The interesting engineering behind the SHAPE of Train wheels!

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Driver (engineer in N America) of 40 years here. I've had to explain this to several trainees over the years and none of them had any clue of this phenomenon before it was explained to them. It's just not something the average person wonders about. I also explained (not to criticise as your video is excellent but you probably should've too) that the further apart the wheels are (the wider the track gauge is) the more differential action is needed because the outside wheel has to travel a LONG way more than the inside wheel but train wheels and the rails they run on are only around 80mm (3") wide so the wider the gauge, the less tight of a curve the train can negotiate. That's why mountain railways are often narrow gauge. Narrow gauge is cheaper to build than standard or broad gauge and when people are told that, they always say "because the sleepers (ties) are shorter?". Well, short sleepers probably are cheaper than longer ones especially when you need thousands of them but narrow gauge is cheaper because you can go around mountains rather than having to tunnel through them because you can't negotiate tight curves.

"The designer knows he has achieved perfection, not when there is nothing left to add, but when there is nothing left to take away."

I knew the shape was to keep the train centered on the track, but I never even thought about the differential action when going around curves to be honest, pretty interesting how simple it is!

I had never considered the necessity of differential action when a train turns a corner, this explained it very neatly and the animation was excellent nice and clear. Thank you very much.

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After working in our subway system, the rails are also pointed slightly inward. It's very slight and looks pretty straight until you take measurement. The plates holding the rails to the ties will show a difference in height from the gauge side to the outside. Turns are also slightly shifted higher towards the outside of the turn which is why when track inspections are done, we have to take cross level readings as well as the gauge.

I have seen lots of train wheels, but never looked close enough to see the taper. Makes perfect sense! I always assumed that it was just the flange that kept the train on the tracks.

0:58 This guy is using the silver play button as train rails Lmao 😂

This is simply incredible. They say simplicity is the cornerstone of brilliance. This invention is extremely simple and even more so brilliant.

I also learned recently that the conical wheels produce much less drag on the rails than flat wheels would, and that is also why the rails are slightly convex: less contact = less friction = less drag.

Only now did I know that the 2 tram wheels are fixed on the same axle but operate as an independent differential. All these simple principles are very well applied by scientists. Thank you for sharing this great video.

I never thought of how conical wheels could compensate for different lengths of travel when rolling around a corner. I just assumed each wheel rolled independently and wasn't firmly attached to an axle. But now that I think about it more, having the wheels firmly attached to axles means the same differential action caused by the conical shape would also cause the wheels to actively steer back to the center of the track if the wheels were shifted off-center. That's brilliant.

Having had toy trains for years, I had no idea that the actual wheels were as cleverly engineered as that. They appear to be far more tolerant of rail gauges than one would suppose.

Makes you wonder when the designed the wheels if they actually understood what forces were actually keeping it on the track, or was it just trial and error and this was the result because it worked the best

I remember Feynman explaining this years back. Was so fascinating to learn how something so simple could have such a profound application and effect.

I am an Engineer in Indian Railways and I was asked about this question in my interview...I know the answer but the way you explain about the acting force is very good. Thanks 🙏 🇮🇳

A worthy note on the conical shape of the wheel is that it prevents achieving higher speeds . as the constant oscillation automatically damps the train speed

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