The way train wheels work is a little more complicated than you might think.
While working on the hovertrain video, we took a trip to Ecclesbourne Valley Railway to get an up close look at train wheels and how they work.
If you're interested in watching the original video, check it out here
Cylindrical Wheels
Rolling cylindrical wheels along a train track, they derail almost instantly, as there’s no mechanism to keep them aligned with the rails.
With non tapered edges or a flange, the cylindrical wheels will roll as straight as they can until the floor beneath them disappears as the track curves, causing them to slip off the track.
While cylindrical wheels are ideal for vehicles with steering systems, trains are designed to rely solely on the track for guidance, eliminating the need for a steering mechanism.
Flanged Wheels
Adding a flange might seem like a simple fix to prevent derailment, and while it helps to some extent, it doesn't address the challenge of navigating curves. The train still pushes straight ahead, unable to adjust its direction to follow the track.
While flanges improve safety by reducing the risk of wheels slipping off, they also hinder the train's ability to move smoothly.
Conical Wheels
These wheels, though, have a cone-like shape that helps them to self-centre, enabling them to navigate turns and stay on the track consistently, thanks to a clever design trick.
As the wheels start to go around a curve, the outer wheel has to cover more distance, effectively acting as if it were larger.
On exaggerated conical wheels, the effect becomes clearer. Like cylindrical wheels, conical wheels initially aim to roll straight. However, as the track curves, different parts of the conical wheels contact the rails—one side with a larger circumference acts like a bigger wheel, while the other acts like a smaller one.
When a set of wheels has unequal sizes, the set naturally rolls toward the smaller wheel. On train tracks, this works perfectly since the smaller 'wheel' side aligns with the curve's direction, guiding the train smoothly along the track.
Hunting Oscillation
There is one major problem with this design, and it has been limiting the speed of trains since it was first implemented.
At higher speeds, conical wheels start to sway more as they self-correct. This can build up until the flanges hit the rails.
Flanges are meant as a backup to prevent derailment, but at high speeds, this contact can slow the train down or even cause it to derail.
If you enjoyed this article we have several more covering other educational topics involved with the channel, check them out over here.
3 comments
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