Le Tourneau was a visionary machine designer. His innovative electric wheel, developed for the L-series Pacemaker motorscraper, is now used in most mining trucks. Only one Pacemaker motorscraper made it to New Zealand – H Allan Mills & Son’s Texas Rose. BY RICHARD CAMPBELL.
When RG Le Tourneau sold his earthmoving equipment manufacturing business and several of his manufacturing facilities to Westinghouse Air Brake Co (Wabco) in 1953, one of the clauses in the agreement was that RG Le Tourneau would not build any earthmoving equipment for five years.
This didn’t stop RG from designing equipment however, and by 1958, when the clause expired, he had a whole range of new equipment ready to go – many radically different than anything that had bee seen previously.
Key to the success of these machines was the electric wheel – a Le Tourneau invention – now commonplace on most major mining trucks but quite revolutionary in the 1950s.
Among the tree pushers, log stackers, weird looking loaders and rubber tyred bulldozers were a range of motorscrapers with unique features.
Le Tourneau designed his new motorscrapers to be quite flexible in their application, so an extra bowl (or two), extra engines or drive wheel sets could be added, even down to where the operator was positioned for best visibility – what today we would call modular design.
The new range of machines were called the L-series Pacemakers, or known colloquially as ‘electric diggers’, (Wabco having bought the rights to the trademark Tournapull motorscraper name).
These machines were available in yardage ratings from 28 cubic yards through to a massive 80 cubic yards on the three-bowl machines.
Power was usually provided by any combination of General Motors 8V-71, 12V-71 or 16V-71 diesels, driving electric generators, which supplied the necessary AC power for the electric wheels and DC current via switching gear for other operating functions. Some early examples were powered with Cummins engines but the majority of machines were GM powered.
The heart of the new machines was Le Tourneau’s electric wheel, which was planetary driven by an electric motor in each wheel hub and featuring regenerative or ‘dynamic’ braking (very similar to a diesel electric locomotive). This arrangement required no transmission, gearbox or differential and had tremendous torque properties.
All functions of the machines were electrically operated via rack and pinion gears, including the steering. This meant a constant supply of electricity was an absolute must and it was this factor, as well as the relatively slow speeds attainable at the time, which were the machines’ biggest drawback.
Problems included motor overheating and any number of electrical short circuits, so much so that a factory trained technician was usually supplied to the purchasing contractor to de- bug the unit when it was put into service.
However, when in operating trim the L-series machines could really move a lot of earth at a very low cost per yard. The most favoured combination appears to have been the two-bowl unit powered with two or three GM 12V-71’s.
For their day, the L-series Pacemakers had good operator appointments, most featuring cabs, and all having control tower visibility of operations.
All functions, apart from acceleration, were controlled by switches – the speed control device operating in the same manner as an electric train controller.
The L-series Pacemaker scrapers appear to have died along with RG Le Tourneau in 1969, with what is now Marathon-Le Tourneau concentrating on producing mining wheel loaders of immense size – still powered by the electric wheel, RG Le Tourneau’s lasting legacy.
The NZ Connection.
Surprisingly, one example of a Pacemaker ‘electric digger’ made it to New Zealand, imported by agents Cable-Price Corp. This was a model L-28, which was owned and operated for its entire life by H Allen Mills & Son of Rotorua.
Christened ‘Texas Rose’ by the company (no doubt due to the fact that the machine was manufactured at Longview, Texas), it was used on a number of projects by Mills, including hydro dam construction.
Unfortunately, by all accounts, once the machine had accumulated some hours it became a mechanic’s (or at least an electrician’s) nightmare, and was last seen by the author languishing in Mills’ yard in Rotorua in the late 70s. Its ultimate fate is unknown.
If the reader is interested in some of the more exotic products produced by RG Le Tourneau, the author highly recommends The Le Tourneau Archive by Philip Gowenlock, published by Paddington Publications, Australia (1998) and also Le Tourneau Earthmovers by Eric C Orleman, published by Motorbooks International, USA (2001).
Brief Specifications – R.G.Le Tourneau L-28 Pacemaker
Engine: General Motors 12V-71 diesel rated at 420 horsepower
Drive: Electric Motors
Brakes: Multiple Disc with additional regenerative braking provided by electric drive motors
Steering: Electric rack & pinion quadrant
Operating Functions: Electric rack & pinion
Capacity: 20.5 cubic yards struck, 28 cubic yards heaped
Tyres: 73” x 48” wide base, unidirectional.