While somewhat better known for its range of scrapers, LeTourneau-Westinghouse (later Wabco) sought to diversify and expand its product range in the late 1950s. The result was some of the best haul trucks of the day and a legacy that continues. By RICHARD CAMPBELL
The ‘35’ series of 35-ton off-highway dump trucks was first introduced in 1957 in conjunction with a range of other LeTourneau-Westinghouse dumpers, the 25, 27 and 30 models (25-ton, 27-ton and 30-ton respectively).
The Model 35 Haulpak was different in appearance to any other off-highway truck on the market at the time.
Euclid, International-Harvester and Mack had held a sizeable share of this market for a considerable period and the appearance of Wabco’s Haulpaks came as an unpleasant shock, especially when sales of Wabco’s new trucks took off.
The Haulpak 35 was very well constructed, with a massive ‘horse collar’ about a third of the way back from the front bumper which helped to resist frame twisting on uneven ground and also served as a support for the rear of the upper deck and cab.
Today, all large off highway trucks have this design feature.
The truck’s chassis was not straight like its competitors, but kinked in order to allow for the deep V-bottom dump bed to sit low and also accommodate the outside mounted dual hoist cylinders.
All the model 35 Haulpak’s featured an Allison powershift transmission but the buyer could specify if they wanted Cummins or Detroit Diesel power to suit their fleet requirements.
Another new innovation was the front and rear suspension systems which were oleo-pneumatic, and completely new to the industry.
Traditional off-highway trucks of the period used packs of leaf springs to cushion shock loads to the chassis and driver.
In the main these did a reasonable job but they were high-maintenance, especially on rough haul roads and tended to flatten out and occasionally shed leaves over time.
Wabco used oil filled, nitrogen gas pressurised cylinders (known by Wabco as ‘Hydrair’) and took out a patent on the design which made them a lot of money over the years as other truck manufacturers followed suit!
The hydra-ride suspension gave the truck a very smooth ride indeed and was certainly responsible for the exceptionally long life of the machine’s chassis.
Rather than use a narrow, medium depth dump bed, Wabco opted for a shallow, wide body with a deep ‘V’ at the front mounted on a short wheelbase chassis.
This provided a low target for the shovel or loader operator, kept the bulk of the load centered and also gave the machine a much lower centre of gravity than its competitors.
The short wheelbase also meant that the truck was very manoeuverable, especially useful in confined quarters.
All in all it was a very good design and soon copied by others.
Production of the Model 35 Haulpak spanned three major versions: the original Model 35, the 35C and the final variant, the 35D.
External changes between the models are not great, which does makes identification a little difficult.
The original model 35 however, does has a different entrance step arrangement to the later 35C and 35D.
Many model 35s are still in daily use throughout the world, testament to their simplicity, ruggedness and reliability.
In the 1980s, Wabco fell on some fairly hard times (as did many other heavy equipment manufacturers).
There was a global downturn in sales of mining and earthmoving machinery and Wabco was struggling to fill its order books for any equipment, let alone off-highway trucks.
So the difficult decision was made to offer some segments of the company’s business units for sale.
A deal was struck with Dresser Industries, which took over the manufacture and distribution of the Wabco Haulpak range in 1984, marketing them as Dresser-Haulpak trucks (as the Haulpak name was still very highly regarded in the industry).
This situation remained in place until Dresser had discussions with Komatsu and divested itself of both Dresser’s motor graders and the Wabco Haulpak truck line to Komatsu.
Unfortunately Komatsu had no need of smaller 35-50 ton off-highway trucks as it already had a successful range of its own.
What it did want however was to penetrate the large mining truck market and take on Caterpillar, which up to then had the market pretty much to itself.
The larger Wabco/DresserHaulpak trucks (which ranged all the way to 320 tons capacity), filled that need nicely and a deal was soon forthcoming.
This left no room for the smaller Haulpak trucks and so the model 35 quietly disappeared once and for all around 1996.
Just as a footnote, R.G. LeTourneau had nothing to do with the design of Wabco’s ‘Haulpak’ range (as they were known), that honor belonging to Ralph Kress who later went on to work for KW-Dart and Caterpillar, having a hand in the development of its model 769A rear dump before going on to form his own company.
The Haulpak heritage still lives on in Komatsu’s mining truck range, all of the larger units which owe their existence to Wabco (and Ralph Kress).
The New Zealand Connection
There had been the occasional sale of Haulpak trucks in New Zealand, with the Ministry of Works purchasing a small number near the end of the Benmore contract.
Things really took off in the mid-1970s however when the Ministry of Works purchased a quantity for work on the Twizel and subsequent Clutha hydro-electric schemes.
These machines did sterling work for the MOW and when they were eventually retired and sold off through the Government Stores Board, were all snapped up by quarries and similar small mining outfits.
Up until the late 1990s a trio of them were in service in the NZ Rail ballast yards in Wiri, Auckland (since closed down), carting blasted rock to the crusher.
For the Model Collector
While there is a 1:50 scale model of the Wabco 35C available, it, like all models of Wabco equipment, is rare, expensive and hard to find.
So much so, even the author doesn’t have one in his collection!
There used to be a kitset of a Wabco Haulpak available (marketed originally by Lindberg), but it was an odd scale (1:40) and better represented a Model 50 rather than a 35.
It does however, make up into an attractive model and is worth seeking out.
As usual, Ebay is probably your best source.
Brief Specifications Wabco 35C (as used in NZ)
Engine: GM Detroit Diesel 12V-71N, V-12 rated at 425 flywheel horsepower at 2100 rpm
Transmission: Allison CLBT750, 5-speed full powershift with integral retarder
Top Speed: 36.5 mph
Brakes: Air over hydraulic, wedge actuated shoes
Suspension: Wabco Hydrair oil/nitrogen cylinders on all axles
Steering: Full hydraulic
Turn Circle: 49’
Std.Tyres: 18.00×33, 28-ply, E3 on all axles
Body Capacity: 34 cubic yards (at 1:1)
Body Hoists: 2 x 3-stage, double acting
Length: 25’ 4”
Width: 12’ 5”
Height: 13’ 1”
Operating Weight: 29 tons (empty), 64 tons (loaded)