Engine CG
Calculating weight and balance requires two formulas....
W X A = M. Weight times Arm equals Moment. And....
Mt / Wt = CG. total Moment divided by total Weight equals Center of Gravity.
The weight part is easy.. we use a scale. For this exercise we're using pounds (lbs).
Arm is the distance the weight is measured at from the Datum..... or zero reference line. We're using inches (").
The resulting moment is a measure of applied force.
For instance, if you torque a bolt to 50in. lbs, you're applying a force equivalent to 1pound of weight at a distance of fifty inches. Wielding a 50in. long wrench seems a little silly, so we can use our formula to build a smaller wrench. My in.lb. wrench is about 8.5" from the center of the handle to the center of the socket. So, if we divide 50 (the applied force we want) by 8.5, we get 5.88. That means that applying 5.88lbs. of force at a distance of 8.5" from our bolt, we get an equivalent applied force (or moment) of... wait for it... 50in.lbs.
Got that? Good... so... moving right along, we set our engine on weight scales at two different points using wood shims to keep it perfectly level.....
The engine stand front cross tube is a convenient place... so we set that on the scale at exactly 12" from the end of the bench and use wood on the back cross tube to level the engine. Our weight here is 82.4lbs. So, 82.4lbs at 12" (W X A=M) gives us a moment of 899.9 .
Now we move the scales to the back tube and level the front....
Here we have a weight of 39.2lbs and our tube is 25.5" from our datum or zero reference line. Gives us a moment of 999.6
We add our two moments for a Mt (total moment) of 1988.5 Both our weights total 121.6lbs (Wt)
1988.5 divided by 121.6 gives us a CG of 16.35"...... So, we now know with mathematical certainty that our engine as it's currently configured (unfinished) will balance horizontally at 16.35" from the end of the bench...
As you can see, if I suspend the engine from the aft upper mount hole, it will stay exactly as it sits.
So... you're probably askin' yourself....
"what's this dipstick up to....?" Stay tuned.