Why does putting a carriage on rails make it much easier to pull? As in, how were the first trams such an improvement from omnibuses when the same weight was still being pulled?

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Why does putting a carriage on rails make it much easier to pull? As in, how were the first trams such an improvement from omnibuses when the same weight was still being pulled?

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Anonymous 0 Comments

Compare what it takes to roll a pool ball (hard ball) on a pool table (hard surface) versus rolling a beach tires(squishy) on a beach (soft).

For the least amount of rolling resistance, you want the hardest possible wheel on the hardest possible surface.

Steel on Steel is the way to go.

This is especially true as early wagons had hard wheels with very little surface area. Great on hard surfaces, but in dirt, mud or grass it would sink and take much more effort to pull.

Anonymous 0 Comments

Great question.

Part of it is materials: metal rimmed wheels roll better. And metal tracks are better to roll on.

But part of it is also infrastructural: building a rail track involves carefully laying down a guide system that covers every meter from point A to point B, and has to be smoothly aligned and joined and so on. *Anything* you do with that degree of precision is going to offer a considerable improvement in terms of energy efficiency.

On the second point, consider the example of an inflated rubber tired automobile on an asphalt surface. Kind of the opposite of a steel wheel on a steel track, in a lot of ways, right? But pushing that automobile is surprisingly easy, at least as long as the grade is close to level.

Try pushing that same automobile across an open meadow. Sure, you’ll probably get a certain amount of distance. If you’re dedicated, and maybe have some friends to help, you might be able to keep it going for a while. But it’s a huge effort to go anywhere — you are constantly struggling against irregular terrain. And sooner or later you are going to hit some dip or shallow depression that you will really struggle to get out of.

By contrast, if you start pushing a car along a decent paved road, a single fit person can keep it up literally for miles.

So, historically, I think to some extent the advantage of rail-guided vehicles was simply that for the first time someone had really laid out a road with a very high degree of care and engineering.

Anonymous 0 Comments

ground wheels = fat

Rail wheels = skinny and more controlled ‘ground’ environment

= way less rolling resistance.

Anonymous 0 Comments

The first railways were made before omnibuses existed. At that time most roads were terrible by modern standards. Steel wheel on steel rail interface was *much* better than the alternative at the time.

Anonymous 0 Comments

Three reasons.

There’s very little deformation in the wheels. If you’ve every tried to ride a bike with a flat tire or pumped the tire up hard to roll better, you know that the harder the wheel, the easier it rolls.

The track is very smooth and flat compared to a road surface. The train doesn’t have to waste energy climbing over bumps and out of potholes, even at the microscopic level.

The track is very well supported. Under very heavy loads, relatively soft road surfaces deform so that the truck is always going “uphill” to get out of the dent it creates when it presses down on the road. The design of the train and rails distributes the load over a wide area preventing most of the deformation.

Anonymous 0 Comments

Rails have far less drag than rubber wheels.

The downside is that rail carriage are heavy, and can’t go everywhere, they need tracks.

Given that you need a strong push to accelerate, and power to keep the speed; given that early engines and horses had very strong traction but low power, rails literally changed the world. They allowed this early engines or horses to do just the acceleration work, and then keep the speed with minimal power usage (horses get less tired and steam engines consumed less of the precious coal)

Now that engines have higher power, keeping the speed is not the biggest concern, so we revert to the less efficient but more flexible wheel on road, at least for the most mundane uses.

Between this two eras, there was a time where another logic was applied: we already have the rails, let’s keep using them. Once the rails were worn down, which takes half a century or more, instead of redo the rails we scrapped them and implemented cars/trucks/buses.

Anonymous 0 Comments

Steel rails are very hard. When wheels roll on a flexible surface, it’s like they are always rolling uphill. When the surface flexes, the contact patch of the wheel sits at the center of a slight dip. When it rolls, it has to climb from the bottom of that dip, which is equivalent to going uphill.

This is also the reason why it makes sense to replace wooden railroad ties with concrete ties. Wood is more flexible than concrete, so the whole rail gets pressed down more when it rests on wooden ties. Since the ties ahead of the train aren’t being pressed down, this means there always exists a small uphill grade ahead of a train rolling on a track with wooden ties.

Anonymous 0 Comments

Actual ELI5: Take a soccer ball, put it on a mattress and roll it along with your hand pushing down.

The effort you have to put in isn’t that much but it is a LOT more than if you set it on a hardwood floor and push the same.

Now imagine you used a wooden ball. (Don’t do it on a hardwood floor please).

The mattress would resist a bit more but the hardwood floor it would practically glide.

The principle is the same.

The ground “feels hard” but only to a foot or hand. To the wheel of a cart it might as well be the mattress. Whilst you can roll it along it still will buckle under it and will take more effort.

The steel rail behaves like the hardwood floor.

Anonymous 0 Comments

Think of your feet on the fwoor in our house. The wood fwoor is swippery, and the carpet is less swippery. Your bare feet are less swippery than your feet with socks, and the clothing maker helped us out by putting dots on the bottom of your socks.
Rail cars are your feet with socks without dots on top of the wood floor, and that’s why I can push you around without your feet even moving. It’s also why you can run and slide on your socks on the wood fwoor. Tires on concrete are your bare feet on the carpet, and you only fall down there because you are bad at staying on your feet and you enjoy falling down.

Anonymous 0 Comments

An order of magnitude less Rolling Resistance. Once a train is going, it takes very little energy to keep it going.

[Great video here](https://youtu.be/4Q22pcC98hY?t=121) about why rail has remained dominant over things like maglev – in which the presenter gives a good overview of why rail is good in the first place. The really important graphic is at [3:05](https://youtu.be/4Q22pcC98hY?t=180).