WI The Rolls Royce Vulture is a success

[wuzak]

I have received an installation drawing of the Vulture II/IV, complete with a number of dimensions.

Scaling from the drawing I found that the Vulture would fit inside a 48" circle - some 4-5" smaller in diameter than a P&W R-2800/R-4360 and 8-9" smaller than a Wright R-1820/R-2600/R-3350 or a Bristol Hercules/Centaurus.

So the Vulture would easily fit up to a bulkhead designed for one of those radials, with space to spare. The downside is that it is longer than all, except the R-4360.

Feeding the exhausts back to the twin turbos, as in the proposed British B-29 version, may be an interesting proposition, as it would have to negotiate the engine mountings and the two speed drive wheel case. Perhaps a single speed drive would provide less impediment to the routing of exhausts.

The drawing also seems to indicate that the Vulture had one piece block/heads - like Merlins post Ramp Head to the changeover to two piece block/heads around 1942.

 

[wuzak]

A Vulture powered Corsair

IIRC the R-2800 in the Corsair was angled to allow the pilot a better view over the nose. Is that correct?

With the Vulture that isn't necessary.

 

[wuzak]

Tried drawing a B 29 with Vulture engines using autocad and photoshop but it just wont work probably need tomopauks skills.

I am slowly working on an alternative history of the Boeing Washington in RAF service with the improved turbocharged Vulture engine. So far its Dec 44 No 617 and No 9 squadrons are training with there Stabilised Automatic Bomb Sight equipped Washington Mk1 bombers. Very soon tallboys and Grand Slams are going to be dropping from great heights and doing some very nasty things to German concrete.

How's the alternative history going fastmongrel?

RT over at The Great Planes Forum posted some pics of the Blackburn B-20 which show how I would do the installation of a Vulture in a B-29. No space for turbos and intercoolers, but that could be fixed by making the scoop larger, and having the turbos either side.

The Vulture installation would be much sleeker than the V-3420 option, but it depends on the size of the bulkhead. I think the bulkhead of the B-29 would be small enough that the Vulture could be installed without an oversized nacelle.

 

[nuuumannn]

This is a fascinating thread;

What WW2 a/c was absolutely 100% perfect in every way?

I'm with Milosh on this one. Despite its many flaws, the Manchester's airframe was the heart of the success of the Lancaster; it was easily manufactured, extremely robust and its capacious bomb bay was not lengthened in the Lanc. As for the issues mentioned that the Manchester suffered, as others have alluded to, these could have been considered 'teething troubles'; the fact that many of them were resolved with the Lancaster shows that they would have been so on the Manchester, or "Man'ster" for short - this from a Mancunian mate I had in the UK.

The early Nash and Thomson mid upper turret of the Manchester was a source of trouble, but was later changed on the Mk.III and had little to do with the airframe. A faulty feathering mechanism has nothing whatsoever to do with airframe design either. The props of the Lanc were licence built Ham Std 'Hydromatic' props by de Havilland - not sure about the Manchester, but I'm thinking the same propeller. I can't remember how exactly the feathering worked on these props (I've worked on them), but I vaguely remember something about electrical issues, which the Manchester had in spades. One interesting fact about it was that it was the first RAF bomber with a dedicated flight engineer's position.

One aircraft that is often over looked as to just how bad it was on entry into service, and was a contemporary of the Manchester was the Handley Page Halifax. A very poor design that entailed quite a number of fundamental design changes as well as a powerplant change before it could truly have been considered rid of its many vices. Perhaps the biggest was its nasty tendency to become uncontrollable owing to rudder over balance. Test pilots and RAF personnel lost their lives as a result of this unfortunate design flaw. This was not rectified until the "D" shaped fins of the Hali Mk.III. Its undercarriage required redesign, it was also too heavy, underpowered and very drag inducing, therefore too slow and unable to meet its performance criteria and the A&AEE requested that a severe drag reduction program be undertaken before it entered service. Most of these issues were not overcome until the Hali III.

The Manchester's issues were almost small fry by comparison, but because of the Halifax' combat record, its design flaws have almost been forgotten with the passage of time. Interesting that George Volkert expended effort into examining ideal bomber designs when his production aircraft, the H.P.57 was such a dog.

Back to the Vulture powered B-29!

 

[fastmongrel]

How's the alternative history going fastmongrel?

Hi wuzak unfortunately it has had to go back to the manufacturers for a complete redesign. Gone back to 1940 and the original British request for a big bomber to be built in the USA. I think the only way the RAF is going to get B 29s is if the Convair B 32 is earlier into service and a much better aircraft than in real life, this takes pressure off Boeing allowing more time to get the Vulture installation sorted. Also I think for RAF service it might be better if the Ministry finds the money for a new factory for Boeing possibly just over the border in Canada.

Nice pics of the Vulture installation there very neat.

 

[wuzak]

Hamilton Standard Hydromatic props used a hydraulically actuatted cam which achieves the desired picth control. Not sure if the propellor governorn had any electrics involved.

Howard Hughes' testing accident in the XF-11 occurred because a leaking seal caused one of the props to reverse pitch.

The Curtiss propellor system used an electrical motor attached to an epicyclic gearbox to drive the pitch adjustment. I believe these had to use brushes to transmit power to the motor inside the hub.

 

[wuzak]

Hi wuzak unfortunately it has had to go back to the manufacturers for a complete redesign. Gone back to 1940 and the original British request for a big bomber to be built in the USA. I think the only way the RAF is going to get B 29s is if the Convair B 32 is earlier into service and a much better aircraft than in real life, this takes pressure off Boeing allowing more time to get the Vulture installation sorted. Also I think for RAF service it might be better if the Ministry finds the money for a new factory for Boeing possibly just over the border in Canada.

I think that the Vulture installation would be relatively easy if the engine systems were developed as QECs. So it would be a matter of unplugging the Wright QEC and replacing it with the Vulture QEC.

Production wasn't a problem with the B-29. Sorting out the systems were.

They had a centre for fixing aircraft coming off the production line. I believe it was called the Battle of Kansas.

 

[wuzak]

I tried to match the Vulture installation from the Blackburn B20 to the Boeing B-29 and discovered that Vulture module is so much smaller than the Boeing nacelle. The Blackburn Nacelle is much more tightly cowled than even for the Tornado.

On this picture the front of the Blackburn Nacelle seems almost square - that's teh clearence over the front of the cam covers.

http://i92.photobucket.com/albums/l23/chris7421/B-20002.jpg

 

[nuuumannn]

Hamilton Standard Hydromatic props used a hydraulically actuatted cam which achieves the desired picth control. Not sure if the propellor governorn had any electrics involved.

No, the governor didn't, but the oil pumps were electrically actuated, though. As you stated, the hydromatic props used differential oil pressure against a piston attached to a moving cam, which altered the blade angle.

To feather the props, a button was pressed in the cockpit, which was held down by a coil until the prop had feathered. Simultaneously a solenoid relay switched power to the feathering motor and electric oil pump fro the a/c battery. Oli was pumped from a separate reservoir to the governor, where the pressure build-up would open a transfer valve, which would shut out the governor, then pass through the distributor valve in the hub and act against the inside of the piston to change the blade angle. ( I had to look this up.)

I've never worked on a Curtiss electric prop, but brushes and slip rings certainly make sense.

Interestingly, Alec Harvey-Bailey in the book Rolls Royce- The pursuit of excellence offers this:

"The Vulture, not a Royce design, was a 24 cyliner x engine based on Kestrel bore and stroke. Investigations showed that there had been master rod bolt failures, allowing the flailing assembly to almost cut the engine in half and in some cases to prevent feathering of the propeller."

The following is probably of interest too:

"The problem of the x layout is how to get four pistons to drive one crankpin. On the Eagle XVI, Royce had chosen two pairs of fork and blade rods, running side by side, but the Vulture had a master rod and three articulated rods on one big end. This was to keep the engine short and light. There was one articulated rod on the master rod and two articulated rods on the big end cap. To accommodate this arrangement the split line for the big end had to be angled to the master rod.

There was so little space that Royce's practise of using long ductile nickel steel bolts, which could be tightened to plastic deformation, was abandoned. The assembly was held together by two longish bolts and two very short bolts, which had to be made in high brinell nickel chrome steel. In such bolts the elastic limit and yield point are very close and in the case of the short bolts the permissable extension was very small and had to be precisely controlled.

Primary failure occurred in the short bolts. Because the rod and cap were located by both saw tooth serrations and fitting bolts, there was a quarrel between the two causing stepping of the bolts at the joint face. There had been problems in tightening the short bolts, which had caused variations in tension. The two factors led to the bolts breaking, but it was found also that at the t/off rpm of 3,000, the bolt loadings were imprudently high.

The issue was tackled by re-working the engines. This included new bolts of a slightly easier fit, concentrating location in the serrations and to avoid stepping during assembly. The bolt tightening operation was revised and meticulously followed. Cyril Lovesey pointed out that at 3,000 rpm plus 6 lb boost at t/off, the engine was running throttled and the same power could be achieved by raising the boost to plus 9 lb and reducing the rpm to 2850. This gave much more conservative bolt loadings. Operations were restarted with an engine life of 80 hours, rising to 120 hours as reliability proved satisfactory.

This dealt with the immediate problem, but Hives was faced with a much bigger decision - what toi do with the engine. The Vultures would only be useful if its power development could continue, but this would entail a new master rod design as well as other changes to cope with various problems, which were also present; a major task in the context of the vast Merlin programme.

...The Manchester had great potential and the answer lay in installing four Merlins..." "...Hives took the decision, which was accepted by the ministry, to stop the Vulture."

I fear this might have been covered in another thread...

 

[wuzak]

Thanks for that Nuuumannn.

I believe one iteration of the master rod had a pin on one side and two bolts on the other.

RR weren't completely scared off the X layout by the Vulture - as evidenced by the Pennine that was designed a few years later, which also used a master and slave rod arrangement. That was also capable of revving to 3500rpm and making 2800hp from 2800 cubic inches.

I would suggest that had a reworking of the Vulture gone forward after 1941 they may have chosen to redo the crankcase to fit Merlin 2 piece blocks and heads. The bore spacing was different enough that the crankcase would need a reworking. They could maintain the Vulture's stroke of 5.5in to give around 3000 cubic inches capacity, or downsize to a 5in stroke and roughly 2750ci (Pennine used Merlin bore size with 5.08in stroke).

Not sure how the Pennine had the master rod. A few of the WW2 radials used single piece master rods and built up cranks (P&W R-2800, Wright R-2600, R-3350). Could possibly have been done for the Vulture - at the cost of crankshaft strength.

 

[vanir]

In 1941 the Vulture V was rated for takeoff at about 1800hp at 2850rpm with +6psi boost. The boost was kept low, and the rpm reduced due to reliability concerns. With the reliability fixed the rpm could be taken back up to the design maximum of 3200rpm, and RR could add more boost. By 1941 the Merlin had already gone to +12psi, and in 1942 the 60 series were cleared for +15 and then +18 by 1943. This was only possible with testing and strengthening of components to cope. If the Vulture had continued then it would have gone through teh same development cycle, resources permitting.

You're right, other engines will go through the same development process but the logic is intrinsically flawed by used a V12 base on a V24 as any kind of measure of what it's going to act like. You have a completely different engine with different dynamics. Just the dynamics for an inverted vee changes a little. A radial performs differently again (lot of horsepower from that stubby, jiggling crankshaft).

They have very different dynamics. The napier is closer to how the X24 is going to behave, it's a flat 24, like the way a Jag 12 is a better indication of how a Porsche flat 12 is going to behave on the track than a Porsche flat 6 even though the 12 is literally two 3.0 flat 6s bolted end to end. It doesn't act like it, it acts like a 12 and gives you the same troubles as a 12, not a 6.

Take the same measuring philosophy, the starfire 4 is a blue 6 with two cylinders chopped off. People turbo both. The 4 actually has a better piston/rod kit than the 6 so a lot of people swap them over. But you can still put 12psi boost on the stock 6 and won't manage more than 8psi on the 4. And calculating any hp relationship between the engines is going to be all over the place. The same timing changes will yield entirely different results. You don't set up a starfire 4 the same way as a blue 6 even if you're doing the same mods or have the same expectations. The motor just won't, they're different motors.

Napier is going to tell you what a cross vee is going to act like. A DB601 doesn't tell you what a DB610 acts like. A flat 24 is closer to an x24 than a v12.

It's all superfluous anyway, the Centaurus was the Vulture alternative (napier more a shared commitment). It found its way into production alongside the napier. Why the vulture again?

 

[vanir]

A Vulture powered Corsair

View attachment 180251

IIRC the R-2800 in the Corsair was angled to allow the pilot a better view over the nose. Is that correct?

With the Vulture that isn't necessary.

No it was designed with a "close fitted cowl" for this effect although the main concern was streamlining, achieved by putting the oil coolers in the wing roots. That would be the main reason the Corsair cowl looks comparatively slender. The problem was the prototype had the fuel tank behind the cockpit and the navy wanted it ahead of the cockpit. When it was all moved around it wound up with the rearward cockpit and long nose. The fix was by adding a raisable pilot seat like Grummans, birdcage corsairs don't have this.

Many aircraft in WW2 did have a nose down attitude in level flight, but this was for wing incidence during take off under heavy loading, not pilot view. Placement of the cockpit was usually about pilot view, and for the Corsair this was dictated by navy requirements rather than design preference.
The thrust line on a Corsair might very well be slightly downward, if so it would most likely be related to carrier launch performance with a heavily loaded plane.

 

[Shortround6]

I believe one iteration of the master rod had a pin on one side and two bolts on the other.

I would suggest that had a reworking of the Vulture gone forward after 1941 they may have chosen to redo the crankcase to fit Merlin 2 piece blocks and heads. The bore spacing was different enough that the crankcase would need a reworking. They could maintain the Vulture's stroke of 5.5in to give around 3000 cubic inches capacity, or downsize to a 5in stroke and roughly 2750ci (Pennine used Merlin bore size with 5.08in stroke).

Some sources claim the Vulture already used a bore spacing that would allow the use of Merlin pistons in a later development. But if you are having troubles with the connecting rods and crankshaft increasing the area of the pistons ( and the force transmitted) by 16.6% may not be a good idea.

Not sure how the Pennine had the master rod. A few of the WW2 radials used single piece master rods and built up cranks (P&W R-2800, Wright R-2600, R-3350). Could possibly have been done for the Vulture - at the cost of crankshaft strength.[/QUOTE]

V-12 and X-24 crankshafts are long and "whippy", even a two row radial has a very short crankshaft. A two row radial can be made in 3 pieces, a V-12/X-24 would have to be in 7 pieces. Hirth did it on some air cooled V-12s but such a crankshaft is very expensive to make.

 

[wuzak]

The Vulture bore spacing was 6.1 inches. The Merlin bore spacing was 6.075 inches. The Kestrel and Peregrine were 5.625 inches.

So yes, theoreticaly the Vulture could have used a Merlin bore.

However, if the Merlin blocks and heads were used the number of unique components for the Vulture would be considerably less.

 

[johnbr]

Me I would have put Vulture R/D money into the EXE engine.I would look at saving lbs and ad more boost.

 

[wuzak]

I don't know that too much weight could have been saved in the EXE.

Adding boost would have raised the power, no doubt, but may have required stronger reduction gear, which would add weight. I think the Exe would have benefitted from an epicyclic reduction gear to bring the prop shaft back to the cranklshaft centreline.

The problem for the Exe was that it was too small in capacity (1350ci) for too much development. The projected performance of the Exe was to be about 1500hp - not sure what boost would have been required for that. Still, that is impressive for an aircooled engine in terms of power to capacity.

The logical development for the Exe was the 2800ci Pennine, with around 2800hp and 2850lb of weight. But that came somewhat later.

 

[Shortround6]

The EXE really does not look like a good idea. The Peregrine was 21.2 liters while the EXE was 22.1 liters. Granted the EXE revs much higher but it weighs 400lbs more (granted it is air cooled) , uses twice as many pistons con rods and it uses sleeve valves. A VERY expensive engine to make.
It used an 8 to 1 compression ratio which may have given very good fuel economy although it would probably have to have been lowered in order to use much more boost. While the small cylinders do promote good cooling A Hercules XVI used a 7:1 compression ratio and about 8.5lbs of boost on 100/130 fuel.

Power figure for the EXE is for take-off. Max power at 5000ft and 15,000ft are given at 3800rpm instead of 4200rpm and using 3.5lbs of boost. Max climb power (30 minutes) is at 3600rpm and 3.5lbs boost. It did use a two speed supercharger which helped low altitude power quite a bit. 1100hp at 5,000ft at 3800rpm and 3.5lbs boost vs 950hp at 15,000ft same conditions. Peregrine could manage 885hp at 15,000ft. EXE offered 7.3% more power while using 4.2% more displacement. Now maybe the Peregrine did have more development than the EXE but the EXE was going to need several more years of development to be a production engine at any power level (sleeve valves weren't quite ready yet before 1940-41).

 

[johnbr]

I found this on the net today.Hope you all like it.Rolls Royce Vulture engine

 

[wuzak]

I found this on the net today.Hope you all like it.Rolls Royce Vulture engine

That looks like the Exe to me.

Separate cylinders. Lower exhaust outlets, exhaust manifolds rather than ejector exhausts.

Plugs in the top of the heads.

 

[nuuumannn]

Yep, I'd say the same. The Vulture had monobloc cylinder casings like the Merlin et al; these are clearly individual sleeve valve cylinder pots as on the Exe.

A little background. It was originally intended for the Fairey Barracuda and performed well in the Battle test bed, but consumed unusually large amounts of oil. First flown 30/11/38. 1,150 hp @ 4,200 rpm 24 cylinder 90 deg X layout, air cooled, sleeve valve. Bore/stroke 4.2 x 4.0 in, Vol 1,348 cu in (22.1 lt), two speed, single stage supercharged. Info from Lumsden; British piston engines and their aircraft.

Neat picture, John.