LeTourneauOff-Highway Trucks

Birth of the Articulated Dump Truck

Developed to a greater potential during the late 1960s with the advent of all-wheel drive, the articulated dump track has actually been around for a lot longer than most folks realise. This is the story of the first ADTs (as they are now called) invented by LeTourneau. By RICHARD CAMPBELL.

RG LeTourneau was responsible for one heck of a lot of earthmoving equipment, and more importantly, ideas and methods.

Constantly striving to gain the lowest possible cost per cubic yard was an obsession that fired his imagination and resulted in many of the machines we take for granted today.

Although they may look a little different now, having metamorphosed over the years, LeTourneau produced many types of machines that changed very little in purpose, and one of those is the articulated dump truck.

LeTourneau’s first articulated dumper, the Tourntailer, was manufactured in 1938 and was based on a Model A Tournapull. Holding 28 cubic yards, the machine was entirely cable operated and featured slide out ejection, the entire upper body moving backwards over a stationary floor and gravity doing the rest.

Next machine to receive the treatment was the 1940 Model C Tournapull, which also featured a slide out body known as the W210, however this machine only held 10 cubic yards.

LeTourneau Australia built a home-grown variant of the dumper body called the ‘Rock-Buggy’ for use behind the Australian manufactured C-Standard Tournapull. The dump bed, which held approximately 10 cubic yards, was scow-shaped, and was raised by cable on a fabricated ladder arrangement. Over 50 of these were manufactured at LeTourneau’s Rydalmere plant. RG LeTourneau saw these machines when he visited the Australian LeTourneau plant in New South Wales in 1949 and was highly impressed. They were the forerunner of what was to become the Tournarocker.

Following the war, LeTourneau set about designing some much tougher articulated rear dumpers which he christened “Tournarockers”. These were made available for all four sizes of Tournapull – A, B, C and D and ranged in capacity from 10 to 50 tons.

The beauty of these units is they could be interchanged with other rear attachments on the Tournapull as they were only connected by four heavy duty bolts and an electrical socket (which provided power to the electric motor that worked the cable winch). Regardless of what attachment your Tournapull was fitted with, you could swap it for a Tournarocker as all the controls for operating it were already in place in the tractor unit, truly a ‘modular machine’.

We should also not forget that now, when 50 ton all-wheel drive ADTs are just beginning to show up, LeTourneau already had in 1948, a 50 ton articulated hauler, the Model A with E50 Tournarocker.

When LeTourneau sold his business to Westinghouse Air Brake Co in 1953, Wabco acquired all the tooling, jigs and patent rights to manufacture Tournarockers.

Wabco was well aware that it had a niche market with these machines as they could traverse much rougher ground than a standard, rigid frame rear dump, and were also more manoeuvrable. Other manufacturers had also taken note of the Tournarocker’s success and, during the mid-1950s, a whole host of Tournarocker ‘clones’ began to appear in the market. Some were good and others of indifferent quality but all were vying for a share of the market.

In a lot of cases the primary manufacturer of the dump body was different to the tractor unit supplier, which resulted in some interesting partnerships and hybrids.

Allis-Chalmers made its own dump body trailers, but also offered a forced ejection dump body built by the Yuba Movall Corp. These were cable operated and some were imported into New Zealand. At least three were later converted to hydraulic control behind Terex S-24 tractor units.

Caterpillar partnered up with the Athey Products Corp, and was a successful relationship that lasted many years. It also produced dump bodies for some post-1968 Terex machines.

Caterpillar also had a short-term relationship with Hardwick which manufactured hydraulically controlled forced ejection dump bodies. Examples of these were also imported into this country and used at their Kopuku mine site in the Waikato.

Euclid had an agreement with Easton, which manufactured a very rugged deep bottomed dump bed. Easton built bodies for the S-7, S-12, S-18 and S-24. This partnership appears to have been terminated in 1968 when GM lost the rights to the trademark Euclid name.

Other minor players included Clark-Michigan and Wooldridge/Curtiss-Wright, both of which manufactured their own dump bodies.

Wabco continued to build Tournarockers up to the introduction of the hydraulic controlled 229 and 339 machines in 1967/68 when they were quietly dropped from the catalogue.

The most popular of all of the four types of Tournarocker was the Model C that started out powered by a straight six GM 6-71 and ended production with a GM 8V-71. A Cummins engine could also be fitted, but these examples seem to be quite rare.

The Tournarocker was well ahead of its time in having air-operated multiple disc brakes on all wheels. All of its competitors used shoe-type brakes which were prone to brake fade on long downhill hauls and needed frequent adjustment.

As the Tournarocker had no chassis as such, only being pivoted on either side of the dump bed, dumping the load could be accomplished in one of two ways.

The operator could set the tractor brakes and raise the dump body which drew the rear wheels forward (away from any ledges), or the dump body brakes could be set and pull the tractor unit backwards toward the rear wheels.

In this configuration the machine took on a very unusual pose which was often referred to rather crudely as looking like a “shitting dog”!

The Tournarockers were highly successful and did the job for which they were intended. They were widely used in the construction of the US Interstate Highway Program when any rock needed to be hauled from awkward places and outnumbered their competitors three to one.

The New Zealand connection

LeTourneau and LeTourneau-Westinghouse Tournarockers have been in use in this country since the early 1950s by various companies and some were used at Manapouri.

Since the late 1960s, by far the star user of the type has been Goodmans of Waikanae, which has maintained the largest operational fleet of them here.

Over time the fleet has included D Tournarockers and both the GM 6-71 and GM 8V-71 powered C Tournarockers.

Your author has operated both D and C Tournarockers and rates the 1956 GM 6-71 powered C Tournarocker as one of his favourites.

For the diecast model collector

As fate would have it you are in luck for a change as there are two models of the C Tournarocker available in 1:50 scale from EMD Models.

These represent the GM 6-71 powered (C Roadster) Tounarocker and GM 8V-71 (V-Power) versions so you can have an example of both if you can afford them. But be aware, prices of these models are not for the faint-hearted, examples of the V-Power version have known to fetch over $1000!

Tin toy collectors also have a choice as Nylint, Structo and Boomaroo have all made reasonably passable representations of the C Tournarocker to roughly 1:16 scale. Regrettably, these are also considered as collectors’ items these days and the prices reflect their collectability.

The Boomaroo version is the most expensive while the Nylint version is the most accurate.

Brief Specifications (I’ve unashamedly chosen my favourite, a 1956 Model C Tournarocker)

Engine:          General Motors model 6-71, 6-cylinder naturally aspirated two-cycle diesel rated at 208 flywheel horsepower at 2000 rpm

Transmission:   Fuller 5A1120 manual 5-speed sliding gear transmission

Clutch:                    Lip-Rollway 17” single plate

Top speed:           32 mph

Brakes:                  Multiple-disc air brakes on all four wheels

Tyres:                      24.00×25 24-ply, E3

Steering:               Positive electric via vertical electric motor and ring gear, 90° each way

Turning circle:   14’ 4”

Capacity:              22 tons

Dumping:              Electric controlled winch, positive up and down on 7/8” cable

Dump angle:       66 degrees

Length:                 29’ 9”

Width:                    11’ 2”

Height:                   11’ 4”

Op weight:           23 tons (empty), 45 tons (loaded).

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