Should Napier have been building the Griffon instead of the Sabre?

[z42]

For some reasons all of the multi cylinder engines of over 24 cylinders seemed to run into difficulties. They sounded real good in the sales brochures but............
Only the P&W R-4360 made it and it's rather troublesome gestation period may have scared off everybody else.

It also saw the development of the first "electronical" engine analyzers for trouble diagnoses. It was one of the few engines that was reputed to be able to shut down in good running condition and had troubles on start up.
Vibration problems seemed to multiply with the number of cylinders. In the days of slide rules this took a lot of time to sort out.

The P&W R-4360s were not popular with the airlines and they only used them when they had to. Once jets showed up they went into the secondary market and the value of the aircraft dropped like rocks. Air freighters with R-3350s and R-2800s survived for considerable periods of time due to cheaper maintenance costs.

I'm not arguing it would be smooth sailing, far from it.

But had turbines been delayed by a decade or two, something else would have needed to be done to provide the ever increasing power demands of new aircraft being developed.

I think liquid cooled radials would have been the most promising path forward after the liquid cooled X/H-24 and two row air cooled radials run out of steam.

A liquid cooled radial could have avoided the cooling problems that plagued R-4360, and using monobloc cylinder banks and heads would have helped provide stiffness, hopefully alleviating at least some of the inevitable vibration issues.

 

[Shortround6]

If you are not aware of this website I strongly suggest it.

Old Machine Press

New Memories of Old Machines

oldmachinepress.com

One of the many articles that pertains to this discussion.

Lycoming XR-7755 36-Cylinder Aircraft Engine

In 1943, Lycoming began work on a powerful and efficient engine intended to power the next generation of very large aircraft. The 5,000 hp XR-7755 ran in 1946, but such a large engine was no longer…

oldmachinepress.com

A major problem is that while you could make engines bigger, you could no longer change the power to weight ratio very much. That needed new materials.

If you had a 2000hp engine that weighed 2000lbs there were only certain applications that called for a 6000hp engine of 6000lbs. There is an economy of scale to be sure but for such things as fighters (and not bombers calling themselves fighters) a 6000lb engine needs 3 times the wing area, and 3 times the fuel (a bit less when cruising) which means 3 times the wing area for the fuel, and 3 times the landing gear weight, etc, etc, etc, The weight savings of using 2 6000hp engines vs 4 3000hp engines is there but it is not great.
Jets won because a jet offered much more power for the same weight.
They were also running into problems with the efficiency of propellers the upper 400mph and low 500mph speed range.
They could not turn the extra power into higher speed or at least effectively.
Speed record planes do not make money

 

[z42]

If you are not aware of this website I strongly suggest it.

Old Machine Press

New Memories of Old Machines

oldmachinepress.com

I'm aware, thank you. And yes, it's very good!

One of the many articles that pertains to this discussion.

Lycoming XR-7755 36-Cylinder Aircraft Engine

In 1943, Lycoming began work on a powerful and efficient engine intended to power the next generation of very large aircraft. The 5,000 hp XR-7755 ran in 1946, but such a large engine was no longer…

oldmachinepress.com

Yes, that project was unsuccessful. And so were things like RR Vulture and Jumo 222, which to an extent can be seen as stepping stones on the path to liquid cooled radials, if not already fullblown such. But I think the takeaway from these failure isn't that the fundamental concept of a liquid cooled radial is unsound, but that there was never the time to develop this branch of engine design to maturity before turbines made high power piston aero engines obsolete. For comparison, how many V-12 aero engines did RR make before the Merlin? And even so, it took a long time before they worked out the various issues in the design and it became the famous war winning engine. Making complex things work just takes time and a lot of elbow grease, no reason to expect that the liquid cooled radial would have been able to somehow take a shortcut on this path.

A major problem is that while you could make engines bigger, you could no longer change the power to weight ratio very much. That needed new materials.

If you had a 2000hp engine that weighed 2000lbs there were only certain applications that called for a 6000hp engine of 6000lbs. There is an economy of scale to be sure but for such things as fighters (and not bombers calling themselves fighters) a 6000lb engine needs 3 times the wing area, and 3 times the fuel (a bit less when cruising) which means 3 times the wing area for the fuel, and 3 times the landing gear weight, etc, etc, etc, The weight savings of using 2 6000hp engines vs 4 3000hp engines is there but it is not great.
Jets won because a jet offered much more power for the same weight.
They were also running into problems with the efficiency of propellers the upper 400mph and low 500mph speed range.
They could not turn the extra power into higher speed or at least effectively.

I fully agree there would have been challenges. And yes, the lower power/weight achievable with piston engines compared to turbines would have limited what was achievable.

However, I'm quite sure that without jets we'd have seen faster prop fighters, as the advantages of higher speed were just too large to be ignored. The historical 'superprops' immediately after WWII wouldn't have been the end of the line if jets wouldn't have been ready. Say something like a single engine fighter using the same tricks the Tu-95 does with swept wings, area ruled, counter-rotating props, and other tricks in the book, should be able to make 900+ km/h like the Tu-95.

I agree with the point that there's an upper limit to how big engines you can find a market for. I guess one reason for the success of engines like R-1820, R-1830, and R-2800 was that they were widely used in everything from single-engine fighters to bombers and civilian aircraft. Still, I think there would be a market for substantially more power than the historical late-war aero piston engines delivered. How much power would the above swept wing single engine fighter capable of 900 km/h need? That might be a suitable size, and that size might be very large indeed. Bigger aircraft could then slap however many of those engines on the wings as they needed.

But perhaps the Tu-95 has help from the Undead Hand of Stalin pushing it along at that ludicrous speed for a propeller aircraft.

Speed record planes do not make money

Military planes seldom do.

 

[Shortround6]

For comparison, how many V-12 aero engines did RR make before the Merlin? And even so, it took a long time before they worked out the various issues in the design and it became the famous war winning engine. Making complex things work just takes time and a lot of elbow grease, no reason to expect that the liquid cooled radial would have been able to somehow take a shortcut on this path.

Well, RR had built 3 V-12s in WW I or just after. But that is part of the materials/technology development'
The 1915 Eagle was about 225hp for around 900-960lbs. got to 360hp by 1917-18 and was fairly reliable (crossed the Atlantic in 1919)
The 1916 Falcon was a 710-715lb engine of 225-285 hp by 1917/18
The Condor was 1920 engine starting at 600hp for 1350-1400lbs and they got it to about 750hp by 1925-27. A lot of changes

Then came the Kestrel (inspired by the Curtiss D-12) which introduced cast engine blocks to RR (Hispano was doing it in 1915) and the race was on.

In the late 20s they got better valve springs, sodium cooled valves, better alloys, superchargers. better casting and forging techniques. Better testing equipment, Better spark plugs, and by 1945 they had 100/150 fuel and in the post WW II years commercial aviation got 108-135 fuel and 115-145 fuel.
Improvements after 1945 were not impossible but they needed a lot more work for small increases.
A commercial Merlin 500 (two speed) was about 1520lbs and rated at 1610hp for take-off and 1635hp at 2250ft and 1510hp at 9250ft.
Change in power to weight from 1920 to late 40s was over 2.5 to 1. and the change in power to weight had gone up for the Merlin (using a two speed blower) from 1.33lbs per hp to 0.93lbs per hp. Using the higher boosts and more exotic fuels got a bit better The Merlin 130 in the Hornet got a 0.86lb to hp ratio using 25lbs of boost and 100/150 fuel, it needed about 200lbs more engine weight (2 stage blower) to get there and without knowing the weight of the radiators, intercooler, and cooling fluid the improvement in actual power to weight might not be quite as great.

It would certainly be interesting to see what the weight of the propellers and gearboxes on the Tu-95 are

 

[J.A.W.]

The R/R Griffon was envisaged as a Royal Navy FAA engine, and did see service there, in the Firefly, & late mark Seafires.

But it wasn't selected for the Firebrand, whereas the Sabre was, & when Sabre scarcity negated that, the Centaurus was
chosen instead, just as it later was for the Sea Fury, given the "disappointing" performance of the Griffon powered Fury.

 

[J.A.W.]

I think the basic Vulture concept was sound, they just never had the time to work out the kinks and optimize the design. So yes, a X-24 with Merlin cylinders and blocks could have been viable.

Or if turbines hadn't taken over, why stop at a X-24? Attach 7 Griffon banks around a common crankcase and you'd have a 42 cylinder liquid cooled radial making something like 7000 hp.

Griffon crankshaft was comprehensively revised - a number of times, with many fundamental palliatives applied - to make a basic V12 work.
After the Vulture X-24 flop (can you name a successful X-crank engine?), they'd be in conniptions over any such concept as you suggest.

 

[wuzak]

Griffon crankshaft was comprehensively revised - a number of times, with many fundamental palliatives applied - to make a basic V12 work.

Care to elaborate?

I know the Griffon firing order was changed to alleviate issues, and that the accessory drive was originally connected to the front of the crankshaft and then later moved to the rear.

What else?

 

[wuzak]

After the Vulture X-24 flop (can you name a successful X-crank engine?), they'd be in conniptions over any such concept as you suggest.

If the Vulture had the time, money and effort spent on it that the Sabre did it would have been successful.

 

[J.A.W.]

If the Vulture had the time, money and effort spent on it that the Sabre did it would have been successful.

Actually, I'd reckon the opposite applies.

Basis being, the Sabre design was fundamentally sound, it was the production issue which cruelled it.
The Vulture design was fundamentally flawed, no amount of "time money effort spent..." could overcome that.

Rolls-Royce had no shortage of "time money effort", since they proposed the Griffon as a big power substitute,
yet it could never make the cut, as an option for airframes designed for true 'big power' (over 2,000hp) use.

Still, R/R then tried to make a real big 'Sabre clone', but that was the other end of the 'Goldilocks' curve...

 

[wuzak]

Actually, I'd reckon the opposite applies.

Basis being, the Sabre design was fundamentally sound, it was the production issue which cruelled it.
The Vulture design was fundamentally flawed, no amount of "time money effort spent..." could overcome that.

What is the fundamental flaw that would have prevented the Vulture from becoming a success with more development?

The main problem was with the connecting rod arrangement. That certainly could have been solved.

The Pennine was an X-24 engine that used a built-up crank and single piece master rod. That sort of crankshaft may have been a possible solution for teh Vulture.

Rolls-Royce had no shortage of "time money effort", since they proposed the Griffon as a big power substitute,
yet it could never make the cut, as an option for airframes designed for true 'big power' (over 2,000hp) use.

The Griffon, as you have previously noted, was originally a project for the FAA. Then someone figured it could fit into a Spitfire.

And no, it wasn't particularly suited for big fat aircraft designed around the Sabre and the Centaurus.

 

[J.A.W.]

Care to elaborate?

I know the Griffon firing order was changed to alleviate issues, and that the accessory drive was originally connected to the front of the crankshaft and then later moved to the rear.

What else?

That & more, like crank counterweighting (inc' the 'pendulum' types).
There is a list of them done in an engine analysis of V12s by Raymond (IIRC).

 

[J.A.W.]

What is the fundamental flaw that would have prevented the Vulture from becoming a success with more development?

The main problem was with the connecting rod arrangement. That certainly could have been solved.

The Pennine was an X-24 engine that used a built-up crank and single piece master rod. That sort of crankshaft may have been a possible solution for teh Vulture.




The Griffon, as you have previously noted, was originally a project for the FAA. Then someone figured it could fit into a Spitfire.

And no, it wasn't particularly suited for big fat aircraft designed around the Sabre and the Centaurus.

Fundamental flaw was the X-crank inherently going 'walkabout' in the crankcases, a flexing that dowelling wouldn't fix.
That 'cranky' motion would fracture the 'weakest link' from conrod fixings on out, its a geometric/dynamic problem.

The Griffon would fit (see Hawker Fury prototype) but lacked the performance, as duly noted - when suggested by R/R to designers of
the 'Super Mosquito' & 'Hawker High-Speed' bomber...

 

[z42]

After the Vulture X-24 flop (can you name a successful X-crank engine?), they'd be in conniptions over any such concept as you suggest.

As I mentioned, turbines killed the large aero piston engine, so there was no motivation to develop ever more powerful aero piston engines.

As for a successful liquid cooled radial engine, the Yakovlev/Zvezda M50x family springs to mind. Not for aero use, mind you, but for missile boats where power/weight isn't entirely inconsequential either.

Yakovlev M-501 and Zvezda M503 and M504 Diesel Engines

One of the largest aircraft engines ever built, the 42-cylinder Yakovlev M-501 was modified into the Zvezda M503 marine engine. A further redesign created the 56-cylinder Zvezda M504.

oldmachinepress.com

But if not liquid cooled radials, if turbines are delayed by a couple of decades compared to the historical timeline, what's your suggestion for higher power aero piston engines after the various 24-cylinder liquid cooled ones and two-row air cooled radials run out of steam?

 

[J.A.W.]

As I mentioned, turbines killed the large aero piston engine, so there was no motivation to develop ever more powerful aero piston engines.

As for a successful liquid cooled radial engine, the Yakovlev/Zvezda M50x family springs to mind. Not for aero use, mind you, but for missile boats where power/weight isn't entirely inconsequential either.

Yakovlev M-501 and Zvezda M503 and M504 Diesel Engines

One of the largest aircraft engines ever built, the 42-cylinder Yakovlev M-501 was modified into the Zvezda M503 marine engine. A further redesign created the 56-cylinder Zvezda M504.

oldmachinepress.com

But if not liquid cooled radials, if turbines are delayed by a couple of decades compared to the historical timeline, what's your suggestion for higher power aero piston engines after the various 24-cylinder liquid cooled ones and two-row air cooled radials run out of steam?

Well, this is what Napier did, a very efficient mill - but were cut-off short by turbines & cheap fuel...

Napier Nomad Compound Aircraft Engine

 

[z42]

Well, this is what Napier did, a very efficient mill - but were cut-off short by turbines & cheap fuel...

Napier Nomad Compound Aircraft Engine

The Nomads are indeed fascinating, but OTOH if we imagine that turbines are delayed for a couple of decades (say, due to materials challenges?), then presumably turbochargers and turbocompound systems are also out of the picture.

 

[J.A.W.]

The Nomads are indeed fascinating, but OTOH if we imagine that turbines are delayed for a couple of decades (say, due to materials challenges?), then presumably turbochargers and turbocompound systems are also out of the picture.

Compression ignition 2-stroke engines were 'a natural' for downstream gas efflux reuse, since they flowed copiously and did not
put forbidding thermal (heat-limitation) demands as gas generators for heat sensitive turbines.

Both the Napier Deltic (derived from the Jumo CI opposed piston design - which uniquely saw service use as a turbo'd German aircraft),
and later series GM Detroit Diesel 2-strokes also added turbos.

Check out this beastly boat, powered by riotous, raucous, Detroit Diesels.


View: https://www.youtube.com/watchv=wqntIr2cKk4

 

[z42]

Compression ignition 2-stroke engines were 'a natural' for downstream gas efflux reuse, since they flowed copiously and did not
put forbidding thermal (heat-limitation) demands as gas generators for heat sensitive turbines.

Yes, good point. Even if turbochargers for gasoline engines or 'pure' turbines are unfeasible due to materials challenges, there's still a window of opportunity for turbos attached to diesel engines.

Check out this beastly boat, powered by riotous, raucous, Detroit Diesels.


View: https://www.youtube.com/watchv=wqntIr2cKk4

Says video isn't available.. EDIT: Actually, now the video above in the quoted message works, but in your previous post it doesn't work. Weird..

But yes, I have a soft spot for two stroke diesels.

 

[MIflyer]

Napier should have been building R-2800's so that Hawker could build P-47's.