[George McKenzie]

Hi First I will say that the older cats pre 1936 numbers stood for horse power .A 30 cat had 30 HP a 60 had 60HP .The 35 was the first deisel .The R series were R being a gas ,RD is a deisel The RD 2,4,6,8 and some U series were the Catipiller modles used in the ww2 .I put a D7 in a Hurculies aircraft in Yellowknife where it was hauled to the artic we had to remove all the dozer parts ,blade and C frame maily because it was too wide ,not too heavy .I might add that these cats did not have canopies on them and when working in the bush kild alot of operaters from the tree tops comming down on them .Some were sheeted in with iron and used in combat They were so reliable that they made a great impact on the out come of the war George