Why Gun Tractor Shape

[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