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Old Jun 5th 2018, 09:35 AM   #1
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Question identification of symbol

Here is the formula in the screenshot figuring piston assembly inertia.

piston assembly inertia = Reciprocating Mass * CRANK RADIUS * W^2*(COS(Wt)+(crank radius/rod length)*COS(2*Wt))

W=angular frequency (crank rotations in 1 second times 6.28)
Wt=unknown
CRANK RADIUS=piston stroke/2

Please identify the Wt (omega t) symbol. thanks

Here's the screenshot:
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Old Jun 6th 2018, 04:43 PM   #2
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If omega refers to an angle then omega t refers to an amount the angle has been through in time t. Suppose omega is the angle a crankshaft has turned during time t. Then angle = omega t
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Old Jun 8th 2018, 09:58 AM   #3
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It seems that they are using the upper case Greek letter omega ( $\Omega$ ) for angular velocity, which is measured in radians/second. Multiplying by time (t) gives the angle of the crank at time t.

The use of the upper case omega is a little unusual, but not unheard of; the lower case version of omega ($\omega$) is more commonly used for angular velocity.
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Old Jun 8th 2018, 01:26 PM   #4
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Originally Posted by ChipB View Post
It seems that they are using the upper case Greek letter omega ( $\Omega$ ) for angular velocity, which is measured in radians/second. Multiplying by time (t) gives the angle of the crank at time t.

The use of the upper case omega is a little unusual, but not unheard of; the lower case version of omega ($\omega$) is more commonly used for angular velocity.
Thanks. I neglected to distinguish between the two omegas.
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