Does anyone know the size of crawler tractors listed in Engineer T/O & Es as crawler tractor 30-50; 50-70; 70-90; or 96?
As a guess the numbers may refer to weight classes. Is it consistent with: Caterpillar in World War Two I see from a serial number plate at that site that a D6 had a shiping weight of just under 24,000 lbs so not sure my guess is correct. Some more pictures with possibly useful captions at: Military Dozers – Dedicated to the men and women of the Army Corps of Engineers, Seabees, and the other construction units of the Armed Services Looking at: Classic Caterpillar Crawlers Perhaps the numbers have something to do with horsepower (drawbar and/or belt).
Thank you. I had the information on the D-4, D-7, etc. And I was guessing, as you suggested, that the 30-50 was the D-4 and the 50-70 was a D-7, and the 70-90 was a D-8. I was not sure what the -96 was. I hope someone can confirm our suspicions.
Can you match the numbers up with the ones from the Engineering Battalion TOE I quoted? That might resolve it.
For the US, crawler tractors are referenced several ways depending on which service they are being used by. For the Army, they were classified as Light, Medium, and Heavy and given M numbers. So, for example, the Caterpillar D4 and International TD9 are classified as "Light Tractor, M2" These have a drawbar pull of about 7,000 lbs. at about 35 - 40 hp. This later description is how the US Navy (Construction Battalions) listed their equipment and given a class number. For the listed tractor these are class 4. The largest tractors, like the D8 were class 1. The Caterpillar D6, Allis-Chalmers HD7, and International TD 14 were all classified as "Medium Tractor, M1." The US Navy classified these as Class 2 or 3. Drawbar capacity for US tractors went from about 2 tons to about 50 (113,000 lbs.). Units, whatever service, also had equipment and fittings that went with the tractors to be installed as the situation called for it. These included, bulldozer blades, angle dozer blades, earth scrapers, crane fittings, etc. An angle dozer blade in use
The numbers represent Draw Bar Horse Power of the Tractors Page showing some of the numbers on your post