The lengths of the links comply with the conditions: D͞C=C͞D₁=D͞₁C₁=C͞₁D and A͞C=A͞₁C͞₁. Cranks AC and A₁Cy are rigidly secured to two meshing gears, 1 and 2, of equal size. Gears 1 and 2 carry two equal counterweights B and B₁ which counterbalance inertia forces of the first order that are developed in the mot ion of the mechanism.
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