Bristol Taurus fighter engine mods?

[Bretoal2]

Alvis gets a little too much credit for the Pelides engine. Air Ministry maybe should get some blame for not at least giving a few more orders?
It is hard to tell.
The Pelides was sort of an anglicized Gnome Rhone 14N engine. At best they used British standard bolts, nuts and threads.
Without trying to make an Alvis version of the 14 R there was little room for growth.
Alcides was a planned version of the GR 18L engine and without a redesign using a central bearing it was not going anywhere.
The Maeonides Major was pretty much a GR 14M under license. I have no Idea if they ever built one or how far drawings got (anglicizing it).
Alvis plant was greatly expanded during the war and did a lot of good work repairing/overhauling other engines.

Getting Fedden to abandon the 4 valve head was also going to be a problem. Most of the advantages of the 4 valve head had disappeared during the 30s with better 2 valve arrangements. Getting him to admit that might be the problem.
I am talking about air cooled aircraft engines here and not 4 valve heads in general.

The Alvis version of the 14M was not the Maeonides Major, but simply the Maeonides.

However, in late 1936, Alvis developed a 9-cylinder engine derived from the Maeonides—initially known as the 9ars—which underwent a slow development process leading up to the outbreak of war. By the time of the Liberation, the engine—now re-named Alvis Leonides and producing between 540 and 650 hp—enjoyed commercial success, notably earning a strong reputation through its use in Westland Sikorsky S-51 and Westland Dragonfly helicopters. Leonides production did not cease until 1966, thirty years after Alvis had acquired the Gnome-Rhône license.

In 1951, the British manufacturer developed the Leonides Major from the Leonides; this 14-cylinder version returned to the original 14M configuration while differing significantly from its distant ancestor—particularly regarding the valve train. Delivering 875 hp, it too was used primarily in helicopters. Ironically, SNECMA (Gnome-Rhône successor) was at one point in negotiations to acquire the license for the Leonides Major, but the deal was cancelled in favor of the Bristol Hercules.

 

[Bretoal2]

The Kinsei and Kasei were both original designs. The M-85 was a licensed GN 14K

Not at all.

We have right here an analysis of the Kinsei (unfortunately somewhat damaged) conducted by US engineers.

The key words appear at the very beginning of the report : "The group responsible for the design did a very ingenious job of combining what they apparently believed to be the most desirable features of a number of foreign manufacture - proved features all. These features are built into a composite design of the sort that has to work the first time - and probably did."

Knowledgeable members of this forum will immediately recognize that the design of many components is borrowed from Gnome et Rhône (cooling fins, valve angles, valve train), Pratt & Whitney (reduction gear, central crankshaft bearing), and Wright (supercharger, main crankcase).

As well as numerous other details borrowed from these three engine manufacturers—companies from which Mitsubishi held all the licenses and whose models it had even manufactured.

M

Thread 'Japanese Kinsei Engine'

Sep 19, 2026

Juts in case it has not been posted yet, here is the article based on the WW2 tear down of the Japanese engine.

• MIflyer
• Replies: 4
• Forum: Engines

 

[Jugman]

Ummm, no, it looks more like an Armstrong-Siddeley design. No surprising sense they had a produced a number of their designs previously. Regardless of superficial appearances the kinsei and Kasei were unique designs. No foreign design shares their principle characteristics or combination of design features. Frankly you could make a stronger claim that the BMW 801 was a copy of Wright technology and that would be still be total bs.

 

[Bretoal2]

Ummm, no, it looks more like an Armstrong-Siddeley design. No surprising sense they had a produced a number of their designs previously. Regardless of superficial appearances the kinsei and Kasei were unique designs. No foreign design shares their principle characteristics or combination of design features. Frankly you could make a stronger claim that the BMW 801 was a copy of Wright technology and that would be still be total bs.

The analysis writes "a number of foreign manufacturers..."

It is also worth noting that, in the years leading up to the war, Armstrong-Siddeley had largely slipped to the status of a secondary manufacturer; market leadership remained with the three engine makers I mentioned—plus Bristol, of course. However, in the 1930s, Gnome & Rhône possessed much of that fourth manufacturer's conventional technology (conventional, i.e. excluding sleeve-valve designs) and offered the advantage (for Japan) of operating according to metric standards.

That said, eighty-four years later, it is difficult for us to know more than the people who dismantled this engine back in 1942. We can only speculate on the question: at what point does a mix of copies cease to be a copy itself?

 

[Shortround6]

There are a lot of things in an engine that can be copied or adapted and unless somebody knows exactly what was changed, and when and why things get murky very quickly.
The Bristol (Cosmos) Jupiter of 1918 was the start of many engines, and the 146mm X 190mm cylinder size can be traced through many engines and along with the shorter 146x165 cylinder size.
But they used 4 valve heads, 2 valve heads, sleeve valves. Heads were poultice (aluminum over steel 2 piece) or cast aluminum or forged aluminum (both screwed and shrunk onto the barrels) and angles between the valves changed.
Wright R-1820 also went through many changes. Even with a common bore and stroke and sticking with 2 valve heads not all engines used the same size valves (or the same kind) or the same size ports or even exhaust ports pointing in the same direction at times.
It was certainly possible for a licensee to adapt later improvements without the benefit of license or to evolve certain improvements in parallel with the home factory.
Many counties could and did improve engines they had licensed in the late 20s or early 30s so a late 30s engine might only have limited parts interchangeability with originals.
Gasoline engines in 1920s and 30s were not that complicated as how to make more power. The problems were how to make them light and how to achieve a decent overhaul life.
Search for improved materials and manufacturing techniques was harder than just trying to turn more rpm or how to use more boost.
Many countries wanted shorter stroke radial engines in the search for better streamlining/and higher rpm. How far some people varied from the original 'inspiration' can be questioned.

Some of the 1920s engines should have been buried deeply and not just left for dead. Bristol tried to make not only 5 and 7 cylinder versions of the Jupiter ( or Mercury) so as to use common parts but also a short stoke 3-cylinder radial of 8.0 liters. problem with such an engine was not only trying to keep the engine from shaking itself apart but keeping any early 1920s airframe from shaking itself apart in flight.

 

[Jugman]

The analysis writes "a number of foreign manufacturers..."

It is also worth noting that, in the years leading up to the war, Armstrong-Siddeley had largely slipped to the status of a secondary manufacturer; market leadership remained with the three engine makers I mentioned—plus Bristol, of course. However, in the 1930s, Gnome & Rhône possessed much of that fourth manufacturer's conventional technology (conventional, i.e. excluding sleeve-valve designs) and offered the advantage (for Japan) of operating according to metric standards.

That said, eighty-four years later, it is difficult for us to know more than the people who dismantled this engine back in 1942. We can only speculate on the question: at what point does a mix of copies cease to be a copy itself?

Not in the late 20s when Mitsubishi bought licenses A-S or in 1931-32 when the A4 project began. I'm not going to get into semantical bs, but sharing features doesn't mean "is a copy". This is like arguing that the AK-47 isn't a unique design because it shares features with the StG 44 and the M1 Garand.

 

[MIflyer]

Did the British build any engines under license in WW2? In order to, say, get a decent radial with a oil leak rate low enough so it would enable at least a couple of hours of confident flight?

E.g., the Short Sunderland, prior to the use of the R-1830, was essentially a three engined airplane with four engines.

 

[Shortround6]

If the Bristol Taurus (shown below on an Fairey Albacore) was considered for fighters, perhaps as a successor to the Perseus (and precursor to the Hercules), what mods are needed? I assume the Taurus' low-altitude single-stage supercharging will need to be modified. What else?

And here is the real problem.
We do have figures for the Allison engine and they figured at a certain airflow (10,000lbs/hour) the engine would make 1672 IHP (Indicated horse power or power in the cylinders) and from this you need to take out friction and internal systems (pumps, magnetos, etc) of about 147hp. then you take out the power needed to drive the supercharger.
For an Allison using 6.44 gears this left you with 1415hp for a very low altitude engine. Using the 9.60 gears for a "medium" altitude engine you had 1285hp.

Working somewhat in reverse the 1130hp low altitude (3500ft) Taurus by changing gears or fitting a two-speed drive would be down to just over 1000hp at 15,000-16,000ft (?).
Still making the same amount of power/heat in the cylinders.
Changing to 100/130 fuel changes the point at which detonation sets in, it does not change the amount of heat generated in the cylinders and in fact, by using higher boost, you can make more power which makes more heat per minute. Better fuel does not do much good for an engine with marginal cooling.
Bristol have been offering engines (Mercury, Pegasus and Perseus) with different supercharger ratios for different applications in the 1930s and was offering the Pegasus with a 2 speed supercharger in 1937-38. It would seem that the supercharger and supercharger drive was not the problem. Pegasus XVIII engine was rated at 1065hp/6.75lb/2600rpm at 1250ft in low gear and 965hp/6.75lbs/2600rpm at 13,000ft in high gear using 100/130 fuel. Pegasus had a few other problems but the supercharger was not really one of them in 1937-38-39,

 

[Shortround6]

Did the British build any engines under license in WW2? In order to, say, get a decent radial with a oil leak rate low enough so it would enable at least a couple of hours of confident flight?

The 1938 'Jane's" lists 23 different companies making aero engines or tooling up to do so (5 were shadow companies) Perhaps not 100% authoritative and a few may have been companies that were in the process of locking the doors (Beardmore?).
What may have been going on behind the scenes may be different but the only "American" engine in production/assembly in GB in 1936-1938 was the 40hp Aeronco flat twin, The British company was in liquidation in 1938.
British were short of machine tools from the late 30s on and tooling needed to ordered quite a number of months in advance. The Air Ministry had repeatedly shut down Fairley's attempts to get into the engine business, and Alvis had spent a decent sum of money for a small plant to make G-R engines which got no orders from the Air Ministry. Without an assurance of orders it would seem to be a very risking undertaking to challenge the existing engine makers. Not Saying in hindsight it would not have been a good idea.

 

[Howard Gibson]

If the Bristol Taurus (shown below on an Fairey Albacore) was considered for fighters, perhaps as a successor to the Perseus (and precursor to the Hercules), what mods are needed? I assume the Taurus' low-altitude single-stage supercharging will need to be modified. What else?

View attachment 897408

A really important feature of the Bristol Taurus was its 5.00" bore, the same as that of the Napier Sabre. Most Bristol radials had a bore of 5.75".

When the officials finally got fed up with Napier, Bristol was able to adapt the Taurus' sleeve valves to fit the Sabre.