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Happy Birthday, D10

Digger Blogger | 16:30, Wed September 20 2017

The Cat D10 dozer, which introduced the elevated sprocket design, is 40 years old this month.

It was September 1977, a month when David Soul wanted a Silver Lady to take his hand and Meri Wilson had an interesting visit from a Telephone Man, that Caterpillar rolled off of its production lines 10 pilot models of what was world’s largest, most powerful dozer.

The Cat D10 dozer’s radical new design, high weight and horsepower, and resilient undercarriage answered the growing calls from large mining and big heavy construction operations for a more powerful dozer.

“We bucked conventional wisdom with the D10 and tinkered with a centrepiece that was a part of the Caterpillar product line since the company was formed in 1925,” says George Alexander, a retired Caterpillar engineer who served on the D10 research team and one of four individuals named on the patent for Caterpillar’s elevated sprocket design.

The D10 was 50% more productive than Caterpillar’s previous largest dozer of that era, the D9 dozer. It weighed more than 86 tonnes (190,000 lbs) and measured 4.6 metres (15 ft) tall and slightly more than 9.4 metres (31 ft) long. Power was supplied by the 522 kW (700 hp) D348, V12 diesel engine.

“The D9 dozer was the best track-type tractor of the day,” says George Alexander. “It worked great for dirt operations, but interstate and heavy rock applications were hard on the solid bottom tracks that were a part of all dozer designs of that era.”

To address market needs, Caterpillar put its research and engineering team to work on a new, more powerful dozer. “The development and product introduction involved every discipline of the company,” recalls Ron Krolak, track-type tractor chief engineer, now retired. “It was highly successful because of the total team effort. The challenge of beating the competition in our core product was a tremendous incentive.”

With management approval in 1970, a test bed was built for the new track. Engineers started by flipping the final drive for a D9G upside down. “We worked on undercarriage geometry a lot, and within six months we had it operational,” George Alexander says. The new resilient track with elevated sprocket design was thoroughly tested to verify its durability, and it showed significant potential for improving undercarriage durability for extreme tasks. 

Two years of testing led to the first elevated sprocket patent application and ultimately building the first two D10 test models in August of 1973. “Our team generated 93 patents involving all systems of the concept,” adds Ron Krolak.

By separating the drive sprockets from the track roller frame and elevating them above the tracks, more track remained on the ground for improved traction. The elevated sprocket design was also better able to absorb ground shocks for longer life and greater operator comfort.

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While initial testing proved the efficacy of the resilient undercarriage with elevated sprocket design, some remained sceptical about the new design. “It didn’t look like any traditional Cat dozer,” explains George Alexander. “The entire dozer was different in almost every way, except for the engine.”

As well as looking different, the new undercarriage design required the transmission to be mounted behind the engine to provide for the only track-type tractor final drive system with a common centreline between the steering clutches and brakes. It also allowed engineers to move both the dozer blade and ripper closer to the tractor, providing a concentrated centre of gravity and improving the balance of the machine. 

Caterpillar says that the pilot D10 dozers built in 1977 were immediately embraced by customers. Their ripping and pushing capabilities made a significant impact on the mining industry, as studies showed the cost/yard to move material using the D10 was comparable to that of larger draglines, the company says. The resilient undercarriage with elevated sprocket conformed to the ground better than solid tracks, it says, which helped to improve machine pushing power and undercarriage life.

The dozer’s modular concept, with removable components, also helped to increase machine transportability. The transmission and bevel gear removal and installation times on the D10 compared to that of the D9H dropped from 30 hours to just six hours, while service time on the final drive plummeted from 45 hours to nine.

The Cat D10 legacy lives on today with thousands of Caterpillar elevated sprocket dozers operating around the world. The elevated sprocket track concept has been expanded to today’s Cat D6N and D6T medium dozers and the D8T, D9T and D11T large dozer models as well as the current D10T2 model.

Georeg Alexander recalls: “After I retired in the 1990s, I gave my presentation on the development of the elevated sprocket design, and a person afterwards said to me ‘wherever you go, you will see the results of your work’.

“He was right. No matter where I travelled in the world, I saw dozers with the elevated sprocket design, and it made me proud to be a part of the original research team.”




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