CMP Roof Hatches

[Alex van de Wetering]

I agree with Ian on the round roof hatches; I have seen several period liberation pictures of F60L GS trucks with round hatch....and also Ford 3 Ton LAAT.

Like Ian and Grant I believe square vs round hatch is an early vs late thing. I am not sure if it has anything to do with air superiority, though. I believe it was more an ease of production thing.....the round hatch is largely made from wood with a canvas cover....much simpler than the square steel hatch with hinges etc.

The roofs without hatch.....you see them a lot when you start checking pictures closely. First I thought the closed roofs might have been fitted to non frontline-vehicles, like the C60X Machinery trucks, Wireless vehicles and medical vehicles........but, they also appear on 3 Ton GS trucks in 1944/45 liberation pictures.....both on Chevs and Fords.
Ian could be right here.....contracts were leading (?)

Alex

Here is a picture taken in Utrecht 6 June 1945, memorial D-day parade. To the left a C60L without hatch....to the right a Ford F60L with round hatch. source: http://www.hetutrechtsarchief.nl

124697.jpg

[Ian McColl]

Aside from timing, an example of differing hatch types (and Hanno is right in that the round version is not so much a hatch but rather a "hole" with a canvas cover) and particular contracts pertain to two 1944 Chevrolets of which I own examples of both. Trucks from contract PE-197-11 came supplied with square hatches while those from contract PE-197-12 came supplied with round hatches. Both contracts have been discussed on this forum before (PE-197-11 C60L's were supplied with winches and PE-197-12 C60L's were supplied with 16" wheels. Both contracts had "REL" (Research Enterprises Limited) tags on the rear inner of the cab roof.) As a result it would appear that trucks could be "ordered" with a limited number of "options" based on what was deemed necessary for that particular contract.

[David Dunlop]

Glad to learn both Chev and Ford both took part in the evolution of the CMP roof hatch.

Purely speculation on my part, but these hatches seem to be primarily a means of getting a better view of ones surroundings. In some theatres that was probably a useful feature. In others, perhaps not so much. Maybe that is why the presence of the hatch varies by Contract.

I just had a further thought. I wonder if these hatches are discussed/covered in the Design Branch books? Maybe they actually had a formal name there, as well as an explained purpose.

David

[Keith Webb]

Many Australian CMPs were fitted with a counterbalanced mount for a Bren gun for anti aircraft defence.

[David Dunlop]

OK, maybe it's late and my brain is getting a bit dotty, but it seems to be wanting to convince me that the early, square metal hatches had a small tubular rail, like a towel rack, mounted on the roof of the cab, at the front of the opening. Looking somewhat like a grab rail. Is this correct? Was it a grab rail, or was it rail to take a sliding gun mount of some sort? Or am I just experiencing another brain fart?

David

[rob love]

I had a look in the design branch records and it confirms Grant's synopsis. It refers to the rectangular as "old style" , and the round ones simply as "hip ring". There is one page of photos (volume V, page 27D)

The front handle was a grab bar as far as I know. The manual calls it a "grip handle - roof.

[Keith Webb]

Yes it is a rail which acts as a grab handle. The Australian Fords had two small grab handles rather than a rail.

Originally Posted by David Dunlop

OK, maybe it's late and my brain is getting a bit dotty, but it seems to be wanting to convince me that the early, square metal hatches had a small tubular rail, like a towel rack, mounted on the roof of the cab, at the front of the opening. Looking somewhat like a grab rail. Is this correct? Was it a grab rail, or was it rail to take a sliding gun mount of some sort? Or am I just experiencing another brain fart?

David

[Hanno Spoelstra]

Originally Posted by David Dunlop

OK, maybe it's late and my brain is getting a bit dotty, but it seems to be wanting to convince me that the early, square metal hatches had a small tubular rail, like a towel rack, mounted on the roof of the cab, at the front of the opening. Looking somewhat like a grab rail. Is this correct? Was it a grab rail, or was it rail to take a sliding gun mount of some sort? Or am I just experiencing another brain fart?

David, as you said: these roof hatches are primarily a means of getting a better view of ones surroundings. Often people speculate about gun mountings fitted on the hatch/roof, as if the sheet metal CMP roof could withstand the recoil of sustained MG fire recoil. Maybe it is just that some collectors or modelers want to pack their CMP with a some punch, akin to the poor overloaded LRDG / SAS jeeps.

Apart from the Australian efforts - see below - I have not seen any documented proof these hatches were to be used for anything else than observation.

Originally Posted by Keith Webb

Many Australian CMPs were fitted with a counterbalanced mount for a Bren gun for anti aircraft defence.

The photo below shows the gallows in the proximity to the cab roof hatch from where the gun would be fired suspended. My question is: how often was this used in practice?!?


Source

[Grant Bowker]

Without being told that the gallows were for a gun mount, I would wonder if they were intended to aid in hoisting spare wheel assemblies into the boxes behind the cab. Possibly making a 2 man job into something one man could hope to do.

[Hanno Spoelstra]

Originally Posted by Alex van de Wetering

The roofs without hatch.....you see them a lot when you start checking pictures closely. First I thought the closed roofs might have been fitted to non frontline-vehicles, like the C60X Machinery trucks, Wireless vehicles and medical vehicles........but, they also appear on 3 Ton GS trucks in 1944/45 liberation pictures.....both on Chevs and Fords.
Ian could be right here.....contracts were leading (?)

Here's another photo taken during the liberation of Valkenswaard, the Netherlands, 11th of September 1944.
About half(!) of the CMP trucks shown do not have a roof hatch.

valkenswaard-1600-1000-100.jpg

[Alex van de Wetering]

Hanno,

Do you know where this picture came from? I see Dutch Lions on the front clips and 5-digit numbers on the doors.......wonder if it could be a post-war picture in stead of 1944?

This doesn't distract from the roof hatch situation though......plenty of examples of 3ton trucks without the hatch!

I will try to post another interesting picture tomorrow......(cliffhanger!)\ )

[Hanno Spoelstra]

Originally Posted by Alex van de Wetering

Do you know where this picture came from? I see Dutch Lions on the front clips and 5-digit numbers on the doors.......wonder if it could be a post-war picture in stead of 1944?

Hi Alex, you could well be right... I found it here https://www.backtonormandy.org/the-h...kenswaard.html and here https://www.rd.nl/artikel/348872-dee...ert-bevrijding where it is credited to the ANP. I did not check details on the photo.