Japanese logistics, purchase programs and war booty, reality and alternatives 1936-44

[ThomasP]

re

What problem should've the sleeve valves solve for the Japanese?

Not sure.

Air cooled sleeve valve engines seemed to weigh a bit more more per displacement, but put out 10-15% greater power for said displacement.

Their diameters were about the same as - or a bit smaller than - a poppet valve engine of equivalent power?

Sleeve valve engines seemed to be able to run reliably at a bit higher rpm.

Unfortunately, there is not much directly comparable usable info for sleeve valve engines to the Japanese engines due to the differing fuel qualities, specific sizes actually developed, and of course the real timeline of development. One can offer the same what if to both the British and Japanese - ie what if they had begun concentrating on the sleeve valve significantly earlier - or solved the problems earlier via some other mechanism.

 

[tomo pauk]

Air cooled sleeve valve engines seemed to weigh a bit more more per displacement, but put out 10-15% greater power for said displacement.
Their diameters were about the same as - or a bit smaller than - a poppet valve engine of equivalent power?
Sleeve valve engines seemed to be able to run reliably at a bit higher rpm.

Power vs. displacement was probably very low on the priority list?
Aircraft designers were probably more concerned with power vs. weight and power vs. drag when it is about the engines, as well as with actual power, and with reliability. Ability of the factories to churn the engines by many hundreds, if not thousands was also a concern - do the Japanese have the where-vital to do it wrt. the sleeve valves?

Diameters of the powerful sleeve-valve radials, like the Hercules or Centaurus don't seem to offer anything vs. what the Japanese or BMW were doing. RPM of the Hercules war 2800, with excursions into 2900 for the war-time Hercules; the high-revving Taurus was a problematic engine. Centaurus was at 2700 rpm, even post-war - no great shakes.

A thing that sleeve valves don't solve for the Japanese is/was the lack of good/great supercharging.

 

[ThomasP]

Unfortunately, I do not know enough about the finer points of the Japanese engine manufacturing technology at the time.

What was their stage of development of the poppet valve, ie in terms of materials and/or sodium filled stems, etc? One of the oft used primary arguments against concentrating on the sleeve valve over the poppet valve is that the poppet valve matured to where the sleeve valve offered little/not enough, or no significant benefit. Would this have been the case in Japan?

In the real timeline, of course, Japan ran into manufacturing problems due to the size of their industry, and to a degree (at least late in the war) to disruption of their material supply chain. Were any of the materials needed to manufacture the sleeve valve in shorter supply than those needed for the poppet valves? Or would there have been less of a problem for the sleeve valve?

If we are saying that the Japanese have a chance to reduce the number of different engines in the pipeline, might that not also allow equal or greater production of the alternate timeline's smaller number of sleeve valve engines? Obviously this applies to reducing the number of poppet valve engine projects as well, but . . .?

From what I am aware of, the Japanese would not have had any particular problem manufacturing sleeve valves and their drive train - at least no any more than the British did.

Also, the British followed a particular design philosophy for their engines (for the most part) but that does not mean that the Japanese had to follow the same philosophy. An example is that they could have used a shorter stroke for their sleeve valves engines, solving a significant part of the higher rpm problem that the British ran into with the Taurus, allowing greater power to weight (maybe) and reduced diameter (drag), if they could solve the cooling issues.

Plus, what would the US and UK development timeline of the sleeve valve vs the poppet valve have been like if they had been limited to lower quality avgas? In theory at least, the British concluded that the sleeve valve held significant advantages when both types of engines are limited to 87, 91, 93 octane.

 

[tomo pauk]

From what I am aware of, the Japanese would not have had any particular problem manufacturing sleeve valves and their drive train - at least no any more than the British did.

'British' in this case are Bristol, and Napier and RR. Bristol did a good job, Napier and RR did not - Sabre was depenant on Bristol-made sleeves, while Exe was neither a powerful engine nor it was trouble-free.

From what I am aware of, the Japanese would not have had any particular problem manufacturing sleeve valves and their drive train - at least no any more than the British did.

For military-grade high power engines?

Also, the British followed a particular design philosophy for their engines (for the most part) but that does not mean that the Japanese had to follow the same philosophy. An example is that they could have used a shorter stroke for their sleeve valves engines, solving a significant part of the higher rpm problem that the British ran into with the Taurus, allowing greater power to weight (maybe) and reduced diameter (drag), if they could solve the cooling issues.

What stroke, rpm, number of cylinders, displacement, power and weight are the targets?

Plus, what would the US and UK development timeline of the sleeve valve vs the poppet valve have been like if they had been limited to lower quality avgas? In theory at least, the British concluded that the sleeve valve held significant advantages when both types of engines are limited to 87, 91, 93 octane.

Have the British really concluded that?

 

[ThomasP]

For military-grade high power engines?

Yes.

What stroke, rpm, number of cylinders, displacement, power and weight are the targets?

That I cannot answer definitively. It depends too much on when we are talking about starting the development. Did the Japanese see a need for a larger engine in the original timeline 1936? In our alternate reality are we saying that they did?

Sakae 12 was a 1701 in3 displacement engine that gave 940 BHP for TO and 950 BHP at 13,800 ft.
Sakae 21 gave 1020 BHP for TO, 1100 BHP at 9,300 ft, and 980 BHP at 19,800 ft.
Taurus II was a 1550 in3 displacement engine that gave 1130 BHP for TO and 1050 BHP at 5000 ft.
All three engines weighed ~1300 lbs+/-.
The Taurus II was rated on 87 octane, while the Sakae was rated on 92 octane. (The Taurus XII was a detail improved II, and the improvements seemed to have resulted in a very reliable engine.)
The Japanese superchargers were significantly better than the Bristol counterparts of pre- and early-war. Match the equivalent single-stage single-speed Sakae 12 or the single-stage 2-speed Sakae 21 supercharger to a 1701 in3 Taurus? RPMs and ultimate BHP would depend on how well the Japanese solved the cooling problems - from what I have read the Sakae 12/21 had no significant problems running at 950/980 BHP for prolonged periods.

What would the rating be on the Japanese 'O Ushi-Za' engine (1701 in3 Taurus) with the better supercharger and 92 octane?

Just one possibility.

Have the British really concluded that?

OK, OK, not the British, but the various parties involved in the development of the sleeve valve engines in Britain.

 

[tomo pauk]

Yes.

Is there a good & easily available source that covers the Japanese sleeve-valve military-grade high-power aero engines ?

That I cannot answer definitively. It depends too much on when we are talking about starting the development. Did the Japanese see a need for a larger engine in the original timeline 1936? In our alternate reality are we saying that they did?

Ho-5 was relatively big for the time, 37.5L. From Japanese Wikipedia (never mid the longevity commnet):
Nakajima also proceeded with the production of the Ha 5 (in-house name NAL), which double-row the longevity, and in 1933 (Showa 8), a prototype type was completed.

Ho-5 morphed into the Ha-41, and further into the Ha 109. Mitsubishi Kasei, 42.1L: Based on Venus, it has a larger displacement It was decided to develop an engine, and development began in February 1938 (Showa 13).

Sakae 12 was a 1701 in3 displacement engine that gave 940 BHP for TO and 950 BHP at 13,800 ft.
Sakae 21 gave 1020 BHP for TO, 1100 BHP at 9,300 ft, and 980 BHP at 19,800 ft.
Taurus II was a 1550 in3 displacement engine that gave 1130 BHP for TO and 1050 BHP at 5000 ft.
All three engines weighed ~1300 lbs+/-.
The Taurus II was rated on 87 octane, while the Sakae was rated on 92 octane. (The Taurus XII was a detail improved II, and the improvements seemed to have resulted in a very reliable engine.)
The Japanese superchargers were significantly better than the Bristol counterparts of pre- and early-war. Match the equivalent single-stage single-speed Sakae 12 or the single-stage 2-speed Sakae 21 supercharger to a 1701 in3 Taurus? RPMs and ultimate BHP would depend on how well the Japanese solved the cooling problems - from what I have read the Sakae 12/21 had no significant problems running at 950/980 BHP for prolonged periods.

What would the rating be on the Japanese O Ushi-Za engine (1701 in3 Taurus) with the better supercharger and 92 octane?

Taurus XII was rated for the 100/130 octane fuel, however the rated boost remained the same as on the Mk.II (at least that is what Lumsden says). It also turned 3100 RPM, vs. Sakae 21 turning 2700, hence the similar power even though the Sakae had more liters.
After everything is said and done, with the sleeve-Sakae making the similar boost and RPM, we'd be probably seeing the very similar power as the historical Sakae was doing.

OK, OK, not the British, but the various parties involved in the development of the sleeve valve engines in Britain.

Japanese taking note on the 2-stage supercharged European engines of the 1930s for altitude records (Bristol Pegasus of such flavor including) would've gave them a far better return of investment than going with the sleeve valves.

 

[Shortround6]

No problem as I see it.



The way I read it, it is a veiled praise to the Nakajima people.



Nakajima tried with the Mamoru. A 55L engine, a bit heavier than the Homare, 200mm greater diameter. Here is from the Japanese Wikipedia, my edit:

Despite the fact that it was under development, Nakajima strongly requested that it be installed in the Tenzan and Fukayama mountains [aircraft], but production was discontinued after only 200 units due to the lack of the specified output, high vibration, lack of reliability, and a series of failures.

Use the Kasei on a fighter, and hope for 380 mph as-is?

A 'classic' 18 cyl engine, like the Ha 42, was 110-120 kg heavier than the Homare, of a greater diameter, and was supposed to be as good on just 92 oct as the Homare was on 92 oct + ADI. OTOH, Nakajima made far more Homares than what the production of the Ha 42 was - Mitsubishi getting rid of the Zuisei might've increased the tempo of the Ha 42 production.
The 'no free lunch' rule applies as ever.

The problem is that the Nakajima people were trying to build the highest output radial engine on a power per liter basis
of all of the engine manufacturers in all of the countries.
While building the lightest high powered radial on a power to weight basis.
While using among the worst fuel. (Germans were using better ? fuel in the BMW 801)
While suffering from raw material shortages.

What could possibly go wrong

Kasei was 12-25mm bigger in diameter than the R-2800.

Wright had a lot of trouble with the so called 'easy' R-3350 even after 6 years of development.
The Mamoru used the same diameter cylinder as an R-2600/3350 but used 10mm more stroke.
The same stroke as the Kasei/Ha 42.
Japan waited too long to really address the big engine problem. The Homare sounds good on paper, but it is a very ambitious engine.
Something a bit less ambitious might have gone into service sooner or had less trouble in service.

 

[ThomasP]

re

Is there a good & easily available source that covers the Japanese sleeve-valve military-grade high-power aero engines ?

Obviously not - since the Japanese never endeavored to make any (as far as I am aware).

 

[Shortround6]

Japanese heavy involvement with sleeve valves could only have helped the allies.

The whole British (Bristol/Fedden) argument with sleeve valves started in the 1920s (yes a few cars used them 10 years before) with Harry Riccardo.
Most of the British engineers/designers knew each other and many had worked together during WW I and just after.
However some design teams were rather autocratic and it took a brave junior to challenge a leader.
Riccardo and Fedden had laid out a strong argument for the sleeve valve in the late 20s and while Riccardo was working on a number of things in his research company/establishment Fedden became fixated on the sleeve valve. Unfortunately it doesn't seem that he was keeping abreast of the improvements that the poppet valve engine companies were doing. Bristol, under Fedden, was concentrating on sleeve valve R&D and only a trickle going to the poppet valve engines. Unfortunately in England there was sort of a vacuum, Napier had lost their best designer to RR in 1929(?), Armstrong Siddeley had lost their designers in the early 20s and the boss, who had no real engineering education thought he knew better than the younger men. RR was making V-12s and was the main competition.

In the mid 30s Fedden gave a speech outlining the advantages of the sleeve valve vs the poppet valve to a British society. He basically just used all the same arguments of nearly 10 years earlier. Now the Bristol (and A-S ) poppet valve radials had changed very little over the years. Unfortunately P&W and Wright had made considerable progress and many of the "advantages" had disappeared. More were about to disappear with much better fuel and higher boost levels.
And we have the old problem of being able to design something and the very different problem of mass producing it.

Wright had gone from around 650 sq in of fin area on the cylinder head of the R-1820 in 1931, to just under 1000 sq in in 1933 to about 1900sq in in 1935 to just over 2000sq in 1937 to over 2300 sq in 1939. Wright used even more fin area on later R-1820 engines. The depth of the fins had roughly tripled in that amount of time.

Now this vast improvement in cooling was achieved without any change in the moving parts (and there were many changes). Wright and P&W and changed over to enclosed valve gear with lubrication by engine oil, not grease guns. Everybody was using sodium cooled exhaust valves, even low powered trainer engines, valve seats were being made of much better materials, valve springs had gotten much, much better. Many of the sleeve valve 'advantages' had disappeared. Fedden continued to list them. Of course the poppet valve Bristol engines were NOT making use of some of these improvements, only the ones that could be incorporated with the least expense and redesign/change in tooling.

A lot of the advantages of the sleeve valves have to looked at very carefully to see how well they actually stack up. We have several long threads on this over the years.

Sleeve valves have several problems in manufacture. The sleeve valve has to be made of a material that is just about identical in regards to heat expansion to both the pistons and the outer cylinder walls. It has to be very, very accurately machined/ground. It has to wear well, it has to 'hold' oil on it's sliding surfaces. maybe more?
It has some problems with use, especially in high performance engines. As boost went up the sleeve valves began to distort, crack, break at the edges of the ports due to the higher pressures. The problems with the sleeves going out of round in early mass produced Bristol engine (engines in the mid/late 30s seemed to work ok) and then the Napier engines.
Bristol only told Napier the 'secrets' just short of being at bayonet point and being marched to the Tower of London.
Yes Napier's problem was "solved" by using a few sets of of Taurus sleeves but this is a bit sketchy. The diameters (or least inside) were correct. Outer size? shape/location of ports?
And getting the Sabre to actually run for much longer than normal using these sleeves just showed it was possible. Does not mean that Bristol was sending over a couple of truck loads of sleeves per week to Napier?
Going by memory here but Napier tried well over 100 different combinations of materials and finishing (surface grinding) before Bristol coughed up the 'secret".
Not saying the Japanese could not do it on their own but it was going to be very difficult. And now they have to mass produce them.
The tale of the 6 grinders being sent to Napier from the US on the Queen Mary (unescorted high speed run) is well known. Less well known is the over 6 week delay caused to the P&W Kansas City plant being tooled up to make R-2800 C series engines. At best this cost about 7-8 engines in 1944 or at worst 600 engines produced in 1944 depending on which end of the year you look at and how much faster production would have gotten started in the Grinders had been delivered on time.
Not saying the Japanese could not have built grinders on their own, but obviously these were not small machines or easily available in Britain, Canada or the US.

 

[cherry blossom]

As Mitsubishi superchargers seem to have been better than those from Nakajima, at least late Pacific War as the J2M was kept in production because it was best against high flying B 29 raids, let us imagine how Mitsubishi might have produced a powerful 18 cylinder radial early enough to change something.

Goodwin and Starkings date the Mitsubishi A18 project with 18 Kasei sized cylinders to an Army contract in 1940 but a post by Shinpachi Japanese WWII piston engines with fuel injection reveals that an A18 was first run in August 1939. The A18 was developed with Army funding into a reliable but heavy engine with rather poor altitude performance and a relatively low rpm for the Ki-67 bomber, which entered service in 1944.

Meanwhile, what else was Mitsubishi doing? Obviously, the Zuisei, Kinsei and Kasei were in production and the Kinsei and Kasei were being developed into engines with direct fuel injection, water injection and relatively good superchargers, the Kinsei 60 and Kasei 20 series. In an ideal world, the time spent on Kaseis with contra rotating propellers and with extension shafts might have been saved. However, the Kinsei 60 and Kasei 20 series were obviously worth developing.

Building 3 mini Zuisei A17 engines with 70% of the already small volume between 1939 and 1942 was less justifiable. However, the Navy was the major distraction by funding the B6 (ME2 or Ha-203) 24 cylinder H type engine from 1940 until 1943. This also attracted some interest from the Army for a Ki-73 fighter project. Mitsubishi also planned a 28 cylinder four row radial with Kinsei type cylinders, the Ha-108 (Ha-118, Ha-218, MK11A or Ha-53) and had some plans for a 22 cylinder radial.

By early 1942, Mitsubishi was also working hard on the A20 (Ha-211, MK9 or Ha-43) which was intended to compete with Nakajima's Homare, despite a lack of official interest. This used 18 Kinsei sized cylinders but departed from previous Mitsubishi practice by having a fore and aft cam ring. It also used relatively high boost (for Japan) with water injection and relatively high rpm of 2900@520mm/50.4" to give 2200 ps for take off. However, this engine was not reliable, mostly due to vibration, until late in 1944. It did power prototypes such as the A7M2 and the Ki-83.

Finally, Mitsubishi redesigned its A18 as the A18E by applying the advances of the A20. The power is quoted as 2400 ps at 2600 rpm and 500 mm. However, when engines were supplied for the Ki-93 (attack aircraft?), the power is quoted as only 1970 ps. I am guessing that water injection was not available for those engines.

So the question is could Mitsubishi have made a reliable 2400 ps A18E by late 1943 if they had been paid to do that and only distracted by the Kinsei 60 and Kasei 20 series? The A18E (Ha-214) was 1,340 mm wide and weighed 1,235 kg. For comparison, a Centaurus VII had a 1,405 mm diameter and weighed 1,222 kg. The Centaurus was more powerful but a Sea Fury with a reliable A18E would still be formidable even if one of its tanks had to hold water/methanol.

 

[tomo pauk]

The problem is that the Nakajima people were trying to build the highest output radial engine on a power per liter basis
of all of the engine manufacturers in all of the countries.
While building the lightest high powered radial on a power to weight basis.
While using among the worst fuel. (Germans were using better ? fuel in the BMW 801)
While suffering from raw material shortages.
What could possibly go wrong

Homare is bad because it worked?
How dare the Japanese make something good. As if they are from some cool country.

Wright had a lot of trouble with the so called 'easy' R-3350 even after 6 years of development.
The Mamoru used the same diameter cylinder as an R-2600/3350 but used 10mm more stroke.
The same stroke as the Kasei/Ha 42.

Seems like that when Nakajima went conservative in search of great power, it backfired badly.

Japan waited too long to really address the big engine problem. The Homare sounds good on paper, but it is a very ambitious engine.
Something a bit less ambitious might have gone into service sooner or had less trouble in service.

Nothing prevented Army and Navy to say to Mitsubishi: we want conservative 2000 HP engines as much as you can make them, you are free from making small engines, and we will support both your production of these engines as well as production in other companies.

So the question is could Mitsubishi have made a reliable 2400 ps A18E by late 1943 if they had been paid to do that and only distracted by the Kinsei 60 and Kasei 20 series? The A18E (Ha-214) was 1,340 mm wide and weighed 1,235 kg. For comparison, a Centaurus VII had a 1,405 mm diameter and weighed 1,222 kg. The Centaurus was more powerful but a Sea Fury with a reliable A18E would still be formidable even if one of its tanks had to hold water/methanol.

Ha 42 was supposed to do 2000 PS on 91 oct fuel (and possibly on 87 oct, the US report on the Ki-67 is ambiguous). Use water-alcohol injection and we might get to 2300? Under 1000 kg.

 

[tomo pauk]

Wrt. the fuel the Taurus used - manual for the Albacore says '100 oct fuel only', for either the Mk.II or Mk. XII engine.
link

 

[ThomasP]

The original rating for the Taurus II with 87 octane was at 3225 rpm (I think it was at +2.75 lbs but I do not remember for sure) at 5,000 ft, while the later rating for the Taurus II and XII with 100 octane was at 3100 rpm and +4.75 lbs at 3,500 ft. They compromised when they rated them on 100 octane - by reducing the rpm while increasing the maximum allowable boost. The supercharger was almost exactly the same on the both Marks (Ø11.25" open type impeller turning at 5.6:1 gear ratio), so the higher boost was accomplished at a 1,250 ft lower altitude. The Taurus XVI had the same ratings on 100 octane but used a smaller (Ø8.75") less efficient (in terms of HP used) fully shrouded supercharger impeller with a higher speed gear ratio (7.5:1).

Possibly of interest, all surviving Taurus II engines were modified as time allowed and redesignated Taurus XII after receiving said mods.

[edited - changed "+3.5 lbs at 3,750 ft" to "+4.75 lbs at 3,500 ft"]

 

[Airborne2001]

To begin with - cooperation between the army and the navy without duplicating development, the same calibers of weapons and so on.
For example, Daimler sold an aircraft engine license to the Army (Kawasaki) and the Navy (Aichi)!
Japan is the only nation whose military had aircraft carriers and whose navy had ground forces (and I don't mean the SNLF as marines).
We can say that Germany lost the race in the development of the atomic bomb because they had 5 ? independent and non-cooperating teams, but Japan had two parallel military forces that (mostly) did not cooperate.

A good example of this I always cite is the Sakae 31. The Navy couldn't get it to work until mid-1945, meanwhile the army got it on the Ki-43-III by the beginning of 1944. Obviously better engine choices existed, but this is a strong example for me personally. Co-operation would mean a working A6M6 by The Battle of the Phillippine Sea.

 

[tomo pauk]

@ anyone - what was the 1st known instance that 'Homare is/was unreliable' appeared in the Western press?

 

[z42]

Keeping on the topic of Japanese engines, what about diesel engines for ships? In particular, low speed two stroke ones, having several advantages (which is why they have dominated oceanic shipping post war) :

• Ability to use the same cheap bunker fuel that steamships use.
• No need for an expensive and heavy reduction gearing nor reversing gearbox as the engine itself is reversible. Thus the engine is directly connected to the prop shaft.
• Very high thermal efficiency, about 40% can be expected in the WWII time frame. Including at part load. This could be a significant advantage, as a large fraction of the Japanese oil supply was used as fuel oil for the IJN.
• With a piston ported design, as was common for two stroke diesels of the time, no valves and valve gear needed.
• If using crankcase scavenging, no need for a blower either.
• No risk for a steam explosion if the ship is hit.

There are of course also a number of significant disadvantages for this kind of engine, particularly for warships:

• Poor power density. Contemporary low speed diesels have about half the power density of medium speed diesels. In the WWII time frame medium speed diesels were somewhat worse than steam plants (the Deutschland class, for instance), but newer diesels at the time being somewhat better. OTOH without reduction gearing, separate cruising and reversing turbines etc, the low speed diesel can claw back some of that disadvantage. Further the much better fuel efficiency allows carrying much less fuel than a comparable steamship.
• Height of the engine. And not only the engine itself, there needs to be space above the engine for piston and conrod replacement. For a gunship, this probably means a bump in the citadel roof above the machine room spaces. OTOH the machinery spaces are probably shorter than for an equivalent steam plant, enabling a shorter citadel.
• Availability of large enough engines. The largest pre war diesel I'm aware of is the 22500 hp B&W 2000. With a four shaft ship, that might be enough for roughly a cruiser sized ship. OTOH with a concerted effort bigger ones might be designed.

Historically, the Japanese experience with diesels for high speed warships wasn't a happy one. They were seriously considering diesels for warships, e.g. several of the design studies leading up to the Yamato class were diesel powered, in part and total. But experience with a ship using the selected engine (sub tender Takei(sp?)) was very bad, and instead an all-steam design was chosen. Somewhere I read that at the time they were chasing the double acting diesel chimera, also resulting in a number of submarines that had to eventually be reengined with lower power single acting engines.

In 1928 Mitsui licensed the B&W marine diesel portfolio, in the interwar years the market leader in that segment. So it seems they could have built decent enough diesels, at least had they avoided the double acting chimera.

 

[cherry blossom]

@ anyone - what was the 1st known instance that 'Homare is/was unreliable' appeared in the Western press?

A fairly early but possibly not immediately published report came from Colonel Henry Watson, who was not impressed when he tested a G8N1. The turbosuperchargers had been disabled by Japanese engineers before the surrender, presumably because of unreliability. He reported that the engines would sometimes surge, pitch control of the propellers was difficult and de-feathering was not possible. Three of the engines would not deliver full rpm and all four had to be frequently readjusted as throttle and fuel feed controls would wander. Engine temperatures were erratic and each had to have its cowl flaps individually adjusted. Even with cowl flaps closed, the aircraft vibrated seriously, which Watson was advised was endemic to the engines, which he was unable to keep synchronised (all from Goodwin and Starkings, page 180).

 

[tomo pauk]

A fairly early but possibly not immediately published report came from Colonel Henry Watson, who was not impressed when he tested a G8N1. The turbosuperchargers had been disabled by Japanese engineers before the surrender, presumably because of unreliability. He reported that the engines would sometimes surge, pitch control of the propellers was difficult and de-feathering was not possible. Three of the engines would not deliver full rpm and all four had to be frequently readjusted as throttle and fuel feed controls would wander. Engine temperatures were erratic and each had to have its cowl flaps individually adjusted. Even with cowl flaps closed, the aircraft vibrated seriously, which Watson was advised was endemic to the engines, which he was unable to keep synchronised (all from Goodwin and Starkings, page 180).

Thank you.
Is there anything about the Homares on the 1-engined aircraft?

 

[TM06]

Thank you.
Is there anything about the Homares on the 1-engined aircraft?

Page 10 of the T-2 Report on the Ki-84 notes that pilots had no lack of confidence with the Homare engine during testing, but this is post-war US testing with a nearly ideal Ki-84 running on 96 octane so take it with a grain of salt.

 

[Geoffrey Sinclair]

The Taurus was in production by end Q2/39 with an average of 12 built per month, peaking an average of 118 per month in Q2/40 then declining into double figures, all up 1,741 II and VI and 1,633 XII, the XII probably starting production in Q3/41 and ending in August 1943. The engine production reports tend to put Taurus under "other", let alone give mark numbers.

When the Ministry of Aircraft Production begins reporting engine conversions in May 1944 it says to end April 1944 17 Taurus II, VI and XVI had been converted to XII. The final time the Taurus conversions are reported, to 26 May 1945, the total is still 17.

From British Piston Aero-Engines and Their Aircraft by Alec Lumsden

Taurus two row sleeve valve air cooled radial, Bore 5.0x5.625 inches, Swept Volume 1,550 cubic inches, Compression Ratio 7.2 to 1, Diameter 46,25 inches, length 49.2 inches though dimensions vary according to accessories, left hand tractor.

Taurus II 1,0560 HP (1940) medium supercharged, geared epicyclic 0.444 to 1 (Basic sleeve used in Sabre) Power curve at 5,000 feet was 3,255 RPM/1,140 BHP/+4.3 pounds per square inch boost, 3,000/1,048/+3.5, 2,800/958/+2.88, 2,600/848/+2.03, 2,400/760/+1.47. Maximum boost 3,225/1,140/+4.25 take off to 1,000 feet or one minute. All out level flight (5 minutes) +4.25, 3,225 RPM. All figures using 87 Octane (DTD230) from A&AEE report M.740 dated 26 October 1939.

Taurus XII 985 HP (1940), supercharger ration 5.6 to 1, larger impeller.

Performance table data
II, 87 octane take off 3,100 RPM/1,060 BHP/+4,25 pounds per square inch, Normal, continuous (ratted) power 2,700/930/+2,75 at 4,000 feet, maximum power (emergency, combat, 5 minutes) 3,100/1,110/+4.25 at 4,000 feet, dry weight 1,300 pounds.

XII, 100/130 octane take off 3,100 RPM/1,090 BHP/+4,75 pounds per square inch, Normal, continuous (ratted) power 2,800/930/+3,5 at 3,750 feet, maximum power (emergency, combat, 5 minutes) 3,100/1,130/+4.75 at 3,500 feet.