How do trains turn without differential ?

We have travelled thousands of kilometers in trains, but we haven’t given a thought about how do trains turn during a curved path ? Both the wheels are connected through an axle & obviously are of same diameter. But,when a train takes turn, the outer wheel has to cover more distance than the inner one…! How is this possible ? How can the outer wheel cover more distance than the inner one even when both the wheels have same diameter ??? 🙁

How do trains turn –


The solution is simple & elegant.
Both the wheels are a bit flanged OR conicle. The part having greater diameter of the frustum of the conical wheels is inward while of lesser diameter are outwards the track.

Now whenever a trains travel on a curved track, the wheels get slide away in either of the direction.

turning of train mechanism

Wheels of a train while taking a turn !

The following happens while taking a turn –

  1. Suppose the train is taking a left turn(as in the above picture). Which means the wheels will slide to the right(→) side, obviously due to centrifugal force.
  2. The outward force-centrifugal force results in increment of diameter of right wheel(↑) & decrement of left wheel(↓) during the turn(the black line on wheels in the above image).
  3. The right wheel covers more distance than the left wheel since the right one has greater diameter than the left one & hence the problem gets solved ! 🙂

Also it solves one more major problem. Whenever there is a bump on tracks, the wheels suddenly slide even when travelling on a straight track & there is a great danger of being derailed, so the same design helps to stabilize the train & to run smoother.

Here is a video which will help you to understand it better.

In engineering,

The most simple designs are considered as the best solutions !

So besides the working, what we also learn is that – It isn’t necessary every time to make complex machines & design complex mechanisms, all it takes is a simple design of the thing what we already have.

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