Balancing connecting rods, different readings

[RMS Boxer Service]

I have a very good digital scale and a solid stand to do the work but I get different readings every time i weight the same rod.

I have tried hanging the rod in 30cm long chains (ball chain that can't twist), no good
I have tried to hang the rod on a fixed piston pin, no good
I have tried to hang the rod on a foating rod with bushing on the top, made just like he one pro shops sells. No good

I need first hand experince, please help. How do you do it and how much do the readings differ from time to time
with the same rod??  I know I might have a too good scale, 0.01 gram increasment, but the readings differ from 0,5 to 10 grams.

The rod in in level and not moving in directions.



Rod balance fixture from a store:

[dangerous]

I always used the chain type.
The secret is to make sure the end that you are weighing,
rests down squarely on the support
on the scale.

The one we got from Sunnen as a part of the balance machine package,
had a small bearing in both ends,
but not a tight fit.

The bearings had probably a 16mm or less outside diameter,
and the support for the crank pin end, had a weight that kept the bearing centered in the rod bore curve.

I used to watch the scale, while repeatedly placing the rod onto the bearings at both ends,
until I got a consistent repeated trend.

You reject the weight measurements that were way out side the trend.

I always tried to get the weights within about 0.1grams,
but the ACTUAL weight of the 'big end' was probabbly only within 0.5 of a gram.

Once I was happy/close,
I would correct the total weights using the 'total weight', and removing the weight from the 'small end'.

Then go back to do the 'big end' again.

Removing weight from one end, most times effects both ends on the scale,
so some 'back and forth' may be needed.