotions and the illusions of religions, politics, art and other social professions, which never provide any tangible guaranteed services or comfort for the family, but a sentimental situation which many people still need.
Relative to what modern humans do, they all wrap around them some sort of engineering prosthetic aid to enable them do what they cannot do when naked, and with no engineering attachments, as land vehicles, sea craft and air craft, including a pair of shoes, as now no one can walk barefoot. As for hospitals, they are full of engineering diagnostic and working tools, and where the surgeon leaves off, as in amputations, the engineers take over, with fitting modern prosthetic aids.
Pilots needs to accept that their prime and principal duty is to always try to save their own lives, under every situation and it is the engineering in the aircraft that buffers their life during all normal flight, and many other not so normal flights, and if the flying prosthetic aid fails, some pilots are lucky to have another change though being provided with other prosthetic aids, as ejector seats and parachutes, where the pilot does not care two hoots where the damaged aircraft lands even on residential areas, as long as the pilot saves his own life provided he finds enough engineered prosthetic aids to wrap around him to do so. Sully of the Hudson river landing saved his life be cause his prosthetic flying aid had enough buoyancy in the nose to counteract the drag forces of the two engines dragging the nose down and as the co- pilot said, " I thought we were going down to the bottom of the river."
Engineering has uncovered the beauty and hidden wonders found in silence and what is not visible to the human sensors and rather than understanding it, most people ar proud to buy and own and operate engineering devices and fill their own homes with tangible guaranteed engineering devices.
This video showed some of the beauty of engineering which laid quiet for too long while other professions were so vociferous exploiting the people around them with, illusions, faiths and selling, promises, entertainment, emotions and indulgences.
I feel sorry for those teeth. They've had a hard life!
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Слава американским инженерам !
It is British!
@@FlightEngineering1 Слава англосаксам !
@@trpptr6623 Yay, thank you!
Wow!