- Apr 17, 2017
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To be fair, the British government at the time, forced a number of mergers on the Aerospace industry.To be fair, Napier (then English Electric) did merge with Bristol, but not until the 1960s.
The RAF was happily moving on from Mercury engined Lysander to Perseus ones with the spare Mercuries going into the Blenheim production lines, so I doubt if the idea of production Glosters having Perseus ones would put them off. Perseus were also being specified for the Blackburn Botha and initial Bristol Beaufort designs at the time.
Good points. Interestingly, Bristol chose the Mercury for their own Type 146, first flying in 1938. You’d think they’d have chosen the Perseus if they believed it had a future.The RAF was happily moving on from Mercury engined Lysander to Perseus ones with the spare Mercuries going into the Blenheim production lines, so I doubt if the idea of production Glosters having Perseus ones would put them off. Perseus were also being specified for the Blackburn Botha and initial Bristol Beaufort designs at the time.
I am not especially supporting the use of the Perseus but it does seem to have had little trouble in service, albeit with low to medium level roles, but did the job insofar as such an engine size could. Had the Gloster gone into production one might wonder if they would have optimised the supercharger for higher levels. My point is merely that the RAF were not opposed to the Perseus itself. More of an issue might be the size and power to do the fighter task in service. My view is that one needs to either bolt more engine on the front or bolt less aeroplane on the rearAnd here is where the sleeve valve Kool-aid really kicked in.
The Perseus may very well have offered a number of advantages over the Mercury in in 1936-37-38. But the Mercury was almost in stasis as far as development went. Just enough development to remain a viable product while the Perseus was to take over.
The original Botha and Beaufort specifications might have been doable. But when the specification was changed from the 3 man crew to 4 man and a newer wider (heavier) fuselage the Perseus could not provide the needed power.
The promised/wished for extra power of the sleeve valve Perseus over the Mercury pretty much vanished. The Perseus X engine offered 880hp at 15,500 vs the Mercury's 840hp at 14,000. Better but not enough to change the performance of any of the aircraft powered by it any meaningful way. Under 8% at altitude and just under 4% at take-off when using 87 octane fuel.
Maybe Bristol had inside knowledge (?) but the Air ministry allowed them to change to the Taurus while Blackburn was stuck with Perseus .
Please note that any higher power Perseus engines that saw production were Medium Altitude (6,500ft ?) engines with cropped impellers.
Perhaps Somebody could have/would have ordered a quantity of Gloster fighters with Perseus engines but there would have been no significant increase in power.
How much of this was known in 1938-39 I don't know. But there were problems with Perseus production as production ramped up during those years. Making scores of engines per month was different than making much lower numbers. The Taurus soon displayed it's overheating problems and whatever problems the Hercules had was compounded by the same problems the Perseus had. They used pretty much the same cylinders/heads and sleeves.
Now for how long it took to change engines and how far they had to plan ahead the Wellington is instructive.
While the Wellington first flew in June of 1936 a much modified form first flew in Dec 1937.
In Jan of 1938 they were already looking at different engines but the engines were not ready for production so orders were placed for the Pegasus powered version/s. IA and so on.
The MK II with Merlin's started at this time. Delay's in Melrin X engines meant that first prototype flew March 1939. It entered service near the end of 1940.
The MK II with Hercules engines also started at this time (Jan 1938) but first flight wasn't until May of 1939. However first operational use wasn't until June of 1941.
The MK IV with P & W R-183) was proposed in late 1939. Problems with US neutrality took until Feb 1940 to sort out. First Prototype flies in Dec 1940 and first operational use was in Aug 1941.
Now for the Hercules we can note it took a very long time to go from prototype to operational use. At times the Sterling had priority, which is one reason for the Beaufighter II with Merlin's. However both Stirling production lines were bombed so planned Sterling production was much smaller than planned in late 1940 and 1941.
The Hercules was having production problems relating to the sleeve valves. It is hard to believe that the Perseus wasn't having problems at the same time as they cylinders were so close to each other.
The "promised/hoped" for increases in power for the Perseus never came.
The Hercules got better but they needed not only to solve the Sleeve valve production problem but they needed more cylinder fins and new cylinder head design to increase cooling among other changes.
Optimized how????I am not especially supporting the use of the Perseus but it does seem to have had little trouble in service, albeit with low to medium level roles, but did the job insofar as such an engine size could. Had the Gloster gone into production one might wonder if they would have optimised the supercharger for higher levels. My point is merely that the RAF were not opposed to the Perseus itself. More of an issue might be the size and power to do the fighter task in service. My view is that one needs to either bolt more engine on the front or bolt less aeroplane on the rear
Getting tired of answering this one. There is not a whole of evidence that the Post war Perseus ever existed. No record it every flew in any aircraft even for a test. No known photograph of it.One might, over simplistically, think of the Perseus as half of a Centaurus with smaller cylinders and, crudely extrapolating just for the fun of it, you get back to the post war Perseus with Centaurus cylinders at 1,200 bhp for civilian use so maybe stressing it a touch further to 1,350bhp in military use. That would make it handy when introduced but soon falling behind the curve by 1942.
You know I thought that I had carefully worded my thoughts as idle musing; but it would seem not.Optimized how????
At 880hp at 15,500ft the engine was already doing pretty well, if you want more altitude you need to put more power into the supercharger. Which means less power to the prop.
WIth a single speed supercharger you are kind of stuck, increasing the power or altitude in the upper teens means less power at all the lower altitudes.
The lower altitude Perseus used crop impellers and/or different supercharger drive ratio. They got them up to about 950hp at 5-6000ft. But power at 15,000ft sucked.
Getting tired of answering this one. There is not a whole of evidence that the Post war Perseus ever existed. No record it every flew in any aircraft even for a test. No known photograph of it.
Radial engines don't like "maybe stressing it a touch". they tend to come apart.
And we are back to the sleeve valve kool-aid.
The post war Perseus 100 was supposed to be 1635 cubic inches.
It took Wright until some time in late 1943 or into 1944 to get 1350hp for take-off out of the R-1820 engines used in the FM-2 Wildcats. They needed a different crankshaft than the 1300hp versions which were and entirely engine than the 1200hp Cyclones, they used different crankcases and crankshafts, thse "H" series engines used more hold down bolts per cylinder. They used a new form of cylinder fins with sheet metal fins rolled into grooves in the cylinder barrel, they used a new cylinder head and most of the other parts (valves etc) were new.
And the Wright engine was about 11% bigger than the Perseus 100. But heck, the Perseus 100 used sleeve valves, it must have made more power
The specifications for Perseus 100 claim 1220hp at 4,000ft, take off is slightly lower and the rating was at 9.5lbs of boost.
Now one problem in using the Centaurus size cylinder is that it is the same diameter as the Perseus/Hercules cylinder. They added 13mm of stroke.
What this means is the when the Perseus is running at 2750rpm the pistons are moving at 2979 fpm. When a Hercules is running at 2800rpm the pistons are moving at 3023 fpm but when a Centaurus is running at 2700rpm the pistons are moving at 3150fpm. Over revving it doesn't look good.
And they had a problem with sleeve valves. When you raise the boost pressure the pressure in the cylinders also goes up, they tended to break, bend, crack the edges of the sleeve valve ports which then lead to the sleeve jamming, freezing in the cylinder. They did a lot of work making stronger sleeves as the war went on (and post war) to handle the higher boost pressures. They also had cooling problems, To get the heat out of the cylinder the heat has to travel through the sleeve and the layer of oil between the sleeve and the cylinder barrel. In a poppet valve engine the heat goes through the oil on wall and then right into to the cylinder barrel.
If set up (designed) right the engine can take the designed load, but there was not the "headroom" that liquid cooled engines had for over boosting.
1935, Folland consults with Bristol on the engine to use with his F5/34 design then on the drawing board, where he learns of the two row, 14 cylinder Taurus and Hercules then in development. Of note, both the F5/34 and Taurus are first flown/run in Nov/Dec 1936, while the Hercules first ran ten month earlier in Jan 1936. Design and build the F5/34 to use the Taurus initially with plans to switch to the Hercules and much of the rest of the F5/34 can be forgiven.So starting with the F5/34 what do we need to get it up to or near 109E standard.
There is a difference between first flight of a prototype aircraft and the first run (on a test stand) of a prototype engine. It was often 1 to 2 years after an engine was first run that that put one in an aircraft to actually fly.Of note, both the F5/34 and Taurus are first flown/run in Nov/Dec 1936, while the Hercules first ran ten month earlier in Jan 1936.
By my last post above I’ve mostly given up on rescuing much of the F5/34. Instead Folland stops his design at the drawing-board stage and starts afresh with Bristol’s new twin row 14 cylinder engines in mind, along with a folding wing, carrier variant from the onset. The prototype Gloster, likely a scaled-up version of Folland’s original concept, will need to fly on a single row radial and ballast until either the Taurus or Hercules is ready. This puts entry into service of any 14-cyl version by 1940 at the earliest, just in time to cancel out the Fulmar.And then you have the problem, mentioned before, of taking an planned 1100lb engine (Perseus) out of a empty weight 4190lb airplane and sticking a 1850lb engine (Hercules I) in it's place. By the time you are done you might save the tail wheel. You might save the external shape of the F5/34 but you have to restress (beef up) the entire airframe.
A bit optimistic.This puts entry into service of any 14-cyl version by 1940 at the earliest, just in time to cancel out the Fulmar.