Classic Machines: The Terex 72-51 loader

Developed from the successful Euclid L-30 and 72-40, the Terex 72-51 was introduced in 1966 (originally as the Euclid 72-51). By Richard Campbell

Euclid had been one of the earliest exponents of articulated steering, or pivot-steer loaders as they were more commonly known in the USA, marketing its first production pivot-steer machine, the L-20, in 1962.

As would be expected with a General Motors manufactured product, the 72-51 was powered with a GM Detroit Diesel engine. In the 72-51 this was the GM model 6-71N, six-cylinder, in-line diesel, rated at 202 flywheel horsepower. The 6-71N was a slightly more powerful development of the engine that had powered the original Euclid L-30 loader and represented an 11 horsepower increase over the previous model machine.

Allison (another GM-owned company) provided the powershift transmission, a model TT4420 which was a two speed, two stage type, giving torque converter drive and direct drive in each of its two speed ranges.

Standard tyre was usually the 23.5 x 25 wide base L3 although other types could be fitted depending on the machines intended application. These could be ballasted with water for extra weight to increase the machines static tipping load.

Brakes were air operated S-cam shoe type acting on all wheels with a shoe type parking brake on the transmission output shaft.

Unlike other articulated steer loader of the time, the Terex 72-51 was set up so that the wheels didn’t actually follow each other (track) during a turn as the actual articulation hinge point was slightly forward of the centre of the machine. This allowed for somewhat tighter turns than opposition loaders but the trade off was the operator had to be careful as to how he manoeuvred in tight spaces due to the unequal tracking. Steering was via two identical double acting hydraulic cylinders with a backup safety steering accumulator.

Terex utilized an unconventional bucket lift arm set up and was one of only a handful of manufacturers who attached their bucket tilt cylinders directly to the back of the bucket rather than through a linkage arrangement

Wielding a bucket rated at three-and-a-half cubic yards, the 72-51 was at home in quarries, aggregate plants and as a useful tool on any potential jobsite.

Optional buckets up to six cubic yards (for lightweight materials) were available. A Drott four-in-one bucket or log forks could be substituted for the standard bucket if necessary. These required the use of an extra (third) valve in the hydraulic system.

Terex wheel loaders were pretty basic machines with few operator concessions. Cabs were not standard equipment until the early 1970s and the operators environment was a little cramped and quite noisy. Visibility was good to the front and sides but restricted to the left rear by the air cleaner and muffler.

The transmission shifter was mounted on the left side of the steering column with bucket operating controls emerging from a control console on the right hand side next to the operators seat. Basic instrumentation was provided on a panel which was bisected by the steering column.

A safety feature ahead of its time was the steering accumulator which allowed for three lock to lock turns of the steering wheel in the event of an engine failure, sufficient to get an operator out of trouble if need be.

Not known for their quietness in operation, many New Zealand machines were fitted with larger, non-standard mufflers in order to meet council noise bylaws and pacify hostile locals who weren’t nearly as fond of the sound of the machine as the owner!

The 72-51 was a no-frills, brutish good looks machine, designed to do a job day in and day out with no fuss – a task which it performed admirably.

It was manufactured in three countries: The United States, Great Britain and Belgium. It was replaced in the Terex range by the 72-51B in 1977.

The Terex 72-51 was a contemporary of the Caterpillar 966C, Hough H-90 , Clark 125B and Allis-Chalmers 745.

The New Zealand connection

A total of 12 Euclid/Terex 72-51s were imported by the (then) franchise holder, Clyde Engineering and these came from all three countries where the machine was manufactured. There have also been a couple of other private imports of these machines, which were British Army surplus.

The 72-51s saw service mostly in quarry operations, feeding aggregate into crushers and maintaining stockpiles of finished materials.

Notable users included Carson Contracting and River Shingle & Sand (both of Wellington), Oldfield Earthworks of Masterton and NZ Forest Products, who had several machines fitted with log forks.

The author has not seen an operational example of a 72-51 in a long time and would be interested to know if any still exist.

Brief Specifications – Terex 72-51

Engine: GM Detroit Diesel model 6-71N, six-cylinder inline diesel rated at 202 horsepower

Transmission: Allison TT4420 two-speed, two-stage full powershift type

Top speed: 15 mph

Brakes: Air operated expanding shoe

Steering: Full hydraulic with safety accumulator

Standard tyres: 23.5 x 25 L3

Turning Circle: 41’ 8”’

Bucket capacity: Standard general purpose bucket rated at three-and-a-half cubic yards

Length: 21’ 10”

Width: 9’ 8” (with standard three-and-a-half cubic yard bucket)

Height (with cab): 11’ 1”

Operating weight: 17 tons

The Terex 72-51 loader

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