## "BALANCE SHAFT CALCULATION"

## "BALANCE SHAFT CALCULATION"

(OP)

Could anybody please help?

I am using the Bosh Automotive Hand book to calculate the necessary mass for a 4 cylinder engine.

I calculated the Oscillating mass, using the sum of the piston mass and 1/3of the Conecting rod mass.

I calculated the Rotating mass using the crank mass plus 2/3 of the connecting rod mass,

then as the book says I calculate the 2nd order free forces of inertia as being

4*mo*r*w^2*lambda*cos(2alpha)

What now?

I need 2 balance shafts rotating opposite directions at double the crank speed.

But what is the excentric mass ?

I am using the Bosh Automotive Hand book to calculate the necessary mass for a 4 cylinder engine.

I calculated the Oscillating mass, using the sum of the piston mass and 1/3of the Conecting rod mass.

I calculated the Rotating mass using the crank mass plus 2/3 of the connecting rod mass,

then as the book says I calculate the 2nd order free forces of inertia as being

4*mo*r*w^2*lambda*cos(2alpha)

What now?

I need 2 balance shafts rotating opposite directions at double the crank speed.

But what is the excentric mass ?

## RE: "BALANCE SHAFT CALCULATION"

http://autozine.kyul.net/technical_school/engine/smooth2.htm

It might be of some help

## RE: "BALANCE SHAFT CALCULATION"

Their centrifugal forces should counterbalance the maximum 2nd order free forces (in Top and Bottom DCs) you have already calculated.

Centrifugal force of rotating excentric mass is: Fc = m*r*w^2

where:

m is amount of excentric mass (the both masses in this case)

r is distance between axis of rotation (balance shaft axis) and CG of excentric mass

w is angular speed of balance shafts

In your case variables (unknown) are m and r so you may play with those quantities (having in mind limiting factors, space for sure) to equalize the Fc with the max 2nd order free force.