Here is the detail of one.
Mt Isa (Qld): Grover bogie. Fri.19.1.68. (Roderick Smith)
I don't know how they worked.
Perhaps over the limited travel required, even on sharp curves, slop in the
joints could cope with the variable-length geometry required.
Or, the rods are mounted onto the crossbeam on a sprung turnbuckle which
provides variable length.
Even then, the best which could happen is that the leading axle bites with
its flange, and so pivots, in turn pivoting the rear axle to reduce wear
Roderick B Smith
Rail News Victoria Editor