I was told that Steam cars were fast, clean, and efficient, and at one time it was the vehicle of choice.
In: 6
Instead of burning the fuel inside the engine, steam engines need a boiler and water. This means more weight and space.
They weren’t efficient compared to todays internal combustion engines.
Steam can be more efficient, but that’s only true for huge systems, and those then take ages to fire up, wich is why we also stopped using them for (non-nuclear) ships
To make a thing move, I need an energy source and an energy-to-movement converter. The goal is to convert as much of my fuel energy into movement as I can. Get the most bang for my buck, literally.
Let’s use gasoline as the energy source. I can combust it, use that energy to boil water, use that steam to move a piston, use that piston to spin a flywheel geared to the wheels on the ground.
I can also just put the gasoline in the piston and burn it there. One less step, one less place to lose heat and therfore thermodynamic efficiency. I also don’t to have to lug around a large tank of water and waste energy heating up my working fluid that (and this is really important) I can’t capture to do work. Every time you stop driving, that tank will cool, and you’ll have to reheat it, costing time and energy. Might as well make the combusting fuel my working fluid, since it would heat itself up when ignited.
They are bigger. Inefficient. Takes mor knowladge to maintain. Must be maintained with way dhorter intervals
In addition to the things already mentioned, steam vehicles operate at high pressure so when something goes wrong, it goes badly wrong (eg Jay Leno got badly burned by a steam car last year).
Lots of people were injured when steam engines were more prevalent – trains were especially bad when the boilers blew up.
Faster than a horse drawn buggy? Sure. Clean? Well, it smelled better than a barn anyway. Burning coal/wood to heat the boiler isn’t clean by any stretch of the imagination, though perhaps a step better than burning petrol. And efficient? That’s debatable depending on what you’re trying to compare it to. Compared to an internal combustion engine, steam engines have lower thermal efficiency. They also took roughly 30 minutes to start/warm up to operation level – hardly efficient as far as time is concerned anyway. There’s multiple reasons it stopped being the vehicle of choice, and those are only a few.
There are two ways to use steam:
Multiple expansion engine (basically moving pistons)
Turbines.
The piston method doesn’t like high rpm at all, it loses efficiency when used fast. You have to fill the cylinder with steam, then use it. At high rpm the piston is like “running away” before the steam is enough to push it. Being forced to use relatively slow rpm, the result is a very heavy slow engine. 2 to 10 times heavier than an combustion engine of the same power.
The turbine system is not viable due to extreme noise, which requires massive shielding, and the turbine inertia would make your vehicle very slow to accelerate and very slow to decelerate. So it’s good for vehicles that don’t change speed often.
There’s a third way, the turboelectric. Your turbine work at fix speed, and rotates a generator, then an electric motor does the work of moving the wheels/propellers/whatever. The power is adjusted by variable steam input and variable load from the electric motor. Problem, this is already 3 devices and we still need to add the boilers. It’s gonna weight more than any other drive system. It does have the advantage of being efficient at most speeds, and can vary its power quickly. In fact, it’s the system we use to make electricity that then drives our devices. As a whole, a country is a gigantic turbo-electric driven machine.
In trains, maybe. Steam road cars were never a vehicle of choice. Insofar as they existed, they had poor range, were inefficient, heavy, slow, and stinky. Even modern steam engines suffer from most of these issues.
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