Balancing forces – the leaning wheel grader

October 24, 2012

If you want to move earth, gravel or snow, then finding some way of steering a pushed board seems a good way to go.  And that’s exactly what the early graders were.

But if the board is at an angle to the direction of travel then the machine becomes very difficult to steer in a straight line.  And if you’re working on a sloped surface (like a cambered road) it can get very tricky indeed.

So, in 1885, when J.D. Adams invented the leaning wheel grader he showed how to use a lean applied to the steering wheels to counteract the side forces and so make the unruly machines much more controllable.  And in the early days of horse-drawn graders with no hydraulic assistance it was vital to keep the opposing forces of earth-moving and steering under control.  And this fundamental innovation has proved vital to grader operation ever since.  Caterpillar introduced the rear-engine configuration for ease of visibility for the operator, then, in 1934, the dual rear axle configuration which addressed the stability of the platform – and the architecture of the grader was fixed into a form still used today.

So, during a recent holiday visiting family in Western Australia, it was great to find an example of Adams’ pivotal early innovation in Cunderdin’s museum – a No 11, Adams grader from the 1920s.

And here’s a detail of the rack and pinion arrangement for the front wheels. (The rack needs to be curved to cater for the arc described by the tie-rod as the wheels lean – obviously! (?)).

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