Image: This HD-41 is working in Europe with another Allis-Chalmers product, an HD-21, in the background. This photo shows how the rear decking was sloped to allow the operator a good view of the ripper (in this case, a CRC-Kelley single shank type).
In its heyday, Allis-Chalmers was known as an innovator, constantly seeking ways to build efficient, cost-effective track-type tractors. By Richard Campbell.
The company led the field following WW2 with its model HD-19 track-type tractor, which, at the time, was the most powerful machine of its type available.
Constantly engaged in a ‘bigger is better’ battle with Caterpillar and International Harvester, the quest for ‘the best’ raged on into the early 1960s.
Allis-Chalmers had been working on a ‘super dozer’ concept for several years, with an initial prototype machine appearing in 1963, but the company had to wait for some considerable time before diesel engines of sufficient horsepower were available, and the metallurgy and technology to manufacture such a large machine had been perfected.
It should be noted at this point that Allis-Chalmers had always been an innovative manufacturer, the company boasting such ‘firsts’ as the application of a torque converter to a track-type tractor, lifetime sealed track rollers and idlers, and sealed and lubricated track chains. And the manufacturer developed and offered these innovations well before other manufacturers followed suit.
Allis-Chalmers’ super dozer concept was targeted at surface mining companies, large quarry operations, bulk earthmovers and operators engaged in surface reclamation where a very large track-type tractor would enhance production significantly, and, in some cases, remove the need for blasting completely.
The new machine was called the model HD-41 and, when it was introduced (with much fanfare) in 1970, it was larger and heavier than any of its competitors, tipping the scales at over 46 tons bare and 60 tons with blade and ripper – truly a formidable piece of machinery.
Sales of the new machine were very promising with some 1900 HD-41 units manufactured in the first four years.
Powering the new HD-41 was a Cummins VT1710-C twin-turbocharged V12 diesel engine rated at 524-flywheel horsepower coupled to a three-speed forward and reverse powershift transmission supplied by Twin-Disc.
As one can imagine, the HD-41 needed a large cooling system and Allis-Chalmers chose to locate the radiator and hydraulic oil coolers in a group at the rear of the machine, behind the operator.
This removed a great deal of heat from within the engine compartment, extending component life, with hydraulically-operated fans providing forced cooling air rearwards through the cooler cores away from the machine (and operator).
The model HD-41 featured a 100-inch gauge and rode on a seven-roller track frame.
Standard track shoes were 32-inch, single grouser type, but Allis-Chalmers allowed for several other optional track shoes depending on the customer’s job requirements.
Final drives, steering clutches and brakes were all designed and manufactured by Allis-Chalmers who employed conventional multiple disc steering clutches and oil-cooled contracting band brakes.
For such a large machine, visibility from the operator’s station was very good with a sloping rear deck providing good vision to the ripper (if fitted). Operating controls were hydraulically boosted for ease of effort.
Equipment
Allis-Chalmers offered a semi-U bulldozer, full-U bulldozer, and a cushioned push blade (for loading large scrapers) for the HD-41.
Two varieties of ripper could be installed: a multi-shank type manufactured by Allis-Chalmers or a very impressive looking single shank-type built by CRC-Kelley (which many of these machines were fitted with).
Equipped with a ROPS, semi-U blade and Kelley ripper, the HD-41 weighed almost 70 tons!
Carco offered a single drum logging/recovery winch. An open ROPS or a ROPS cab could be installed, and some machines manufactured prior to 1972 featured a ‘soft’ cab.
Although a very capable machine, there were some bugs that needed to be ironed out, with the most troublesome of these being in the machine’s final drives, which were prone to failure in heavy going; a fault that was never really resolved satisfactorily.
As experience in actual work conditions mounted, the findings were relayed to the factory, and modifications and other fixes were constantly being produced to extend the service life of those machines already operating in the field.
As a result of these modifications, plus other improvements, an upgraded version of the machine, known as the model HD-41B, was introduced in 1974.
While the engine and the rest of the powertrain remained practically unchanged, structural strengthening and other improvements increased the weight of the new machine by some 6000lbs!
Some 760 HD-41B’s were manufactured before production of the type ceased.
They say that all good things come to an end, and in this case, it was Fiat who spoiled the party.
With a controlling share in Allis-Chalmers since 1974, Fiat decided to exercise its options and merged the company into what became known as Fiat-Allis. The Allis-Chalmers/Fiat-Allis HD-41 was a contemporary of the Caterpillar D10, Komatsu D455A and Dresser TD40B.
This proved to be the beginning of the end for Allis-Chalmers, which went through a series of downgrades and limited edition track-type tractors (including the models FD40 and FD50 under the Fiat-Allis banner) before all tractor production ceased in 1982.
It is rather ironic that Allis-Chalmers, who had begun the giant tractor race, was also the first to exit.
For the model collector
There have been three models of the Allis-Chalmers HD-41 issued to date, two in 1:50 scale and one in 1:25 scale.
The first to appear was from Conrad and represents a Fiat-Allis HD-41B. This model is under-scale and closer to a 1:60 scale rather than 1:50. It has rubber tracks, a semi-U blade and a multi-shank ripper. Crude by today’s standards, examples can be found on eBay.
The next example is EMD’s offering which is to 1:50 scale and represents an early Allis-Chalmers HD-41. It comes equipped with a cushioned push dozer or, alternatively, can be purchased with an open ROPS, full U-blade and multi shank ripper. The model is expensive and hard to find but is very well detailed and has realistic metal tracks.
Last is the magnificent 1:25 scale Allis-Chalmers HD-41 by First Gear, which represents a mid-production example.
This is a very big model, even in 1:25 scale, and weighs almost seven kilograms!
Fitted with a soft cab, semi-U blade and single shank CRC-Kelley ripper, this model is so well detailed that the only thing missing is the smell and the oil leaks!
