The Curtiss-Wright CW-27 & CW-28

Mention the name Curtiss-Wright earthmoving machinery to someone today and they will probably give you a blank stare. By Richard Campbell.

Curtiss-Wright was a company with a very long history, being originally founded in July 1929.

Far better known for its aircraft including the legendary Jenny, Kittyhawk, Helldiver and an array of successful aircraft engines, Curtiss-Wright also once had an earthmoving division!

Curtiss-Wright entered the earthmoving business through the acquisition of the Wooldridge Corporation, of Sunnyvale, California. Wooldridge was also a company with a long history and, along with LeTourneau, Wooldridge could trace its ancestry well back into the early 1900s when Mack Wooldridge originally set up the company.

Wooldridge was a division of Continental Copper and Steel when Curtiss-Wright bought it, and CC&S were keen to exit the earthmoving business and dispose of the Wooldridge subsidiary.

The deal was sealed in June 1958 for about US$5 million, making Curtiss-Wright an instant member of the earthmoving industry. At the time Wooldridge’s prime products were a range of motor scrapers and towed scrapers.

Wooldridge also had a manufacturing deal with M.R.S (Mississippi Road Supply) where Wooldridge supplied M.R.S with scraper bowls for its four-wheeled prime movers. Curtiss-Wright cancelled this agreement not long after taking over, leaving M.R.S to go it alone and design and build its own scrapers.

All the completed Wooldridge machines, patterns, jigs, equipment, and sales data were uplifted from Sunnyvale, California and shifted to South Bend, Indiana where Curtiss-Wright had a very large manufacturing facility that had become idle following the end of WW2. Existing stock was re-decalled with Curtiss-Wright logos and it was back to business as usual!

Wooldridge also had a range of dozer blades, rippers, and cable control units, but Curtiss-Wright chose not to continue with these due to very intense competition from other manufacturers. However, the cable control manufacture segment was retained, as that was the method of operation used by Wooldridge’s scrapers.

The CW-27/CW-28

When purchased, Wooldridge had a range of five different models of motor scraper in production – the CW-27, CW-215, CW-220, CW-226 and CW-320, with the CW-27 being the smallest at seven cubic yards struck and 10 cubic yards heaped.

The designation was changed to CW-28 not long after Curtiss-Wright took over the Wooldridge company and was a nod to the extra cubic yard the machine now held due to Curtiss-Wright sideboarding the bowl of the scraper!

Otherwise, both CW-27 and CW-28 were identical machines and contemporaries of the Euclid S-7, LeTourneau-Westinghouse Model D Tournapull, Allis-Chalmers TS-160 and Michigan 110.

The CW-27 had made its first appeared in 1955, at which stage it was known as the Wooldridge T-70 ‘Cobrette’.

Powered by a General Motors model 4-71 diesel rated at 148 flywheel horsepower, it featured a Twin-Disc torque converter (unusual at the time) between the engine and the Fuller 5C-720, 5-speed manual gearbox. This gave the machine extra lugging ability, especially when loading or ascending steep grades.

A push plate was fitted to the front of the machine so that it could assist other scrapers of similar size loading.

The machine had full air operated shoe type brakes on both axles and was usually equipped with 18.00×25 tyres although 23.5×25 tyres could be supplied as a factory option.

Weighing just over 14.5 tons empty, the CW-27 featured an all-cable operated bowl with roll out ejection, power for cable operation coming from a Wooldridge WFA-2 Power Control Unit (PCU).

Perhaps the most controversial feature of the machine was the Wooldridge-developed “Roto-Gear” steering, which was unlike anything else fitted to competitors’ machines then or since. Roto-Gear consisted two rotary hydraulic motors with gears that acted on the machines king post when the steering valve was opened.

This innovation was a little bit ahead of its time, and the system was prone to failures and wore quite quickly, leaving the owner with an expensive repair bill.

To add to the machine’s woes, steering speed was governed by engine RPM, which could make steering response slow.

Roto-Gear steering was supplied standard on all of Curtiss-Wright’s motor scrapers except the CW-320 (which was a three-axle machine).

In the field, a great many Curtiss-Wright scrapers had its Roto-Gear systems removed and replaced by more conventional hydraulic cylinders and linkage, thus curing the problem.

A New Zealand connection

 Cory-Wright and Salmon were the New Zealand distributor for Curtiss-Wright and imported a total of three CW-28’s.

All these machines ended up with New Zealand Roadmakers and saw service all over the upper North Island on roading projects (including the Auckland Motorway), housing development jobs, and significantly, the construction of Mangere Airport.

While no complete examples are left, the bowl of one of the machines still survives as a towed scraper.


Apparently not knowing what to do with its  new baby, Curtiss-Wright made very few improvements or alterations to any of the motor scrapers in the Wooldridge product range during the time they held the franchise.

To further compound matters, all the scrapers were cable-controlled machines in a world that was rapidly changing to hydraulics in the early 1960s.

Adding to the problem, not a great deal of money was invested into promotional advertising for their new product (which is why information on Curtiss-Wright earthmoving equipment is so hard to come by these days).

Unwilling (or unable) to invest sizeable amounts of cash in modernizing or improving the product range, Curtiss-Wright made the decision to exit the earthmoving business almost as quickly as it had arrived, closing the South Bend production line in 1963, a scant five years after acquiring Wooldridge.

For the model collector

Regrettably, I knows of no models that are currently available of a CW-27 or CW-28 scraper, or in fact any Curtiss-Wright motor scrapers, so if you want one, it will have to be a scratch build.

It seems that models of C-W equipment are harder to find than their literature (which is also next to impossible!)

There is, however, an extremely nice model available of one of Wooldridge’s big, towed scrapers in 1:50 scale, and there is always the ancient Matchbox model (to 1/110 scale) of a Curtiss-Wright CWD-321 rear dumper.

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