It is a great thing when an equipment manufacturer ‘gets it right’. The Euclid (later Terex) S-24 motor scraper is an excellent case in point. By Richard Campbell.
Developed from the earlier Euclid S-18 motor scraper, the Euclid model S-24 came into being as somewhat of a necessity as the S-18 was getting old, its engine, the GM 6-110 had been discontinued by General Motors and developments in transmission technology had also been steadily advancing.
To rework the S-18 would have involved far too many compromises, so GM engineers set out with a clean sheet of paper and the S-24 was the result.
The first iteration of the S-24 was the model 39LOT that was introduced in 1961 and powered by the (then) new General Motors 12V-71 naturally aspirated V12 diesel, which had a rating of 392-flywheel horsepower, and considerably more than the previous S-18s 300 horsepower GM 6-110. Another feature was a five-speed Allison powershift transmission that gave a wider range of gear options than was previously available.
As a result of the extra horsepower offered by the GM 12V-71, Euclid engineers took the opportunity to increase the carrying capacity of the bowl by the addition of small side extensions, increasing capacity from 18 cubic yards struck to 24 cubic yards struck, (hence the S-24 model designation). However, the bowl of the S-24 was not entirely a new design and still retained the cable operated apron of the former S-18.
In 1962, further developments at Allison Transmissions produced an improved six-speed powershift transmission (the CLBT5865), which was installed in S-24s on the production line, further enhancing the machines performance.
Other small modifications were also undertaken between 1963 and 1969 including introduction of GM’s N-series fuel injector which increased engine output up to 423 flywheel horsepower, the addition of another air cleaner, and the replacement of the cable operated apron by a power-up, power down model which boosted loading efficiency considerably.
The Euclid division of General Motors were slapped with an anti-trust lawsuit in 1968 resulting in a brand name change to Terex (from the Latin terra meaning Earth and rex meaning King). All subsequent product shipped from the Hudson, Ohio factory was branded Terex, even though it may have had its origins well before the name change.
Terex undertook another update of the model S-24 in 1969 replacing the naturally aspirated GM 12V-71N motor with a turbocharged GM 12V-71T.
This change did not affect the engines output but did lower fuel consumption and the machines ability to work at higher altitudes without the need to de-rate the engine. It also added an extra exhaust pipe to help relieve exhaust back-pressure
This version of the S-24 was known as the model 49LOT-76SH, and it was manufactured in greater quantities than any other variant of the S-24. Most of the Terex S-24’s imported into New Zealand are of this variant.
By the late 1970s, the Terex S-24 was becoming obsolescent, and sales were dropping off. So, in order to remain competitive, GM Terex completely redesigned the machine, incorporating front axle suspension to give the operator a safer, less punishing ride, and outfitting the bowl with double acting bowl lift cylinders which allowed positive down force at the machines cutting edge.
All previous iterations of the S-24 had had a gravity lowered bowl which was not always conducive to easy loading in dense packed material.
The new machine was called the S-24B ‘Loadrunner’, and apart from the S-24 designation, the machine bore no resemblance to its predecessors apart from bowl capacity! Power was supplied by a GM 12V-71T turbocharged V12 diesel which was rated at 475 flywheel horsepower. The first S-24B Loadrunners began leaving Terex’s manufacturing facility in 1977.
In 1986, a systematic upgrade of the S-24B was undertaken by Terex resulting in the model S-24C. This machine had the option of a 480-flywheel horsepower Cummins KTA-19C diesel in place of the GM 12V-71TA.
However, things were not going well for Terex in the late 1980s and very few of the S-24C model were manufactured; the last unit shipping out in 1988.
S-24s competitors
All the usual players were vying for a slice of the 24-cubic yard scraper market, and all of them fell by the wayside apart from chief rival Caterpillar, who are still building motor scrapers to this day.
Through the years the Allis-Chalmers TS-460, Michigan 310, International 295 and Wabco 339 have all competed for a share of the S-24’s market share, and all these companies have either gone bankrupt or exited the earthmoving business entirely.
However, the overall victor must be the Caterpillar 631, which has spawned seven different versions during a production run that started in 1962.
The early 1970s Terex S-24
The Terex S-24 was a single engine, overhung motor scraper powered by a General Motors 12V-71T diesel engine, which in turn was married to an Allison CLBT-5965 6-speed powershift transmission.
The transmission incorporated a hydraulic retarder (the ‘B’ in the CLBT designation) which was designed to save the service brakes, especially on long downhill hauls. This powertrain combination gave the S-24 a top speed of around 30mph.
Air operated S-cam shoe type brakes were fitted to all four wheels. Although there were several tyre options available, the usual tyre equipment was a set of 33.5×33 E3 type.
Steering was provided by two identical double acting hydraulic cylinders mounted low down on the gooseneck and Terex used a split-yoke design gooseneck to connect the scraper to the tractor. In the ‘V’ created by the split design were located the two single-acting hydraulic cylinders that raised and lowered the bowl via a lever and solid link.
The bowl, which held 24 cubic yards struck and 32 cubic yards heaped, was raised under hydraulic power but lowered by gravity and the sheer weight of the bowl. Two identical double-acting cylinders opened and closed the apron which was hinged to the outside of the bowl. A four-piece cutting edge was used.
The bowl floor was hinged directly behind the cutting edge and ejection was affected by rolling out the load by means of a three-stage, single-acting hydraulic cylinder, the floor returning to the loading position by gravity.
The New Zealand connection
Of the 31 Terex S-24s that were imported into New Zealand by distributor Clyde Engineering, the vast majority worked in the South Island on hydroelectric dams, and the massive Waitaki Basin irrigation scheme and gave an excellent account of these rugged and dependable earthmovers. All of them used here, bar one, were the later 49LOT series with the power down apron. A sole 39LOT machine with cable apron (which was the first S-24 imported here) was sold to Burnetts Motors of Ashburton.
For the model collector
There is currently only one model of the Euclid/Terex S-24 available, and it is manufactured by EMD models. Imposing and well detailed, it is to 1:50 scale but is very expensive and it is to be hoped that some other manufacturer will produce a more affordable version in the near future.
As Dan Models of Romania has recently released a model of the earlier Euclid S-18, perhaps they will fill the void and release an S-24.
Brief specifications – 1972 Terex S-24 (49LOT-76SH)
Engine: General Motors 12V-71T, V-12 turbocharged diesel engine, rated at 423 flywheel horsepower at 2100 rpm.
Transmission: Allison CLBT-5865 6-speed powershift transmission with in-built. hydraulic retarder for braking assist.
Top Speed: Approx. 30 mph.
Brakes: Air operated, four shoe internal expanding type.
Steering: Twin, double acting hydraulic cylinders giving 90° turn each way.
Std. Tyres: 33.5×33, 32-ply, E3 on all four wheels. Other options available.
Capacity: 24 cubic yards struck, 32 cubic yards heaped.
Operation: Full hydraulic
Length: 43’ 7”.
Width: 11’ 11’.
Height: 12’ 4” (to top of exhaust stack).
Operating Weight: 37 tons empty, 72 tons loaded.