Crankshaft Balancing, I got a problem with Step 4?

[Toadmund]

Step 4- Measure the weight of the bottom end of the crank shaft and bottom end wrist pin bearing. To do this you’ll have to break open the halves of the crankshaft to have access to the lower wrist pin bearing and bigger end of the crankshaft. If you do not have the tools to this this, the value is usually around 47.5g +- 1 gram.

Why would he ADD the weight of this if he is already statically balancing his crankshaft with this con-rod and bearing still ON his crankshaft?

Would this not be additional weight that should not be there?

Just trying to understand this crankshaft balancing thing as I believe bad vibrations may have contributed to killing my last large end con-rod bearing and as a consequence my piston and cylinder.

 

[Arnold Layne]

You need to factor in the weight of the bottom half of the connecting rod with the top half of the rod so you know how much weight to add, or subtract if you wish, from the flywheels to get them to balance in the rpm range you choose. The bottom half of the rod probably affects the balance of the rotating assembly where as the top half of the rod and the piston assembly has more effect on the reciprocating balance issues. That's why the top end is calculated with a balancing factor and the weight of the bottom is just added to that number. That's my basic WAG anyway.

 

[Toadmund]

OK, I was thinking ballast added after removing stuff, not total numbers needed for calculations.
Just trying to wrap this around my head and sometimes I am lacking the wrapping.