Bristol Taurus fighter engine mods? (1 Viewer)

[Admiral Beez]

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?

 

[yulzari]

It has been suggested in earlier threads and much made of the CoG concerns over the far greater weight of the Hercules but it looks to me that, if you can relocate the assorted gubbins behind the engine and before the firewall/forward bulkhead, the the whole engine might be mounted much further back and reduce the CoG issue.

However, closer to the OP, the Hercules maxed out at @2000bhp so, for the Taurus that translates to @1450bhp by comparative capacity. That makes sense with the Hercules as a twin Perseus and the Taurus as a twin Aquila. The special Aquila used in the Vickers Venom prototype was 650bhp which translates into 1,300bhp.

The obvious model is doing much the same to the Taurus as was done to the Hercules IOTL including the input from Napiers.

 

[EwenS]

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

The Bristol Taurus was offered as a fighter engine in 1939.

Fairey tendered designs for Spec N.8/39 & N.9/39 offering 4 engine choices:-
RR Griffon - 1,600 bhp at take off, 1,445 at 15,000ft. AUW 10,775lbs
Fairey Queen - 1,320 & 1,170 AUW 9,975lbs
RR Boreas (aka Exe) - 1,150 & 950. AUW 9,570lbs
Bristol Taurus - 1,200 & 1,170. AUW 9,355lbs

Four other companies made submissions but I don't have details. None of the proposals were found acceptable and everyone went back to the drawing board. Eventually the Firefly emerged from the process.

The very earliest Blackburn proposal around the same time for what eventually became the Firebrand was based around the Hercules.

 

[Shortround6]

I assume the Taurus' low-altitude single-stage supercharging will need to be modified. What else?

Main thing is to throw the cylinders and heads out and start over. There were a couple of prototype engines used the Gloster twin that disappeared after the crash and never came back again. The Service engines had a lot of trouble overheating and if the engines are overheating at 3000ft trying to make good power (1200hp?) at 15,000ft and up is going to be very, very difficult in the thinner air.
The Taurus was not a precursor to the Hercules, it was concurrent. Delaying the Hercules to work on the Taurus would definitely have been a bad discission.
The Hercules didn't make 2000hp in WW II until the very end. Assuming you can match the power of a Hercules VI running on 100/130 fuel in high gear at 15,500ft of 1545hp that means the Taurus would be good for about 1014hp at that height. Adjust as needed for slightly rpm or other things? Hercules VI was already using 8.25lbs of boost to hit this power level.
It seems like a lot of hoops to jump through for not much result.

 

[Shortround6]

Perseus = 24.9 liter engine
Taurus = 25.4 liter engine

we are depending an awful lot on higher rpm and the advantages of small cylinders for a significant increase in power.
R-1830 = 30.0 liter engine for comparison.

 

[Admiral Beez]

Perseus = 24.9 liter engine
Taurus = 25.4 liter engine

Makes one wonder why Bristol bothered. More government money I suppose. Is a jump from Perseus to Hercules unrealistic?

Bristol should have thrown out the sleeve valve idea and made their own 30L twin row sodium valve engine.

 

[tomo pauk]

A mod that would've helped with the Taurus becoming a half-decent engine for not just a fighter would've been a better supercharger, preferably with a 2-speed S/C. With hi-oct fuel, some luck and a lot of development and testing, it might've mimic the Ha 102 engines from the Zuisei family, that gave 950-1050 HP at high or low altitudes, respectively.
OTOH, betting on a 1000 HP engine in the time 1500-2000 HP engines are on the test benches would've not been seen as a good thing to do by the people making the decisions.

 

[yulzari]

Makes one wonder why Bristol bothered. More government money I suppose. Is a jump from Perseus to Hercules unrealistic?

Bristol should have thrown out the sleeve valve idea and made their own 30L twin row sodium valve engine.

There were sound reasons for sleeve valves when the projects began. However further developments in fuels and poppet valve materials made deep inroads into the differences in the meantime but, when Bristol settled on the sleeve valves, they had still not eradicated the benefits that sleeve valves were to bring. Bristol manufacturing was committed to the sleeve valve in materials, machinery and tooling. By the end of the war the Hercules had become a sound 2,000bhp engine with long servicing intervals and reliability and went on being used in post war civilian aeroplanes and in licence production abroad. I agree that, with our hindsight, something along the lines of a double Pegasus would have been a better choice but, at the point of decision, it would not have been able to make the power that the Hercules eventually made even if we look at Alfa Romeo's try at a double Pegasus. The sleeve valve at that time promised to get past the inherent limitations found in period poppet valve engines. I note that the Hercules suceeded in the civilian market post war whilst the Rolls Royce Merlin did not. I also note that the last Rolls Royce Eagle 24 cylinder of 1944 was also sleeve valved.

However, the Taurus by 1940 was simply too small and any serious attempt at enlarging it would just be making a small Hercules in practice.

 

[Shortround6]

The Hercules got a substantial redesign in the 200 series. This included new main bearings with larger diameter rollers in the rolling bearings, Only the new power section was rated at 2000hp or close to it. It was an amazing achievement but effective use was post-war. 1938-39 Bristol was having trouble meeting the late 30s promises for the Hercules and the Taurus predictions were wishful thinking at best.
In 1925 the sleeve valve had a lot to offer. In 1930 not so much. In 1935-35 many of the advantages only existed in the minds of the Bristol engineers. Or to be a bit kinder the sleeve valve advantages did exist and were coming to fruition. The problem was that most of the poppet valve problems had been solved closing the gap between the sleeve valve and poppet valve.
Unfortunately, a double Mercury or double Pegasus would have been rather bad engines. Bristol did the bare minimum to bring their poppet valve engines into the 30s. They may have given good power and been somewhat durable, but they required a crap load of maintenance. Bristol still relying of grease guns for valve train lubrication. Spark plug change may have been easy but having 36 valves to adjust on a 9 cylinder engines was a bit much for the power you got.
Bristol always touted their sleeve advantages over their own poppet valve engines. They never compared them to P&W and Wright in public.

 

[Admiral Beez]

Unfortunately, a double Mercury or double Pegasus would have been rather bad engines. Bristol did the bare minimum to bring their poppet valve engines into the 30s. They may have given good power and been somewhat durable, but they required a crap load of maintenance. Bristol still relying of grease guns for valve train lubrication. Spark plug change may have been easy but having 36 valves to adjust on a 9 cylinder engines was a bit much for the power you got.

They needed a British competitor for radial engines. Unfortunately Armstrong-Siddeley wasn't up to the task. The failed 39L Alvis Pelides looks interesting. Having a monopoly on the type may have help to lead Bristol down harebrained paths. All they had to do in the early 1930s was buy a P&W engine, tear it down and exclaim, "Fedden your sleeve valve nonsense is now off the table."