In 1907 Felix Caldwell and Norman Laurie Caldwell of South Australia applied for a patent to cover Improvements in and connected with driving and steering motor propelled vehicles. The patent described four wheel drive with four wheel steering:
Drive to both front and rear axles is by propeller shafts and bevel gears. Half shafts carry the drive along live axles to open-style steering knuckles. Modern looking universal joints allow steering, and the drive continues through hollow stub-axles to drive fully floating hubs and the wheels.
Front and rear wheels are shown steering in opposite directions. (This improves manoeuvrability and reduces transmission wind-up in turns, without the need for a differential between the axles.)
A later patent application from Felix Caldwell in 1912 covers Improved power steering gear for heavy motor driven road vehicles. The steering wheel indicates an intended direction for the road wheels. The difference between the actual and intended directions is used to engage cone clutches which bring power assistance into play to turn the steering arms in the intended direction. One can only speculate on the durability of the cone clutches.
The Caldwells combined with Henry Vale of New South Wales and formed the Caldwell Vale Motor and Tractor Construction Company in Auburn NSW. From 1910 on they constructed perhaps 40 large four wheel drive trucks some of which were used as early road trains. The trucks had the Caldwell four wheel drive system and power steering, but apparently only steering the front wheels.
This Caldwell Vale truck (left) from the Waikerie settlement was working as a tipper for the South Australian Roads and Bridges Department in 1914[Ham83].
About 1913 the Caldwell Vale company lost a court case
over the performance guarantee of its trucks
and was subsequently taken over by another firm [Gil81].
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