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Contra-rotating, also referred to as coaxial contra-rotating, is a technique whereby parts of a mechanism rotate in opposite directions about a common axis, usually to minimise the effect of torque. Examples include some aircraft propellers, resulting in the maximum power of a single piston or turboprop engine to drive two propellers in opposite rotation. Contra-rotating propellers are also common in some marine transmission systems, in particular for large speed boats with planing hulls. Two propellers are arranged one behind the other, and power is transferred from the engine via planetary gear transmission. The configuration can also be used in helicopter designs termed coaxial rotors, where similar issues and principles of torque apply.

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  • Contra-rotating
  • Motrotation
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  • Contra-rotating, also referred to as coaxial contra-rotating, is a technique whereby parts of a mechanism rotate in opposite directions about a common axis, usually to minimise the effect of torque. Examples include some aircraft propellers, resulting in the maximum power of a single piston or turboprop engine to drive two propellers in opposite rotation. Contra-rotating propellers are also common in some marine transmission systems, in particular for large speed boats with planing hulls. Two propellers are arranged one behind the other, and power is transferred from the engine via planetary gear transmission. The configuration can also be used in helicopter designs termed coaxial rotors, where similar issues and principles of torque apply.
  • Motrotation innebär att två objekt roterar i motsatt riktning kring samma axel. Principen används bland annat för propellrar på vissa flygplan, båtar och torpeder. Principen har följande fördelar: * Det vridmoment som behöver tas upp av propellerns infästning blir mycket litet * Verkningsgraden blir bättre då rörelseenergin i massflödet som "följer med" den första propellern länkas om och omvandlas till "nyttig" propulsion i den andra propellern * Den överförbara effekten för en given propellerdiameter ökar
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  • Contra-rotating, also referred to as coaxial contra-rotating, is a technique whereby parts of a mechanism rotate in opposite directions about a common axis, usually to minimise the effect of torque. Examples include some aircraft propellers, resulting in the maximum power of a single piston or turboprop engine to drive two propellers in opposite rotation. Contra-rotating propellers are also common in some marine transmission systems, in particular for large speed boats with planing hulls. Two propellers are arranged one behind the other, and power is transferred from the engine via planetary gear transmission. The configuration can also be used in helicopter designs termed coaxial rotors, where similar issues and principles of torque apply. Contra-rotating propellers should not be confused with counter-rotating propellers, a term which describes non-coaxial propellers on separate shafts; one turning clockwise and the other counter-clockwise. Tandem-rotor helicopters such as the CH-47 Chinook also use a counter-rotating arrangement. The efficiency of a contra-rotating prop is somewhat offset by its mechanical complexity. Nonetheless, coaxial contra-rotating propellers and rotors are moderately common in military aircraft and naval applications, such as torpedoes, where the added maintenance cost is not a primary concern.
  • Motrotation innebär att två objekt roterar i motsatt riktning kring samma axel. Principen används bland annat för propellrar på vissa flygplan, båtar och torpeder. Principen har följande fördelar: * Det vridmoment som behöver tas upp av propellerns infästning blir mycket litet * Verkningsgraden blir bättre då rörelseenergin i massflödet som "följer med" den första propellern länkas om och omvandlas till "nyttig" propulsion i den andra propellern * Den överförbara effekten för en given propellerdiameter ökar Till nackdelarna hör en mer komplicerad konstruktion med en växellåda som förmedlar vridmomentet för två olika rotationsriktningar, samt att vinster i hydrodynamisk verkningsgrad kan förloras i mekaniska förluster i transmissionen. Principen är vanlig i torpeder, där motroterande propellrar ger största möjliga hastighet med en begränsad propellerdiameter, och minskar behovet av att stabilisera torpeden mot rotation kring sin egen axel. Samma fördel kan uppnås för helikoptrar, där behovet av horisontell stabilisering minskar. Denna teknikrelaterade artikel saknar väsentlig information. Du kan hjälpa till genom att tillföra sådan.
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