Today in WW II: 22 May 1939 Fascist Italy and Nazi Germany sign the Pact of Steel, a declaration of trust and cooperation that also included secret provisions on military and economic matters.

R-4 Caterpillar Bulldozer / Tractor

Caterpillar introduced the R4 (6G series) in 1938, based on the earlier Caterpillar Thirty, and the R4 was produced until 1944. It was powered by a 4 cyl. gasoline engine and had both a 44 inch and a 60 inch track gauge (width). The R-4 had only one upper track roller, compared to two rollers on the Cat Thirty. The later D4 Caterpillar tractor was based on the R-4.

The rear winch was a Hyster D4 while the power control unit was by LaTourneau.

The dataplate states that the maximum drawbar pull is 7,332 lbs. and the maximum ground speed is 5.4 mph.

Thanks to Stephen A. Sarkany for help with this page.

USN Seebee R-4 Caterpillar Tractor with bulldozer blade, Carswell Strategic Air Command Base, Ft. Worth, TX. Photographed 10 November 2006. Photo: Courtesy of Bob Pettit.

Data plate of USN Seebee R-4 Caterpillar Tractor with bulldozer blade, Carswell Strategic Air Command Base, Ft. Worth, TX. Photographed 10 November 2006. Photo: Courtesy of Bob Pettit.