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    Compound Gear Train

    Uploaded by

    Almaas Khan
    This document discusses a compound gear train. A compound gear train has two or more pairs of gears that are meshed together so they rotate together. This compound gear train has gears on three shafts, with the input gear meshing with a larger gear on the counter-shaft, which then meshes with a smaller gear on the output shaft. The motion and rotation direction are transferred through each pair of gears, resulting in an overall reduced ratio and increased torque between the input and output.

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    Compound Gear Train

    Uploaded by

    Almaas Khan
    808 views3 pages
    This document discusses a compound gear train. A compound gear train has two or more pairs of gears that are meshed together so they rotate together. This compound gear train has gears on three shafts, with the input gear meshing with a larger gear on the counter-shaft, which then meshes with a smaller gear on the output shaft. The motion and rotation direction are transferred through each pair of gears, resulting in an overall reduced ratio and increased torque between the input and output.

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    This document discusses a compound gear train. A compound gear train has two or more pairs of gears that are meshed together so they rotate together. This compound gear train has gears on three shafts, with the input gear meshing with a larger gear on the counter-shaft, which then meshes with a smaller gear on the output shaft. The motion and rotation direction are transferred through each pair of gears, resulting in an overall reduced ratio and increased torque between the input and output.

    Copyright:

    Attribution Non-Commercial (BY-NC)
    Download as DOC, PDF, TXT or read online from Scribd
    Download as doc, pdf, or txt
    808 views3 pages

    Compound Gear Train

    Uploaded by

    Almaas Khan
    This document discusses a compound gear train. A compound gear train has two or more pairs of gears that are meshed together so they rotate together. This compound gear train has gears on three shafts, with the input gear meshing with a larger gear on the counter-shaft, which then meshes with a smaller gear on the output shaft. The motion and rotation direction are transferred through each pair of gears, resulting in an overall reduced ratio and increased torque between the input and output.

    Copyright:

    Attribution Non-Commercial (BY-NC)
    Download as DOC, PDF, TXT or read online from Scribd
    Download as doc, pdf, or txt
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    Below is a question regarding 'compound gears'.

    Gears C and B represent a compound


    gear as they appear 'fixed' together. When drawn with a compass they have the same
    centre. Two gears 'fixed' together in this way rotate together and at the same RPM. When
    answering a question like this split it into two parts. Treat gears A and B as one question
    AND C and D as the second part.

    This is an example of a “compound gear train”. Gear A rotates in a clockwise direction at


    30 revs/min. What is the output in revs/min at D and what is the direction of rotation ?

    GEAR A GEAR B GEAR C GEAR D

    120 T 40 T 80 T 20 T

    First find revs/min at B;

    B is smaller therefore it rotates faster and revs/min increase.

    C is fixed to B and therefore, rotates at the same speed.

    90 REVS/MIN at C

    Next find revs/min at D


    D is smaller than C, therefore rotates faster (increased revs/min).

    A revolves in a clockwise direction, B is therefore anti-clockwise, C is fixed to B and is


    also anti-clockwise, which means D revolves in a clockwise direction.

    Summary
    Compound gear trains have two or more pairs of gears in mesh, so that they rotate
    together.

    Compound gear trains have two or more pairs of gears in mesh, so that they rotate
    together.

    This compound gear train has gears on three shafts.

    The gear on the input shaft meshes with a larger gear on a counter-shaft or cluster gear.
    The counter-shaft has a smaller gear formed on it, in mesh with the output shaft gear.

    The motion of the input is transferred through the large gear, along the counter-shaft to
    the smaller gear, to the output.

    The output turns in the same direction as the input, but at a reduced ratio, depending on
    the relative sizes of the gears.

    Since two pairs of gears are involved, their ratios are “compounded”, or multiplied
    together.
    The input gear, with 12 teeth, drives its mating gear on the counter-shaft, which has 24
    teeth. This is a ratio of 2 to 1.

    This ratio of DRIVEN over DRIVER at the Input - 2 to 1 - is then multiplied by the
    Output ratio, which has a DRIVEN to DRIVER ratio of 3 to 1.

    This gives a gear ratio of 6 to 1 between the input and the output, resulting in a speed
    reduction and a corresponding increase in torque.

    Gear reductions in the lower gears of manual transmissions can be provided by


    compound gear trains. Typical ratios are, 1st gear - 4.41 to 1 2nd gear - 2.63 to 1, and 3rd
    gear - 1.61 to 1.

    Fourth gear is normally a ratio of 1 to 1. The input and output shafts turn at the same
    speed. There is no torque multiplication. A fifth gear is normally an overdrive ratio,
    typically with a value of .87 to 1.

    Then the output shaft turns faster than the input, but the output torque is reduced.

    A further reduction is always provided by the final drive gears. Their ratio is included
    when calculating overall gear reduction.

    The overall gear ratio is the gearbox ratio multiplied by the final drive ratio.

    A gearbox ratio of 3 to 1 with a final drive ratio of 4 to 1, gives an overall ratio of 12 to 1.

    12 revolutions of the crankshaft result in 1 turn of the driving road wheels. Assuming
    100% efficiency, the torque applied is 12 times the engine torque, although this is divided
    equally between the driving wheels

    Compound Gear Train - For large velocities, compound arrangement is preferred. Two
    keys are keyed to a single shaft. A double reduction train can be arranged to have its
    input and output shafts in a line, by choosing equal center distance for gears and pinions.

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