Build an improved Gloster F5/34

Shortround6 · Jan 23, 2025

Admiral Beez said:
They have the F5/34 prototypes, drawings, preliminary tooling.

They have the F5/34 prototypes
When????
The 2nd F5/34 didn't fly until March 1938. In Sept 1937 the Australians were flying the fixed landing gear NA-16-1A supplied by NA and they were assembling the NA-16-2K with retracting landing gear, also supplied by NA. So in Australia they had two airframes either flying or being assembled while the F5/34s were still in England.
drawings
Drawings are drawings. They are not parts or manufacturing capability. Remember the 600 companies/ sub-contractors involved in the Wirraway production? You want to sellect a more complicated airplane to manufacture?
preliminary tooling
What preliminary tooling?
This is one of the reasons for big delays between adoption of an aircraft and first production example, unless ordered off the drawing board. And even that can take a year or more.
There is no production tooling for prototype aircraft. Prototype aircraft are built using general purpose tooling. This is why it takes so long to make prototypes. You need skilled workmen had fitting/bending/cutting just about everything.

Admiral Beez said:
Plus part of the Australian deal with Hawker to acquire their Gloster F5 could be to receive development and production support.

What support did NA provide the Australians?

Admiral Beez said:
Perhaps Folland, having resigned from Hawker in 1937 can be persuaded to continue his aircraft's development in Oz.

So Folland cancels his purchase of British Marine Aircraft Company and any hopes of staying in the Aviation business in the UK and sails to Australia to become the lead designer for CAC? With their small contract of around 40-100 planes? With a single seat fighter and not a general purpose (trainer/light bomber)?

Admiral Beez said:
We can definitely find reasons why an Oz Twin Wasp F5 would not, could not or should not have occurred. That's easy.

It is easy.
Trying to twist history and time over 5 years to come up with a not very good airplane for Australian use in 1942 is hard.

Admiral Beez said:
With this in hand, a Bristol-powered F5 should be in production in Australia by 1940, leading to a P&W version by 1942.

Powered by what? It is easy to say Bristol-powered F5 but which Bristol engine and made by who?
Maybe England can send out a few dozen Mercury engines, maybe not.
Are the Australians buying engine making machinery from America?
The main reason for this whole aircraft built in Australia thing is the idea that the England could not/would not supply Australia with either enough aircraft or the production ability
as things got hotter in Europe.
American machines can make Mercury engines. Bristol had enough trouble trying to make the sleeve valve engines in the Bristol factory. Pegasus or Taurus engine production in Oz would have been a horror show at the start. Bristol could not make sleeve valves on a mass production basis in 1939/early 40?
Even if you can get the sleeve valve engines from England (not sunk by U-boat) neither the Pegasus or Taurus engines are going to give you much more than cannon fodder against the A6M2 Zero in early 1942. How many pre P&W planes flying in Dec 1941 vs how many P&W powered planes?

The F5/34 may have been a bit ahead of it's time in 1936 in some ways and a bit behind in a few others. But it was well behind the times in 1939-40 in just about everything except cockpit vision.
The P&W Wasp engine used in the Wirraway dated from 1926 with improvements over the years. It was a tried, true and not complicated engine well suited for a beginning company to get it's feet wet. Trying to detour to Bristol engine and then go back to a P&W engine was not going to make things easier.

yulzari · Jan 23, 2025

Shortround6 said:
Pegasus or Taurus engine production in Oz would have been a horror show at the start.

I am unsure why a Pegasus would be as you say. Licence built by PZL and Alfa Romeo who both went on to ultimately develop it further than Bristol did but a solid choice off the shelf as is. Other than having (commendably) four valves per cylinder it is deeply conventional.

Shortround6 · Jan 23, 2025

yulzari said:
I am unsure why a Pegasus would be as you say. Licence built by PZL and Alfa Romeo who both went on to ultimately develop it further than Bristol did but a solid choice off the shelf as is. Other than having (commendably) four valves per cylinder it is deeply conventional.

You are correct.
I switched the Pegasus with the Perseus, my mistake.
The Perseus being the intended engine for the F5/34.
The Perseus never seemed to get a large increase in power over the Mercury engine that was promised, it did get an increase but not what was hoped?
And by using the same cylinders as the Hercules it was subject to the same teething problems that the Hercules had.
Perseus was a bit earlier and the low production engines seem to have been OK?
Later production engines may have been fine.
But trying to get the Australians to build sleeve valve cylinders in 1939/40 when some of the Bristol cylinders in the Hercules were having trouble lasting more than 20-30 hours?

yulzari · Jan 23, 2025

Shortround6 said:
You are correct.
I switched the Pegasus with the Perseus, my mistake.
The Perseus being the intended engine for the F5/34.
The Perseus never seemed to get a large increase in power over the Mercury engine that was promised, it did get an increase but not what was hoped?
And by using the same cylinders as the Hercules it was subject to the same teething problems that the Hercules had.
Perseus was a bit earlier and the low production engines seem to have been OK?
Later production engines may have been fine.
But trying to get the Australians to build sleeve valve cylinders in 1939/40 when some of the Bristol cylinders in the Hercules were having trouble lasting more than 20-30 hours?

Oh quite. Sleeve valves would be a very large step too far.

GTX · Jan 23, 2025

Shortround6 said:
Powered by what? It is easy to say Bristol-powered F5 but which Bristol engine and made by who?
Maybe England can send out a few dozen Mercury engines, maybe not.
Are the Australians buying engine making machinery from America?

Well, if we use the real world as an example, the first Australian manufactured P&W R-1430 Wasp engine performed a test run on 21 December 1938. This was all part of the rapid build up in capability stemming from the Lawrence Wackett led technical mission to Europe and the United States in 1936. The degree to which he and ones like Essington Lewis created the Australian Aerospace industry in the late '30s/early '40s from next to nothin is an incredible story. Not only were they setting up for aircraft and engine manufacturing but they also had to create factories for these, but also supporting elements such as smelters, tool makers etc. Not to mention all the training for the staff involved.

Under the scenario of this thread, one could conceivably have the technical mission recommend some Gloster products instead of the Nth American ones. This would of course be dependent upon licence sharing and the like. Presuming this was achieved than one could conceivably have the Bristol Mercury enter production. This was also used on RAAF Bulldogs so there would be some benefit there. The Mercury could be conceivablky followed by the Taurus for use on a developed Gloster F5/34 (as the CAC Boomerang) as well as on DAP Beauforts. Further developments might even to produce the Hercules (for DAP Beaufort's and possibly a more developed Boomerang) and even Centaurus (CA-15?).

Admiral Beez · Jan 23, 2025

Shortround6 said:
What support did NA provide the Australians?

I don't know. Can you tell us?

SaparotRob · Jan 24, 2025

Shortround6 said:
They have the F5/34 prototypes
When????
The 2nd F5/34 didn't fly until March 1938. In Sept 1937 the Australians were flying the fixed landing gear NA-16-1A supplied by NA and they were assembling the NA-16-2K with retracting landing gear, also supplied by NA. So in Australia they had two airframes either flying or being assembled while the F5/34s were still in England.
drawings
Drawings are drawings. They are not parts or manufacturing capability. Remember the 600 companies/ sub-contractors involved in the Wirraway production? You want to sellect a more complicated airplane to manufacture?
preliminary tooling
What preliminary tooling?
This is one of the reasons for big delays between adoption of an aircraft and first production example, unless ordered off the drawing board. And even that can take a year or more.
There is no production tooling for prototype aircraft. Prototype aircraft are built using general purpose tooling. This is why it takes so long to make prototypes. You need skilled workmen had fitting/bending/cutting just about everything.

What support did NA provide the Australians?

So Folland cancels his purchase of British Marine Aircraft Company and any hopes of staying in the Aviation business in the UK and sails to Australia to become the lead designer for CAC? With their small contract of around 40-100 planes? With a single seat fighter and not a general purpose (trainer/light bomber)?

It is easy.
Trying to twist history and time over 5 years to come up with a not very good airplane for Australian use in 1942 is hard.

Powered by what? It is easy to say Bristol-powered F5 but which Bristol engine and made by who?
Maybe England can send out a few dozen Mercury engines, maybe not.
Are the Australians buying engine making machinery from America?
The main reason for this whole aircraft built in Australia thing is the idea that the England could not/would not supply Australia with either enough aircraft or the production ability
as things got hotter in Europe.
American machines can make Mercury engines. Bristol had enough trouble trying to make the sleeve valve engines in the Bristol factory. Pegasus or Taurus engine production in Oz would have been a horror show at the start. Bristol could not make sleeve valves on a mass production basis in 1939/early 40?
Even if you can get the sleeve valve engines from England (not sunk by U-boat) neither the Pegasus or Taurus engines are going to give you much more than cannon fodder against the A6M2 Zero in early 1942. How many pre P&W planes flying in Dec 1941 vs how many P&W powered planes?

The F5/34 may have been a bit ahead of it's time in 1936 in some ways and a bit behind in a few others. But it was well behind the times in 1939-40 in just about everything except cockpit vision.
The P&W Wasp engine used in the Wirraway dated from 1926 with improvements over the years. It was a tried, true and not complicated engine well suited for a beginning company to get it's feet wet. Trying to detour to Bristol engine and then go back to a P&W engine was not going to make things easier.

Shortround6 · Jan 24, 2025

GTX said:
Well, if we use the real world as an example, the first Australian manufactured P&W R-1430 Wasp engine performed a test run on 21 December 1938. This was all part of the rapid build up in capability stemming from the Lawrence Wackett led technical mission to Europe and the United States in 1936. The degree to which he and ones like Essington Lewis created the Australian Aerospace industry in the late '30s/early '40s from next to nothin is an incredible story. Not only were they setting up for aircraft and engine manufacturing but they also had to create factories for these, but also supporting elements such as smelters, tool makers etc. Not to mention all the training for the staff involved.

Well said. What they did was truly incredible. Speeding the whole thing up or trying to make more difficult products (airframes or engines) might have actually delayed things.

GTX said:
Under the scenario of this thread, one could conceivably have the technical mission recommend some Gloster products instead of the Nth American ones. This would of course be dependent upon licence sharing and the like. Presuming this was achieved than one could conceivably have the Bristol Mercury enter production. This was also used on RAAF Bulldogs so there would be some benefit there.

This requires either Gloster or parent Hawker to actually have a viable product in the pipeline at the critical time in question. Dusting off the drawings for a 1932 3 seat torpedo bomber is not what the Australians are looking for? Or buying up the rights for Australian production for Hart biplane derivative? Hawker has two families of aircraft in hand at the time. The Harts coming to their end and the Hurricane and bigger winged Henley/Hotspur but trying to fly that family with non RR engines in 1937-39? Gloster had the Gladiator and the F5/34.
No Gloster light bomber or general purpose planes or advanced trainers.
This is also a difficult time for Bristol. Just enough R&D to keep the poppet valve engines from falling too far behind but not enough really look good for the future. And the whole sleeve valve thing. It might be the wave of the future, it might be a colossal failure. Which way does Australia bet? They will not be able to play a 2nd hand.
Wiki on the Perseus is more than a bit biased.
"The first production versions of the Perseus were rated at 580 horsepower (433 kW), the same as the Mercury model for that year, which shows that the sleeve system was being underexploited. The engine was quickly uprated as improvements were introduced and by 1936 the Perseus was delivering 810 hp (604 kW), eventually topping out at 930 hp (690 kW) in 1939, while the Perseus 100 with an increased capacity of 1,635 cu in (26.8 L), produced 1,200 hp (890 kW) at 2,700 rpm at 4,250 ft (1,296 m).[3] This far outperformed even the most developed versions of the Mercury."
This starts out historically correct but veers into fantasy land at the end. The 580hp was in 1932/33 and aside from being tested in one or two airplanes at a time, the Perseus doesn't show up in quantity until 1936-37 (?) and quantity is questionable. There were 42 Empire class C flying boats build but out of 42 only 7 had Perseus engines. There were around 200 Vickers Vildebeests built, 18 had Perseus engines and 12 of the them were fobbed off onto New Zealand. The Botha, Skua/Roc saga starts in 1939 which is rather late for the Australians to take it into consideration in 1937-38. The Perseus 100 is almost an Aviation unicorn. Doesn't show up until the end of the war (?) supposedly using Centaurs cylinders.
And there don't seem to be any photos of the actual engine? Lots of press releases.

GTX said:
The Mercury could be conceivablky followed by the Taurus for use on a developed Gloster F5/34 (as the CAC Boomerang) as well as on DAP Beauforts. Further developments might even to produce the Hercules (for DAP Beaufort's and possibly a more developed Boomerang) and even Centaurus (CA-15?).

The Mercury is not really a good development path to the Taurus and while unknown at the time, the Taurus was a path to nowhere.
Just because you can make a radial engine does not mean that any of the production tooling transfers over to a significantly different sized engine. Maybe you can adapt a small amount?
The Taurus had cooling problems in 1940 and we are guessing as to what they did solve them. And that was at the home factory.
One thing we do know, they only used the engine in the very low altitude role. OK for a torpedo plane, not so good for the only fighter plane being made in all of Australia.
Best they ever got out of it in a production engine was 1130hp at 3500ft and that was with 100/130 fuel (?). Now this means it is going to be around 20% lower in power at 13500ft and around 40% lower in power in the low 20,000ft range.
This may not have been a supercharger problem only. IF you don't have enough cooling fins trying make big power in thinner air doesn't end well.
Bristol may not have had the R&D staff to handle the Taurus and the Hercules at the same time in 1939-40 and by 1941 nobody was ordering new planes with 25 liter air cooled engine. The Market had passed the Taurus by.

GTX · Jan 24, 2025

Not disagreeing with anything there - in the real world I believe they made the right choice aligning with Nth American. Had to do some stretching to make this whatif scenario work...

Some interesting related relevant commentary from the real world here involving the Beaufort production:

The Mission proposed a joint order by the Australian and British Governments of 180 Beauforts with no guarantee of follow-on orders. The project envisaged assembly from imported parts, rather than manufacture. The production timetable was optimistic with the first Beaufort to be produced in 1940, despite the aircraft and its sleeve valve Taurus engine experiencing developmental problems.
The Taurus problems were well-known, for in January 1939 Wackett had already suggested that the Beaufort be re-engined with the P&W R-1830 twin row Wasp, a 20 per cent more powerful engine. The twin row Wasp could readily be manufactured by CAC and it was cheaper. The British Mission argued that the Beaufort already had sufficient power and that sleeve valve technology was the way of the future.

The Lyons Government ignored all the technical advice and accepted the recommendations of the British Air Mission. The only qualification was that CAC be allowed to manufacture the twin row Wasp as assurance against failure of the Taurus.

The British Mission was only interested in the re-establishment of British aircraft technology in Australia and they tapped into veins of similar thinking in the Australian Government and bureaucracy. The Mission played a hard game of self-interest by having nothing to do with CAC and Wackett in particular. Wackett was even made the subject of some discreet adverse comment. The British Mission not unnaturally recommended a solution that was advantageous to British interests. The Australian Government and its advisers were foolish not to anticipate this. The Australian Government had a responsibility at least to analyse the proposal from a perspective of Australia's interests; it neglected this responsibility.

The Government decided to establish the Aircraft Construction Branch of the Department of Supply and Development to assemble the Beaufort. CAC, faced with being idle by mid-1940, sought orders for whole Beauforts. This was denied although CAC was offered the prospect of orders for sub-assemblies.
The Menzies Government came to power following the death of Lyons in April 1939. One of its early tasks was to consider on 23 May a submission from the new Minister for Supply and Development, Richard Casey, for CAC to build only the twin row Wasp for the Beaufort. Casey, who had some insight into technical matters, accepted the logic that the 1200 hp twin row Wasp, which used 50 per cent of the parts from the single row Wasp already being built by CAC, was the best operational and engineering solution.
The Menzies Government, apparently on the advice of the British High Commissioner, rejected the approach and determined that CAC was to build the 1000 hp sleeve valve Taurus. Casey was embarrassed, the Air Board again went to ground and CAC was put further out on a limb.
At a CAC Board meeting on 17 June 1939, the Chairman of CAC, Harold Darling who had replaced Essington Lewis, pointed out to Casey that: 'The Company had built up a technique which CAC considered was very desirable from the Australian point of view. All Australian materials were used except aluminium ingot. The whole engine can be built in Australia except magnetos... It took two and a half years to build up this technique and CAC now feels that all their efforts are now discounted. Gear cutting machines are useless for the manufacture of sleeve valve engines; fully 50 per cent of the engine plant will be useless.'
The ironic situation facing CAC was that after production of the 130 Wirraways, its only order was for the Taurus engine—an engine that CAC did not presently have the capacity to build.
The Air Board monitored the routine Air Ministry technical summaries, which continued to report the problems with the Taurus. But prior to re-approaching the Government, the Air Board astutely had the Air Ministry agree that it would be desirable to manufacture the twin row Wasp in Australia. The British soon advised that they could only supply 100 of the 250 Taurus engines promised. Prime Minister Menzies agreed the decision on 31 October 1939 to manufacture the twin row Wasp at CAC. Notwithstanding, some in the Aircraft Construction Branch still attempted a rearguard action to stick with the Taurus.
In this ill-informed and incoherent way, the Australian Government arrived at the decision to embark on Australia's largest and most difficult manufacturing project—the manufacture of the Beaufort bomber complete with its Pratt & Whitney twin row radial engines. It did not bode well for the success of the project.

https://airpower.airforce.gov.au/sites/default/files/2021-03/WP12-The-Australian-Aviation-Industry.pdf

Admiral Beez · Jan 24, 2025

GTX said:
Had to do some stretching to make this whatif scenario work...

Agreed. But getting the F5/34 out of the hands of Gloster's new owner Hawker is the best path to viability. If we go to Australia, we need to swap out their Bristols for locally-made engines, like the Twin Wasp. I can't see any other country wanting it - maybe CC&F in Canada instead of their dead end Gregor FDB-1.

I'd like to have seen what the F5/34 could do with its originally-spec Bristol Perseus, but having undergone aerodynamic refinement to reduce form drag from the undercarriage (and other protruding components) and interference drag (caused by the junctions of different surfaces). So, clean it up, put on the intended engine, and we might get the best single-seat, monoplane, radial-engined fighter out of Europe until the Fw 190 enters service in Aug 1941. Though the competition is still stiff, especially with the underpowered Perseus, including the Bloch MB.150-155 series, Reggiane Re.2000, Macchi C.200, Fiat G.50, PZL P.11 and Polikarpov I-16. There's also the IAR 80, but it's a later design arriving around the same time as the Fw 190.

Shortround6 · Jan 26, 2025

Admiral Beez said:
Agreed. But getting the F5/34 out of the hands of Gloster's new owner Hawker is the best path to viability

Is this about saving the F5/34 or getting Australia a useable fighter, not really the same thing.

Admiral Beez said:
If we go to Australia, we need to swap out their Bristols for locally-made engines, like the Twin Wasp.

We are back to the time warp. There are no locally-made Twin Wasps until 1941(?), If you start building Twin Wasps in Australia in 1938-39 they are not the 1100-1200hp versions and the early Twin Wasps were very low altitude engines in general.

Admiral Beez said:
I'd like to have seen what the F5/34 could do with its originally-spec Bristol Perseus,

About the same, unless you have drunk deeply of the sleeve valve kool-aid and believe sleeve valves are a good substitute for high octane fuel, lots of boost from good superchargers and better cooling than poppet valve engines.

Admiral Beez said:
Though the competition is still stiff, especially with the underpowered Perseus, including the Bloch MB.150-155 series, Reggiane Re.2000, Macchi C.200, Fiat G.50, PZL P.11 and Polikarpov I-16.

Expecting a 9 cylinder, under 900hp engine in a plane with a thick 230sq ft wing to out perform Bloch 152 (1080-1100hp/186 sq ft) or Re 2000 is tough. The C 200 and G.50 are easier but that is not saying much. Beating the PZL P.11 is a really, really, really low bar.

I do wonder what a 'production' F5/34 would have done for performance. It seems that the Hurricane and Spitfire both gained 4-600lbs from prototype to early service versions? Not all of which can be attributed to changing the propellers. And this is before fitting them with even sketchy protection for the fuel tanks and BP glass and an armored seat back.

Zmauky · Jan 26, 2025

It seems to me that the Gloster F.5/34 was designed at exactly the wrong time.
Yes, it is a step above the Fury and Gladiator with 650-850 hp, but also a good step below the 1000+ hp Merlin chased Hurricane (and Spitfire). The comparison with the (then) Bf 109 is a little weirder (or more favorable) because of the Jumo 210, which is the Kestrel/Mercury generation in terms of power.

If Bristol (or someone else) had managed to develop a 14-cylinder Mercury (with 50% more volume, weight and power), the story would certainly be different. The Gloster F.5/34 probably shouldn't grow in size, of course it would be much heavier, but the 1200-1300 hp 14 cylinder Mercury would nullify that.
Yes Hercules ... but Bristol got tangled up in long development and forgot the KISS principle. It may be normal to want your next engine to be a also a technological step better than the competition, but for that you usually have to sacrifice time, and that same competition never sleeps and a wrong assessment is critical.
One could say that an almost identical parallel existed in Germany with the Bramo /BMW - double row 14 cylinder version of 323 or 123 so 1300+ hp Do 17/He 111 or the Fw 190 in 1939?

Shortround6 · Jan 26, 2025

Zmauky said:
If Bristol (or someone else) had managed to develop a 14-cylinder Mercury (with 50% more volume, weight and power)

The Mercury and the Perseus and the Hercules all used the same size cylinders, the nearly incestuous 146mm x 165 mm size also used by the G-R 7, 9 and 14 cylinder engines and their clones, licensees.
Only the Hercules was developed with a bottom end to handle 1400-1800hp so weights get a somewhat convoluted.

The F5/34 just seems a little (or a lot) too good to be true.
Thick wing, much like the Hurricane, but actual taper could be different.
High drag landing gear.
No exhaust thrust.
Not great cowl.

And yet it is just about the fastest radial engine fighter of it's time or for several years after for it's installed power????
Hurricane has a larger wing but it needs 19% more power to go the same speed (not including the exhaust thrust) ???

Zmauky · Jan 26, 2025

The reason for mentioning the 14 cylinder Mercury is that the Mercury worked reliably (unlike its sleeve valve cunterpart) and the Hercules is a sleeve valve so ... and we know when it was finally ready for mass production.
True, the Perseus was more powerful than its poppet valve cousin the Mercury but by the time the Hercules was ready for installation in the critical years of '38-41 maybe 14 cylinder Mercury would be ready.
The 14 cylinder Mercury would certainly have found a field of application perhaps for the Gloster F5/34 if not for the Hurricane, Battle, Blenheim cousins ...

Admiral Beez · Jan 26, 2025

Zmauky said:
The 14 cylinder Mercury would certainly have found a field of application perhaps for the Gloster F5/34 if not for the Hurricane, Battle, Blenheim cousins ...

Britain did produce a poppet valve-actuated 14 cylinder, double-row, air-cooled radial engine, just not Bristol.

Armstrong Siddeley Tiger - Wikipedia

en.wikipedia.org

If only Armstrong-Siddeley had a backer or merged with a larger firm to develop their Tiger into P&W Twin Wasp territory, including ditching the "bearingless" crankshaft. That'll give those sleeve valve obsessed folks at Bristol something to think about.

Shortround6 · Jan 26, 2025

Admiral Beez said:
Britain did produce a poppet valve-actuated 14 cylinder, double-row, air-cooled radial engine, just not Bristol.

If only Armstrong-Siddeley had a backer or merged with a larger firm to develop their Tiger into P&W Twin Wasp territory. That'll give those sleeve valve obsessed folks at Bristol something to think about.

Mercury/Perseus....................25 liters/2750rpm.........................around 1100lbs for the Perseus
Tiger..........................................32.7 liters/2450rpm.................................1300lbs
Twin Wasp...............................30 liters/2700rpm.....................................1460lbs
Hercules...................................38.7 liters/2800rpm ...............................1845lbs
G-R 14 N.................................38.7 liters/2400rpm (?)...........................1370lbs

The Tiger had no center bearing. Neither does the GR 14.
There is no developing the Tiger into a much better engine. Throw it out and start over. You need a new crankcase and crankshaft, you need new cylinder barrels, even if you keep the same bore and stroke you need longer, skinner fins, you need new cylinder heads, stronger and with better cooling. You need a new supercharger. You are going to need new pistons and connecting rods and so on.
And after you have done all of that and taken several years, if you are lucky you have an engine that is roughly equal to the R-2000 engine used in the C-54 transport plane.
Which in the rare versions that had two speed superchargers was good for 1100hp at 16,000ft. It also weighed 1580lbs.
The GR 14R with the 3 bearing crankshaft wound up weighing 1800lbs post war.

Now if you are the British do you actually spend any money at all on the Tiger? In 1938/39 the British banned all over water flights by Tiger powered Whitley's in training.
The Blackburn Sharks that had them were plagued by oil leaks and having spark plugs unscrew in flight and other/more minor troubles.

The Twin Wasp was only about 20% larger in displacement than the Mercury. You need a bigger engine to a first rate fighter in late 1941 or in 1942 in the west.
Japanese stuck with the 27.9liter Sakae way too long.

Elvis · Jan 26, 2025

Admiral Beez said:
Agreed. But getting the F5/34 out of the hands of Gloster's new owner Hawker is the best path to viability. If we go to Australia, we need to swap out their Bristols for locally-made engines, like the Twin Wasp. I can't see any other country wanting it - maybe CC&F in Canada instead of their dead end Gregor FDB-1.[/B]

Admiral Beez, what do you think of using the Twin Wasp Junior?
Technology is similar to its big brother, the Twin Wasp, so the Aussie's would already be familiar with the construction technique.
Displacement is slightly more than the Mercury (1535 vs 1520).
Dimensions yield less frontal area (44.13" diameter vs 51.5" diameter), but only slightly longer (53.27" vs 47")
Weight appears to be slightly less than the Pegasus engine (1087 lbs. vs 1111 lbs.) and way less than the R-1830 (1087 vs. 1438 lbs.).
Power is roughly the same as the Mercury, but it seems the 1535 was never developed to the point of utilizing a two speed/two stage supercharger. I'm thinking if one could implement that, it's possible to achieve a similar power increase to the Twin Wasp. That should put the R-1535 at around 1000 HP.
Anyway, just another idea I thought I'd throw out there.

P.S. - Just noticed the "14-cylinder Mercury" side conversation. Wouldn't this be that, or a fairly close approximation, anyway?

Shortround6 · Jan 26, 2025

Elvis said:
Twin Wasp Junior

It was nearly an orphan. By the far the largest customer was the US Navy who were entranced by the small diameter and view over the nose. P & W in the late 30s realized they were fooling around with too many engines at the same time and they axed the R-1535 from R & D while completing existing contracts.

Elvis said:
Technology is similar to its big brother, the Twin Wasp, so the Aussie's would already be familiar with the construction technique.

We are getting into the time warp again. Aussies are familiar with P & W R-1340 Wasp several years before they try making the Twin Wasp. Please note the names are not strictly accurate. The Twin Wasp actually uses slightly smaller cylinders than the Wasp. The R-2800 Double Wasp uses the same diameter cylinders as the Wasp but a bit longer stoke. Cylinders and cylinder heads are not interchangeable.

Elvis said:
That should put the R-1535 at around 1000 HP.

And that is why P & W gave up on it. They had a 600 hp Wasp, they had a 1000-1200hp Twin Wasp. The market for a 900-1000hp Twin Wasp Junior was small. P&W also abandoned the R-2180 Twin Hornet at about the same time. P&W was also still selling a trickle of R-1690 9 cylinder Hornets for customers that wanted an 875hp engine that was fatter but cheaper. Some went into Lockheed 14s and 18s.
They gave up on the R-2180 because it did use the same cylinders as the R-2800 and it was just about the same diameter so you could get about 28% more power for the same frontal area. They wanted to beat the Wright R-2600 and not trail behind it.

Admiral Beez · Jan 27, 2025

Elvis said:
Admiral Beez, what do you think of using the Twin Wasp Junior?
Technology is similar to its big brother, the Twin Wasp, so the Aussie's would already be familiar with the construction technique.
Displacement is slightly more than the Mercury (1535 vs 1520).
Dimensions yield less frontal area (44.13" diameter vs 51.5" diameter), but only slightly longer (53.27" vs 47")
Weight appears to be slightly less than the Pegasus engine (1087 lbs. vs 1111 lbs.) and way less than the R-1830 (1087 vs. 1438 lbs.).
Power is roughly the same as the Mercury, but it seems the 1535 was never developed to the point of utilizing a two speed/two stage supercharger. I'm thinking if one could implement that, it's possible to achieve a similar power increase to the Twin Wasp. That should put the R-1535 at around 1000 HP.
Anyway, just another idea I thought I'd throw out there.

P.S. - Just noticed the "14-cylinder Mercury" side conversation. Wouldn't this be that, or a fairly close approximation, anyway?

Challenge is the F5/34 was never intended to run the Mercury, but instead the more powerful, but then unavailable Perseus. How does the Junior compare in hp, etc?

tomo pauk · Jan 27, 2025

Shortround6 said:
The Perseus being the intended engine for the F5/34.
The Perseus never seemed to get a large increase in power over the Mercury engine that was promised, it did get an increase but not what was hoped?

One wonders what kind of math would've supported the partizans of the Pereseus wrt. all that power increase over the Mercury.

Build an improved Gloster F5/34

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