Classic MachinesTractors

The Allis-Chalmer’s HD-14 tractor

The Allis-Chalmers HD-14 was introduced in 1939 and was broadly based on that company’s earlier and very successful Model L and LO gasoline powered crawlers. By Richard Campbell.

At the time of its introduction, the HD-14 was the largest track type tractor that Allis-Chalmers had manufactured and joined two other machines, the HD-7 and HD-10, which Allis-Chalmers had also released that same year.
Weighing in at approx 14.5 tons bare, the HD-14 was a contemporary of the Caterpillar D7 and International-Harvester TD-18.
Allis-Chalmers needed a large diesel engined tractor as diesel engines were the way the market was headed and its biggest competitors already had a head start.
But there was a problem – A-C did not manufacture its own diesel engines.
It had experimented in the early 1930s with Atlas engines but these were deemed to be too heavy and cumbersome.
A couple of years after this initial experiment, a small number of tractors were fitted with Hesselman spark ignition diesels which ran at low compression but these also failed to make an impact.
So, after examining several options, A-C entered into an arrangement with General Motors for the supply of suitable power plants.
It was to be a highly successful arrangement which lasted almost 15 years.

The HD-14 went into full production in late 1939 and was well received by contractors, loggers and the agricultural sector.
During WWII Allis-Chalmers supplied a quantity of HD-7s, HD-10s and HD-14s to the US military and these largely saw service in the Pacific theatre of operation.
They were highly regarded by the armed forces and shared an engine commonality with the US Navy’s landing craft which also used GM 71-series diesel engines.
Following WWII, many of these HD-14s were disposed of in government auctions in Australia and New Zealand to the delight of equipment starved contractors.
These ex-military machines can be identified by the numbers “US7” stamped into the serial number plate.

Allis-Chalmers was never a manufacturer to rest on its laurels and was constantly striving to improve its products.
One such improvement was the introduction of the torque converter, the first ever application of this device in a track type tractor, fitted to the HD-14 in 1946.
The torque converter was an earthmover’s dream as it allowed fewer gear changes and automatic compensation to changing loads without stalling the tractor.
For a time it gave Allis-Chalmers quite a competitive edge within the industry.
Torque converter equipped HD-14s were known as HD-14Cs

By 1946 it was obvious that the HD-14 was in need of a serious makeover to keep up with technology trends.
Lessons learned during WWII and the explosion of technology that resulted from this conflict allowed Allis-Chalmers to embark on an even bigger tractor to replace the HD-14 and HD-14C.
This new machine would become the HD-15.

Over 6400 HD-14 and HD14Cs were manufactured between 1939 and 1947 when the type was discontinued.

The HD-14 described

It is worth noting at this point that Allis-Chalmers was a great innovator within the earthmoving industry when it came to track type tractors, having introduced many of the things that are inaccurately attributed to its biggest competitor.
Items such as duo-done roller seals, sealed and lubricated (SALT) track links, lifetime lubricated track rollers/idlers, bi-metallic steering clutches and torque converter drives were all first invented by Allis-Chalmers!

The engine chosen for the HD-14 was the ultra-reliable GM 6-71 and this was connected, via a dry type clutch, to a six-speed constant mesh gearbox.
In this application, the 6-71 diesel generated 132 flywheel horsepower, so it was quite a ‘grunty’ tractor for 1939!
It was also a very stylish looking machine with very curvaceous lines.
Its panel work was designed by the design team of Raymond Loewy who was a highly noted and respected designer of the period, responsible for a number of firsts including streamlining locomotives.
There was no mistaking the fact that the HD-14 or its siblings were Allis-Chalmers machines.
A spotting feature of HD-14s was the twin air cleaners whose tall intake stacks were mounted side by side on the rear hood.

HD-14s had single reduction final drives and rode on a 5-roller track frame with spring and oil tensioned idlers and a fully pinned equaliser spring to prevent track frame misalignment.
Steering was by multiple disc bi-metallic clutches and conventional contracting band dry brakes.

The operator was provided with a full width bench type seat with wide armrests which could be used to sit on if the machine was engaged in scraper towing operations.
A wide deck gave ample legroom and a centrally placed instrument panel contained all the necessary gauges.
Of all the large track type tractors of the period, the HD-14 was the easiest to start as it had direct electric starting and was not reliant on petrol-diesel conversion or a separate gasoline starting engine.


From the factory, Allis-Chalmers HD-14s were available with a number of optional attachments. These included a canopy (non-ROPS of course), cabin with heater, lighting package, power take off (PTO) and a factory installed push plate which mounted directly to the chassis side rails.

Prior to WWII tractor manufacturers were just that, relying on specialist builders to supply blades, winches, scrapers, cable controls etc.
Allis-Chalmers was no exception and relied on several manufacturers to outfit its machines for duty.
Those preferred suppliers included:

LeTourneau – cable controls, cable operated bulldozers and angledozers, towed scrapers, land clearing equipment.

Baker Manufacturing – hydraulic and cable controlled bulldozers and angledozers, towed scrapers, snow plows. (Allis-Chalmers later went on to acquire Baker.)

GarWood – cable controls, cable operated bulldozers and angledozers, towed scrapers.

Carco – hydraulic and cable controlled bulldozers and angledozers, land clearing rakes, logging winches and arches.

Buckeye – cable bulldozers and cable controls.

LaPlant-Choate – towed scrapers.

It would appear that the Tractomotive Corporation, which manufactured a line of front-end loaders for Allis-Chalmers (often known as the ‘G’ series) never manufactured a loader for the HD-14 as the author can find no record whatsoever of an HD-14G variant.

The New Zealand connection

Unfortunately, all records concerning the importation of Allis-Chalmers HD-14s have been lost/destroyed so no accurate number of those that arrived in NZ can be given. This also applies to the HD-14C variant.
All those machines your author has ever sighted have had the “US7” stamp on their serial number plates, marking them as ex-military machines sold through war surplus.

For the diecast model collector

A very dismal outlook here as to date there has been only an odd-scale zamac cast, one piece model of the HD-14 issued, back in the early 1950s.
It is crude and wildly expensive in the “collectors market” (if you can find one) and doesn’t fit into collections as such other than as a curiosity.
This is a great pity for such a groundbreaking tractor.

Brief Specifications – HD-14 (standard)

Engine: General Motors 6-71, 6-cylinder, inline diesel engine rated at 132 flywheel horsepower @ 1500 rpm

Transmission: Allis-Chalmers 6-speed sliding gear, manual.

Clutch: 15″ single plate, dry type

Top Speed: 7 mph

Track Gauge: 68″

Track Links 35-section

Std.Shoe 22″

Rollers 5 per side

Drawbar Pull: 28,000 lb in 1st gear

Length: 13′ 9″ (bare)

Width: 7′ 8″ (bare)

Height: 8′ 8″ (bare)

Operating Weight: 14½ tons (bare), up to 18 tons fully equipped

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