Thank you very much William!
Another helpful photo to the subject.
http://news.webshots.com/photo/25096...39564579DcHccz
This seems to be one of tractors which you have been talking about. Judging by caption, South Africans did use them not only to tow 60 pdr guns but also for 6 inch howitzers!
BTW: I'm still wondering why South Africans did not modernize all their guns with pneumatic tyres instead of using "portee" method (that was not too convenient)? I think they could...
Yours sincerely
Leon
