There was also a design with a layer of rubber between an inner steel wheel and a thin outer steel tire.
That was used by high speed trains in Germany - until one of the steel tires broke at 300 kilometers per hour and got stuck in a switch, causing the train to detail and hit the support column of an overpass, which collapsed on top of the train. 101 people dead: https://en.wikipedia.org/wiki/Eschede_train_disaster
> a comparable carriage fitted with pneumatic tyres could need as many as 20 wheels.
How does a bus get by with far fewer wheels?
I think the answer is that they are still building with the same weight as a train, rather than a bus.
That points out an unexplored engineering envelope for modern trains, made possible by newer technologies:
* Very light trains. Think lighter than road cars, since they don't need crumple zones or crash worthiness.
* Virtual coupling. Basically platooning on rails. Now the cars need to at most push/tow one other disabled car, so they don't need a beefy chassis to support towing long trains, coupling forces, etc.
* Homogenous cars. They all have traction motors, small batteries and sensors and compute. Think a low-range Tesla on rails.
* Autonomous control. Self-driving on rails. No operator cab. Since the train is now quite light, with a reasonable stopping distance, obstructions on the track can be potentially avoided so long as the sensors are adequate.
* Much faster acceleration and deceleration. With leaning, they could also corner faster.
* Probably intrinsically quieter, but now pneumatic tires would probably have reasonable life.
> Not just inefficient
What? I thought wheel deformation was a huge source of drag and steel tires were one of the main reasons why trains were comparatively efficient.
Still in use on a few lines of the Paris Métro
Can somebody explain to me the difference between this „short lived experience“ and the actual ongoing decades long operations of tire based metro/subway systems?
The fun experiment was the paper wheels.
I remember this thread from hn. Tire dust makes up the majority of ocean microplastics - https://news.ycombinator.com/item?id=37726539
Link to the article - https://www.thedrive.com/news/tire-dust-makes-up-the-majorit...
Japan has a train-on-tires on an elevated overpass track around Tokyo bay.
It's pretty neat.
The author keeps asserting the "inherent weakness" of steel-on-steel railways; however, there are very good reasons it has been settled on as a good choice. Friction and sound losses are generally minimized, thanks to a very small contact surface and smooth, hard materials with little give; wheels can be re-machined back into spec a couple times rather than being replaced; rails can be re-used for lower-speed applications when worn; unlike pneumatic tires, steel can be machine into conical, self-centering, turn-adapting geometries with fixed axles and no need for differentials; the list continues and is quite long. Apparently, a recent change to wheel geometry reduced wear and extended lifetime by as much as 40%.
See Practical Engineering's latest video: https://www.youtube.com/watch?v=Nteyw40i9So