The Caterpillar 666 motor scraper

Following requests from a number of our readers, this month’s featured machine is the Caterpillar 666, however, no 666s were ever imported into New Zealand. By Richard Campbell

The largest production twin engined motor scraper to be offered by any earthmoving equipment manufacturer, the Caterpillar model 666, was introduced in 1962 along with a raft of other ‘600 series’ motorscrapers that Caterpillar had been developing.

Boasting a whopping 54 cubic-yard-heaped bowl, the 666 was also offered as a single engined scraper, which was known as the 660.

From the outset, the Cat 666 was designed for high volume earthmoving and situations where it would spend most of its operational life, rather than being moved from job to job.

Applications in opencast mines, where grades were an issue, were ideal 666 territory.

Its three-axle configuration made it a fast and stable machine to handle, despite its size.

Initial machines had a 450horsepower Caterpillar D346T turbocharged V8 diesel installed in the tractor unit while a 335 horsepower Cat D343T inline six-cylinder diesel was fitted in the scraper. During its production life, the horsepower ratings were progressively increased to 550 horsepower and 400 horsepower respectively in the model 666B.

Caterpillar’s nine-speed powershift transmission provided the necessary gears to get the 666 moving, and move it sure could. A loaded machine, weighing over 118 tons, could reach speeds in excess of 42 miles per hour on a level haul!

The final production model, the 666B, had Caterpillar’s eight-speed semi-automatic transmission.

In order to save the service brakes on long downhill hauls, a hydraulic retarder was a standard part of the powershift transmission package.

Resembling one of Caterpillars 1950 offerings, the DW20 on steroids, layout of the 666 was actually quite conventional.

The steering axle was pinned in its centre to allow vertical movement and featured hydraulically boosted steering. A small V-shaped windrow breaker was placed slightly forward of the axle to help ease the way through poorly maintained fills.

A standard universal type hitch connected the tractor and scraper together and allowed lateral oscillation of up to 22 degress to either side of centre. The hitch was also fitted with anti-jack knifing stops which must have been of some comfort to the operator.

With easy access from either side of the machine the operator was seated slightly to left of centre, with a good view all around.

All operating controls were within easy reach and required minimum effort to use.

Standard operator comforts included a windshield and wiper, plus Cat’s bucket type torsion-flex seat. Post-1972 machines were available with an optional ROPS cab.

Three sizes of tyre were required to outfit a 666: 18×25 on the steering axle, 37.5×39 on the tractor drive axle and a massive 37.5×51 on the scraper. Other sizes were available depending on the machine’s intended application.

Operation of the scraper was all-hydraulic with double acting cylinders used on all circuits. As previously mentioned, the 666 had a huge bowl and was rated at 40 cubic yards struck and 54 cubic yards heaped (even more with sideboards).

Some of the first machines off the line were put to work in the vast Kennecott copper mine in Nevada while others found homes in coal mines in Wyoming, Colorado, New Mexico and Pennsylvania.

In some of the more unusual applications a 666 fleet realigned a five-mile stretch of the Santa Fe railroad in Arizona while in the most bizarre instance, eight 666s built a cemetery in the California hills.

The Caterpillar 666 was phased out of production in the late 1970s and it is unlikely that a scraper of this size will ever be offered again by any manufacturer.

The New Zealand Connection

A tentative one at best, but during the late 1960s, Auckland mega Cat fleet owner W Stevenson & Sons seriously considered adding Cat 666’s to its spread of scrapers at the Kopuku opencast coal mine in the Waikato. Regrettably this wasn’t to be.

It is also rumored that Downer & Co looked at putting 666s into its opencast coal mining operation in Huntly but the ground pressure footprint of a loaded Cat 666 made this unfeasible, the soil being too elastic to effectively support the machine.

Brief Specifications – Caterpillar 666 (mid-production)

Engine (tractor):          Caterpillar D346T turbocharged V8, 500hp

Engine (scraper):         Caterpillar D343T turbocharged six-cylinder, 400hp

Transmission:             Caterpillar nine-speed barrel planetary powershift with retarder

Top Speed:                 42.6 mph

Brakes:                        Expanding shoe, cam operated

Steering:                      Hydraulically boosted

Turning Circle:            46’

Tyres (steer):              18.00×25

(drive):                          37.5×39

(scraper):                     37.5×51

Capacity:                    40 cubic yards struck, 54 cubic yards heaped

Operation:                   Full hydraulic

Length:                        56’8”

Width:                         14’4”

Height:                        13’10”

Operating Weight:       61 tons (empty), 118 tons (loaded)

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