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Could a mainspring be used to generate train acceleration during starting-up from the kinetic energy stored during its slowing down?

I found that on some Spanish lines, the kinetic energy during braking is converted to electricity and used by other trains from the same line (research paper), but why not keeping the mechanical ...
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Could a mainspring be used to generate train acceleration during starting-up from the kinetic energy stored during its slowing down?

On the London Underground, many stations use gravity. The line runs uphill into the station, and then departs downhill. This gives a large amount of energy storage, for free, with no additional moving ...
• 406
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Why aren't counterweights used more for garage doors?

It makes me wonder why some sort of counterweight system isn't used instead. I'd guess it's because residential garages are normally a bit limited on space and the counterweights need somewhere to go....
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Can I weaken a coil spring consisting of spring steel?

You could try a bath of concentrated acid. As long as you could maintain circulation so the concentration was fairly constant, a spring presents a very uniform cross-section and should be dissolved at ...

Could a mainspring be used to generate train acceleration during starting-up from the kinetic energy stored during its slowing down?

Note also that springs are subject to eventual (and very sudden) failure as they develop cracks with age and a very sudden 5.6MJ energy release inside a railroad car would be exceptionally dangerous!
• 12.4k

Metal spring thermal expansion

Assuming the spring is not fully compressed/bottomed out, it doesn't really matter if the spring material is expanding or not because it's a spring - it will deform to fill the space between the coils....
• 3,535
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• 7,707

Can I weaken a coil spring consisting of spring steel?

By "strength" do you mean stiffness/modulus? The modulus does not change with tensile or yield strengths. Make it with wire of 1/2 the diameter for 1/2 the modulus. Acid will hydrogen stress crack ...
• 5,932
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What is the purpose of dead coils in the middle of a compression spring?

The dead coils on the ends of the spring furnish an (almost) flat surface, perpendicular to the spring axis, for the spring to engage the mating parts with. The dead coils in the middle effectively ...
• 12.4k