Rolling stock axles

[Rick Fischer]

Question that has always intrigued me.

Why do rolling stock have L&R wheels on an axle that not only rotates but the wheels are locked, ie no differential action for bends? Why don't the wheels rotate separately on their own bearings on a fixed axle?

Cheers

RF

[Ausfree]

Interesting question!!!!:D Maybe because the bends in a railway line are very shallow, so the axle does not "wind up". Only my guess, not an expert.;)

Maybe somebody here with railway experience could answer that with some authority!!!:D

[isuzutoo-eh]

Railway wheels are tapered, with the smallest diameter on the outside and largest diameter adjacent to the flange.
The flanges of both wheels on a set are not hard up against the rail at all times, there is slop. When going around a curve, the wheelset moves towards the outside of the curve, so the flange on the outside wheel is hard against the rail on the outside of the curve.
As the diameter of the wheel is greatest adjacent to the flange, the wheel on the outside of the curve has a greater rolling diameter. This somewhat 'steers' the wheelset around the curve, without need for differential action.

Or at least that's how I think it works... :angel:

[drivesafe]

And to add to Marks post, the wider the gauge, the larger the curve has to be to allow the wheels to act as Mark posted.

Queensland’s narrow gauge allows for tight curves while Vics broad gauge means you need very large radius curves.

[JDNSW]

Probably mainly tradition - curve radius is usually large enough that the problem is minimal, and the structure of axle with fixed wheels and bearings outside the wheels means that the bearings were easy to inspect and service - a frequent requirement when plain bearings were used (which was until quite recently).

John