Classic Machines Tractors

Classic Machines: The International TD-24 tractor

As soon as material constraints were removed prior to the end of WW2 the major earthmoving machinery companies set about designing new equipment to cater for the expected post war machinery boom and International Harvester was no exception.

International had achieved a measure of success with their first large track type tractor, the TD-18, which had been supplied in quantity to the US armed forces where they performed fairly reliably.

IH engineers scaled up the basic TD-18 giving it heavier, extended track frames and a brand new engine and transmission resulting in a machine which they called the TD-24.

The first prototypes were put into the field in 1946 for test under a variety of job conditions and surprised even IH with how productive they were.

Following these tests and a little fine tuning the machine was put into full production in 1947.

At the time the largest track type tractor available was the Allis-Chalmers HD-19. The arrival of the TD-24 quickly deposed the HD-19 making it the new world’s most powerful tractor.

Heart of the TD-24 was a 6-cylinder inline naturally aspirated International Harvester D-1091 diesel rated at 200 gross horsepower. This employed the same unusual starting system as previous IH diesels whereby the engine was initially started on petrol and then converted to diesel once it warmed up (unlike Caterpillar who used a separate 2-cylinder starting engine).

In a machine as large as the TD-24 this was to ultimately cause more than its fair share of problems, principally because the engine cylinder heads had two full sets of valve gear – one for gasoline running and the other for diesel.

Not a great deal of room was left in the heads for coolant which resulted in two types of TD-24 – those that had cracked their cylinder heads and those that were going to!

In order to increase cooling and reduce exhaust back pressure IH had equipped the TD-24 with two exhaust stacks from the outset which indicated that they were already aware the TD-24 had overheating issues when the machine went into production.

Unfortunately cylinder head cracking was to plague the machine for its entire production life and was not ultimately cured until the advent of its replacement, the larger TD-25 in 1959.

Another problem area for early production machines were the steering clutches.

These were pretty revolutionary for the time and allowed full power to both tracks during turns giving more precise control of the machine.

Of planetary construction they permitted one track to be in low range while the other was in high thus allowing turning under power. A contracting band brake for each track was also provided to permit spot turns.

Early machines had many failures forcing IH to instigate a recall so the problem could be rectified.

This took the form of a complete redesign of the mechanism which eventually resulted in a sturdy reliable steering clutch.

Unusual for the period was the 4-speed synchromesh transmission, most tractors of the time having constant mesh types.

This undoubtedly aided operators in making faster, smoother gear changes.

Later on, a torque converter drive option with 2-speed transmission was also offered.

The operator’s area was fairly cluttered with clutch, gearshift, direction and steering levers all protruding through the floor plate along with the brake pedals.

International provided a full width deeply padded bench type seat but very little else in the way of creature comforts.

Visibility was very good however to both front and rear mounted attachments.

A wide range of attachments were available to outfit the TD-24 for any task.

Bucyrus-Erie, Carco, Heil and Isaacson supplied the majority of attachments from blades to winches and cable controls as International Harvester did not manufacture their own until 1954.

(International acquired the attachments division of Bucyrus-Erie and Heil in 1953 and Isaacson in 1952 thereby taking care of future attachment requirements).

Total production figures for the International TD-24 are unknown but would exceed 10,000 units.

The NZ Connection

The International TD-24 was a very popular bulldozer in New Zealand with most of the major contractors of the period having at least one in their machine roster.

Fleet owners included Dryden Construction, Earthmovers Waikato, F&J Bognuda, Bitumix and NZ Roadmakers to name but a few.

Usage of the TD-24 was New Zealand wide and on all manner of earthworks & quarrying.

Many of these machines had several subsequent owners with the type finally disappearing from service in the early 1980’s.

There are several preserved examples including a beautifully restored machine which belonged to the late Bill Ward of Mataura, Southland.

Diecast Model Collectors

For those readers who are model collectors there are excellent models of the TD-24 produced in both 1:50th and 1:25th scales. These are manufactured by Spec Cast and are available in several configurations of cable and hydraulic blade.

There is even a pipelayer variant.

Brief Specifications – International TD-24 (241 series)

Engine:                      International D-1091 6-cylinder inline naturally aspirated diesel rated at 180 flywheel horsepower

Clutch:                       18” single plate with ceramic facings, Automatic clutch brake

Transmission:         4 speed synchromesh

Steering:                    Planetary, two speed

Brakes:                      Contracting band, dry

Gauge:                       80”

The International-Harvester TD-24 crawler tractor

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