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A6M Zero's central drop tank attachments

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  • Member since
    February 2023
  • From: Indiana
Posted by buitre on Thursday, March 2, 2023 1:45 AM

Tcoat:

Here are all the graphics references that I have found that are relevant to "the" rectangle:

the following planforms viewed from below:  (1) an "A6M5" (definitely not an A6M5c) in the Sakaida/Osprey book (see above); (2) an A6M5a by T. Skwiot (I can't remember where I found it); (3) an A6M5c by T. Skwiot (https://naval-encyclopedia.com/naval-aviation/ww2/japan/mitsubishi-a6m-zero.php); (4-9) 6 views from below that I downloaded (with some trepidation!) from a Romanian website (http://www.mediafire.com/file/lu9da8pbvub2cw9/Mitsubishi-A6M-Zero-Scale-Model-Aircraft-Plans-Drawings.zip) that show two A6M2s, two A6M3s and two "A6M5" (definitely not A6M5c); and also (10) several drawings in the instructions for Tamiya's 1:32 scale model of the A6M5 (definitely not an A6M5c).  

All but one of the above show the rectangle centered on the midline.  The only exception is the Tamiya instructions, which show the rectangle offset to starboard.

Interesting points:

#1. The off-center rectangle hardly ever shows up in line drawings (one out of ten drawings).

#2. The off-center rectangle shows up in a Zero that has 2 hood machine guns, which argues against my hypothesis that the off-center rectangle occurs when there is only one hood machine gun.

#3. The fact that another one of those graphics shows an A6M5c with a centered rectangle also argues against my hypothesis that the off-center rectangle occurs when there is only one hood machine gun.

I have seen other line drawings for Zeros, but sometimes they don't show THE rectangle at all, and other times they present a hybrid top+bottom view (like the one provided by HooYah Deep Sea in the present thread) that can be very useful for many purposes, but that by their very nature can't address asymmetry questions.

Can you give me references to more line drawings that show the elusive asymmetric rectangle?  I'd love to find a logic that tells us when the rectangle will be centered and when it will not.

buitre

You can see two of my models here: https://www.youtube.com/watch?v=pdrzPW7cMls

  • Member since
    February 2023
  • From: Indiana
Posted by buitre on Thursday, March 2, 2023 2:20 AM

Jeaton01:

Yes, I am aware of the Tamiya 1:32 Zero, I have heard that it is an outstanding kit.  When I was looking for an A6M5 to build, I almost went for this kit.  But then I decided that I wanted a kit at the same scale (1:24) as a FW-190F3 from Heller that I had just completed.  So I bought an ancient 1:24 scale A6M5 from Bandai.  Ugh, it has given me a lot of headaches, and I am still working on it!  I think it will work out OK in the end.

In regard to the feed chutes, in spite of the graphics I still don't quite understand in which direction the shells move prior to and after reaching each machine gun.  Were the two machine guns mirror images of each other?  If they weren't (and I assume that they weren't!), how could the spent casings travel to the left and down from the port gun and to the right and down from the starboard gun?

By the way, looking at the Tamiya instructions (I don't have the kit but I do have the instructions), I just noticed that "scene #52" shows beautifully the fat pin of the drop tank going into the big hole of the "keyhole" area, which confirms what we had concluded here.  In this model, the drop tank can actually drop: It can be pulled out and stuck back in again!

At this point, I have no questions about the drop tank connections, I consider it a resolved issue.  But I'd like to pin down what is the story with the centered vs not-centered rectangular hole.

buitre

You can see two of my models here: https://www.youtube.com/watch?v=pdrzPW7cMls

  • Member since
    December 2002
  • From: Northern California
Posted by jeaton01 on Thursday, March 2, 2023 10:26 AM

Looking at the chute I think the guns were both fed from the outside and the spent cartridges both came out in the middle.  I guess in that event the guns could either feed both ways or they were different for left and right.

John

To see build logs for my models:  http://goldeneramodel.com/mymodels/mymodels.html

 

  • Member since
    February 2023
  • From: Indiana
Posted by buitre on Thursday, March 2, 2023 1:36 PM

jeaton01:

Until this thread, I had never given any thought to shell pathways inside airplanes.  I had always assumed that any given type of machine gun model always got fed through one particular side, and ejected through the other one.  I never considered the complexities that such rigidity might create for airplane designers.

The attached graphic, taken from Robert C. Mikesh's "Zero Fighter" chapter in "The Great Book of World War II Airplanes", shows very clearly that the Zero's wing-mounted cannon existed in mirror-image versions.  By extension, I think it's very likely that the "hood" machine guns were also mirror-image versions of each other.

So that is clear to me now, Duh!

What I still can't picture is the paths followed by the shells in the drawings from the Tamiya instructions.  For instance, for the port gun I see a channel that goes up from just left of the midline of the plane, then goes horizontally toward the port side, then goes down, then goes up along the port edge of the fuselage, and finally reaches the port gun.  OK, so that could be either (a) the "feed" channel or (b) the "exit" channel.  But where is the other channel, the exit channel in case "a", or the feed channel in case "b"?  Or is that channel a double-channel, with internal inbound and outbound halves??

 

Gun arrangement in a Japanese Zero fighter, taken from Robert C. Mikesh, "The Great Book of World War II Airplanes".

buitre

You can see two of my models here: https://www.youtube.com/watch?v=pdrzPW7cMls

  • Member since
    February 2023
  • From: Indiana
Posted by buitre on Thursday, March 2, 2023 2:04 PM

jeaton01:

I just noticed in the Tamiya instructions that the two hood machine guns are mirror-images of each other, at least as far as can be seen in the drawings.  (And I just realized that, in my Bandai Zero, I made --from scratch-- the two cocking levers be symmetrical, both on the inside of each 7.7 mm gun.  So at some point I was subconsciously? aware that in at least some aspects the hood machine guns were mirror images of each other.  DUH!  Why was that concept such a mental block for me?)

 

My Bandai Zero's scratch-made hood guns

buitre

You can see two of my models here: https://www.youtube.com/watch?v=pdrzPW7cMls

  • Member since
    July 2004
  • From: Sonora Desert
Posted by stikpusher on Thursday, March 2, 2023 2:36 PM

Many aircraft machine guns have the ability to be switched between right or left hand feed by the armorers. This come in handy for aircraft installation. Just look at the twin mount .30's and .50's used on many US aircraft for obvious examples.... or wing gun installations, with the guns installed at the some position on both wings, and the ammo trays on opposite outboard sides. Otherwise to acheive the same balance that would require the gun to be installed inverted, and introduce a new host of jam inducing headaches.

 

F is for FIRE, That burns down the whole town!

U is for URANIUM... BOMBS!

N is for NO SURVIVORS...

       - Plankton

LSM

 

  • Member since
    February 2023
  • From: Indiana
Posted by buitre on Thursday, March 2, 2023 2:49 PM

Right.  I have seen the light!

buitre

You can see two of my models here: https://www.youtube.com/watch?v=pdrzPW7cMls

  • Member since
    February 2023
  • From: Indiana
Posted by buitre on Thursday, March 2, 2023 3:06 PM

stikpusher:

The drawing from Mikesh's book chapter (artist = Rikyu Watanabe) shows every single item in the wing cannon to be a mirror image of the equivalent item from the other cannon.  This cannon seems to be something that came straight out of the factory in two versions: a right-handed gun and a left-handed gun.

 

buitre

You can see two of my models here: https://www.youtube.com/watch?v=pdrzPW7cMls

  • Member since
    February 2023
  • From: Indiana
Posted by buitre on Thursday, March 2, 2023 3:13 PM

stikpusher:

The rear end of the right wing gun, which got chopped off in my scan (book wider than scanner!) also shows perfectly mirror-imaged parts.  EVERYTHING is a perfect mirror image.  (Well, maybe the spiral groove inside the barrel was not mirror-imaged. Big Smile)

buitre

You can see two of my models here: https://www.youtube.com/watch?v=pdrzPW7cMls

  • Member since
    July 2004
  • From: Sonora Desert
Posted by stikpusher on Thursday, March 2, 2023 5:40 PM

buitre

stikpusher:

The drawing from Mikesh's book chapter (artist = Rikyu Watanabe) shows every single item in the wing cannon to be a mirror image of the equivalent item from the other cannon.  This cannon seems to be something that came straight out of the factory in two versions: a right-handed gun and a left-handed gun.

 

 

I don't know the specifics of the Japanese designs. But on the M2 .50 cal., a design that I used to be very familiar with, the gun could be switched from right hand to left hand feed by the operator. That was a feature of the design, out of the factory. That's how it can look that way in photos, artwork, etc. I was shown how to do that, but it's been over 35 years since I've played with a Ma Deuce, so I'd need a manual to do it again if I had the opportunity. 

 

 

F is for FIRE, That burns down the whole town!

U is for URANIUM... BOMBS!

N is for NO SURVIVORS...

       - Plankton

LSM

 

  • Member since
    February 2023
  • From: Indiana
Posted by buitre on Thursday, March 2, 2023 5:48 PM

stikpusher:

From what you say and from the Watanabe drawing, some gun models seem to be switchable in the field, and others come in two versions out of the factory.

buitre

You can see two of my models here: https://www.youtube.com/watch?v=pdrzPW7cMls

  • Member since
    September 2005
  • From: North Pole, Alaska
Posted by richs26 on Friday, March 3, 2023 1:19 AM

The Japanese Navy 7.7mm mg was a licensed copy of the British Vickers Model E mg which used the same .303 British cartridge.

https://en.wikipedia.org/wiki/Type_97_aircraft_machine_gun

The Japanese Navy 13.2mm mg was a copy of the American M2 Browning which as noted before had a dual left or right feed system.

https://en.wikipedia.org/wiki/Type_3_aircraft_machine_gun

More Type 97 info:

https://www.rockislandauction.com/detail/68/1647/japanese-97-machine-gun-77-mm-japanese

It seems that the Type 97 was made in left or right only feeds, not like the Browning dual feeds.

WIP:  Monogram 1/72 B-26 (Snaptite) as 73rd BS B-26, 40-1408, torpedo bomber attempt on Ryujo

Monogram 1/72 B-26 (Snaptite) as 22nd BG B-26, 7-Mile Drome, New Guinea

Minicraft 1/72 B-24D as LB-30, AL-613, "Tough Boy", 28th Composite Group

  • Member since
    February 2023
  • From: Indiana
Posted by buitre on Saturday, March 11, 2023 12:14 AM
I wanted to build my 1:24 scale Bandai Zero without the drop tank.  So a couple of weeks ago I filled in the model’s 7 belly holes intended for the attachment of the drop tank.  (See Image 01 in the attached pictures.)  At that point, I believed that I was done with all drop tank issues, haha!  Then I started this thread, and it quickly became clear that Zeros were not left with perfectly clean bellys after the ejection of the drop tank.  So I had work to do!
 
Since I found 9 line drawings from 6 independent sources that showed the casings exit hole centered on the Zero’s midline, and only the instructions for Tamiya’s 1:32 scale Zero showed it off-center (toward the starboard side), for my model I decided to construct a centered casings hole.
 
First I marked with a pencil the outline of the casings ejection hole (Image 02), and then I carved out the hole with a Dremel (my first ever use of a Dremel, a somewhat scary tool!), an X-Acto knife, a file, and sanding utensils (Image 03).
 
Then I marked out (Image 04) and carved out (Image 05) another rectangle, this one behind the forward main spar.  This second rectangle was a little bit larger than the intended “keyhole”.  Then I constructed the “keyhole” section out of a 2.5-mm-thick piece of Plasticard sandwiched between two 0.5-mm-thick pieces of Plasticard (Image 06).  I built it using an X-Acto, a Dremel, a regular drill, and sanding utensils.  I glued it into the new rectangular hole using epoxy (Image 07).  As expected, this left some cracks between the keyhole section and the edges of the rectangular hole.  To eliminate them, I used a technique that I have been testing lately. First, I sanded to get rid of any keyhole section plastic that might be sticking outward (Image 08).  Then I airbrushed with Vallejo Model Air paint (Image 09), making sure that some paint went into the cracks between the keyhole section and the edges of the rectangular hole. Then I applied Vallejo Model Color paint with a brush along the periphery of the keyhole section, again making sure that paint went into the cracks, in fact covering them completely this time (Image 10). The main idea here is that I expected paint to stick to paint better than putty sticks to plastic or to paint.  That way, the paint (which I am using as a substitute for putty) wouldn’t pop out of the crack when I later sanded.  I used Vallejo Model Color paint as the filler because it is thicker than Vallejo Model Air paint.  I let the paint cure for 72 hours (which was probably an overkill). Then I sanded off the Vallejo Model Color paint (Image 11), re-scribed the rivets, added two square panels behind the keyhole, and airbrushed with Vallejo Model Air paint (Image 12).
 
I’m fairly happy with the results.  The only issue that I found was that it was hard to sand the Model Color paint (Step 11).  When fully cured, I think that this paint is harder than plastic! Next time I think I will try using Vallejo Model Air also for the brush application, and see what happens.
 
Thank you all for your help! 
 
cartridge exit and keyhole modifications

buitre

You can see two of my models here: https://www.youtube.com/watch?v=pdrzPW7cMls

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