Classic Machines Motor Graders

Classic machines: Caterpillar’s No.12 motor grader

What makes a classic motor grader? Looks, ability, ease of operation and longevity are all pertinent factors as are resale value if you’re looking to buy another. Whatever the criteria, Caterpillar’s No.12 Motor Grader had them all. By RICHARD CAMPBELL

Of the thousands of motor graders manufactured by Caterpillar since their takeover of the Russell Grader Manufacturing Company in 1928, none have lasted in production longer, or have been produced in as many numbers as the No.12 which remains as part of Caterpillar’s motor grader line-up to this day.

We will take a look at the evolution of the type up to (but not including) the ‘G’ series.

A bit of background on graders is necessary here.

Note to all: Neither Caterpillar or Robert LeTourneau invented the motor grader.

The very first form of a “grader” as such dates back to Roman times when a log or plank of wood was drawn between two animals, usually oxen, thereby smoothing the surface, and we are all aware of how good Roman roads were as many still survive today!

In the early 1900s the grader re-invented itself with the advent of the automobile, as those new fangled, smoke belching, horse scaring things needed a smooth road to drive on.

These very early road graders, made of channel steel and riveted together had very few control adjustments were known as “Terracers” and were drawn by a team of horses or a small agricultural tractor. An operator stood on a platform at the back and made adjustments as best he could while being bounced along eating dust.

A great many companies manufactured them during this period, and some were much better than others.

Three companies can claim rights to inventing the modern motor grader as such – J.D.Adams, Austin-Western and Russell.

All three of these companies independently had the idea of attaching a steel frame which held a grader blade and its adjustment controls along with a set of front wheels to a track type tractor chassis thereby creating a single operator, self propelled unit.

These “Hi-Way Patrols” or “Motor Patrols” as they were known then, considerably speeded up the process of finishing off a surface to an acceptable standard and you didn’t have to feed them oats!

While Adams’ and Austin-Western’s frames were removable, allowing the chosen tractor to be used for other things, Russell’s frame was a dedicated attachment and was part of the tractor. (Russell had actually built their first experimental self-propelled grader as early as 1919).

The hierarchy at Caterpillar began to take notice of the increase in sales of track type tractors to Russell and obviously saw the large potential opening up as sales of automobiles began to skyrocket.

Accordingly, an approach was made to Russell about a buy out and in 1928 Russell became the first new acquisition of the fledgling Caterpillar Tractor Co.

All of these early Russell/Caterpillar graders were attached to a track-type tractor, usually a gasoline powered Caterpillar Twenty or Twenty-Eight.

The rubber didn’t hit the road however until 1931, when, after much design & testing Caterpillar released their first all-rubber tyred grader, the No.9 “Auto patrol”.

This was quite simply a revelation in road maintenance as the entire machine was built from the outset as a grader and not as a compromise of two types of machine.

The No.9 was followed into production by the No.7, No.10 and No.11 Auto Patrols between 1932 and 1933.

At this point in time, all Caterpillar’s graders had been gasoline powered but during 1934 the first of the Diesel Auto Patrols was introduced marking a major milestone in motor grader development and the existing gasoline powered machines were withdrawn from sale in favour of the vastly more economical diesels.

Caterpillar produced their last gasoline engined motor grader in 1947.

It was discovered that two axle motor graders had a tendency to ‘lope’ (rock forward and backward in motion) at higher speeds making smooth blading difficult so a move was made to tandem drive wheels which cured the problem and is why all Caterpillar motor graders have tandem drive to this day.

The subject of our article, the No.12, was first introduced in 1938 powered by a 70 flywheel horsepower three-cylinder Caterpillar D6100 diesel engine and weighed about 9½ tons. It was known as the 9K series.

This was manufactured right through WWII up until 1945 when it was replaced by the 7T series.

Incorporating a few changes that had been shown to be necessary in service, the 7T series No.12 was only manufactured for two years before being replaced by the 8T series.

Featuring a new diesel engine, the 100 flywheel horsepower four-cylinder Caterpillar D318, the 8T series No.12 which was introduced in 1947, struck the perfect balance for the time and well over 17,000 were manufactured.

During its ten year production life, the 8T No.12 was modified several times getting Cat’s famous oil clutch and receiving a couple of horsepower increases as well.

A late production version of the 8T No.12 weighed approximately 11 tons and put out 115 flywheel horsepower.

Demand for the No.12 was so high that a separate manufacturing line was established in Australia to produce them. These had the designation 94C series.

By the end of 1957 it was obvious with the advances in technology that an upgrade of the No.12 was due.

This took the form of the 80C and 70D series machines, still rated at 115 horsepower but with in-seat starting and a few more creature comforts. Weight of the machine had now risen to approximately12 tons.

These two machines were also only interim types being phased out after only three years in production.

The next version of the No.12 was a major redesign, the 12E which came along in 1959.

Extremely popular and an excellent blading platform, the 12E featured for the first time, a six-cylinder engine, the model D333, de-rated to 115 horsepower.

Operating weight was almost 13 tons.

Last of the No.12 motor graders to feature direct mechanical operating controls (“wrist breakers”), the 12E was the epitome of a simple, well designed and easily maintained motor grader and operators and owners alike loved them.

Another rework was made to the basic No.12 grader in 1965 resulting in the No.12F.

This featured new power-assisted planetary operated blade controls and the D333 engine was boosted to 125 flywheel horsepower. Power steering was now standard rather than an option

The 12F was the final variant of the No.12 grader to have a rigid straight through chassis, and is where we end this segment on the No.12 grader.

All subsequent versions of the No.12 from the G series onwards have been articulated frame steering and will be covered in a future article.

An extremely versatile tool, the No.12 could be used for ditching, snow removal, haul raod maintenance, county road rehabilitation and dozens of other uses and can truly be called a machine for all seasons!

Why the No.12 ?

Easy. Nothing to do with weight or horsepower – it simply referred to the width of the graders moldboard blade – 12 feet wide!

The New Zealand Connection

Up until the late 1950s, all versions of the Caterpillar No.12 could be found throughout the country and there were a lot of them.

Then the Government of the time put restrictions on imported motor graders as Aveling-Barford had set up shop here and the Govt. were “protecting local manufacture” which meant that unless you were the Ministry of Works, licence to import a Cat grader (or any other brand for that matter) was a very uphill battle.

That is why there are so few 12E and 12F graders in New Zealand compared to earlier versions.

The relaxing of this dumb piece of legislation after 1980 allowed contractors free choice of what they wanted again.

For the Model Collector – Early No.12’s

Fortunately, there are several models of the No.12 available representing the machine across it’s career.

In 1:87 scale there are two models – one by Norscot of the No.12 which isn’t too bad compared to other Norscot models (probably to do with the HCEA having a hand in supplying details).

The other is made by Roco Minitanks of Germany and is currently out of production. It is a very good copy of a No.12 8T series and is all-plastic.

To 1:50 scale there is the beautiful No.12F by Gescha.

Regrettably this model is long out of production, hard to find and expensive but can be the basis for a very accurate model of the type if you add further detail.

If money is no object there is the 1:24 scale No.12E by Classic Construction Models.

Epitome of the model makers art, this brass/white metal beauty will set you back over US$2,500 + post and lacks nothing in detail.

For your sandpit there is a 1:16 scale 8T series No.12 made by Reuhl in the USA.

Considering it was cast in the early 1950s, it is a very well made model and not all that hard to obtain if you’re looking on Ebay.

So far no-one has a brought out a model of the very first No.12’s but time will tell.

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