1936-1941: your best RAF

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I like the idea of a two speed supercharger for the Mercury, I am not so sure about improving the supercharger. I am not saying it could not be improved, just wondering what it buys you? The Mercury was about 83% the size of a Wright Cyclone. Find a Cyclone that makes 1000hp at 14,000feet. Cyclone's supercharger wasn't first rate either but there is only so much you can do with an engine the size of a Mercurey (it also needs a lot more fin area if you are going to try to get any more power out of it).
As explained in another post the the Hampden is more duplication of effort. Part of the problems with the Blenheim was that it was never really allowed to grow. Maybe it couldn't, but some of the later versions were certainly much heavier for little change in war load. The Blenheim was never really allowed to trade fuel for bomb load. It could carry 1000lbs about 1400 miles in the MK IV but no mention is made of what might be possible over the much shorter ranges. It would never come close to the Hampden but it might have been possible to carry 1500-2000lbs over short distances?

I will repeat myself in the case of the Battle, what 1000 to 1200 3 seat bomber crew trainers are you planning to build to replace the Battles in "training command" that you didn't build?







There were only 100 Herefords ordered, some may have left the production line as Hampdens. Others were converted after production. In the grand scheme there isn't much difference, less than 7% of actual production was even planned to be Herefords.
As for the Twin Wasp, get Alvis to take out a licence instead of going for the Gnome-Rhone engines. At least the Twin Wasp had a center Bearing on the crankshaft and didn't need a total redesign to be a 1940 engine
At least gets you a useable Beaufort much sooner.

The Whitley is an example of what was possible at certain times vs what was desirable. The Tiger Powered Whitley's were hidden away in training units well before the shooting started.
But when they were built there were no Merlin X engines to power them with, You might want to check to see exactly which Pegasus engines were available then. The prop situation sure didn't help engine out situations. I don't believe the Whitley ever got the Merlin XX.
In fact the two speed Pegasus might have been a year or more behind the two speed Tiger and if the shooting war had started in 1938 a few dozen Whitley's with Tiger engines may have been the extent of the RAFs Heavy bomber force. First Wellington MK Is don't get to an operational squadron until Oct 1938. The Whitleys replaced Heyford biplane bombers in their first 3 squadrons.

The Ensign didn't fly until 22 months after the first Whitley (and 31 months after the A.S. 23) so while it might have been the basis (or at least learning experience) for the A-S team it is much too late to equip much of anything in the way of active squadrons in 1938-39.

This what the British faced and this is what drove some of the decisions. Planes like the Whitley were not what was desired but they were what was possible and trying to wait for for better planes meant an Air Force that would be blasted from the skies without accomplishing much of anything if the shooting had started in 1938 or early 1939.
Granted the Luftwaffe wasn't that great either but anyone fancy their chances in that biplane against a Bf 109C?
 
Kevin J said:
IIRC the Stirling I as first delivered in 1940 only did 210 mph. You'd have to check that on thehistoryofwar site.
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Note the engine on prototype: Hecules II. It provided ~900 HP at 15000 ft, being outfitted with 1-speed S/C that gave max power down low - max power 1375 at just 4000 ft. 4x900 HP at 15000 ft will not propel the huge Stirling prototype well.
Series-produced Stirlings had much better engines, the Hercules VI, that made about 1500 HP at 15000-17000 ft.


Superchargers of Bristol engines were outfitted with straight vanes until ~1944, only Centaurus and series 100 Hercules received impellers with parrabolic vanes. For comparison, even the early V-1710 C series have had impellers with parrabolic vanes, let alone the Merlin I/II/III or DB 601.
(impeller of Mercury XV S/C, from here)
Cyclone that made 1000 HP at 14000 ft was installed on Martlet IV; Mercury was turning better RPM than that Cyclone.



FWIW, I fancy a torpedo-carrying Blenheim - max weight of Blenheim V went up by 4500+ lbs vs. Benheim I, so there was quite a stretch on the basic airframe.
It was not explained that Hampden was a duplication of effort

I will repeat myself in the case of the Battle, what 1000 to 1200 3 seat bomber crew trainers are you planning to build to replace the Battles in "training command" that you didn't build?
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Nothing, the Battles will rarely go in service units just to be killed by Germans, so the attrition is far smaller.


Annual of the British empire of 1938 lists the 2-speed supercharged Peagasus for all the world to see: link
Even the high-supercharged Pegasus offers same power/weight ratio for take off as the best Tiger, with less weight and far better reliability, and much better altitude power.


Without a 2-engined bomber to deal, A-W design team can put more effort into a 4-engined bomber.
Against Bf 109C, Blenheim will suffice, there is probably 5 of them for each Whitley in 1938/39.
 
IMO until the Bf 109E comes along in 1939, the Blenheim I with a top speed of 285 mph is more than adequate as a fast light bomber. Likewise against the Ki-27 in SE Asia up until 1941 when the Ki-43 is introduced. In the Mediterranean, against the G 50, again adequate until 1940. If you want to improve the performance of the Blenheim as a bomber why not put the 2 speed pegasus in it.
 
Kevin J said:
...
If you want to improve the performance of the Blenheim as a bomber why not put the 2 speed pegasus in it.
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The outright speed probably will not improve that much, due to Pegasus being a bulkier engine - 55 in diameter vs. ~51.5 in - while engine power high up was just around 5% greater. What should be much improved is payload capacity, a 2-speed S/Ced Pegasus was making about 20% more power down low than the original Mercury installed on most Blenheims.
OTOH, RR Merlin III, provided it can be installed without much of problems, should add much more. The Do-17 outgrowth to Do-215 saw speed increase by more than 15%.
 
tomo pauk said:
This is why I've said 'shop at Oerlikon'. They can sell actual cannons (so there is someting to install at aircraft and test it out), as well as licences already in 1936 - by what time the Hispano cannon was still undergoing tests in France.
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Can they?

Hispano got into the cannon business when Oerlikon could not deliver guns to the French fast enough. Hispano was building an Oerlikon under licence and thought he could do better.
 
Kevin J said:
The Hampden was more manoeuvrable than the Wellington, and you could put it into a dive, to dive bomb for greater accuracy.
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The Hampden may very well have been more maneuverable than the Wellington. However it was not more maneuverable than a fighter plane.
We may have very different ideas of what dive bombing was. Neither plane had dive brakes. Neither plane was stressed for a 5-6 G pullout (or even close)
BTW max speed for the Wellington MK I was 320mph I.A.S. I am assuming that is in a dive
This may actually be higher than the limit on the Hampden. At least according to one source.
Max angle for bomb clearance in a dive was 60 degrees and 20 degrees when climbing for the Wellington.
I am not suggesting using a Wellington in a steep dive but certainly some sort of diving attack could be done.

Wellington manuals are available on this site.
 
Shortround6 said:
...
Hispano got into the cannon business when Oerlikon could not deliver guns to the French fast enough. Hispano was building an Oerlikon under licence and thought he could do better.
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Perhaps the French judged that, if they will pay for cannons, these cannons might as well come out from their factory?
At any rate, UK government can make a deal to licence produce Oerlikon cannons and have a few dozens shipped to test, iron out the bugs and suggest improvements/modifications, all before the French even inform them about the Hispano cannon project, .
 

Most of the Bristol poppet valve engines rarely went over 5lbs of boost, those that did topped out below 7lbs. A better supercharger would have reduced power to drive it and heated the intake charge less but since the boost level was low (1200hp P & W R-1830s were using 9lbs of boost for take-off) the actual change in power is not going to be large.

tomo pauk said:
Nothing, the Battles will rarely go in service units just to be killed by Germans, so the attrition is far smaller.
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British lost about 200 Battles in France and very few in combat in Europe otherwise, accidents may be another story. Saving 200 or so Battles by not sending them to france does not make up for not building 1000-1200 planes.

That maybe so but announcements and/or listings don't always mean immediate production. The Merlin X engine was announced (with an engine on display) at the Nov/Dec 1938 Paris Airshow. Of the 7 Whitley squadrons in service on Sept 1 1939 only two were just starting to receive Whitley MK Vs with Merlin X engines.

tomo pauk said:
What should be much improved is payload capacity, a 2-speed S/Ced Pegasus was making about 20% more power down low than the original Mercury installed on most Blenheims.
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To some extent the ability to use 100 octane fuel made up for the failure to use a two speed supercharger on the Mercury. Take-off power went up by over 100 hp.
I don't know who knew what when but it seems like trying to put a two speed supercharger on the Mercury would have been a good idea in 1938/39 when supplies of 100 octane fuel were not exactly a sure thing.
 
British were aware of the Hispano project in either 1935 or 1936. A stumbling block was a failed attempt by a new company to licence Hispano engines and start production in England. The People at Hispano didn't trust the British at the beginning of the cannon negotiation.
 

Hampden's limit was 290 mph IAS.

Bomb clearance angles were the same as the Wellington.
 
Thank you.

I am not saying the Hampden was a bad plane like the Botha but rather, if people are looking to cut the number of different planes the British used, it is a candidate. It does a few things a bit better than the Wellington and few things a bit worse. It did take part in some historic actions but was it really irreplaceable?

It would have been harder to upgrade like the Wellington was and narrow fuselage was a drawback for long distance or long endurance flights.

For 1939-41/42 it may have been a perfectly acceptable use of resources.
 
Getting back to the guns. The British had decided that the Vickers and Lewis guns needed to be replaced. Vickers had managed to get the rifle caliber machine gun up to about 900rpm but it still had a higher number of jams (not breakages) than they wanted. This is what lead to the adoption of the Browning, an even higher rate of fire and fewer jams meaning the guns could be mounted out of reach of the pilot (or crew). Vickers was working on the "K" gun which had nothing to do with the belt fed Vickers and quite a bit to do with the Vickers-Berthier light machine gun. This gun was adopted for "observers" or basically any flexibly mounted gun to replace the Lewis. Since it fired over 50% faster it was a useful if not startling improvement. Things brings us to the decision points of the 1930s,
1. Adopt a heavy machine gun (12.7mm) and if so which one?
2. Adopt a shell firing cannon and if so, which one?
3. adopt both?

Much is made of the tests of the late 20s and early 30s but the American .50 was using much less powerful ammunition that it would use in WW II.
I would also note that by the late 30s the British army was looking around for a different gun than the old Vickers to use in armoured vehicles for two basic reasons. 1 was to rid of the water jacket and go to air cooling, the 2nd was to get a gun that jammed less or needed less access in the confines of an armoured vehicle turret or hull, enter the Besa gun/s. Not aircraft guns but just to show that the British were less than happy with reliability of the basic Vickers even though it's durability was legend (they are not the same thing).

Ideally the British should have taken the Browning and scaled it to take the British 12.7mm ammo and wound up with a gun much like the Japanese Ho-103. The Italians took the big Browning (basically) and set it up to fire basicly the British cartridge (added a small rim at the back) but failed to cut the weight significantly making for a very heavy gun for it's power.

However on a power for weight basis this theoretical gun (British Ho 103) fires about 2 1/2 times the metal of a .303 Browning but weighs just over twice as much. It is a subtle improvement for fighters but perhaps better for power turrets?

For the shell firing cannon there are only about 3 choices of which the danish Madsen can probably be ruled out. Oerlikon has 3 choices of cartridge and wight of gun in proportion.
But make sure you are comparing the early 30s guns to each other as some of the early Oerlikons were rather slow firing (a problem of the Madsen) and needed development work.
Some of the guns sold to Eastern European nations seem to have been taken out and replaced by machine guns? Germans viewed the Oerlikon as an interim gun. Then got stuck with it when the German gun/s took a bit longer in development and more resources were devoted to the Oerlikon which they then could not abandon quickly.

Can our "improved" RAF afford several interim guns so as to have the right gun in each year or period of the war?
 

That is all fair enough - I don't plan on pushing Mercury beyond 1000 HP, or Pegasus beyond 1100.

British lost about 200 Battles in France and very few in combat in Europe otherwise, accidents may be another story. Saving 200 or so Battles by not sending them to france does not make up for not building 1000-1200 planes.
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Making Merlin-engined Battles past even 500 pieces is not something I fancy. Stick something else in the nose (Pegasus, Mercury, Perseus) and then make another 700-800 of such Battles as trainers, use Merlins on 1st line aircraft from here on.
Perhaps a good idea would've been to farm out production of the Battle to Canada.


The 'Air Annual of British Empire' of 1938 does not mention any Merlin bar the Mk.II, however two types of 2-speed S/Ced Pegasus are listed.
Prototype(s) of 4-engined bomber can use whatever engine type the prototypes of Wellington and Hampden used.


Thank you.
 
Engine situation.
We've discussed Bristol a lot. Not making Taurus leaves more time & resources for Hercules to be perfected and produced earlier.
Rolls Royce: no Exe, Peregrine and Vulture? Again. this leaves more resources for perfecting the Merlin, and possibly militarize the R engine? Best case would've probably been that there is more of 'Hooker's Merlin's' available in 1940, with 2-stage Merlins being installed in Spitfires by late 1941. Merlin will also need better carb ASAP (improves performance a bit, no negative G problems, easier to deal with carb icing), as well as the less draggy exhausts, at least on fighters.
Not sure what Napier to produce. Something simple, yet useful from Bristols? For better or worse, between September 1939 and December 1941, Napier engines powered zero 1st line aircraft, even the 2ndline aircraft were mostly using something else.
 
While not making the Taurus frees up some resources I am not sure it does the Hercules much good. Some yes but the big hang up was mass producing the sleeves and having them stay round. They either were right on the edge of being round when installed or went out of round in just few dozen hours.
Legend has it that the problem was "solved" when a workman accidently used a couple of grinding wheels in the wrong order (several hundred combinations of materials and manufacturing processes had already been tried). Wither they would have stumbled on this solution earlier or discovered it (or an alternative) after another few hundred tries I wouldn't want to guess. But it does cast doubt on the more resources speeding things up, it could have gone either way, speeded up or historical time line despite more effort.

tomo pauk said:
Rolls Royce: no Exe, Peregrine and Vulture? Again. this leaves more resources for perfecting the Merlin, and possibly militarize the R engine?
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Well, the "R" was a beefed up Buzzard modified for racing, the Griffon used the same bore and stoke as both of them but the externals were repackaged to make it fit smaller cowls.
A vast oversimplification but one could say the Griffon was a militarized "R" anyway.
The Merlin by 1939/40 didn't need a whole lot of "perfecting" as opposed to developing. Semantics one might say but the work on the Speed Spit showed that the basic Merlin was much stronger than needed for the existing power levels and a lot of room for growth without much modification. How to get that power with service aviation fuel instead of a special racing brew was the question. Until you can develop the fuel needed to support the higher pressure ratios you are kind of stuck. Wiki gives the followong for th efuel used in one of the "R"s.
" 30% benzole, 60% methanol, 10% acetone, plus 4.2 cc of tetra-ethyl lead per gallon" and we have problems using this to develop engines because the fuel to air ratios are going to be off, The heat of vaporization is going to be off and the heat value per gallon is going to be off. Just taking the methanol, it has much less heat value per gallon but works well as a racing fuel because one gallon of Methanol needs very roughly 1/2 the amount of air that one gallon of gasoline needs so on a power per 100lbs (or 1000lb) of air basis the Methanol comes out ahead. Really helping things is the fact that Methanol has much higher latent heat of vaporization so the intake charge is cooler (and indeed the temperature inside the cylinder is cooler, helping the cooling problem). Some of these race engines were also started on one set of spark plugs and then the plugs were changed to the "service/race" plugs once the engine was warmed up. In part to avoid lead fouling the plugs while the engine warmed up but the service plugs were a different heat range.
To get more of "Hooker's Merlins" you have to hire Hooker earlier
 

Bristol has process of sleeves well under control by our start date here - start of 1936. They are making Perseus already by several years. It was Napier that had problems making durable sleeves.
Problem with Bristol was that they were making and/or improving 5 engine types by 1939 (three featuring sleeve valves), and each of the types was required by RAF/AM for aircraft they were intendint to send in harm's way. Compare with RR making one for 1-st line aircraft.

To get more of "Hooker's Merlins" you have to hire Hooker earlier
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Agreed pretty much.
 
tomo pauk said:
Bristol has process of sleeves well under control by our start date here - start of 1936. They are making Perseus already by several years. It was Napier that had problems making durable sleeves.
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Actually they didn't. They were able to make sleeve valves in small numbers during the early and mid 30s but with the huge increase in production needed quality fell off. The majority of the Perseus engines going into planes that started entering service in late 1938/ealy 1939. Throw in the Hercules production (and Taurus) and the mass production of sleeves overwhelmed Bristol. Bristol did get it figured out but only shared it's knowledge with Napier under pressure from the government. (and then under protest). Napier had a similar problem. They could build hand fitted prototype engines that performed well but when trying to deal with increased production that required truly interchangeable parts things went sideways in a hurry.



Improvements to the poppet valve engines were pretty much limited to figuring out what they needed to run on 100 octane fuel, like if they needed different spark plugs or any problems like with the valves burning. Increases in power were obtained but max boost only went up around 2lbs. No attempt was made to increase the cylinder/head fins or any other changes that would allow for any real increase in power (the Mercury increases were as good as it got).
RR was making 3 engines. in 1939/40 the Vulture was still considered a first class engine.
We know now that the Manchester wasn't a first line aircraft but it was considered one in 1939/40.

I would suggest reading "I Kept No Diary" by AIr Commodore F.R. Banks for one man's point of view on the British air industry in WW II. This is the man who came up with the fuels used in the Schneider cup racers, the Speed Spitfire and others. He was also put in charge of Sabre development about the time English Electric took over from Napiers. British manufacturing was in pretty chaotic state in the early part of the war.
 

Let's agree there.
Cancelling Botha frees another 1100+ Perseus engines, so there is a lot of slack the Hurricane production can pick up early on - they shared the bore & stroke.


That again raises the question - what should Napier be making in these 5 years?


UK out-produced Germany, Italy and Japan combined between 1939 and 1943 - not a small feat for a country with pretty chaotic state of manufacturing.
Granted, all of the 4 countries could improve on that - hence this sub-forum
 
284 Botha's were built so we'd could have another 568 Skuas to deploy in SE Asia and the Pacific.
 
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