Classic MachinesWooldridge

Wooldridge’s first motor scraper

The name Wooldridge will not be familiar to many contractors here. However, it was the third manufacturer to offer a motor scraper, right up there with LeTourneau and LaPlant-Choate, at the dawn of the motor scraper age. By Richard Campbell.

Mack Wooldridge set up the Wooldridge Manufacturing Company in the early 1930s, building bulldozer blades and towed scrapers, predominantly as a supplier for other machinery manufacturers.

Wooldridge based his manufacturing facilities in Sunnyvale, California and his first four-wheel towed scraper, a 12 cubic yard machine, was known as the ‘Digancarry’ and sold reasonably well.

Although never as big as some of his competitors, Wooldridge kept on inventing and improving into the late 1930s when things began to change for the company after it produced two newly designed ranges of towed scrapers and began selling these directly to customers, rather than through a distributor.

Wooldridge referred to these scrapers as ‘Terra-Clippers’ and ‘Boiling Bowl’ scrapers and they became quite popular.

Wooldridge was granted important supplier status during WW2 and delivered quite a volume of attachments to the US Armed Forces (particularly scrapers) that were used mostly in the Pacific theatre of the conflict by the US Naval Construction Battalions (Seabees).

After WW2 a lot of this equipment was just left to rot in the Pacific islands, although some did make its way to New Zealand during the scrap drives of the early 1950s.

Wooldridge was not slow to notice the success that RG LeTourneau was having with his motor scrapers, the famous Tournapulls, and although WW2 put a hold on any new developments, once the conflict was over the gloves came off.

Utilizing the bowl of a 14 cubic yard model TCR Terra Clipper towed scraper, Wooldridge designed an all-new two-wheel tractor unit to pull it, the end result being the Wooldridge model TC-Y ‘Terra-Cobra’ motor scraper.

A 150 flywheel horsepower Cummins HBI-600 diesel engine was picked to power the new Terra-Cobra and this was mated, via an extension shaft, to a four speed Fuller manual transmission and 17” Lipe-Rollway clutch.

Apart from the clutch and the previously mentioned engine and transmission, the entire balance of the machine was manufactured or assembled by Wooldridge, and was put into full production as the model TCY in February of 1945.

Some very unusual features

The steering system of the TCY Terra Cobra was unique amongst all motor scrapers to this day. It consisted of two hydraulic cylinders with a wide sheave at each rod end that acted on a fairly substantial length of multi-linked chain.

The chain was routed around a concentric pulley on the scraper’s kingpin, so when the steering ‘tiller’ was activated, the hydraulic cylinders would push or pull the chain, thereby steering the machine.

As one can imagine, the possibilities for all manner of mishaps with this type of steering system were quite high! (For the record, LeTourneau’s Tournapull was not much better with clutch and brake steering, the only ‘normal’ machine of the three was LaPlant-Choate’s TS-300!)

Although the TCY had a normal clutch, drive shaft and differential, the final drives were roller chain drive as well and needed to be inspected or replaced every 500 hours!

Full air brakes were installed on the scraper axle only, and the machine rode on 21.00×24 tyres as standard equipment.

Operator comforts were at best minimal with only a deeply cushioned bench type seat. Visibility was good to the left and ahead, but very poor to the right as the machine’s cable control was directly in the sight line of the operator!

The scraper was all-cable controlled by an air operated 2-drum PCU (cable control) of Wooldridge’s own design and manufacture.

Bowl functions were separate from the apron and ejector which were sequenced.

When the apron was at maximum lift, the ejector rolled out the load. In service, this PCU gave some trouble and when the model TC-S14 Terra-Cobra was introduced in 1948, it featured a new three-drum PCU in which the bowl lift, apron and ejector functions had their own separate control.

The bowl floor was hinged behind the cutting edge and rolled out the load, very similar to a Terex TS-14.

Another cool little touch engineered by Wooldridge was a cushioned push block that had a very large spring inside it, making for smoother push loading.

Wooldridge also offered a rear dump wagon version of the Terra-Cobra called the TC-W14 that held 14 cubic yards and featured a fixed floor with sliding upper body, very similar to todays forced ejection ATD’s.

Not very many of these machines were manufactured.

Time for an upgrade

As a result of field experience and customer requests, Wooldridge upgraded its TCY Terra Cobra into the model TC-S14 in 1948.

Principal changes included a new Cummins power plant, the supercharged model HBIS-600 which put out 200 flywheel horsepower, and a minor revision to the scraper increasing the struck capacity to 18 cubic yards.

While retaining the original four-speed Fuller transmission, a 10-speed Fuller model was also made available as an option.

Final TC incarnation

The last production version of the model TC Terra-Cobra was introduced in 1951 and was the called the model TC-S142.

This featured yet another new engine, the 225 flywheel horsepower Cummins HBISD-600, plus an extensive revision to the scraper that included relocating the bowls’ draft arms and a major redesign of the rear axle support assembly. Bowl capacity was not altered and remained at 18 cubic yards.

This model was in production until 1953 when it was replaced by a brand new Terra-Cobra, the model TH (reviewed  in a future article).

It is not known exactly how many TCY, TC-S14 and TC-S142 Terra-Cobras left the Wooldridge production lines, as the company ran its serial numbers consecutively along with all the other equipment they produced.

For the model collector

Due to the relative obscurity of the brand, and the fact that Wooldridge had disappeared completely by 1962, models of any Wooldridge equipment are extremely rare.

No models of the TCY, TC-S14 or TC-S142 motor scraper are known to exist.

There are, however, two models of Wooldridge equipment of which I am aware of.

The first example is by American pressed steel toy maker Dopeke which produced a 1:16 toy of a Wooldridge TCS bottom dumper in the early 1950s. Not really for serious collectors, examples can be found on Ebay with varying prices.

The other example is a beautiful 1:50 model of a 40 cubic yard Wooldridge OS-400 towed scraper that is sold along with an MRS 250 tow tractor.

Not an inexpensive model, it can be obtained through Buffalo Road Imports in New York.


BRIEF SPECIFICATIONS – Wooldridge TCY Terra-Cobra (first production model)

Engine:                        Cummins HBI-600, six-cylinder, diesel rated at 150 flywheel hp

Clutch:                        17” Lipe-Rollway, dry type

Transmission:             Fuller, 4-speed manual with 1 reverse gear

Top Speed:                  21 mph

Brakes:                        Bendix, full air operated on rear wheels only

Steering:                      Hydraulic, via multi-link roller chain

Final Drives:               Multi-link roller chain with a conventional differential

Std.Tyres:                   21.00×24

Scraper Capacity:       14 cubic yards struck, 18 cubic yards heaped

Operation:                   Cable

PCU:                           Wooldridge 3-drum, full air operated

Length:                        34’ 8”

Width:                         11’ 6”

Height:                                    10’

Operating Weight:      19 tons empty


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