Designed as a direct replacement for its existing S-18 single engined motor scraper, the Euclid (later Terex) S-24 had a long career and was the company’s most successful single engined, open bowl scraper. By Richard Campbell
Responding to industry requests for more horsepower and the fact that General Motors was going to discontinue manufacture of the series 6-110 engine, Euclid set about a redesign of the S-18 to utilise the new GM 12V-71 diesel engine. (The former 325 horsepower GM 6-110 had previously been the principal power unit for the S-18, SS-24 and TS-24 scrapers.)
Several pilot models were trialled until an acceptable layout was reached.
Euclid replaced the 3-speed Allison powershift transmission previously used with a 5-speed model increasing the unit’s top speed and made the 33.5×25 tyre standard (it was previously an option).
The GM 12V-71 engine chosen for the new machine put out 392 flywheel horsepower, a considerable increase over the former 6-110 engine, so Euclid took this opportunity to increase the carrying capacity of the bowl, boosting it from 18 cubic yards struck to 24 cubic yards struck.
However it still retained the S-18’s cable-operated apron.
In this format, the new machine was released to the contacting world in 1961 as the Euclid S-24 or Euclid model 39LOT-46SH.
Immediately successful, Euclid began producing the S-24 in quantity.
As with all good machines, there is always room for a little improvement and it wasn’t long before Euclid began tweaking the new S-24 to further increase its performance and customer acceptability.
The first minor alteration was in 1962 when the 5-speed Allison transmission was replaced by a 6-speed model, further increasing the machine’s top speed.
In 1963 the cable apron was replaced by a dual hydraulically actuated model, very similar to that which had been tried experimentally on the twin-powered TS-24 scraper.
An increase in engine horsepower was also made from 392 up to 423 flywheel horsepower. This was made possible by utilising the new N-series fuel injectors.
Euclid also added an extra air cleaner at this point to cater for the engine’s increased air demands.
The machine’s serial number designator was changed to reflect these modifications and became 39LOT-55SH.
Next major modification came in 1969 when the naturally aspirated 12V-71N engine was replaced by the turbocharged 12V-71T.
Horsepower remained the same but the engine now burned slightly less fuel, “breathed” better and was more efficient at altitude.
The scraper was structurally reinforced in a number of places and several hydraulic revisions were undertaken.
This machine was known as the S-24 model 49LOT-76SH and was the most numerous of all the S-24 models.
In order to remain competitive in the earthmoving marketplace, Terex (the name changed from Euclid to Terex in 1968) completely redesigned the S-24 in the late 1970s to incorporate a power down bowl and axle suspension.
The new machine was known as the Terex S-24B “Loadrunner” and bore very little resemblance to its predecessors other than its bowl capacity, 24 cubic yards.
Power was provided by a turbocharged 475 horsepower GM 12V-71T engine connected to an Allison CLT-5865 6-speed powershift transmission.
Standard tyre size was increased to 37.5×33.
A further revision of this design was introduced in 1986 as the Terex S-24C.
Terex offered an optional Cummins diesel for this model, the 480 horsepower KTA-19C and raised the heaped capacity to 34 cubic yards but it was all sadly to little avail.
Very few of these powerful and imposing looking scrapers were actually manufactured.
The S-24C was the last S-24 to be produced as not long after the company was wracked by bankruptcy, the IBH scandal, several takeovers and a general downturn in the earthmoving industry worldwide.
Production of the TS-24 and TS-14 models was moved to Terex’s still profitable Scottish plant and the S-24 was discontinued.
Unlike the S-24’s predecessor, the S-18 which was also manufactured for a time in the UK, the various models of S-24 were only produced at Terex’s Hudson, Ohio US facility.
The S-24 operated in quite a hotly contested size range which included the Caterpillar 631 and 641, Wabco 339, Allis-Chalmers TS460, Michigan 310 and International-Harvester 295, all vying for a share of the market.
The Euclid/Terex S-24 described
(We will examine a model 49LOT, the most common of all the S-24s.)
The S-24 was a conventional design, single-engined, two-axle, overhung motor scraper powered by a General Motors 12V-71T V-12 diesel engine which produced 423 flywheel horsepower at 2100rpm.
Attached to the engine was an Allison CLBT-5865 6-speed powershift transmission which gave the machine a top speed of around 30mph.
The transmission incorporated a hydraulic retarder – the “B” in the CLBT designation – to help save the service brakes and assist in machine control coming down steep grades or in the wet.
Brakes were air operated S-cam shoe type on all four wheels.
Another aid to traction was a power-locking differential, operated by a foot switch next to the air brake pedal. This activated a clutch pack in the diff, preventing the drive wheels from spinning.
Standard tyres were 33.5×33 E3 with several other options available.
Steering was provided by two identical double-acting hydraulic cylinders giving a 90° turn in either direction.
Terex used a split yoke design hitch to connect the tractor to the scraper assembly.
In the well created by the split were located the two single acting bowl lift cylinders.
These attached to the bowl via a lever and stiff link. Raising was by hydraulic power while lowering was taken care of by gravity.
Bowl capacity was 24 cubic yards struck and 32 cubic yards heaped.
Retaining the load was a hydraulically controlled apron whose arms and hydraulic actuating cylinders were located on either side of the bowl and didn’t have to be forced through loaded material to close as was the case with some of Terex’s competitors.
The bowl’s floor was hinged behind the 4-piece adjustable cutting edge and rolled the load out via a directly attached 3-stage single acting hydraulic cylinder.
Once emptied, the bowl floor returned to loading position by gravity.
At the tail end of the bowl was a roller push block which was a Terex exclusive and was promoted to reduce push tractor blade wear and maintain better control of the scraper bowl when loading.
For the operator, a Milsco air suspension seat was standard.
Controls, even for the 1970s were pretty basic but full instrumentation was provided.
Options included a cab (resonating chamber!), heater, Bostrum hydraulically damped seat, optional tyres, Wiggins fast refueller, fenders and bowl spillguard.
The New Zealand connection
Clyde Engineering, Euclid/Terex distributor for New Zealand, sold 32 S-24s into the NZ marketplace – 1 x 39LOT and 31 x 49LOT examples.
They were mainly concentrated in the South Island and were extensively used on all the big hydro projects of the 1960s and 1970s.
Due to their rugged simplicity and the ease with which they could be rebuilt, there are several still in operation.
Original fleet users included Burnetts Motors, Higgins Earthmoving, Doug Hood, Earthmovers Waikato, Downer & Co and McBreen-Jenkins.
For the diecast model collector
Despite all the odds there are actually models available of the Euclid/Terex S-24 in 1:50 scale manufactured by EMD Models and Roger Renaud (RR Models).
All of these represent the later 49LOT-76SH machine and, due to their limited run nature, are hideously expensive.
They are, however, worth seeking out if you have deep pockets as they are all of good quality.
There are no models available of later production machines such as the S-24B and S-24C “Loadrunner” series.
TEREX S-24 49LOT series
GM 12V-71T, V12 turbocharged diesel rated at 423 flywheel horsepower at 2100 rpm
Allison CLBT5865 6-speed full powershift transmission with integral hydraulic retarder
Top speed: Approx 30mph
Full hydraulic, 90° turns either side of center
Turn circle: 37’ 7”
Air operated S-Cam shoes
33.5×33, 32-ply E3 (earthmover)
24 cubic yards struck, 32 cubic yards heaped
Operation: Full hydraulic
Length: 43’ 7”
Width: 11’ 10½”
Height: 12’ 4”
40.4 tons (empty), 80.4 tons (loaded)