50 Years of Q & A: Two-headed excavators

If you classify a dragline as an excavator, then this machine built by George Henry Dunlop seems to fit the bill. Although largely unknown, George appears to have been quite a significant engineer in his era and he lodged numerous patents from the 1890s to the late 1930s.

Unlike many who have lodge patents, George seems to have built a reasonable proportion of the machines he patented. Indeed many of his patents are refinements of earlier patent applications, suggesting that the refinements came about through practical experience.

Plant records showed that the Victorian State Rivers & Water Supply Commission had 11 rail-mounted steam dragline-excavators.

As George Dunlop contracted in addition to building equipment for sale, it is likely that he operated some of his own equipment, and the twin boom excavator shows the name of another contractor W. Solomon.

George also built 3 pairs of channel scrapers (see picture), which used the principle of the ploughing engine in winching a flip-over scoop between 2 winching engines to excavate a channel. The engines were winched forward as work progressed. The scoop was quite large for the era (early 20th century) at around 3 cubic yards.

The principle was actually quite efficient. Only the scoop and the excavated earth moved. The heavy winching engines stayed clear of the soft ground in the channel and change of direction was simple: the winching force pulled the cutting edge into the ground. There was a cutting edge on each end of the bucket so that it could dig in either direction.

Research by Matthew Churchward at Scienceworks Museum also shows that George devised soft ground tunnelling methods that were successfully employed in Coode Island Silt in 1898. Even over a century later, this is still regarded as extremely difficult material to dig in.

Bonus picture: This Austin ditcher came from the US but was used in digging channels in South Australia in the 1910s. It uses 2 side arms with buckets that run along the arm to side cast earth from the channel excavation.

Question for next week:
Did anyone other than Caterpillar (in its early days at Tullamarine) build or part-build a medium size crawler tractor in Australia? (Since it’s a simple Yes/No, you also have to name what was built, where and by whom.)
NOTE: conversions of war surplus tanks do not count: only recognised manufacturers.