With sales of its electrically operated B series Tournapull scrapers slowing down significantly, Wabco realised that it was time to upgrade its large open-bowl scraper line or they were about to get left behind in the large motor scraper market. By Richard Campbell
The Wabco B series, introduced in 1959, and particularly the model B-70, had been good sellers for Wabco but was, by the late 1960s, decidedly old technology and still featured cable controlled bowl functions. Wabco’s design team totally revamped the old B series tractor unit but elected to stay with the former’s GM 12V-71N powerplant.
This was attached to an Allison CLBT5960 6-speed transmission with in-built retarder. In this configuration the B339F (the ‘B’ was retained for a short time in the machine’s designation) put out 475 horsepower and was capable of 33 mph. A totally redesigned, fully hydraulic steering system was fitted which was a mirror image to that fitted to the smaller C222 and C229 scrapers, only larger.
What really set the machine apart from its predecessor was the all-hydraulically operated bowl, apron and ejector. Rated at 25 cubic yards struck and 34 cubic yards heaped, the B339F was more than capable of taking on its contemporaries, the Caterpillar 631, Terex S-24 and Allis-Chalmers 460.
Weighing in at 39½ tons and possessed of very good riding qualities (unlike some of its competitors), Wabco saw no need to fit any form of suspension system to the machine which was formally introduced to the contracting world in late 1968.
The B in the designation had been dropped by 1970 and now the machine was known simply as the 339F.
Manufactured up to 1972 with only a few cosmetic alterations, Wabco changed the powerplant in this year to the turbocharged GM 12V-71T V-12 diesel rated at 500 horsepower and replaced the transmission with an Allison CLBT5965.
The single aircleaner was replaced with dual units, one on either side of the machine’s radiator cowl. Capacity and other basic operating specifications remained the same.
The last major change came in 1974 with the addition of all the OSHA mandated equipment that was by now necessary on motor scrapers in the USA. These included a ROPS, seatbelt, exhaust mufflers, emergency brake and mudguards on the scraper.
Horsepower and bowl capacity still remained unchanged but by now the 339F had gained over two tons and now weighed 41.3 tons empty! The 339F was dropped from production during 1976 due to a worldwide decline in the sales of large scrapers, however the tractor unit continued in production as the prime mover for the models 333F and 333FT elevating scrapers.
The 339F described
Based on the former chassis of the model B-70 Tournapull tractor, all the driveline components of the 339F were housed safely away inside this ‘tub’ which made them well protected but sometimes a little difficult to access.
At the front was the engine, a General Motors model 12V-71N connected directly to the Allison powershift transmission. From there the output was directed through a Detroit no-spin differential and then to the final bull gear and pinion-type drives.
Braking was provided by air operated, hydraulically actuated wedge shoe brakes. These were identical on both tractor and scraper.
At the back of the chassis tub was the 200-gallon fuel tank. An all-new hitch and gooseneck assembly had been developed to connect the scraper to the tractor.
This held the dual low-mounted hydraulic steering cylinders that allowed 90 degree turns either side of centre.
Advanced for its time, the 339F had a variable displacement hydraulic pump supplying the steering circuit that allowed for a very smooth steering response.
The bowl was very clean and modern looking and cast a nod in the direction of Caterpillar to its design influence with inside mounted apron arms, straddle mounted bowl lift cylinders and an apron opening and closing device that closely resembled that of its rival.
Fitted with a 4-section cutting edge, the bowl held 25 cubic yards struck and 34 cubic yards heaped and featured bulldozer ejection via a single hydraulic ram buried in the push block.
Standard tyre size on both tractor and scraper was the 33.5×33, 38-ply E-3 but other types were also available including Michelin radials.
Differing from most other manufacturers of motor scrapers, Wabco placed the operator on the centerline of the tractor unit (which probably accounted a great deal for its superior riding qualities).
A broad instrument panel was provided with the instruments on the left side, steering column in the centre and bowl operating controls placed unusually on the right of the panel. A full bonnet width windshield was fitted as standard equipment.
With most motor scrapers the operator looks over his right shoulder during loading, but, due to the placement of the seat on a 339F, the operator looked over his left shoulder, a bit of a plus when working stockpiles or drop-offs.
Milsco air suspension seats were standard. Visibility from the seat was very good except to the front when loading as the machine had a “nose up” attitude during this part of the work cycle.
Few optional extras were offered for the 339F but those that were included a cab, heater, air dryer, windscreen wiper and of course the different tyre sizes mentioned previously.
New Zealand connection
No Wabco 339Fs were ever imported into New Zealand.
ISP/Domtrac (NZ franchise holders at the time) had tried to sell some 339Fs to various contractors that were working on the Twizel/Pukaki/Ohau hydro electric schemes but it appears that none of them were prepared to give the machine an opportunity.
For the model collector
No one has yet produced a model of the Wabco 339 as either a mainstream diecast or a “limited edition” collectable in any scale.
This is indeed a great pity as the tractor unit from this model could also be used to produce other machines in Wabco’s ‘300’ series, notably the 333FT elevating scraper.
A model of the 333FT does exist, but it is a kitset, very hard to find, and if that wasn’t bad enough, it is to a very odd scale (1:70) making it incompatible with most people’s collections.
Brief Specifications Wabco 339F (mid production)
Engine: GM 12V-71N naturally aspirated V-12 diesel rated at 475 horsepower at 2100 rpm.
Transmission: Allison CLBT5965 6-speed full powershift transmission with integral hydraulic retarder.
Top Speed: 33 mph.
Steering: Full hydraulic, 90° turns to each side of centre.
Turning Circle: 40’ 7”.
Brakes: Air operated, hydraulically actuated, wedge type shoe on all Axles.
Std.Tyres: 33.5×33, 38 ply E3 on all axles.
Capacity: 25 cubic yards struck, 34 cubic yards heaped.
Operation: Full hydraulic.
Cutting edge: 11’ wide, made up of four 33” wide reversible and interchangeable sections.
Length: 47’ 2”.
Height: 3’ 3½”.
Operating Weight: 40 tons (empty), 81 tons (loaded).