Cylinder’s Area Ratio


  • Understanding the Cylinder Area Ratio

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By the definition, the “Cylinder Area Ratio” is the relation between the complete area of the bore and the same area minus the area of the rod:

\[ CR = \frac{A_b}{A_b – A_r} \]


For the ratio there is important a diameter of the rod (but not rod side annular area!) because when you choose the cylinders for your project in hydraulic catalogs you pick out them using Piston and Rod diameters.

This is why the area ratio CR is always >1.

Sometimes, you can meet records like:

\[ \frac{A_b}{A_b – A_r} : 1 \]

For example, for cylinder 4″ bore diameter and 2.5″ rod diameter, the ratio is:

\[ CR=\frac{A_b}{A_b-A_r}=\frac{\pi\frac{D^2_b}{4}}{\pi\frac{D^2_b}{4}-\pi\frac{D^2_r}{4}}=\frac{D^2_b}{D^2_b-D^2_r}=\frac{4^2}{4^2-2.5^2}=1.64 \]

So, \(CR=1.64\) or \(1.64:1\)

1 Comment

  1. Snr Jhay

    I saw someone that the area ratio is = area of the rod itself / bore area. So for the problem I saw, the aspect ratio was given as 0.2. Can you please help me understand that?


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