Why don't cars use something like a rail gun instead of combustion?

[J3J33J333]

TL;DR Summary

Why don't cars use something like a rail gun instead of combustion to drive pistons?

Why don't cars use something like a rail gun instead of combustion to drive pistons?

 

[russ_watters]

Why don't cars use something like a rail gun instead of combustion to drive pistons?

Because that would require electricity, and would be a cumbersome/inefficient electric motor.

 

[Baluncore]

The vehicle must transport its energy supply for the range between recharging or refuelling stations. Liquid fuel is energy dense when compared to electric batteries, so range and economy are increased by the use of liquid fuel.

 

[Borek]

Car needs a _source_ of energy to move. You suggest something that only _consumes_ energy.

 

[tech99]

I remember making a model of what the book called a Magneto Electric Engine. It used reciprocating action, like a steam engine, but it was very inefficient. Rotary engines, like turbines, are much better and that is how modern electric motors are made.

 

[Baluncore]

Why don't cars use something like a rail gun instead of combustion to drive pistons?

The inverse is actually more useful, where the motor becomes a linear generator.

There are engine designs that mount ring magnets on the piston, with 3PH windings around a ceramic cylinder. When that IC engine runs, it generates AC, which is rectified to DC, for battery charging, and to power electric drive motors.

The crankshaft and connecting rods can then be eliminated and the free-piston thrown back and forth between cylinder heads at both ends. To start the free-piston engine, the 3PH coils are powered like a linear motor, to throw the piston through a compression stroke. The engine can be built as 2 or 4 stroke, with spark or compression ignition.

The free-piston configuration has also been used as an air compressor, and evaluated as a gassifier to drive a turbine.
https://en.wikipedia.org/wiki/Free-piston_engine
For examples, google: free piston linear generator

 

[Vanadium 50]

The title was truncated on the front page, and I ws thinking "instead of horns? Harsh - but I like it. You'll see much more polite driving, for sure."

As @russ_watters points out, this is an electric motor. Electric motors are already close to fully efficient. The limiting factor is energy storage, not engine efficiency.

 

[Rive]

Why don't cars use something like a rail gun instead of combustion to drive pistons?

Well. Not much can be said what was not mentioned before: cars needs energy, and when you have the kind of energy needed for any railgun-like thing, there are better solutions.

In the same time, 'railgun-like' ideas for pistons actually do work and have their own niche