Why Gun Tractor Shape

[David Herbert]

And of course Morris did the same changes eventually in the UK.

David

[Mike Cecil]

I wonder how much the development and manufacture of the Australian No.8 tractor influenced the Canadian re-design of 1943 to arrive at the 7B3, if at all, or if this was simply independent experience coming up with the same or at least similar result for a common 'problem'?

Certainly the Canadians were conversant with the development of the various Australian bodies for the CMP chassis, as the DME monthly information bulletins were circulated to the UK, Canada, New Zealand, USA and so on (the circulation list is extensive). In the case of the No.8, the pattern was sealed before the end of 1942,and construction orders issued in early 1943.

In profile, the two are very similar except the Canadian body has a 'rag roof' whereas the Australian body is solid steel. There are of course, other differences, such as the spare wheel stowage, but they do have some striking similarities.

The Australians then went on to design the No.9 body with the stepped roof & stowage for the spare wheel (the switch from four run flats to five standard bar treads having been ordered in March 1943.) The No.9 body was considered superior to the No.8, and production contracts of the No.8 were switched to the No.9 in September 1943, after the No.9 had been in production for a few months.

Mike

[Lynn Eades]

On that same line of thought, I wonder who at Ford USA had seen an Australian LP1, When they came up with the higher pitched front armour and shorter drivers front armour (obviously to clear levers)

[chrisgrove]

OK, I'm only a modeller (but with 30 years in the army behind me). Everything I have read says that the sloping back to the various gun tractors were designed to make it easier to decontaminate the vehicles in the case (which seemed quite likely at times) of chemical warfare. Once chemical warfare seemed to be less likely, square back FATs were produced.

In addition, a limber beside the gun was a lot less conspicuous than a gun tractor. If the gun line came under enemy fire, it would seem safer for the gun tractor to be some distance away at the wagon lines and thus less likely to be targetted.
Chris

[Lang]

Chris

My two cents worth is the sloping back/chemical warfare theory does not hold water. The back only makes up about a third of the horizontal surface area and a flat roof would be just as easy to wash down.

Guns can only be inconspicuous until the first shot is fired then they are immediately the subject of counter battery fire. A relatively large percentage of all artillery resources are solely dedicated to this task. If the object is aerial surveillance camouflage before firing then the trucks will certainly be in the hiding plan.

The truck "wagon line" will always be very close (less than 100 metres usually from the guns) if they are not co-located. The driver is a gun-number and must run back from parking the truck when they come into action. If it is open country you may as well leave the trucks behind the guns. If there are a few trees it is wise to take advantage of them.

All the crew gear is also carried in the truck and they must have their living arrangements very close to the guns to come into action within a couple of minutes day or night.

None of this seems to have any bearing on the sloping back design. The 18 pounder ring theory still gets my vote from those offered so far.

Lang

[Owen Evans]

Thought these photos of supposedly prototype Morris and Guy Ant gun tractors might be of interest. Also, the CDSW gun tractor here: http://www.mapleleafup.net/forums/showthread.php?t=6333 also has the sloping back...sort of.

What's the framework on the back of the Guy GT 'prototype'?

Owen.

[Lang]

After 300 years of towing guns maybe the gunners wanted to keep looking at something that resembled a horse's a.....?

[Hanno Spoelstra]

Originally Posted by Lang

None of this seems to have any bearing on the sloping back design. The 18 pounder ring theory still gets my vote from those offered so far.

I think this subject is being beaten to death. The sloping back was designed to accommodate the gun's mounting base. Period.

Note: when the design and use of field guns evolved, the design and manufacture of Field Artillery Tractors apparently had to catch up later. Also, don't forget that it is often more effective to keep manufacturing a proven design, rather than disrupt mass production of an otherwise adequate vehicle. This is what helped to win the war: while the Germans were designing new tanks, the North American arsenal of democracy mass-produced an adequate medium tank.

HTH,
Hanno

[David Herbert]

A Sherman has a sloping back too.....

David