Author Topic: Ki84  (Read 4590 times)

Offline Wilbus

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Ki84
« Reply #30 on: July 20, 2005, 03:12:11 PM »
Correct Karnak unless this page is lying. Scroll down to just bellow middle of the page, last section just before "Specification of Nakajima Ki-84-1a:".

This is what it says:

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In 1946, a captured late-production Hayate was restored and tested at the Middletown Air Depot in Pennsylvania. At a weight of 7490 pounds, the aircraft achieved a maximum speed of 427 mph at 20,000 feet, using war emergency power. This speed exceeded that of the P-51D Mustand and the P-47D at that altitude by 2 mph and 22 mph respectively. These figures were achieved with a superbly maintained and restored aircraft and with highly-refined aviation gasoline, and were not typical of Japanese-operated aircraft during the later stages of the war.


Definatly a top end machine had it been flown on good fuel and with proper maintanance!


Here  is an interesting link comparing the production Ki 84 (well, Production Ki 84 in theory, most of them were poorly built) with some US planes, very interesting link sugest you read it!
Rasmus "Wilbus" Mattsson

Liberating Livestock since 1998, recently returned from a 5 year Sheep-care training camp.

Offline Wotan

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Ki84
« Reply #31 on: July 20, 2005, 03:23:23 PM »
Wilbus,

All this was argued over before the K-84 was introduced.

There are many variables. For instance in FB/AEP/PF the Ki-84 is modelled with at its best, even with water-methanol.

In AH they chose the low (safer) end. The old threads are there if you are interested in how they arrived at their conclusions. They are spread out between the the A & V forum and the General discusssion forum.

Offline Wilbus

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Ki84
« Reply #32 on: July 21, 2005, 04:51:08 AM »
Wotan? What are you on about? :)

Not sure you've read the discussion but only my last post.

I haven't said a thing about making the Ki84 better, just having a friendly discussion with people about adding the Ki84 1b.

The last post I made was to show Karnak two interesting links I found about it, nothing more, not in any way ment to lobby for an improved Ki84.

Please read the whole thread and nothing but the thread :)
Rasmus "Wilbus" Mattsson

Liberating Livestock since 1998, recently returned from a 5 year Sheep-care training camp.

Offline Wotan

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Ki84
« Reply #33 on: July 21, 2005, 05:24:14 AM »
My referrence to the 'past discussions' has no bearing on making the Ki-84 in AH 'better'.

You mentioned:

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A Captured Ki84 was brought up to over 420 (430?) mph in the US on US fuel.


The use of 100 octane fuel in that captured  Ki-84 may have been used to simulate water/methanol.

Higher octane fuel detonates at a higher temp / pressure and should allow for a higher boost. But high Octane fuel run in an engine with a low compression ratio would not burn as clean and you would end up with a dirty intake and not much of a performance boost. Engine wear would be a problem as well because of the higher temp. Its not clear that simply putting US 100 octane gas in the Ki-84 tank would mean greater performance.

If the Ki-84 is without water/methanol then MAP limits for 87 octane will indeed mean a much slower plane then one with 100 octane or one with 87 + water / methanol. It wouldn't make sense that the US would have tested the Ki-84 with higher MAP settings then were used by the Japanese with 87 + water.

My point being is that the Ki-84 didn't necessarily need 'US fuel' to be a 'top performer'. Fuel is only one issue.

Below is a quote I provided from another forum (J-Aircraft Forum) in a past Ki-84 discussion on this A & V forum:

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My argument is to eventually show that the American test claim of 427mph @ 20,000ft was quite naturally to be expected of a FRANK powered by the Homare Model 21 (and-it W-A-S a Model 21...), if the (older) figure of 388mph was derived from a prototype powered by Homare Model 11, and that it could have hardly done otherwise if the later model engine, in fact, did fully-attain its intended "design-to" power-level, especially @ higher altitudes.

Had the Americans captured some very early FRANK (especially-if powered by the (first) Model 11 engine...and, obviously, without the exhaust augmentation...), its "fame" would be nonexistent as we know it today; its max speed would hardly differ from that already quote in Rene Francillon's book:

“During the flight trials, the Ki-84 reach a speed a speed of 388 mph..."(pg.231)

I assert that the obvious difference in the two max speeds - merely shows the steady but intensive Nakajima effort at improving the "total" power plant output, by whatever means - more then the use of American avgas. (Although, ultimately, it may have needed to depend on the very high-octane gasoline-only the Americans had-to reach its "design-to" power-level, especially @ higher altitudes. Perhaps fortunate too was a "good" (production sample) engine that happened to be found in the FRANK example falling into Yankee hands...)

Anyway, here's a profile of how the two Homare models markedly different in their respective power levels @ all altitudes (AIREVIEW's General View of Japanese Military Aircraft in the Pacific War, Vol.1, pg.320):

Ha-45/11 NK9-B (IJN-nomenclature)
HP (T.O.): 1,800 @ 400mmHg & 2,900rpm
HP (2,000m/6,562-ft): 1,650 @ 250mmHg & same-rpm
HP (5,700m/18,701-ft): 1,460 @ 250mmHg & same-rpm

Ha-45/21 NK9-H (IJN-nomenclature)
HP (T.O.): 2,000 @ 500mmHg & 3,000rpm
HP (1,800m/5,901-ft): 1,860 @ 350mmHg & same-rpm
HP (6,400m/20,997-ft): 1,620 @ 350mmHg & same-rpm

Notes:

1- The Ha-45/21's more-oft quoted T.O.HP is: 1,990, in most other literature and the less often quoted (fully) 2,000Hp was more reserved for the "finally-arrived & matured" Ha-45/22, as the very next step, i.e., that the Model 21 was "almost" the Model 22.

2- Manifold Pressures (given in "inches") following the "boost” pressures (I translated the Japanese practice of merely quoting only the "boost” pressures (i.e., “gauge" pressures / above Standard Atmosphere (980mb), instead of the "total" pressure - that the Americans call: “Manifold Pressure"-which already includes the basic: 29.92-within their figures, become-translated:

Ha-45/11: (1st-speed): 400mm= 45.7" (2nd speed): 250mm= 39.8"

Ha-45/21: (1st-speed): 500mm= 49.6" (2nd-speed): 350mm= 43.7"

From this(and other sources...I also assert that the (earliest ) Homare (-11) engine can best be "profiled" as an:"1800/1400"engine, at best(meaning:

1,800Hp@S.L./1,400Hp@20,000-ft. (This is just my way of "stereotyping" these engines, for sake of illustration...)
Yet, Nakajima's goal was really "the mature Homare," as a fully arrived: "2000/1700"engine (meaning:2,000Hp@S.L./1,700 Hp@20,000-ft), and this power goal was to be "attained" by the Model 22. (Further power-improvements were also forthcoming, also w/more sub-models w/different blower-schedules, but I think "everyone" would just finally be happy when the "genuine" (and reliable...)"2000 / 1700" Homare, finally arrived...

Now, I do understand that these are (likely) “design to” goals, specified by contract as figures to-be-attained for a given production assignment, and not what really resulted in delivered products, to the field.

But anyway - so, what would (ideally) happen? Just what were the "simple" consequences of bringing your horsepower, up, from: 1,400 to-say...1,700? Well, if you did-388mph (on just 1,400Hp...), than by the simple cubic-root/law, you must now go-414mph! (In fact-you couldn't help it...)

So the next step remains: How do you finally get to: 427mph?
Simply by increase your "horsepower" to: 1,866. That's only just another 166Hp-would give that extra: 13-mph... So, where’s another way to get that extra boosting - without putting your engine in the garage?

That's all for now,

Robert

P.S. Tomorrow, I want talk about :

1- Exhaust Augmentation w/"actual"(likely) figures of: “pounds-of-thrust" including its real effect on speed...

2- Why power must still "drops / increasing altitude, even @ constant manifold pressure & rpm / delivery, and perhaps why high octane may be more efficacious here @ these higher altitudes, more than the lower-altitudes... (Although I think the two "engine" experts...we all know about...can explicate this better than I can...)

3- Further (more advanced) Homare models @ their (internal) dynamic specs...

4- What "may have happened" to the hapless Homare Model 22 engine in the original Reppu an (unexplained?) first class disaster for Nakajima (I was a propulsion-engineer / junior officer @ Wright Patterson AFB - and I know a "performance event / catastrophe" when I hear of one...)

Remember, I don't necessarily have the answers, but I want to bring attention to certain things, in certain ways...


Anyway my point was that you seem interested in the Ki-84 and I thought you may have an interest in the past discussions. I figured it be easier to point you in that direction then re-posting the above here once again.
 
I read the current discussion completely and can only wonder given your last reply:

Quote
What are you on about?


:p

Offline Wilbus

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Ki84
« Reply #34 on: July 21, 2005, 07:50:17 AM »
Thanks Wotan, very nice info!

As for my last reply, it seemed to me as if though you thought I was lobbying to have the Ki84 improved in AH2 and you answered to tell me that "been there done that there is nothing wrong with the Ki84..." sort of thing.

As I was aay from AH due to Studies when the Ki84 was added I haven't been able to keep up on the discussions about it, I've merley fallen in love with it since I got back.

Quote
But anyway - so, what would (ideally) happen? Just what were the "simple" consequences of bringing your horsepower, up, from: 1,400 to-say...1,700? Well, if you did-388mph (on just 1,400Hp...), than by the simple cubic-root/law, you must now go-414mph! (In fact-you couldn't help it...)     So the next step remains: How do you finally get to: 427mph?   Simply by increase your "horsepower" to: 1,866. That's only just another 166Hp-would give that extra: 13-mph... So, where’s another way to get that extra boosting - without putting your engine in the garage?


So what you are sayin is that, the max speed of 388mph was achieved with the HA 45/11 engine with far less HP then the 21 engine modelled in AH's Ki? If that is the case, then why does the Ki in AH not go faster? You said low octane fuel might be part of the issue but not the whole issue what would the other problems be? One would think HTC modell all planes in "good condition" so the engine in AH really should give a maximum of 1990Hp...
Rasmus "Wilbus" Mattsson

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Offline Wotan

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Ki84
« Reply #35 on: July 21, 2005, 08:29:00 AM »
Quote
So what you are sayin is that, the max speed of 388mph was achieved with the HA 45/11 engine with far less HP then the 21 engine modelled in AH's Ki? If that is the case, then why does the Ki in AH not go faster? You said low octane fuel might be part of the issue but not the whole issue what would the other problems be? One would think HTC modell all planes in "good condition" so the engine in AH really should give a maximum of 1990Hp...


Here's what Pyro said:

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Top speed is 388, except for the fact that it's not making full power right now.

The WEP issue is a confusing one. Busa has been doing a lot of research for me over in Japan on the N1K and also the Ki-84. It's not very clear-cut as the engine had various restrictions placed upon it at various times and the IJA and IJN did not treat the engines the same. His research leaned toward the Ki-84 not making use of WEP while the N1K did, but again, it is not a clear-cut situation and is the source of much debate.

__________________
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HiTech Creations


Busa posted:

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The performance is as follows.

1820H.P. of takeoff power. (MP+350 RPM2900)
1670H.P/ 2400m of military power. (MP+250 RPM2900)
1500H.P./ 6550m of military power. (MP+250 RPM2900)


Seems to me the AH2 Ki-84 is mounted with Ha-45/11...

Offline Wilbus

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Ki84
« Reply #36 on: July 21, 2005, 10:23:03 AM »
Uhmmm OK....
Rasmus "Wilbus" Mattsson

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Offline Loddar

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Ki84
« Reply #37 on: July 21, 2005, 10:31:23 AM »
Are we talking about the armament of
the Ki84 or the engine  :confused:

I thought B & C only have different and
stronger armament. Ki is fast enough
in the game.

Offline Wilbus

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Ki84
« Reply #38 on: July 21, 2005, 02:10:17 PM »
We're discussing armament :)

Wotan posted some more info for me though which I found very interesting.

Only difference between a, b and c was armament.

But there were different engines used within those versions.

Wotan just said he thinks our Ki uses the 45/11 engine while I've heard others say it uses the 45/21 engine. I don't know.
Rasmus "Wilbus" Mattsson

Liberating Livestock since 1998, recently returned from a 5 year Sheep-care training camp.

Offline Karnak

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Ki84
« Reply #39 on: July 21, 2005, 02:42:10 PM »
I recall being told the -21, but I could be wrong.
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Offline Wilbus

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Ki84
« Reply #40 on: July 21, 2005, 03:28:53 PM »
Rgr Karnak would be nice to know. The little info I have about it states the 21 was the most common.
Rasmus "Wilbus" Mattsson

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Offline Karnak

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Ki84
« Reply #41 on: July 21, 2005, 04:04:25 PM »
Quote
Originally posted by Wilbus
Rgr Karnak would be nice to know. The little info I have about it states the 21 was the most common.

What I have read says the same thing.

But, using a fighter with a much clearer record, the Merlin 66 was by far the most common engine for the Spitfire Mk IX, and ours has the Merlin 61 which was the rarest and least powerful.

So....
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Offline 1K3

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Ki84
« Reply #42 on: July 23, 2005, 02:49:34 PM »
I went searching for old Ki-84 threads and Busa said ours is powered by NK9H-B (Ha-45-12) engine (a derated NK9H Ha-45-21)

The performance table of Homare is exhibited.
http://homepage2.nifty.com/amraam/ah/tmp/bbs002.zip
« Last Edit: July 23, 2005, 03:03:09 PM by 1K3 »

Offline 1K3

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Ki84
« Reply #43 on: July 23, 2005, 02:54:09 PM »
Looks like the NK9H-B (Ha-45-12) engine for AH Ki-84 is temporary until Busa figures out RPM. WEP, M/P  WEP, and Power   WEP for NK9H (Ha-45-21) engine.

Offline 1K3

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Ki84
« Reply #44 on: July 23, 2005, 03:05:42 PM »
here's an interesting note from busa
http://homepage2.nifty.com/amraam/ah/tmp/bbs002.txt