https://contractormag.co.nz/classic-machines/allis-chalmers/hd-11-tractor/

Designed as a replacement for an earlier tractor, the  https://en.wikipedia.org/wiki/Allis-Chalmers" rel="nofollow - Allis-Chalmers  HD-11 was a very worthy successor and was in production for over 25 years.  By Richard Campbell

THE ALLIS-CHALMERS model HD-11 was introduced in 1955 as a replacement for the company’s model HD-9, which had been in production since 1950, and the earlier model HD-10, the 10-year production run of which began in 1940.

Both the HD-9 and HD-10 were powered by  https://en.wikipedia.org/wiki/Detroit_Diesel_Series_71" rel="nofollow - 71 series GM Detroit Diesels  as at that stage, Allis-Chalmers did not manufacture its own diesel engines.

This all changed in 1953 when Allis-Chalmers bought the https://en.wikipedia.org/wiki/Buda_Engine_Co." rel="nofollow -  Buda Diesel Engine Company  and began development of its own engines.

Allis-Chalmers introduced several new track type tractor designs in 1955, all powered by the “new” Allis-Chalmers diesel engines.

These included https://contractormag.co.nz/classic-machines/allis-chalmers-2/" rel="nofollow -  the HD-6 ,  https://contractormag.co.nz/classic-machines/allis-chalmers-hd16/" rel="nofollow - HD-16 ,  https://contractormag.co.nz/classic-machines/allis-chalmers-hd21/" rel="nofollow - HD-21  and the subject of our story, the HD-11.

Rather than just inserting a new powerplant into an existing chassis, the HD-11 was an all-new design from the ground up, utilising experience gleaned from the previous HD-9 and HD-10.

From the outset of track type tractor production, Allis-Chalmers had always been an innovator, developing many of the systems that have been incorrectly attributed to other manufacturers.

Items such as torque converter drive, permanently sealed rollers, power-boosted braking and even sealed and lubricated track (SALT) were all pioneered by Allis-Chalmers.

The first production version of the HD-11 was powered by a six-cylinder naturally aspirated A-C model D-516 engine which produced around 85 flywheel horsepower and had a six-speed direct drive transmission. Track gauge was 74 inches and the machine had a six-roller track frame.

A mid-sized tractor, weighing around 11 tons without attachments, the HD-11 was a contemporary of  https://contractormag.co.nz/classic-machines/classic-machines-the-early-caterpillar-d6-tractors-long-term-survivors/" rel="nofollow - the Caterpillar D6 ,  https://en.wikipedia.org/wiki/International_Harvester" rel="nofollow - International  TD-15,  https://contractormag.co.nz/classic-machines/oliver-tractor/" rel="nofollow - Oliver OC-12  and  https://contractormag.co.nz/contractor/eimco/" rel="nofollow - Eimco 106 .

By 1958, two improved versions of the original HD-11 were available, the HD-11E and HD-11B.

Primary differences were a change in engine to the new model A-C 10000 series diesel with a consequent rise in horsepower – 99 flywheel horsepower for the HD-11E and 111 flywheel horsepower for the HD-11B, seven roller track frames for each, and a torque converter drive transmission for the HD-11B.

These machines remained in production until 1962 when three new versions were introduced, the HD-11EC, HD-11EP, and an improved HD-11E.

All three were powered by an updated version of the A-C 10000 engine known as the A-C 11000 series which featured for the first time, a turbocharger.

All three machines featured different horsepower ratings.

The direct drive HD-11E was rated at 130 flywheel horsepower, the torque converter drive HD-11EC at 140 flywheel horsepower and the powershift HD-11EP at 150 flywheel horsepower.

Further changes included the addition of oil-cooled steering clutches and brakes, and a 6-roller track frame for all three machines.

In these configurations, all three remained in production until 1971 apart from the HD-11EC which was dropped in 1967 due to declining sales volumes for the torque converter drive/manual transmission type of tractor.

HD-11s saw service in the complete spectrum of earthmoving, agricultural and forestry applications where they were very popular.

In order to retain a competitive edge, Allis-Chalmers undertook a complete redesign of its track type tractor range and this revamp naturally included the HD-11.

Bearing little resemblance to its predecessors, the new HD-11 series B was introduced in the middle of 1971 in two versions, a powershift and a direct drive model.

Still featuring the A-C model 11000 turbocharged engine, the powershift version was rated at 140 flywheel horsepower and the direct drive model at 125 flywheel horsepower.

It was also around this time that Fiat, which had a substantial share holding in Allis-Chalmers, exercised its options and the company changed its name from Allis-Chalmers to  https://en.wikipedia.org/wiki/Fiatallis" rel="nofollow - Fiat-Allis .

Unfortunately, this was also to lead to the gradual decline of the brand as once Fiat’s influence began to take hold, sales in North America, the brand’s naturally biggest market, began to drop off drastically.

For the HD-11 series B, now known simply as the Fiat-Allis 11B, the writing was pretty much on the wall and the machine was discontinued in 1981, in favour of one of Fiat’s own models, the European-designed FD10.