Info needed on Nakajima Ha-5/41/109 radial

[msxyz]

This thread goes on par with the other one about the Nakajima Kotobuki, as this engine may be considered a close relative

The Ha-41/109 (Army type 2 Radial ???) share the same bore, stroke and possibly head design with the Nakajima Kotobuki model 3 engine. It's a compact two row, 14 cylinder radial engine. It was used in the Ki-44 interceptor and in the Ki-49 twin engined medium bomber. It's slightly smaller and lighter than contemporary engines of similar layout and capacity (37.5 liters, 1500 HP class) and gave good service.

Nakajima Ha-5/41/109:

14 cylinders, two row, air cooled radial engine.
Lenght: ???mm
Diameter: 1260mm
Weight: 630Kg (Ha-5/41), 720Kg (Ha-109)
Bore: 146mm
Stroke: 160mm
Capacity: 37.5 liters
Compression ratio: 6.7:1
Supercharged: yes, 8.39x (Ha 5/41); 6.55x and 8.66x (Ha-109)
Redution gear: 0.6875x (11/16 gear mesh)
Fuel: Gasoline (RON ???)

Performance data:

Ha-5: 890 HP @ 2200 rpm, -50mm Hg, 4700 meters
Ha-41: 1260 HP @ 2450 rpm, +150mm Hg, 3700 meters
Ha-109: 1440 HP @ 2600 rpm, +200mm Hg, 5200 meters (highest blower setting)

Take off power:
Ha-5: 950 HP @ 2200 rpm, +50mm Hg
Ha-41: 1260 HP @ 2500 rpm, +250mm Hg
Ha-109: 1500 HP @ 2650 rpm, +30omm Hg

I'm looking for any additional info and good resolution photos, drawing, schematics, etc about this engine. Since there's no surviving Ki-44 or Ki-49 airplane, I know info is hard to find. I think at NASM there's one engine (possibly from a Ki-44) preserved in storage. Maybe someone can share more info on it.

 

[Piper106]

I have seen on the internet that the 18 cylinder Nakajima Ha-219, unified designation [Ha-44] shared the same bore and stroke.
Possibly this also shares design traits with the Ha-5/41/109 line.

Side comment. It is interesting that most of the other radial engine builders concentrated their wartime efforts on a single cylinder size. P&W a 5.75 x 6" cylinder, Wright, a 6.125 x 6.3125" BMW and Shethov nearly the same size as the Wright, yet Nakajima spread their efforts over three different cylinder sizes; the 130 x 150 mm Sakae and Homare, the 146 x 160 mm Ha-5/41/109, and the 155 x 170 mm Mamoru. My opinion is that Nakajima did not have enough resources to develop that many projects under wartime conditions.

 

[msxyz]

The radial engine modularity allows an entire family of engines developed from a single pot design, hence why we've so many radials from a certain manufacturer sharing the same dimensions.

In case of Nakajima, the Kotobuki and type 2 bore and stroke dimensions betray an english ancestry, being close to 5.5" and 6.3" respectively. These engines were developed in the 30's, the latter being the ultimate evolution of the basic Kotobuki design.

Once the japanese switched to completely indigenous designs they embraced nice, rounded centimetric dimensions for their engines (130x150, 140x130, 140x150 and 150x170). 130x150 seemed to be the most popular (it was used not only by nakajima but also by hitachi nd mitsubishi). Pistons of this size are reasonably light and allow a compact, high revving engine (less stress on the rods, smaller counterweights, etc).

Nakajima two most developed engines, the Sakae and the Homare, used these dimensions, the rest of their projects reached dead ends or were not pursued further.

In any case, the Ho-109 is probably an "underappreciated" engine. It developed the same power of the Kasei 13 weighting 50 kg less and with a diamater of only 1260 mm (Kasei was 1340-50). At 6000m, with the low octane fuel issued on the field, it was probably better than the Homare, not to mention that the Homare was probably not safe to be pushed at the advertised 1900 hp at low altitude either due to failure prone bearings.

Did I mention it was available from the onset of the war? I often wonder if designs like the Ki-84, the N1k and the P1y would have reached the field sooner and be more effective if Nakajima managers swallowedtheir pride and admitted that the Homare wasn't a feasible design given the current state of metallurgy and fuel available in Japan during war time.

 

[Piper106]

An 18 cylinder version of the Ha-41 might have been the best fit for the Ki-84, N1K, P1Y, C6N, and others.
Bigger cylinders running at only 2450 rpm and +250mm Hg boost (about 40" Hg absolute) might have been easier to develop than the Homare which ran at 3000 rpm and 500 mm Hg boost (about 50" Hg absolute)

Mitsubishi seems to have done well with a similar concept developing the 14 cylinder Kasei into the 18 cylinder Ha-104 (used in the Ki-67 among others). Only 1850 HP from a 54L / 3300 cid engine isn't impressive, but what little I think I know, the Ha-104 was 'produce-able' and reliable, something the Homare seems not to have been.

 

[msxyz]

It seems the Ha-5/41/109 engines derived from the Gnome Rhone Mistral Maior 14K, although these are not exact copies... Not only they differ in the stroke, (160mm versus 165mm) but the distribution is different: Gnome Rhone engines drove all the valves from a single front radial cam while Nakajima followed the american approach and used a second radial cam between the crankcase and the compressor to drive the valves of the rear row.

Many engines derived from the Gnome Rhone 14K Mistral: design was licensed to Nakajima in Japan but also to Piaggio in Italy

In this respect the italian "offspring" of the 14K, the Piaggio P.XI, is much closer to the original; interestingly, it and also evolved into a 18 cylinders, 53 liters monster for bomber use: the Piaggio P.XII . Unfortunately, the international ban imposed on Italy prevented them to stockpile strategic materials much in need to build a reliable engine. Not only power was limited to 1000 HP for the 14 cylinder Mistral copy and 1500 HP for the 18 cylinder evolution (versus the 1500/2200+ HP reached by the Ha-109 and Ha-219), but the engines ran hot and were prone to catastrophic failures. One the good side, these engines were lighter than their French/Japanese counterparts, mainly due to abundant use of alluminium/zinc/magnesium alloys (these metals were readily available in Italy from domestic sources and Italy also had plenty of hydroelectric power stations to drive the galvanic cells needed to smelt these light metals)

 

[msxyz]

I found an image of what is possibly the sole surviving example of a Type 2 radial:

http://www.preservedaxisaircraft.com/Japan/Engines/Ha34-11 NASM.jpg

As I remembered, it's owned by NASM and sits currently in the Paul Garber facility along with several other forgotten treasures of that period. I wonder if someone here who happened to visit the Paul Garber storage facility has better pictures of it or knows someone who I could contact directly for more info.

 

[tomo pauk]

Many thanks for the very informative posts.

 

[msxyz]

Many thanks for the very informative posts.

You're welcome. I hope to spark some interest in this rather obscure engine and, of course, I hope someone can give me better graphic material and / or information on this eninge than I could find using search services alone!

Maybe, I'll have better luck if I contact Robert Mawhinney of the NASM. I think he was working a book about Japanese engines. Does anybody know if he completed it?

 

[msxyz]

Some more info... still not any new picture/drawing whatever...

Some sources state (including copies of documents I've downloaded from these forums) that the original Ha-5 (Type 2 Army radial) had a maximum power of 1080 HP at 4000m. This is not in contradiction to the quoted figure of 890 HP at 4700m, -50mm HG... This is probably the highest possible continuous power available in the air, while 1080 HP is probably 'emergency/war power' for a short period of time.

I'm also trying to locate some info about the gasoline employed in these engines. I've found found various references to a Technical Air Intelligence Report No. 2, on Japanese Engines (march 1945) which should contain quite a good deal of info on this

It was not uncommon for Japanese aircrafts, especially later in the war, to fill one tank with 92 octane gasoline, to be used at take off, and then switch to 87 octane for cruise. Emergency power was either attained with 92 octane or by spraying some methanol mixed with water in the carburetor inlet while opening the throttle further to increase boost pressure.

This is pure speculation o my part: in case of the Ha-5, the modest boost pressure and low level of specific power obtained (below 20KW/l) could be obtainable with 87 octane gasoline alone. In case of the Ha-109, however, I think the quoted figures are for 92 octane gasoline, possibly with ADI for TO and Military power.

Usage:

The Type 2 Army radial was used in several aircrafts:

Ha-5 (950 HP):
Army Type 97 light bomber (Mitsubishi Ki-30)
Army Type 97 heavy bomber (Mitsubishi Ki-21)
Army Type 100 Transport Model 1 (Mitsubishi Ki-57)

Ha-41 (1250 HP):
Army Type 100 Heavy Bomber Model 1 (Nakajima Ki-49)
Army Type 2 Single-Seat Fighter Model 1 (Nakajima Ki-44)

Ha-109 (1500 HP):
Army Type 100 Heavy Bomber Model 2 (Nakajima Ki-49-II)
Army Type 2 Single-Seat Fighter Model 2 (Nakajima Ki-44-II)

 

[Aurum]

130x150 seemed to be the most popular (it was used not only by nakajima but also by hitachi nd mitsubishi).

Mitsubishi never used 130/150 cyl. size

Nakajima two most developed engines, the Sakae and the Homare, used these dimensions, the rest of their projects reached dead ends or were not pursued further.

That's wrong. Dear Shinpachi posted general list of Nakajima's engines that shows that either Ha-5/41/109 or Hikari/Mamori engines designes had been developing into their 18-cyl. versions.

In any case, the Ho-109 is probably an "underappreciated" engine.

And I am fully agreed with this thought! I also consider Ha-109 as the BEST Nakajima's engine of the war begining that might be installed on EVERY plane that was equiped by Sakae in reality, including Zero Hayabusa. In this case Zero speed 600-610km/h would be guaranteed!

I often wonder if designs like the Ki-84, the N1k and the P1y would have reached the field sooner and be more effective if Nakajima managers swallowed their pride and admitted that the Homare wasn't a feasible design given the current state of metallurgy and fuel available in Japan during war time.

I consider Homare as advanced quite prominent but also appropriate for technology design. But it might be used only for maneuverable fighters definitely Ki-84 Zero. N1k might be powered by Jusei (Ha-104) P1Y woukd be best with Kaseis 25 as in fact P1Y2 in reality were.

...while Nakajima followed the american approach and used a second radial cam between the crankcase and the compressor to drive the valves of the rear row.

Such configuration was more advanced so Mitsubishi also turned to it in it's latest engines' designes

 

[Aurum]

I have seen on the internet that the 18 cylinder Nakajima Ha-219, unified designation [Ha-44] shared the same bore and stroke. ... this also shares design traits with the Ha-5/41/109 line.

Yes of course! So on the contrary to msxyz's statement that
Nakajima ..., the rest of their projects reached dead ends or were not pursued further
Ha-5/41/109 family was successfully prolonged into 18 cylinder Nakajima Ha-44 [Ha-219] so everyone can see