Friday, March 3, 2017

1921 Mack AC “Bulldog” truck

The Mack Brothers Company was established in New York in 1902 but by 1911 the founding Mack brothers sold their interest in the company.  The AC, Mack's all-time most famous product introduced as a 1916 model was manufactured continuously for a remarkable 24 years through the end of 1939 with a total of 40,299 units built. 
The AC with an available load capacity of 3½-, 5 ½-, or 7 ½ tons, is powered by a massive 471-cubic inch inline-four cylinder engine rated at 45 horsepower. The engine uses a cast-aluminum crankcase and separate, cast-in-pairs cylinders with five-inch bore and six-inch stroke connected to a three-speed manual transmission with an aluminum alloy case. Interestingly the 15 ½ gallon radiator is located behind the engine which is hand cranked to start.   

Like all AC trucks, the maximum speed like our feature, a 1921 model on display in the Grand Gallery of the Columbia Gorge Interpretative Center, is determined by the diameter of its chain-drive sprocket; in this case, the top speed is 17 miles per hour (MPH).  Which is plenty fast when one considers that the rear axle provides the Mack's only stopping power with a pair of expanding-band mechanical brakes.  
This particular AC with a unique 204-inch wheelbase chassis was used up until the nineteen fifties hauling timber on the Oregon/Washington Coast and is fitted with what the Museum says are the original hard rubber tires. The AC’s load of cedar logs was donated to the Museum by the US Forest Service from trees blown down in the Gifford Pinchot National Forest; the forest’s southern boundary is directly across Route 14 from the Museum.

Visit the Museum’s website at
all photos by the author

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