Steam Trucks and Steam Wagons

Steam trucks (or steam wagons) are a decided oddity in the U.S. but in Australia examples of the breed still survive

In comparison to the Aveling & Porter (left), the Super Sentinel (right) looks more like a traditional truck rather than a converted locomotive

In comparison to the Aveling & Porter (left), the Super Sentinel (right) looks more like a traditional truck rather than a converted locomotive.

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Traveling in the U.S. last fall, I discovered that most people I talked to had little knowledge about steam trucks (or steam wagons, as they were called in the early days). Indeed, most people had no idea what steam trucks or steam wagons looked like.

There were, to my knowledge, two main types of steam wagons built: the over type, i.e., the engine on top of the boiler; and the under type, i.e., the engine underneath the chassis.

The second photo in the photo gallery shows my Aveling & Porter number 7758 when new, Sept. 2, 1912. Aveling & Porter, Rochester, Kent, England, were well-known steamroller and traction engine builders, and in 1909 produced their first steam wagon. They made a total of 291, with the last steam wagon leaving the works on Jan. 14, 1925. Two models of steam wagon were produced – a three tonner and a five tonner. The one in the photo is the F.G.P. type built to carry five tons. When new it was ordered with end tipping, a steel-lined tray and 1,000-gallon (Imperial) water tank. It was imported by Noyes Brothers of Sydney for the municipality of Goulburn, 120 miles southwest of Sydney.

It was sold in 1937 to Perc Apps, who removed the boiler and used it to steam chaff. It fell into disrepair and was bought in 1969 and restored by 1971. The original wheels were steel but rubber tires were required to run on roads after it was restored.

My other steam wagon is a Sentinel, made by Alley & McLennan of Polmadie, Glascow. Alley & McLennan made steam engines for many years, and they were famous for their steering engines for ships. They also had a valve factory. They constructed their first steam wagon (a three tonner) in 1906 and exhibited it at the Brewer's Exhibition. It had a vertical boiler at the front, the engine was placed beneath the frame and it had duplex cylinders with a displacement of 6-3/4-inch x 5-inch.

The steam was controlled by a sliding camshaft running in an enclosed crankshaft. Sentinel maintained this arrangement (with the exception) with the vertical boiler and the totally enclosed engine until the final few left the works in 1950. In 1915 the wagon side of the business was separated and a new factory was built at Shrewsbury, Wales, where all the wagons were built from that date.

The wagon you see here was the second model and was named the Super Sentinel when it was exhibited at Olympia in 1923. There was a new tube layout in the vertical boiler, which was pressed to 230 psi. The steam was further heated in a super-heater in the uptake, providing a superheat of 150 degree F.

The engine was a new design, yet similar to the previous model where the cylinders were 6-3/4-inch x 9-inch bore and stroke. It had two separate sliding camshafts, and at the then legal speed (in England) of 12 mph, the engine ran at 240 rpm. It could develop up to 70 BHP for short periods.

The camshafts were arranged in four positions: reverse, mid-position where all valves were lifted for warming the engine; slow forward (80 percent admission); and fast forward (30 percent admission). Another feature of the engine is the differential that is built into the crankshaft, which also had a clutch in the center making it a limited-slip differential.

The driveline was by two roller chains of 1-3/4-inch x 1-1/4-inch pitch. The pneumatic tires are a later conversion as it originally had solid rubber. The history of this Sentinel is relatively unknown, except its last main work was on a water supply dam for Sydney. It was then used to haul logs in the forest, a task to which it was not suited, owing to the solid rubber tires in the soft ground. It then fell into disrepair. It had no boiler and had been burnt in a bush fire. It was finally restored in 1979 and its first outing was to go to a drive-in movie show.

The Sentinel can cruise comfortably at 15 MPH and it can travel 50 miles on a tank of water. The windscreen was an optional extra, as were the electrical lights. This wagon is number 5721 and left the works in early 1925. It also features a three-way tipper - tips either side or at the rear. The lift cylinder is powered by a steam injector. The coal is fed to the boiler by a central chute in the top of the boiler. Sentinel used the old spelling on the nameplate, i.e., "waggon."

Aveling & Porter Specifications

Working pressure: 200 PSI
Compound Cylinders, Bore and Stroke:  4-5/8 x 7 x 7
Heating surface: 82 square feet
RPM: 400
BHP: 24
Weight Empty: 11,200 pounds
Weight Loaded - British: 26,400 pounds
Body size: 9-foot 9-inch x 6-foot 8-inch
Maximum Speed: 8 MPH
Driveline: Chain Drive: 2-1/2 x 1-1/2 pitch

Contact steam enthusiast Robin Gibb at: Markwood, RMB 2175, Wangaratta VIC 3678, Australia.