International introduced the model TD-18 track type tractor in 1938, primarily aimed at the growing construction market.
Initially known as the TD-65, the machine’s designation was changed to TD-18 almost as soon as it was put into production.
It was the largest track type tractor that International had manufactured up to this point and proved to be quite a success.
As was popular at the time, two different track gauges were offered – a 62 inch standard gauge, and a 74 inch wide gauge.
The majority of the machines sold were the wide gauge version as it had better side slope stability and could be fitted with a wider range of commercially available attachments.
A 6-cylinder International model D-691 diesel engine was chosen to power the new TD-18. The four-cycle design engine produced around 88 horsepower at the flywheel (71 at the PTO).
International used quite a novel method of starting this engine, but it also turned out to be one of the machine’s major drawbacks.
Unlike Caterpillar, which at the time used a separate 2-cylinder gasoline “pony” motor to start its diesel engines, International took this concept a step further and turned the main engine into a gasoline engine for easy starting, converting to diesel when it was properly warmed up!
This was accomplished by incorporating two complete sets of valves into the cylinder head with spark plugs and a hi/low compression control device along with a carburettor and distributor.
Unfortunately, the addition of all this extra gear in the cylinder head reduced the amount of area available to circulate coolant within the cylinder head and on grades the cylinder heads would often crack due to inadequate cooling.
It was said at the time that there were two kinds of TD-18 – those that had cracked a head and those that were about to.
(International spent quite a bit of R&D work on this issue and eventually rectified the problem in 1955 by fitting a large water header tank on top of the machine’s bonnet to ensure that a supply of water was always available to the engine, even on slopes.)
First generation TD-18s had a 6-speed manual transmission, 5-roller track frames with two carrier rollers per side. They weighed approximately 11 tons bare.
The TD-18 was manufactured continuously from 1938 onwards and supplied in some numbers to the US armed forces during WWII, seeing widespread service, especially in France and the Pacific.
International introduced the upgraded TD-18A model in 1949.
Changes were restricted to a redesigned cylinder head (to try and cure the overheating problems), a 10″ increase in track frame length and a raise in engine output from 88 to 107 flywheel horsepower.
Tare weight of the machine also rose to 13 tons.
This particular model was produced from 1949 through to 1955 virtually unchanged.
The last of the TD-18s
During 1955, International-Harvester produced what was to become the last of the TD-18 series, the TD-18 models 181 and 182.
Manufactured for a scant 16 months, the TD-18 181 series featured a raft of improvements, not the least of which was the new water header tank mentioned earlier. The engine was again uprated, this time to 124 flywheel horsepower, and the air cleaner was relocated from in front of the operator to a position on the left hand side of the engine.
Revisions were also made to the instrumentation and operator’s seat, and the track frame was strengthened.
The TD-18 181 was discontinued in 1956 and replaced by the TD-18 model 182 which had a further engine boost to 128 horsepower and now tipped the scales at 14 tons.
This was to be the last version of the TD-18 manufactured, the type being replaced by the all-new TD-20 in 1958.
During a 20-year continuous production run, approximately 38,000 TD-18s of all types were manufactured by International-Harvester.
As International-Harvester did not manufacture any of its own attachments until the late-1950s, supply of attachments to suit customer requirements was handled by a range of other manufacturers, many of whom had contracts with International for just this purpose.
Bucyrus-Erie manufactured a wide range of bulldozers, angledozers, rakes and towed hydraulic and cable scrapers for use on the TD-18 and was International-Harvester’s No 1 supplier of attachments.
Carco built logging winches to suit all sizes of track type tractor and also towed logging arches. Carco winches were by far the most common winch to see on the back of a TD-18. Up until the early 1950s Carco also built bulldozer blades but it is rare to see an International-Harvester TD-18 tractor with one of these attached.
Drott was a specialist manufacturer of front end loaders and buckets. International was its major customer. International would ship its bare tractors to Drott which would fabricate a loader frame, arms and hydraulics to suit.
So great was their popularity that for a time in the 1950s, any track type front end loader would be referred to as a Drott.
Heil was another major supplier to International, so much so that International bought it out in 1953. Heil manufactured cable controls, blades and a wide variety of towed cable scrapers.
Superior manufactured tractor-mounted cranes and cable controls, but its greatest seller by far was side boom attachments, now known as pipelayers.
As with Drott, International would send its new tractors to Superior which would fit all the necessary equipment to the machine and turn it into a pipelayer.
These were major conversions and were not undertaken in the field. Superior and Trackson dominated this particular market for decades until Trackson was absorbed by Caterpillar.
Isaacson specialised in cable controls, bulldozer blades and towed cable scrapers. It is quite common to see its cable control units on the rear of International-Harvester (and other manufacturers’) track type tractors of the 1950s. Not so common are its bulldozer blades and scrapers. Isaacson went through a few ownership changes during the 1950s, firstly to Pullman Standard and then to the Young Corporation. This basically sealed its fate and by 1960 it had practically vanished.
The New Zealand connection
Although exact figures are not available, a great many International TD-18s were imported into New Zealand and saw service nationwide in all manner of jobs, including agriculture.
In fact the very first track type tractor your author operated was a TD-18 pulling a sheepsfoot roller.
The vast majority of these have now gone to the big jobsite in the sky but preserved examples still exist throughout the country.
For the Diecast Model Collector
EMD Models makes several versions of the International-Harvester TD-18 to 1:50 scale. This model is a bit of a collector’s piece and as such, is quite expensive at over US$230 each (+ postage). It is available with both cable and hydraulic blades and also as a bare tractor with or without cab.
As it is the only model so far issued of the TD-18, it is just as well that it is of reasonable quality.
Brief Specifications – International TD-18A (1949)
Engine: International-Harvester D-691, 6-cylinder inline, naturally aspirated diesel rated at 107 flywheel horsepower @ 1800 rpm
Transmission: International-Harvester direct drive 6-speed manual
Clutch: 16″ single plate ceramic faced clutch
Steering: Multiple disc clutches
Brakes: Contracting band type
Track gauge: 74″ (wide) gauge
Shoes: 18: single grouser (standard)
Operating weight:Approx. 13 tons bare