Why Gun Tractor Shape

[rob love]

I think Bruce had it right. The early trucks had run flat tires so no need for a spare. The ring for the 25 pounder was not kept on the gun for any long distance...it was stowed on that slanted back. After Burma fell, and rubber became scarce, the vehicles were built without runflats, so needed a spare. At that time the stowage location for the firing platform went onto the top of the limber, and the spare tire location was the slanted backside of the truck.

The move to mechanization was the death of the limber. As mentioned, the limber removed the weight of the gun trail from the backs of the horses. But with mechanization, the towed loads actually need the weight on the hitch for stability. And why not just build a bigger truck so you can carry all the ammunition, tooling, and the gunners kit as well as the gunner? The limber also would have made it a real bitch to back up more than a couple feet.

The Canadians actually built artillery tractors in the early 30s out of locally sourced Leyland trucks. The purpose built DND designed bodies had a large stowage capacity, but the setup still retained the 18 pdr limber. I suspect that when we started building trucks for the British, we ended up following their basic design of the artillery tractor.

[Lang]

Why didn't somebody say "Give us a proper truck so our regiment workshop guys don't need to build racks on the sloping back to carry all the required gear".

[rob love]

They did. From the AEDB Design Records:

"Reports from the field, however, indicated that the 7b2 -FAT did not full-fill all the requirements that had been anticipated, in that the payload was restricted, due to the design of the body. It was decided, therefore, to pilot a new FAT using the same chassis as heretofore, but considerably modifying the body. The sloping after deck was eliminated, and an all steel, open roof body, with superstructure and tarpaulin, was pilotted, the spare tire being housed in a compartment at the rear of the body. Considerably more stowage space was provided, particularly for ammunition which was for either the 17pdr or 25 pdr, role, and more room was available inside the body for the personal and their kits. This was the 7b3 body, and proved to be quite satisfactory."

[Lang]

Well done Rob!

Answers the question.

Lang

[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)

[m606paz]

Originally Posted by rob love

They did. From the AEDB Design Records:"Reports from the field, however, indicated that the 7b2 -FAT did not full-fill all the requirements that had been anticipated, in that the payload was restricted, due to the design of the body. It was decided, therefore, to pilot a new FAT using the same chassis as heretofore, but considerably modifying the body. The sloping after deck was eliminated, and an all steel, open roof body, with superstructure and tarpaulin, was pilotted, the spare tire being housed in a compartment at the rear of the body. Considerably more stowage space was provided, particularly for ammunition which was for either the 17pdr or 25 pdr, role, and more room was available inside the body for the personal and their kits. This was the 7b3 body, and proved to be quite satisfactory."

A pity that the 7B3 body was never used during the war.

[rob love]

Originally Posted by m606paz

A pity that the 7B3 body was never used during the war.

The real pity is that they all seem to have been exported and few to none remain in Canada.

Also odd that being this late in the war, they used POW cans in the racks instead of the 5 gallon jerry-can.

[m606paz]

Hi Rob
It is true, that in Canada there is none.
Here in Argentina 2 survive in very good running condition and another 10 with many missing, according to my records.

Those racks are prepared to mount 3 pow or one Jerrycan. Very well designed.

[Richard Scott]

Originally Posted by rob love

I think Bruce had it right. The early trucks had run flat tires so no need for a spare. The ring for the 25 pounder was not kept on the gun for any long distance...it was stowed on that slanted back. After Burma fell, and rubber became scarce, the vehicles were built without runflats, so needed a spare. At that time the stowage location for the firing platform went onto the top of the limber, and the spare tire location was the slanted backside of the truck.

The move to mechanization was the death of the limber. As mentioned, the limber removed the weight of the gun trail from the backs of the horses. But with mechanization, the towed loads actually need the weight on the hitch for stability. And why not just build a bigger truck so you can carry all the ammunition, tooling, and the gunners kit as well as the gunner? The limber also would have made it a real bitch to back up more than a couple feet.

The Canadians actually built artillery tractors in the early 30s out of locally sourced Leyland trucks. The purpose built DND designed bodies had a large stowage capacity, but the setup still retained the 18 pdr limber. I suspect that when we started building trucks for the British, we ended up following their basic design of the artillery tractor.

I have some memory that the odd Shape was for the ease of chemical decontamination?