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  1. #1
    la vache fantôme phantomcow2's Avatar
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    explain mechanical efficiency?

    I have an understanding i think of what mechanical efficiency is, but it is not concrete.
    FOr example I read on McMaster Carr how an Acme screw has a mechanical efficnecy of roughly 30%, versus a ballscrew with up to 90%.
    Does this mean that with an ACME screw, 70 percent of the loads produced by the source (be it a motor, a human turning a handle, a water wheel or anything else) are used in moving the screw and nut? ANd 30% reaches the final outcome?
    And with a ballscrew 90% of the energy reaches the final outcome? Thanks
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  2. #2
    That darn Yankee TexasGuy's Avatar
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    stop giving me nightmares

  3. #3
    That darn Yankee TexasGuy's Avatar
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    That's a pretty accurate description. I like the explanation here
    http://www.encyclopedia.com/html/sec...ofMachines.asp

  4. #4
    My Alphabit's say "Oooo" InfamousG's Avatar
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  5. #5
    Feral Member Nicodemus's Avatar
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    Off the top of my head, that's pretty much it. To me, it's the percentage of energy output from a system relative to the input.

  6. #6
    Senior Member
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    Quote Originally Posted by Nicodemus
    Off the top of my head, that's pretty much it. To me, it's the percentage of energy output from a system relative to the input.
    Yeah, pretty much. For example, a modern internal combustion engine, like that in a car, is about 30% efficient, ie. roughly 30% of the energy (btu's) in the fuel burned actually gets converted to horsepower at the rear wheels. The rest goes out the tailpipe and cooling system as waste heat.

  7. #7
    Senior Member DannoXYZ's Avatar
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    I think it's less than that...

  8. #8
    Footballus vita est iamlucky13's Avatar
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    Right on phantomcow. Those losses in the ACME screw are due to friction, and you'll see that manifested as heat if you use it in a high speed, continuous application.

    mtnroads is correct, the efficiency of an internal combustion engine is around 30%. This actually the thermal efficiency, however, which tells you how much of the theoretical energy contained in the gasoline is available as power at the crankshaft. There is a little bit more loss from the transmission, deformation of the tires, etc, but the total mechanical efficiency, I believe is over 90%.
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