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Special Type 3 Motorboat "Ka-Chi" Amphibious Tank


aizenns
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Just now, Pony51 said:

Not ideal, still useful.

 

The Ka-Mi might have been based on Ha-Go, but I doubt the Ka-Chi is based on any tank.  I think it is based on a submarine.

I thought the Ka-Chi is based off of the Chi-He? That's at least what is referenced everywhere.

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4 minutes ago, Wiggly_Armed_Man said:

I thought the Ka-Chi is based off of the Chi-He? That's at least what is referenced everywhere.

The mechanical and turret (systems), but the hull is new.

To call it "based" is misnomer.

 

For example a FlakVerling is based on Panzer IV.  Or a Marder based off a PzKwg 38(t), or a Duster based off a... what is it?  Chaffee?

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19 minutes ago, Pony51 said:

The mechanical and turret (systems), but the hull is new.

To call it "based" is misnomer.

 

For example a FlakVerling is based on Panzer IV.  Or a Marder based off a PzKwg 38(t), or a Duster based off a... what is it?  Chaffee?

Close enough, the M19 is based on the M24 Chaffee, the M42 Duster is based on the M41 Walker Bulldog.

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On 30/07/2021 at 08:54, aizenns said:

As you see, structure of this vehicle is very unique: turret, side sponson, and suspensions are equipped on the pressure-resistance shell. Simply to say it was submergible tank to launch from submarine. (Maximum depth was about 100m !) 

That's epic. 100 Meters, that's 330 feet, really deep. Almost near the max depth of the average WWII era submarine. I can't wait for this thing. :yes_yes_yes:

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On 02/08/2021 at 17:05, tester188@psn said:

The Type 3 Ka-Chi has 50 mm of armor on the front, 16-20 mm on the sides, and 12 mm on the top. 

 

 

The front armor is now 50 mm.

Spoiler

Not sure why the UFP and LFP are in different color despite the same thickness.

 

There is no 16 mm or 20 mm on the side but interesting inside the vehicle is a cylinder of 10 mm, so even on the side is spaced armor and is 20 mm in total with external and internal armor combined.

Spoiler

The whole cylinder is 10 mm but is not the top part supposed to be 12 mm ?

 

Rear is 20 mm

Spoiler

 

Both pontoons are 4 mm RHA.

On 06/08/2021 at 04:28, tester188@psn said:

The Type 2 Ka-Mi's snorkel functions as a gun mount for a 7.7 mm machine gun, so the Type 3 Ka-Chi should have been the same.

 

Are you making a report on this ?

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5 hours ago, I_NAMELESS_I said:

The whole cylinder is 10 mm but is not the top part supposed to be 12 mm ?

12 mm will be top of turret. Most of sources says top of the hull is 10 mm.

 

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13 hours ago, aizenns said:

12 mm will be top of turret. Most of sources says top of the hull is 10 mm.

 

 

If that is the case then i think the armor porifle looks really good now.

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Armor thickness values are certainly not considering the pressure hull. So the side should still be increased to 16-20 millimeters, and this will make crew immunity to .50 cal from the sides.

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Data as provided by @tester188@psn is unfortunately incomplete.  Should he, Aizenns, __qaz__ , or someone else dig up something more, the model will be changed.

 

Call it the Japanese Maus.  :lol2:

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The front and rear lids of the pressure hulls may have served as armor, but the sides of the cylinder may have been high tensile steel (HTS). The main submarines of WWII had pressure hulls made of high tensile steel, and I heard that the Type 4 Ka-Tsu only had armor on the front, so the pressure hull must have been made of high tensile steel. 16-20 mm RHA + around 20 mm HTS might be realistic. I will investigate this further.

 

Reference for submarines

Quote

USS Pampanito has a cylindrical all-welded pressure hull made of thirty-five pound (approx. 7/8") high-tensile steel (HTS) and is divided in to 8 compartments separated by pressure bulkheads with watertight doors. There are 137 frames numbered from the bow to the stern that strengthen the hull and serve as reference points. A double hull extends from frame 35 aft to frame 107. The outer hull is made of 3/8" mild steel and the space between the hulls is bulkheaded and used for fuel and water ballast. Torpedo rooms, located at each end of the vessel, are located in the single hull sections of the submarine. 

https://maritime.org/tech/descon.htm

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56 minutes ago, tester188@psn said:

The front and rear lids of the pressure hulls may have served as armor, but the sides of the cylinder may have been high tensile steel (HTS). The main submarines of WWII had pressure hulls made of high tensile steel, and I heard that the Type 4 Ka-Tsu only had armor on the front, so the pressure hull must have been made of high tensile steel. 16-20 mm RHA + around 20 mm HTS might be realistic. I will investigate this further.

 

Reference for submarines

https://maritime.org/tech/descon.htm

I thought it had RHA because Japanese army’s transport submarines used 16 mm RHA for tanks (for army, priority of submarines seems to be higher than tanks)

But it used HTS sounds like reasonable, too.

 

Anyway now we need more sources …

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10 minutes ago, aizenns said:

RHA

What is this?

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7 minutes ago, Pony51 said:

What is this?

 

Rolled homogenous armor; it's the standard type of armor found in most WW2 tanks in War Thunder. According to the Wiki it has a 1.00 armor modifier (in comparison, cast homogenous armor has a 0.94 modifier). I'm not sure how strong HTS would in comparison to RHA though.

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25 minutes ago, Rieskaruisku said:

So any news of getting a machine gun to that empty looking pintle?

I still don't know if anyone reported it.

But  i don't think it will get a MG on its deck vent by the time people completed the fifth task.

It better be reported now or else they will give it a MG three years later like the Chi-To.

 

 

 

Edited by I_NAMELESS_I
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31 minutes ago, I_NAMELESS_I said:

I still don't know if anyone reported it.

But  i don't think it will get a MG on its deck vent by the time people completed the fifth task.

It better be reported now or else they will give it a MG three years later like the Chi-To.

 

 

 

 

Several books on the Ka-Mi explain that it was able to place a 7.7mm machine gun on its snorkel in case it encountered enemy PT boats or aircraft before landing. I haven't written any reports on the Ka-Chi, but I believe it is probably passed on to the devs. However, I'm not sure if GJ will accept it, since it is strictly a source for Ka-Mi, not Ka-Chi. :dntknw:

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23 hours ago, Tasty95215 said:

 

Rolled homogenous armor; it's the standard type of armor found in most WW2 tanks in War Thunder. According to the Wiki it has a 1.00 armor modifier (in comparison, cast homogenous armor has a 0.94 modifier). I'm not sure how strong HTS would in comparison to RHA though.

In case of DS (Ducol Steel, a high grade high tensile strength steel for naval vessels) modifier is about 0.85.

Spoiler

vqfl5Sm.jpg

 

Also, according to navweaps, modifier of HTS (Japanese called it "HT") is about 0.8~0.85.

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23 hours ago, aizenns said:

I thought it had RHA because Japanese army’s transport submarines used 16 mm RHA for tanks (for army, priority of submarines seems to be higher than tanks)

But it used HTS sounds like reasonable, too.

 

Anyway now we need more sources …

 

It's called "Maruyu" and is an interesting submarine. I read in the book that this Army submarine was designed with reference to the declassified Matchanu-class submarine blueprints. However, since many books mention that Type 3 Ka-Chi was made of armor steel provided by the Japanese Navy, it seems that the steel provided by the Army is not used. The Ka-Chi's side armor is probably 20 mm thick, which is equivalent to Japanese medium tanks. However, Japanese medium tanks used carburized armor (class II bulletproof steel, used by Type 97 Chi-Ha) or face-hardened armor (class III bulletproof steel, used by Type 1 Chi-He) developed by the Japanese Army (ignored in the game), while Ka-Chi is rolled homogeneous armor (NVNC or CNC) developed by the Japanese Navy. Ka-Chi's rear pressure bulkhead is riveted, so the pressure hull is probably Ducol steel or medium carbon steel, commonly used in submarines. Ducol steel is known to degrade in performance when welded. Until the Type IXC U-boat U511 was offered by Germany and acquired the welding technology for submarines, the Japanese Navy used reliable riveting.


Army Supply Submarine Yu-3

Spoiler

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Weekly Intelligence bulletins, Vol. I, No. 35, 12 March 1945. pp. 20-25. Report No. 11-c(3), USSBS Index Section 6

https://dl.ndl.go.jp/info:ndljp/pid/4009858/638?itemId=info%3Andljp%2Fpid%2F4009858&contentNo=638&__lang=en

 

 

  • I-361 class transport submarine: 16 mm medium carbon steel riveted, depth of dive tested 75 m
  • Ha-101 class transport submarine: 16 mm medium carbon steel welded, depth of dive tested 100 m
Spoiler

jfALoS7.jpg

S-01-6; Characteristics of Japanese Naval Vessels – Article 6, Submarines, Supplement 1

https://pacificwararchive.wordpress.com/2018/04/21/reports-of-the-u-s-naval-technical-mission-to-japan-1945-1946/

 

The book describes the Type 4 Ka-Tsu, which has the same pressure hull as the Type 3 Ka-Chi, as having "no armor (10 mm on the front of the coxswain)", while the Type 3 Ka-Chi has 20 mm thick armor on its sides. It does not consider pressure hulls as armor.

Spoiler

kDnUhqI.jpg

 

Armor           None

装甲(mm)  ナシ

 

(10 mm on the front of the crew only)

(乗員前面のみ10mm)

Japanese Tanks and Fighting Vehicles. by Tomio Hara and Akira Takeuchi. 1961. p. 105.

 

TL;DR

My guess: 

Side armor: 20 mm RHA

Pressure hull: 16 mm HTS

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Any record on the gun elevation and depression ? In the game it says -10 degree depression and +24 degree elevation, it seems strange* because the turret seems identical to the Chi-He but it doesn't share the -15 degree of gun depression nor +20 degree of elevation. Judged from the Xray there is alot of room for the gun to depress.

And i don't think it should be +24 degree of elevation because the gun is slighly clipping through the turret ring, it is most likely +20 degree just like the Chi-He.

 

And i don't even think that this is actually -10 degree at all.

Spoiler

9anvYCJ.png

This looks much lower.

 

Another issue is the gunner elevating the gun as soon as he has to traverse the turret pass the vent despite there is still a plenty of space for the gun barrel to pass through just completely fine.

Spoiler

tqf6WL8.png

 

Regarding the pontoons armor, the game calcurated the whole thing as 4 mm instead of 4 mm outer + 4 mm inner so it should be 8 mm in total.

Spoiler

ZCeeyPy.png 5CNw0Tt.png

The hull rear armor is 20 mm + pontoon 4 mm.

 

One of the wheels is missing weathering effect.

Spoiler

IQsU0Cu.png

 

 

Edited by I_NAMELESS_I
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From Japanese wiki 

Quote

特三式内火艇の主砲である 一式四十七粍戦車砲 は、砲身長が48口径の2250 mmであり、俯仰角度は-15度から+20度だった。

 

Well, apparently the verticle guidance of the Ka-Chi is copied from the Ka-Mi which is weird because both vehicles have completely different turret and gun.

 

And also the +24 degree of elevation is strange, no other tanks have such elevation. and just like the Ka-Chi the gun is clipping through the turret ring on the Ka-Mi aswell :facepalm:

Spoiler

qycJXQl.png

 

 

Edited by I_NAMELESS_I
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On 16/08/2021 at 13:37, I_NAMELESS_I said:

From Japanese wiki 

 

Well, apparently the verticle guidance of the Ka-Chi is copied from the Ka-Mi which is weird because both vehicles have completely different turret and gun.

 

And also the +24 degree of elevation is strange, no other tanks have such elevation. and just like the Ka-Chi the gun is clipping through the turret ring on the Ka-Mi aswell :facepalm:

Reveal hidden contents

 

 

Ka-Chi is based on the Chi-He, the Ka-Mi is based on the Ha-Go. Not the same thing

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Hopefully gaijin is still working on the Ka-Chi because it still has problems that need to be fixed (some have already been talked about in this thread)

  • Incorrect side armor
  • gun depression and elevation is incorrect should be the same as Chi-He
  • gun depression is locked to a few degrees when pontoons are equipped when it should only have its depression restricted when aiming over the front or rear pontoon
  • one of the wheels is missing weathering effects (like rust and dirt)
  • fuel tanks are don't have individual damage model (destroying one of the fuel tanks leads to the loss of all fuel tanks on the side which lost a fuel tank)
  • pontoons should act more like 8mm armor not 4mm as the round should be passing though 2 4mm plates (the front and back armor plates of the pontoon)
  • Arty rounds hitting the pontoons can cause a overpressure kill
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Thank you to all that have contributed. Had some good fun in this thing a few nights back, people not having any idea what it was and coming to approach it in the water then backing off :D Fun times and got a few kills. She's a really big girl though, dang! Quite the presence. 

edit: tip for getting in and out of water on steep access points: reverse up you have better approach angle :)

Edited by N4CR_
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