Blitz Sun roof
 

Can somebody tell me how the blitzes had a sun roof and some of the history about it. Colin

Good question
 

Hi Colin,
This might be a question for Mike, but it it is interesting that it is an Australian adaptation seen pretty much exclusively on 15CWT Ford and Chevrolet CMPs although I have seen photographs of a No6 Bofors tractor with one.

For those who are not familiar this type of roof has most of the centre open, with a hood bow in the middle and a folded steel front piece used to close the roof over a pair of bolts on the inside of the brow secured with wing nuts. When rolled back into the open position it is held in place by a pair of leather straps riveted to vertical pieces welded onto the back of the cab. The lower part of the rear has a rope system to keep it in place.

pics always help
 

Here are a couple of pics of a C15A with the sunshine roof.

Body
 

With a 2C1 body from a Canadian built Ford F15, many of which were imported here before we started to build our own version of the rear body.

The grab handles for the front part of the roof are the same as the ones on the Australian Ford roof in front of the hatch.

The Sunshine Cab was developed as an Australian requirement for artillery units in the first instance, for fitting to 'Trucks, 15cwt, Battery Staff (Aust)' of which there were several variants. It followed the earlier requirement for a sunshine 'roadster' cab on Battery Staff and Artillery tractors built on MC type vehicles, eg the O1Y and 11Y 1 ton Fords, and Tractors, Artillery, LP, No.s 1, 2, 3, 3A, 4 and 4A.

The CMP sunshine cab was developed by engineers at GMH Woodville at Army request, and subsequently manufactured by both Ford and GMH.

The cab type was, however, not wholly restricted to BS vehicles, having been noted on small numbers of several other types as original build standard, including Truck, 3 ton, Ambulance (Aust) No.1.

When the CMP BS vehicles were returned to Ordnance vehicle parks in 1943, they were stripped of artillery fittings and re-issued as 15cwt GS, so it is therefore common to see the sunshine cab on GS 15 cwts.

Mike C

Haha, thanks Mike! I'd just finished composing a lengthy response to Colin's question, speculating on the purpose of the sunroof, and when I went to post it I saw your reply! I'll post it anyway as it discusses the canvas door as well.


It's an excellent question you raise Colin. As a purely Australian innovation, the use of a sunroof is commonly, and not unnaturally, explained as a climate adaptation. However this makes no sense, because as Keith points out, it was used exclusively on the 15 cwt. Furthermore, the canvas doors introduced on all late production Australian CMPs, which are also commonly explained as a climate adaptation, were never used on the 15 cwt.

Therefore it becomes clear that these two Australian innovations are related primarily to vehicle function, and only secondarily, if at all, to driver comfort. Hence we need to look to vehicle role, rather than climate, for an explanation of their purpose.

To my mind the clue lies in the canvas door, which is specifically designed to be removable, as evidenced not only by the hinges, but also by the accompanying strap across the doorway, to prevent the driver falling out of the cab with the door removed, and the accompanying metal strip along the floor edge, to prevent articles sliding or rolling out of the cab. All of which tells us these are not canvas doors per se, they are removable doors which just happen to be canvas covered. Just like the canvas covered sidescreens, their principal purpose is removability.

The question then becomes, why the need for removable doors? The clue here may lie in the fact that late production Australian CMPs were almost exclusively 60S specialist vehicles, plus the aforementioned 15 cwt vehicles which never received removable doors. The majority of these 60S specialist vehicles appear to have been tippers, plus a few water tankers, the operation of which would require the driver to be constantly in and out of the cab. For example, tippers engaged in airfield construction in the islands, ferrying crushed coral back and forth all day, and doing lots of reversing. If you've ever reversed a blitz on hot days you'll know that the door must be opened, unless you want to burn your right underarm on hot steel! Once opened it invariably swings wide open, which is not only a nuisance but can also result in destruction when you reverse past a fixed object! Hence while passenger doors are plentiful today, driver's doors are rare as hen's teeth - they've all been removed in commercial use for this very reason, either prior to or after destruction!

Conversely, the vast majority of early production CMPs in Australia were 60L troop transports, intended for use over some distance without constantly alighting the cab, and generally driven in the forward direction, even when retreating! As such they have no need of removable doors, and apart from these 60L CMPs we see mostly 15 cwts, with very few early production 60S vehicles. Of these 15 cwts only a small percentage are fitted with sunroofs, and if like the removable door we look upon them as removable roofs, rather than canvas roofs, we may discern their purpose.

Is it possible they were intended to replace the earlier commercial bodied pickups which had undergone rag top conversion? These are commonly seen in arty units, along with the rag top LP3 gun tractors, and while I'm not sure of their intended purpose, I imagine they'd be useful in artillery spotting work, or general reconnaissance work in gun siting. Apart from that I can only think of parade work, for the brass to ride in standing! Mind you they did seem to have more than the usual frequency of parades in arty units, what with demo shoots and the like, with brass in attendance.

I have an idea the sunroof included provision for a sun compass, which if true would lend weight to the reconnaissance theory. Anyway that's all I can think of myself, and I notice they do seem to have been quite common in arty units, like the 2/7 Fd. Regt. vehicles seen below.

Attachment 63694

Nicely deduced, Tony.

To add a little to the Sunshine Roof discussion, GMH produced the 'Roadster Cab', as they called it, for wide-track 8441, 8442, 8443 and 8444 chassis (Aust cab model number 41/5410A) and for the narrow track 8421 chassis as cab model 41/5610A. But as we have seen, the Roadster Cab was primarily used on the 15cwt.

The canvas demountable doors, however, were developed in response to climatic conditions. GMH engineers were tasked with coming up with demountable doors for increased ventilation following a recommendation from GMH after road tests on the North-South Road in 1942. The re-design was then incorporated in production from 1944 onwards: the cab became the 1944 (Aust) Pattern cab, with the '44' prefix to the GMH cab model number. The '44 Cab' also included the wide-back seat, with 2 extra inches added to the top width, and a redesigned curtain bag to accommodate both side curtains and doors.

I think you are seeing it dominant on late-production specialized vehicles because by then, most of the standard GS type contracts had been fulfilled and the contracts still to be completed were mainly those specialized vehicles - ambulances, the tail end of the No.9 artillery tractor production, tippers, and the like.

By 1944, GS CMPs were being rapidly displaced in jungle-scaled units by vehicles of US origin, and there was an over-abundance of GS CMPs available. CMPs, however, still dominated in the specialized roles throughout the Army, and hence there was still a demand for them.

The demountable door was produced as both a new production (complete cab) item and as a retrofit kit, but only those units still equipped with CMPs and in environments hot enough to warrant the conversion work ever considered installing them.

Mike C

Thanks Mike, it all makes perfect sense to me now. The canvas doors were a climate adaptation, and any other advantage they may have conferred, such as ease of cab access as I speculated, would have been purely incidental. I guess the precedent was there in the Cab 12 door, designed to be fixed partially open for increased ventilation, but obviously not transferrable to the forward hinged Cab 13 door.

In relation to the 15 cwt though I think the point about vehicle role remains valid, in that it wasn't considered necessary to provide increased ventilation. That makes sense to me as it really was little more than a base tender, small wheeled and low geared, and the uses to which it was put in artillery units, including designated gun tractor on occasion, were well outside its expected role. As such it would logically be best catered for by retrofit where necessary, which seems to have been the view at the time. I didn't know such a kit was available, and it may explain the one and only F15A I've seen with canvas doors.

I'm still curious about the timing of their introduction, which was simultaneous with the introduction of 6" steering ends and 400 steering box. I'm yet to encounter a single early production chassis with a canvas door cab, or a single late production chassis with a steel door cab, except of course the 15 cwt. And yet the two developments are functionally unrelated, and they even arose in different countries. Which leads me to wonder if there was a break in production between the early and late chassis, during which time the '44 cab was tooled up and ready to go upon resumption. I just can't see how they could coincide so closely otherwise, seemingly on the same day.

I'm not sure I'd go so far as to equate the DAY of introduction of the heavier chassis items with the 44 pattern Aust cab. Same year, perhaps, but the two are not related in any of the Aust production reports and paperwork I have. Indeed, there is no reference to the heavier chassis fittings (what you term a 'late model' chassis) or any chassis differences at all in the Aust production info: they were all treated the same by the Aust assembler/manufacturer as far as I can see.

Rather than a break in production, perhaps the 'break' is in deliveries to Australia?

Incidentally, another climatic change to the cab construction was the deletion of the sliding rear window from all Aust cab production: this was another Australian change to the CDN design driven by an early requirement to increase the air flow through the cab, ie greater ventilation.

Mike C