: Tom, I dont understand. If you set up the scale, with the platforms and cups
: in place, at the total mix postitions, and zero it, and then you move the
: weight side in by the proper ratio, doesnt the mass balance itself out?

: A higher mass of the arm would add to it's inertia, making it tend to
: accelerate slower and take longer to come to rest, but it shouldnt throw
: the accuracy off. Or am I missing something?

I thought I was following all this up to now. What Paul was describing were two different ways to obtain an indication of near balance to prevent adding too much of the second part of the mix. (BTW, this is only needed when the balance point of the arm is placed too close to the vertical center of gravity to move before reaching balance. Ideally it will be above the C.G.) In the first case, a small weight is placed on the side of the balance where you are pouring. This is REMOVED after the balance trips, and you slowly add more to reach the final balance. The second method is to use a spring, which is weak enough to compress from the disbalanced load, but strong enough to uncompress when near balance, to show some movement. The spring would not be under any load at final balance. His other two references were to digital scales and to a plumb bob type postal scales.

I hope this helps.

Al