Classic Machines Contractor Scrapers

Classic Machines: LeTourneau’s Model A Tournapull

R.G LeTourneau conceived the idea of the self-propelled motor scraper while recovering from a near-fatal auto accident.  He approached Caterpillar with the concept but they rejected the idea, so LeTourneau decided to go it alone. The rest, as they say, is history. By Richard Campbell

One wonders how long it would have taken another company to come up with the idea of the motor scraper, however, LeTourneau was definitely the first.

LeTourneau, who had been supplying the bulk of tractor attachments to Caterpillar since 1934, approached Cat management with an idea of them building and marketing his new invention.

Caterpillar didn’t like the idea, they were in the business of selling track type tractors, not new-fangled gizmo’s like motorized scrapers.

How wrong they were.

It took Caterpillar almost eleven years to catch up to LeTourneau and by that time they had other competitors to contend with as well.

LeTourneau took a big financial gamble with the Tournapull as nothing like it had ever existed and the financial outlay required could have finished the Company for good if the idea failed.

For a start, no tyre companies made a large enough tyre required for the machine, and there were no commercially available transmissions fit for purpose either.

LeTourneau eventually persuaded Firestone to build him tyres (after footing the bill for the molds) but the transmission he had to deign and manufacture himself.

Chosen powerplant was a Caterpillar D17000 V8 which put out 160 flywheel horsepower.

The first Tournapull, called the Model A, was rolled out of the factory and into trials in 1937.

It was a one-of-a-kind machine designed to fully test the concept and was not put into series production at that point.

It also featured an experimental Carryall scraper, the Model Z25 which was also a “one-off”.

After intensive testing, it was decided to put the machine into production, albeit with a few tweaks.

And herein lies the problem, model identification.

LeTourneau records are very sketchy at best about Tournapull type designations.

A model A Tournapull from say 1941 could bear little resemblance to it’s predecessors and yet was still known as a model A.

LeTourneau, who was constantly experimenting, used to draw his modified engineering patterns in the dirt floor of the workshop and introduce changes immediately on the production line without making any alterations to type designation.

Therefore it is very difficult to positively identify some A Tournapulls as some versions may have lasted for only a couple of production machines!

Add to this the fact that many had different Carryall combinations and you can get a feel of what it is like trying to identify one.

What is known however, is that the third iteration of the machine (which we’ll call A3) seems to be the most numerous and appears in most of the published photos of actual owners using the machines.

In all there were approximately eight different versions of the machine, all called “Model A Tournapull” before LeTourneau went from lever steer (clutch/brake) machines to the electric steered models which began to appear at the end of WWII.

Some of these prototypes – for that’s what they were – had twin engines and a torque divider connecting twin transmissions.

None of these machines were ever produced in quantity.

As mentioned previously, the most common version appears to be the third model, usually fitted with a model TU or RU Carryall depending on the buyer’s capacity requirements.

LeTourneau sold between 20 to 25 of these in total before WWII curtailed production completely and the factory focused on manufacturing machinery for the US armed services.

The Model “A3” Tournapull Described

The main chassis of the tractor unit was a welded steel tub into which all the drive train components were placed.

Although LeTourneau also experimented with different engine combinations, the A3’s all had a Caterpillar D17000 V8 engine rated at 160 horsepower connected, via a dry-type clutch, to a four-speed transmission of LeTourneau’s own design.

This allowed the Model A3 to trundle along at up to 25 mph.

While this may not seem all that fast, it has to be remembered that the average track type tractor/scraper setup of the day was only capable of 8 mph at best!

Final drives were also manufactured in the LeTourneau factory and were double reduction, herring tooth design, heat treated and utilizing the (then) new Timken roller bearings.

Brakes were hydraulically activated drum type acting on the scraper axle only!

The A3 Tournapull rode on 30×24, 28-ply tyres supplied by Firestone with either a traction or uni-directional (diamond) tread pattern.

Steering the beast.

The term “widow maker” was coined for these and the other lever/brake steered LeTourneau Tournapulls of the late 30s, early 40s – NOT, the later electric steered models as so many people seem to mistakenly think.

The A3 Tournapull was steered by releasing the clutch on the side of the machine you wanted to turn and apply a little brake to make it go in the direction you wanted, just like a track type tractor.

When going downhill, you “cross-steered” using the opposite clutch to the side you wanted to steer to.

An alert operator had no problem with this but get it wrong and you could end up in all sorts of difficulty (and many did).

Jacknifing was an ever-present problem and even though the machine had large bumper stops welded to the scraper frame to prevent the machine going past 90 degrees, accidents were frequent.

Normal towed equipment for the A3 Tournapull was a Model RU Carryall rated at 23 cubic yards struck and 30 cubic yards heaped.

This was activated by a Model T double drum PCU driven directly from the front of the engine, the entire unit being mounted in front of the radiator with the associated cables reeved up and over the top of the operators compartment, to the scraper.

The Model RU was what LeTourneau called a “double-bucket” scraper and featured a sliding rear bowl portion which telescoped out when being loaded and retracted when dumping, a very ingenious design.

The scraper assembly was attached to the back of the Tournapull by a ball and socket joint at the top of the gooseneck and by drawbar arrangement at the bottom.

This allowed some sideways oscillation of the machine to allow it to traverse uneven ground.

Operator’s Compartment

This was about as rudimentary as it gets – an instrument panel, engine clutch, gearshift lever, two steering levers and brake pedals plus the two PCU control levers.

The operator sat centrally on an unsuspended pressed steel seat with the wind in his hair and the sound of an un-muffled Cat D17000 burbling along in front of him.

Doesn’t get any better than that!

Problems in Service

Alongside the steering issues mentioned previously, the A3 Tournapull suffered from tyre failures (it was new technology after all), a fragile transmission (failures were common) and a nasty habit of breaking in half at the hitch, again reinforcing the “widow maker” appellation.

To R.G.LeTourneau’s credit, his mind was always active improving on his existing designs.

By the end of WWII, the clutch/brake steering system had gone and the new all-electric era had begun.

We will take a look at the electric-control A Tournapulls in a future issue of Contractor.

The New Zealand Connection

No LeTourneau A Tournapulls of any type have ever been imported into New Zealand, the closest possible “blood relative” being the Wabco 333FT elevating scraper.

However, the basic A Tournapull design concept exists in all motor scrapers produced since 1938.

For the Model Collector

No models at all are available, outside of hand-built, one-offs of any of the A Tournapulls.

A disgrace considering the historic nature of the machine.

Related posts

Don’t try this on the motorway

Charles Fairbairn

Parting words from Jeremy Sole- a final column

Charles Fairbairn

Crushing big time

Charles Fairbairn