Hawk 75 Royal Thai Air Force cannon pods

[elbmc1969]

Visible in this thread about the RTAF museum is a Hawk 75 with cannon pods: Royal Thai Air Force

The Hawk 75 was offered with Madsen 20mm and Madsen 23mm in underwing pods.

1. Are these 20mm or 23mm?

2. Are the cannon pods in the museum original or reproductions?

3. How much did the cannon pods weigh with and without ammunition?

4. Did the cannon pods supplant wing-mounted MGs?

Thanks!

(H75A-5 "zerstrorers" in the Battle of France? We know that the pods absolutely wrecked maneuverability, though.)

Ethan

 

[FLYBOYJ]

See link below;

RTAF Hawk 75N

 

[elbmc1969]

Thanks, FLYBOYJ. I'd seen that link. It's not clear if the aircraft in these pictures are carrying the pods (gondolas): http://www.wings-aviation.ch/11-RTAF/2-Aircraft/Curtiss-Hawk75/RTAF-027-001.jpg http://www.wings-aviation.ch/11-RTAF/2-Aircraft/Curtiss-Hawk75/RTAF-027-007.jpg but it is clear in others. In particular, you can see how clear the barrels are here http://www.wings-aviation.ch/11-RTAF/2-Aircraft/Curtiss-Hawk75/RTAF-027-003.jpg and here http://www.wings-aviation.ch/11-RTAF/2-Aircraft/Curtiss-Hawk75/RTAF-027-003.jpg

Some sources say that the cannon were removed because of their severe effect on performance. It's possible that cannon, ammunition, etc. were removed, but the gondolas had to be left in place because the wings didn't have a lower surface there. It would be reasonable that the ammunition drum extended into the wing. While this wouldn't reduce form drag, the reduced rate would improve maneuverability, especially roll rate, and would have the typical small effect on induced drag, which helps with range.

From what I can find, the cannon weighed 53kg (each). Drum, ammunition, and mount would add some weight. Cartridges weighed around .3 kg each (different for AP and HE), with either 40 or 60 round drums available. Assuming only 40 round drums, that's 12 kg. The drum itself should be at least 2 kg (a low estimate). So, 67 kg per cannon as a minimal estimate, or 134 kg total (essentially 300 pounds), which is a significant load for a fighter of this size.

On question 4 above, I haven't found any photos of Thai Hawks where I can make out wing-mounted machine guns. I'm hoping someone can point me to some! Peter Bowers' Curtiss Aircraft 1907-1947 states that the Hawk 75Ns delivered to Thailand had four wing guns (p. 356), but has no photo. Bowers lists the same serial number as the web page you linked to, helping confirm that 12 were delivered to Thailand; other sources state 16 or 25.

 

[A.G. Williams]

The Madsen cannon were also advertised as being available with belt feeds, mainly for the aviation market.

AFAIK, the only users of the 23mm version were Chile, fitted to Breda Ba.65 bombers, although it is possible that a couple of Hawk 75s with 23mm guns were sold to China.

 

[elbmc1969]

The Madsen cannon were also advertised as being available with belt feeds, mainly for the aviation market.

Do you have any sources showing the belt feeds? I haven't been able to find anything. Edit: Found various photos and a book! I've only found ground mounts so far, such as the dedicated AA mount with 2 seated gunners (azimuth and elevation tracking).

The IWM has an 8 page booklet published by DIS (company that made the Madsens), titled "Madsen Gun Installation in Curtis [sic] Hawk 75. However, I can't afford the 50 pounds+ to have it digitized.

I've been searching the Danish national archives and other sources without much luck. I'm going to try writing to DISA and Maersk to see if they maintain any archives of their own.

BTW, I updated the Wikipedia Madsen 20mm page yesterday so that it links to your current site.

 

[A.G. Williams]

This is from a DIS publication dated 1946: "Automatic Standard Arms of Modern Warfare Vol XI: Madsen Arms during the World War 1939-1045 and after 1945" by Colonel Halvor Jessen.

 

[elbmc1969]

Oh, my gosh, that is awesome! Is the whole publication available anywhere?

Do you happen to have the page number, so that I can cite it? Thanks!

 

[elbmc1969]

That's clearly heavily airbrushed. Any idea if that's supposed to be a .30 MG barrel also sticking out of the wing?

I still wonder if it was possible to mount wing MGs in addition to the cannon (with reduced ammo for both, no doubt), or if it was possible to retrofit wing guns if you removed the cannon. The Thais do seem to have removed the cannon after the Japanese invasion/Japanese alliance.

 

[elbmc1969]

This is from a DIS publication dated 1946: "Automatic Standard Arms of Modern Warfare Vol XI: Madsen Arms during the World War 1939-1045 and after 1945" by Colonel Halvor Jessen.

OK, getting off topic here, but Jessen developed a concept for using automatic rifles (the original Madsen gun) in 1912! Developing the Fire Team It appears to be the earliest concept of using a "fire team," although it's a bit more like MG teams as part of a very small MG platoon perhaps, and clearly inspired by skirmishers.

In 1942 he published, "Why have the Danish people lost the will to defend themselves?" which was either a call for resistance to the Nazis or a call for collaboration. I have no idea which ...

 

[Capt. Vick]

That's clearly heavily airbrushed. Any idea if that's supposed to be a .30 MG barrel also sticking out of the wing?

I still wonder if it was possible to mount wing MGs in addition to the cannon (with reduced ammo for both, no doubt), or if it was possible to retrofit wing guns if you removed the cannon. The Thais do seem to have removed the cannon after the Japanese invasion/Japanese alliance.

I think you are looking at part of the pitot tube.

 

[elbmc1969]

Ah, you're right. I saw the vertical element as part of the support structure around the fuel tank.

It's a lot further inboard than on production Hawk 75s, where it's generally all the way out by the wingtip.

 

[Wurger]

The pic above shows the gun attached to the Fokker D.XXI ...

And two pics more with the Madsen gun seen in the post #6 ...

the source: Question Danish Fokker D.XXI Madsen Cannon

And the another pic of the D.XXI seen in the post #6 but with the pod cover attached.

the source: the net.

 

[elbmc1969]

Ah! I just glanced at it and assumed it was one of the fixed-gear versions of the H75.

 

[Wurger]

Unfortunately it is not. But it is a good example of the Madsen 20mm gun. IMHO, the difference between the 20mm and the 23 mm guns can be seen in the pics below. There is the gun pod with the Madsen 23mm mounted to the XP-36F. The gun seems to have the longer perforated jacket of the barrel. So the distance between the front of the barrel cover and the nozzle is smaller than for the 20mm gun. What is more there is something looking like the fastening with small and shorth pipes ( screws ) at the front of the barrel jacket.

and closse-up shot of the gun pod ...

and the 23mm Madsen gun ...

Contrary to that, the Curtiss Hawk 75N displayed in the museum has the gun exactly looking as the 20mm gun of the Danish Fokker D.XXI. Although the barrels don't have the nozzles ( are removed for some reason ) it can be noticed that the distance between the front of the barrel jacket and the thread for the nozzle is larger than for the 23mm gun. And of course the barrel cover doesn't have the small pipes or screws at the front.

and a close-up shot ...

The source of all images: the internet

 

[GrauGeist]

When the Madsen 20mm was used as a ground-based weapon, had a muzzle brake screwed onto the end of the barrel.

It appears it was removed when mounted to an aircraft.

 

[Wurger]

A shell for the 23mm Madsen gun ...

the source: Działko lotnicze 23 mm Maskinkanon (Madsen) | Encyklopedia Uzbrojenia II Wojny Światowej

 

[elbmc1969]

Unfortunately it is not. But it is a good example of the Madsen 20mm gun. IMHO, the difference between the 20mm and the 23 mm guns can be seen in the pics below. There is the gun pod with the Madsen 23mm mounted to the XP-36F. The gun seems to have the longer perforated jacket of the barrel. So the distance between the front of the barrel cover and the nozzle

"muzzle brake"

is smaller than for the 20mm gun. What is more there is something looking like the fastening with small and shorth pipes ( screws ) at the front of the barrel jacket.

I'm confused. Are you saying that all three of the pictures below are 23mm? Or is the middle one supposed to be 20mm? Or, does the middle photo show the aircraft being serviced with the muzzle brake and barrel jacked removed?

View attachment 640557
View attachment 640558

and closse-up shot of the gun pod ...
View attachment 640564

and the 23mm Madsen gun ...
View attachment 640560

Contrary to that, the Curtiss Hawk 75N displayed in the museum has the gun exactly looking as the 20mm gun of the Danish Fokker D.XXI. Although the barrels don't have the nozzles ( are removed for some reason )
it can be noticed that the distance between the front of the barrel jacket and the thread for the nozzle is larger than for the 23mm gun. And of course the barrel cover doesn't have the small pipes or screws at the front.

and a close-up shot ...
View attachment 640563

The source of all images: the internet

Those are set-screws for the barrel jacket. However, I can't find any photos of a 20mm Madsen with set-screws there.

There are versions of the 20mm Madsen both with and without muzzle brakes:

The Universal Mounting and Heavy AA mounting, for instance.

I think the Thai cannon are 20mm, unless there's particularly strong evidence otherwise.

 

[elbmc1969]

So, Die automatische Praezisions- und Einheitswaffe des modernen Schlachtfeldes, Vol. IX by Obert Halvor Jessen (Danish Army--mentioned above), published by Madsen (Dansk Industrei Syndikat, Compagnie Madsen A/S) in 1938 shows the 20mm cannon with at least three distances between the heavy cylinder at the end of the barrel jacket (no set screws, all are explicitly identified as 20mm) and the muzzle brake. The short distance looks the same as the distance on the P-36F.

I don't think that distance is by any means an indicator of whether the gun is 20mm or 23mm.

 

[Wurger]

"muzzle brake"

I wish you could speak Polish

I'm confused. Are you saying that all three of the pictures below are 23mm? Or is the middle one supposed to be 20mm? Or, does the middle photo show the aircraft being serviced with the muzzle brake and barrel jacked removed?

Maybe the pic can help to understand ..

I think the Thai cannon are 20mm, unless there's particularly strong evidence otherwise.

I think the same. What is more the pods seem not to be the original ones. In all pic both with the XP-36F and D.XXI it can be noticed that there were inspection panels, etc... Those in the museum seem to be without any of a such hatches and appertures. Also these used for the XP-36F and those seen in the blurry images of the RTAF Hawks seem to be more streamlined.

 

[elbmc1969]

Maybe the pic can help to understand ..

View attachment 640601

I got what you were saying. If you look at the 20mm in a variety of mounts, you'll see that what you've labeled as "different distance" varies tremendously. There are also barrel shrouds (jackets) with different numbers of ports, so Madsen manufactured a variety of shrouds.

The sources that I've found state that the 20mm and 23mm were identical, except for bore size and a slightly different chamber. The cartridges were identical except that the 23mm had a slightly wider neck to fit the 23mm shell.

I think the same. What is more the pods seem not to be the original ones. In all pic both with the XP-36F and D.XXI it can be noticed that there were inspection panels, etc... Those in the museum seem to be without any of a such hatches and appertures. Also these used for the XP-36F and those seen in the blurry images of the RTAF Hawks seem to be more streamlined.

I noticed the apparent lack of a casing ejection slot as well, but I haven't been able to find a photo that shows the inboard sides of the pods, etc., so it's vaguely possible that we're missing something.

I've found one photo that show the upper surface of the wing at a modest angle, but I can't make out covers for the ammunition trays. I would dearly love to be able to examine the aircraft and open some bits up.