Alternate Bristol Engine Development (Mercury & Pegasus)
- Thread starter LoftonHenderson
- Start date
I don't think any of the established firms did both at the time, so it would be very ambitious of Napier to attempt it.
The Treasury wanted competition in supplies on cost grounds (no being held to ransom by one supplier) and the Air Ministry also wanted it do keep designers keen and pushing the envelope, also so there was always a backup if a new engine proved to be a pup.
Bristol are first choice for radial, AS mainly do backup, engines for their own designs and trainers/civilian. RR and DH do inlines, but as mentioned DH engines are trainers and civilian market only. Hence Napier fitted in as alternate/backup/competition for RR around inline engines, so the Air Ministry would prefer if Napier-Alvis stay doing inline.
If Alvis do want to go radial then the 1935 sale of Armstrong-Siddeley is a possibility, Hawker wanted the airframe side but had to take the engine side with it. There might be a chance to do a deal and get Alvis to buy AS aero-engines while Hawker takes the airframe firms. Alvis could then give AS the long over-due kick up the arse, ideally getting Stewart Tresilian in earlier than OTL so Deerhound/Wolfhound actually work.
Thanks! It’s an area I have done some thinking on.
I mean, he was a businessman. If the customer made it clear that further orders would not be available at current level of work, but that a fairly significant orders could be guaranteed if a certain quality was reached, he would probably get to work on it the next day. But that would require the customer to know what is required in the future of engine design. And that is generally the manufacturers job, not the governments.
Maybe if Bristol’s new engines are tearing up the market and it is made clear that AS needs to match them or be removed from government list? That would probably get Siddeley moving. And it might be in time to get something useful out of AS before the war?
I haven’t actually considered Vickers for that very much. But that might be a good fit. Their tanks could probably benefit from a dedicated engine manufacturer on hand. That said, I don’t know if it would make sense to Vickers at the time. Tank orders weren’t exactly flowing in until the war broke out.
Halford designed it. However, as a consultant that didn’t have to have anything to do with the production floor, he would design for performance without regard for how to actually build the thing. The Napier team was missing a lot. But they got very good at refining Halford’s ideas for a production process. The Sabre still had a ton of problems that way (in the early years the only ones that worked well were those coming from Napiers own hands) but they still much improved it.
As mentioned the Monarch and Sabre were pretty different design philosophies. The Monarch saved weight by using integral air passages while the Sabre went for high rpm and short stroke for higher power.
I don’t think Canadian Vickers was in a position to buy out Napier. Vickers-Armstrong itself, possibly.
I found the post:
“I dont normally bother much with "alternative history" stuff, but I did get a question a few months ago, about how much bigger the Sabre would have been with poppet valves.
I just very quickly schemed this up using DB605 valve diameter and lengths as a rough starting point for typical valves of the era.
I think that a poppet sabre would be about four inches wider overall, although this is just my first attempt, and I think with some refinement, and maybe using finger followers instead of cam-and-bucket designs, it would be possible to make it nearly the same size, but I am not very convinced that WW2 era design practises could have done it.”
Darn it! I knew I was missing somebody!
That’s, actually an interesting possibility. Alvis did have the funds and the drive.
One thing that should be kept in mind, however, is when most of these outside companies (Wolseley, Alvis, EE) started gaining interest. I have seen rearmament be described as the dot.com bubble of its day. Once the money started flowing in 1934-1936, everyone wanted in. But they may or may not have been as interested before that.
As to Richard Fairey, I think you are correct. However, A.G Forsyth, his designer, might not be quite as attached to Fairey? Certainly there doesn’t seem to be any recorded problems between them, but theoretically it might be possible for Alvis/Napier to poach him. Or, if the buy out happens early enough, to pick him up directly after he leaves the Air Ministry. That would allow him to develop the whole range a little faster and with more support. Which would possibly allow the Prince to come in at a time when it’s horsepower is useful and, with development, possibly at least shadow the Merlin in power. The H-16 “Queen” could possibly be more than a speculative development on the way to the Monarch, and the Monarch itself could get the development it needs to at least be more useful. If the separate running of either side of the engine is developed in the Queen or available early enough in the Monarch, theRN may be interested earlier than they were IOTL. And this sidesteps both the need for huge investment by the government to get it off the ground and the difficult relationship between the Air Ministry and Richard Fairey.
Not in the same way, they weren’t.
The Aero Engine Ring was established in 1920 or 21 I believe. The end of the war had led to its usual whiplash for military suppliers, with orders disappearing after considerable investment in capacity. This was exacerbated by the ABC Dragonfly disaster. The new Secretary of Staye for Air, Lord Weir, and much of his department had bought heavily into the promised performance and light weight of the proposed ABC Dragonfly and ordered thousands of them. Only to find that the hype was overblown and the whole lot was useless, and dangerous to use. Worse, they had already canceled all other engine orders, with serious consequences. Bentley left the engine business, and Rolls and Napier were looking to do the same, Cosmos, with Fedden at the helm, was bankrupt.
So, the Air Ministry took steps to save domestic aero engine capacity by organizing a ring of producers around the promising engines available at the time. Napier had the Lion, designed by Arthur Rowledge with limited help from the ailing company founder. RR had the Eagle, designed to meet Naval requirements (actually most of the higher go engines of the time were to Navy spec). Bristol was convinced to buy Cosmos with Fedden and his Jupiter engine. And AS had the Jaguar, a developed version of the RAF 8 that Heron and Greene had come over from the Royal Aircraft Factory with plans of. They guaranteed orders for these 4 if they maintained engine capacity. And, having done so, they would only send orders to these manufacturers if those had engines in that class. This was partially why Fairey’s use of the Curtis D-12 as the “Fairey Felix” was a problem.
De Haviland originally used ADC Cirrus engines made from leftover Renaults. When these began running out they began making their own based off them. These were in a weight class far under the standard for military aircraft. And they were intended for commercial use. When the Air Ministry had them it was because they bought the plane as a unit with the engine in it. Since these were light trainers it didn’t make sense for the Air Ministry to launch their own spec and have it built when they could just buy popular civilian trainers.
What you ended up with, as a result of the ABC Dragonfly disaster, was a species of 18th century patronage with the difference that the patron had power, not as a result of fixed class or title, but because of appointment. As senior RAF and Air Ministry staff changed so did their patronage and the duration of each change was less than the duration of bringing an engine design from concept to service.
A non engine example is the ‘no allowance shooting’ system, briefly a darling of the Air Ministry, and was the method the Boulton Paul Defiant was intended to use for firing the four turret guns fixed forward in an inclined plane. The airframe was made complete with a fixed for ward turret setting and a pilot’s firing button. However, changes in personnel resulted in no work on the sights, no sights and no training in using the sights.
Had the ‘patronage’ remained in place then the Defiant would have had the option of forward firing fixed guns to deal with escorting fighters with short bursts and turret firing guns to engage bombers in more extended firing. Not to mention using the turret guns defensively to boot. But that subject is not for this thread.
A non engine example is the ‘no allowance shooting’ system, briefly a darling of the Air Ministry, and was the method the Boulton Paul Defiant was intended to use for firing the four turret guns fixed forward in an inclined plane. The airframe was made complete with a fixed for ward turret setting and a pilot’s firing button. However, changes in personnel resulted in no work on the sights, no sights and no training in using the sights.
Had the ‘patronage’ remained in place then the Defiant would have had the option of forward firing fixed guns to deal with escorting fighters with short bursts and turret firing guns to engage bombers in more extended firing. Not to mention using the turret guns defensively to boot. But that subject is not for this thread.
Does anyone have a guess at what a fully developed redesigned (read: functional) Hydra would be able to put out HP-wise?
And how would the existence of these improved and earlier radials affect aircraft development? I still doubt a Pegasus/Draco or especially a bored-out version would fit a Gloster f.5/34, but maybe an Andromeda could? Or a Hydra? What about Fairey Battles, p.4/34s, or Fulmars? What other airframes would this improve/change/butterfly away?
And how would the existence of these improved and earlier radials affect aircraft development? I still doubt a Pegasus/Draco or especially a bored-out version would fit a Gloster f.5/34, but maybe an Andromeda could? Or a Hydra? What about Fairey Battles, p.4/34s, or Fulmars? What other airframes would this improve/change/butterfly away?
Original author reviving this thread –
There's that Calum E. Douglas post about a poppet-valve Sabre:
I can roughly calculate displacement easily enough when theoretically turning a 9-cyl into a 14- or 18-cyl using proportions. But if I was trying to mock up stats of a poppet ALT Sabre, how would I calculate that?
OTL Sabre was:
82.25" length
40“ width
46“ height
5" x 4.75" bore and stroke
When he says 4" wider overall, I assume that implies a 44" width, but I'm not sure how to plug that into the engine displacement formula to ascertain what the new, larger displacement should be.
Anyone know what the calculation would be?
There's that Calum E. Douglas post about a poppet-valve Sabre:
I can roughly calculate displacement easily enough when theoretically turning a 9-cyl into a 14- or 18-cyl using proportions. But if I was trying to mock up stats of a poppet ALT Sabre, how would I calculate that?
OTL Sabre was:
82.25" length
40“ width
46“ height
5" x 4.75" bore and stroke
When he says 4" wider overall, I assume that implies a 44" width, but I'm not sure how to plug that into the engine displacement formula to ascertain what the new, larger displacement should be.
Anyone know what the calculation would be?
Pretty sure Calum was talking about the same engine displacement but with poppet valves rather than sleeves. The space requirement of the valve assemblies and supporting components would be what would drive the wider engine, not an increase in displacement.Original author reviving this thread –
There's that Calum E. Douglas post about a poppet-valve Sabre:
I can roughly calculate displacement easily enough when theoretically turning a 9-cyl into a 14- or 18-cyl using proportions. But if I was trying to mock up stats of a poppet ALT Sabre, how would I calculate that?
OTL Sabre was:
82.25" length
40“ width
46“ height
5" x 4.75" bore and stroke
When he says 4" wider overall, I assume that implies a 44" width, but I'm not sure how to plug that into the engine displacement formula to ascertain what the new, larger displacement should be.
Anyone know what the calculation would be?
Oh interesting, I think that makes sense. Displacement isn't increasing, it's just that the actual "box" is bigger?
Driftless
Donor
Technical question from a non-tech... If the engine block were wider to accomodate the poppet valves and associated gear, would there have been some design work to reduce the weight gain from additional metal in the block and manifolds? Basically, four inches of gained width also would come with some notable weight gain, or is that not so?
As another very much non-tech I'd be interested to know this as well. Where does the "cost" come in from using poppets and being 4" wider rather than sleeves?
There shouldn't be much extra metal in the block and if anything the manifold might be a bit smaller as you'd (probably) have fewer valves per cylinder. You'd gain weight from the larger cylinder head, but save by removing the sleeves themselves and the valve train probably ends up being lighter as it's doing a simpler job. Overall I don't think it nets out as being significant either way, if anything the poppet valve version might come out a tad lighter if it follows the pattern of the Bristol radials. Then again all else being equal the poppet valve version would be lower power and less efficient due to the smaller and fewer ports.
Of course if you had designed the Sabre as poppet valve from scratch then you would have compensated for that, for example in general poppet valve engines could run at a higher boost pressure than an equivalent sleeve valve. But higher pressure means you need stronger components which are of course thicker/heavier.