Should Napier have been building the Griffon instead of the Sabre? (3 Viewers)

[z42]

One does wonder what a 24 cylinder engine using Merlin cylinders would do though

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.

 

[ThomasP]

re what "a 24 cylinder engine using Merlin cylinders" would do?

Eagle XXII was close with Ø5.4" x 5.125", vs Ø5.4" x 6" for the Merlin.

CR was 6.5:1 for the Eagle, vs 6:1 for the Merlin.

The Eagle's max demonstrated reliable boost at end of the test program for Wyvern was +18 lbs, which would be equal to about +21 lbs boost if the CR was reduced to 6:1 as for the Merlin.

NOTE: The data and curve below are for the version with a CR of 6.5:1.

 

[tomo pauk]

If I am not mistaken, the last 3 major piston engine projects taken on by RR were sleeve valve engines - ie the Crecy, Pennine, and Eagle. They obviously thought the sleeve-valve was worth pursuing. The output powers - actually achieved and projected - speak for themselves.

How much of the power was due to the later two being heavy, big-displacement engines turning high rpm, and how much it was them being with sleeve valves? Eagle weighted more than two 2-stage supercharged Merlins, and more than one R-4360; Pennine weighted more than the 2-stage S/Ced R-2800s.
Crecy - 1400 HP on the bench.

 

[ThomasP]

Part of the greater weight of the Eagle was the reduction gear box for the contra-rotating props (~400 lbs more than for a 'normal' single prop reduction gear box).

As has been pointed out in other threads, the poppet valve matured a lot during the inter-war and war years, possibly making the development of the sleeve valve unnecessary. On the other hand, a large part of the development problem with the sleeve valve was the manufacturing of the sleeves themselves - in terms of the process development and of quality control. Today there would be no inherent problem manufacturing the sleeves or the fiddly bits like the sleeve valve gear train.

As to how much the sleeve valve design contributed to the power I do not know - by the end of the war it was probably a wash vs poppet valves.

A major factor in the lack of market share post-war was the increased complexity and cost associated with the sleeve valve and its gear train. For a given displacement the sleeve valve seemed to cost about 1/3 more per BHP relative to the poppet valve engine, though how much of this was due to economy of scale and/or the difference in competence of the makers is a question.

Also for the same approximate displacement, the 2817 in3 Eagle put out about the same power at max cruise as the max war-rime power (without ADI) of the 2805 in3 R-2800, while weighing about 66% more but having a smaller cross section (10.7 ft2 vs 15.2 ft2 - note that this does not count the cross section for the coolant radiator for the Eagle, or the oil coolers for either engine).

 

[tomo pauk]

Also for the same approximate displacement, the 2817 in3 Eagle put out about the same power at max cruise as the max war-rime power (without ADI) of the 2805 in3 R-2800, while weighing about 66% more but having a smaller cross section (10.7 ft2 vs 15.2 ft2 - note that this does not count the cross section for the coolant radiator for the Eagle, or the oil coolers for either engine).

Engine weight was/is an important consideration for the aircraft designers. An extra 1500 lbs was a big difference for the aircraft of ww2, that will demand bigger wing, bigger undercarriage, stronger fuselage - the things that push up the weight and drag. More fuel needed, bigger tail, heavier prop - again pushing up the weight, and with it the size of wing, so again we have more drag. Do we get a fighter that is better than the late-marque P-47, P-51 or (Sea) Fury?

 

[z42]

As has been pointed out in other threads, the poppet valve matured a lot during the inter-war and war years, possibly making the development of the sleeve valve unnecessary. On the other hand, a large part of the development problem with the sleeve valve was the manufacturing of the sleeves themselves - in terms of the process development and of quality control. Today there would be no inherent problem manufacturing the sleeves or the fiddly bits like the sleeve valve gear train.

As to how much the sleeve valve design contributed to the power I do not know - by the end of the war it was probably a wash vs poppet valves.

A major factor in the lack of market share post-war was the increased complexity and cost associated with the sleeve valve and its gear train. For a given displacement the sleeve valve seemed to cost about 1/3 more per BHP relative to the poppet valve engine, though how much of this was due to economy of scale and/or the difference in competence of the makers is a question.

Sometimes it feels people succumb to nostalgia wrt sleeve valves (not pointing fingers at you here, just as a general observation). Poppet valves are these boring clattering things even my lawn mower has, surely these exotic high end aero engines must use sleeves because they are inherently superior!

But if you think about it, in all their everyday banality, poppet valves are pretty ingenious. There's no surfaces that must glide against each other under high pressure, and when the pressure is at it's highest the valve isn't in fact moving at all. And the higher the combustion pressure is, the tighter the valve seals against the valve seat (Which brings to mind a saying I saw somewhere about steam engines: "There's two kinds of valves. Poppet valves, and those that leak.").

In contrast the sleeve valve must move over an oil film covering a very large area (well, practically the entire sleeve), subject to varying pressures, side loading of the piston, sometimes supported by the cylinder wall, sometimes not due to the intake/exhaust ports in the cylinder wall. Seems inherently a much more sensitive mechanism.

 

[gruad]

And yes, that plane would have been smaller than the Typhoon. And sure, have Napier design and build that engine, if the ministry is concerned about avoiding a RR monopoly.

Ironically, Rolls-Royce were very occupied in keeping Napier out of the market and it took a champion in the MOD to get the go ahead for the Sabre, IIRC.

 

[tomo pauk]

Ironically, Rolls-Royce were very occupied in keeping Napier out of the market and it took a champion in the MOD to get the go ahead for the Sabre, IIRC.

Please, do tell.

 

[gruad]

Please, do tell.

View: https://youtu.be/Hk1-P5iksIc?si=ETQxY0muq_DN2AYY

George Purvis Bulman?, I think I hear, at 2:50 to about 3:50.

This is Flight Dojo I got this from.

 

[tomo pauk]

George Purvis Bulman?, I think I hear, at 2:50 to about 3:50.

This is Flight Dojo I got this from.

Thank you.
Unfortunately, the video mixes up the 1 HP/cu in hi-per mantra adored by the US Army with what was going on in the UK. It also over-sells the Rapier and Dagger by a good deal.
Even if RR was hard lobbying against Napier, Napier made their job very easy.

 

[gruad]

Unfortunately, the video mixes up the 1 HP/cu in hi-per mantra adored by the US Army with what was going on in the UK. It also over-sells the Rapier and Dagger by a good deal.

Agreed, no source is perfect and you and other members with your superior knowledge are more likely to spot errors.

It would be good to compile a rough reliability list of YouTube contributors to WW2 Aviation videos

Eg, Rex's Hanger, Dronescapes, Dark Skies etc

Thanks

 

[ThomasP]

Hey tomo pauk, re:

Engine weight was/is an important consideration for the aircraft designers. An extra 1500 lbs was a big difference for the aircraft of ww2, that will demand bigger wing, bigger undercarriage, stronger fuselage - the things that push up the weight and drag. More fuel needed, bigger tail, heavier prop - again pushing up the weight, and with it the size of wing, so again we have more drag. Do we get a fighter that is better than the late-marque P-47, P-51 or (Sea) Fury?

I have always assumed that the Eagle was intended for the next generation of significantly larger airframes (ie Spearfish, Wyvern, Skyraider, Mauler, BT2D, etc size - maybe F2G Corsair size at the smallest?). If as seemed the case, you are going to larger high performance airframes anyway, you are going to want the more powerful engine - even if the engine is heavier.

Also, an Eagle powered airframe would be capable of using the Meredith effect to the level of the Mustang, if that was wanted. Air-cooled engines not so much. P&W wrote an article for one of the aviation magazines just after the war, in which they admitted that an air-cooled engine installation would have ~15% more drag vs a liquid-cooled engine installation of the same power (both installations including appropriate cooling systems but not including the Meredith effect). Meredith effect plus ~15% less engine installation drag equals ?

Whether any of the single-engine airframes potentially powered by the Eagle would surpass the earlier airframes, who knows.

Would the F2G Corsair benefit from the R-4360 being replaced by an Eagle?

In the F2G Corsair (13,350 lbs TOGW clean) Eagle installation you would have a single(?) 4- or 5-blade prop, with an approximate total installation weight increase of ~500-600 lbs (including engine coolant system) with 3500 BHP, vs the R-4360 as actually installed with 3000 BHP. A 500 BHP increase with ~15% less engine installation drag and excellent Meredith effect equals ? Is the F2G/Eagle gain in Vmax of ~40 mph (~470 mph vs 430 mph) worth it?

The A1D Skyraider (~14,000 lbs TOGW clean) used the R-3350 engine (2500 BHP without ADI). The AM-1 Mauler (~20,000 lbs TOGW clean) used the R-4360 (3000 BHP without ADI). The Eagle (3500 BHP without ADI) was originally planned for the Wyvern (~20,000 lbs TOGW clean) and was installed in a few very early production TF Mk 1.

The P-82 Twin Mustang(~20,800 lbs TOGW clean) used either 2x Merlin (~3700 BHP total without ADI) or 2x Allison (~3500 BHP total without ADI). 1x Eagle w/counter-rotating props or 2x Merlin/Allison engine installation weights would be about the same overall. A single-engine/single-fuselage airframe with the Eagle should have significantly less drag than the twin-engine/twin-fuselage P-82 Twin Mustang, and probably less overall weight.

The Eagle also had lower sfc than the air-cooled engines, although if it would be enough to really matter I cannot say.

 

[tomo pauk]

Whether any of the single-engine airframes potentially powered by the Eagle would surpass the earlier airframes, who knows.

Would the F2G Corsair benefit from the R-4360 being replaced by an Eagle?

In the F2G Corsair (13,350 lbs TOGW clean) Eagle installation you would have a single(?) 4- or 5-blade prop, with an approximate total installation weight increase of ~500-600 lbs (including engine coolant system) with 3500 BHP, vs the R-4360 as actually installed with 3000 BHP. A 500 BHP increase with ~15% less engine installation drag and excellent Meredith effect equals ? Is the F2G/Eagle gain in Vmax of ~40 mph (~470 mph vs 430 mph) worth it?

Corsair does not need a 3500-4000 lb engine to make close to 470 mph - the -5 was supposed to do 469 mph (347 kt). Super Corsair was with 1-stage S/C, it will not be as good at high altitudes as the -4, let alone -5.
P-47M was also doing 470 mph, again without the need for a 3500-4000 lb engine. The XP-72 was supposed to do 500 mph with the 2-stage R-4360.
P-51H was in the ballpark with P-47M and -5 Corsair.

The A1D Skyraider (~14,000 lbs TOGW clean) used the R-3350 engine (2500 BHP without ADI). The AM-1 Mauler (~20,000 lbs TOGW clean) used the R-4360 (3000 BHP without ADI). The Eagle (3500 BHP without ADI) was originally planned for the Wyvern (~20,000 lbs TOGW clean) and was installed in a few very early production TF Mk 1.

Yes, Eagle would've probably been used the best in the naval 1-engined attackers.

The P-82 Twin Mustang(~20,800 lbs TOGW clean) used either 2x Merlin (~3700 BHP total without ADI) or 2x Allison (~3500 BHP total without ADI). 1x Eagle w/counter-rotating props or 2x Merlin/Allison engine installation weights would be about the same overall. A single-engine/single-fuselage airframe with the Eagle should have significantly less drag than the twin-engine/twin-fuselage P-82 Twin Mustang, and probably less overall weight.

Check out the Hornet, very fast and nimble, with better power/weight ratio than it should've been possible with the Eagle. There is also a redundancy of having a second engine.

Problem that all of the very late, very heavy and very powerful piston engines were having was propelling something beyond 450-470 mph, while the less powerful and widely available engine were able to do the same.

 

[yulzari]

Problem that all of the very late, very heavy and very powerful piston engines were having was propelling something beyond 450-470 mph, while the less powerful and widely available engine were able to do the same.

Agreed but they could haul more weight and airframe volume. This translating into more available load appropriate to whatever the assigned tasks. At this point it therefore increased their advantage against short ranged jets. Also they were in the early stages of further development and would likely have produced even more power in due course. In the case of passenger and transport aeroplanes the ICE was still the norm until the 1960s and big ICE engines still had a potential role. For the Mk1 Bristol Brabazon they went to the trouble of combining two Centaurus engines each driving one of the two contra rotating propellers at IIRC 3,500bhp the set. Yes they wanted to then go on to turboprops but the very big ICE engines in the 5,000bhp class would be a simpler alternative. Yes I know the Brabazon was not successful but it worked fine and it's fault was in marketing not engineering. On speed, with the right aerodynamics the Russians got over 900km/hr out of the propellor driven Tu95 so there is no reason not to expect it to be possible with the big ICEs.

 

[tomo pauk]

Agreed but they could haul more weight and airframe volume. This translating into more available load appropriate to whatever the assigned tasks. At this point it therefore increased their advantage against short ranged jets. Also they were in the early stages of further development and would likely have produced even more power in due course.

What kind of load vs. combat-radius we're talking about?

In the case of passenger and transport aeroplanes the ICE was still the norm until the 1960s and big ICE engines still had a potential role. For the Mk1 Bristol Brabazon they went to the trouble of combining two Centaurus engines each driving one of the two contra rotating propellers at IIRC 3,500bhp the set. Yes they wanted to then go on to turboprops but the very big ICE engines in the 5,000bhp class would be a simpler alternative. Yes I know the Brabazon was not successful but it worked fine and it's fault was in marketing not engineering.

Very big piston engines of 5000 HP were very complicated alternative to anything, not simpler alternative.
Lockheed didn't get the memo that 8x 18 cyl engines are required. People that green-lit the Brabazon should've gotten the comfy & cozy post in the Falklands, counting penguins or whatnot.

On speed, with the right aerodynamics the Russians got over 900km/hr out of the propellor driven Tu95 so there is no reason not to expect it to be possible with the big ICEs.

The 15000 HP engines on the Tu-95 were ICE, but not piston engine. A 15000 HP piston engine would've been a sight to see.

 

[SaparotRob]

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[Shortround6]

The 15000 HP engines on the Tu-95 were ICE, but not piston engine. A 15000 HP piston engine would've been a sight to see.

Just use sixteen 3750hp engines
Simple, IF DB could put two big engines together just use four................................on 2nd thought

 

[yulzari]

What kind of load vs. combat-radius we're talking about?



Very big piston engines of 5000 HP were very complicated alternative to anything, not simpler alternative.
Lockheed didn't get the memo that 8x 18 cyl engines are required. People that green-lit the Brabazon should've gotten the comfy & cozy post in the Falklands, counting penguins or whatnot.



The 15000 HP engines on the Tu-95 were ICE, but not piston engine. A 15000 HP piston engine would've been a sight to see.

I don't want to divert the thread to a Brabazon one but it had the ability to change from the high price low number passenger marketing model to a large number low cost one for key long distance routes on the model of the transatlantic Icelandair CL44 service in the 1960s. As Freddy Laker put it, it is a greater achievement to fly people at half the price than in half the time. It was simply a market that was not considered. The airframe was up to the job, with a suitable interior and limited baggage. Pack in the peasants into cattle class. As an airframe it worked fine. The Mk2 would have been even better and there are simpler ways to provide 14,000bhp plus than 8 engines, 8 propellers, 4 gearboxes with with 144 cylinders and, IIRC, 288 spark plugs. However, a separate thread would be a more suitable one to discuss that matter. Working full time 24 hours the time to change all spark plugs will be 3 days with one man permanently on the job. One begins to see why the turbines seemed attractive solutions.

 

[z42]

Problem that all of the very late, very heavy and very powerful piston engines were having was propelling something beyond 450-470 mph, while the less powerful and widely available engine were able to do the same.

As long as you can produce engines in the same ballpark in terms of power/weight, the bigger engine should be able to result in a faster aircraft, as the frontal area grows slower than the size (=power) of the engine, and various equipment like cockpit and pilot, guns, etc. become a smaller portion of the whole weight. Though it's of course hard to compare, as many of these late prop planes were developed in an era where it was clear that jets were the future for pure fighters emphasizing speed, and thus they had to emphasize other attributes like being able to operate from carriers, or ground attack in general rather than a pure fighter role.

Further, at such high speeds you start to run into issues with props, as the prop efficiency rapidly starts to drop at high speeds. So it becomes harder and harder to increase speed, you need both very good aero as well as massive amounts of power. No idea really how the Russians manage to push the Tu-95 to such high speeds, it almost seems to defy physics.

As specifically for the Eagle, at least based on the specs on wikipedia, Eagle has substantially lower power/weight than the Merlin 130 used on the Hornet. Don't know why, maybe the sleeve valves limited boost, or just that the Merlin 130 was pretty much the end of the road for the Merlin and they hadn't really pushed the envelope on the Eagle yet?

The 15000 HP engines on the Tu-95 were ICE, but not piston engine. A 15000 HP piston engine would've been a sight to see.

My money would be on liquid cooled radials. Take 9 banks of Griffon cylinders and connect them to a common crankshaft, and you have a 56 cylinder engine making around 9000 hp. Put two of these back-to-back driving contra-rotating props. Or cheat a bit, and have push-pull nacelles with one engine driving a tractor propeller ahead of the wing and the other engine driving a pushed prop behind the wing. But yes, maintenance guys are going to hate it. Or be extremely happy about the job security!

 

[Shortround6]

Take 9 banks of Griffon cylinders and connect them to a common crankshaft, and you have a 56 cylinder engine making around 9000 hp.

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.