by **Steve Smith** » Fri Sep 01, 2017 11:30 am

Hello and thank you for the posts, sorry again for a late reply.

This has rolled around my head for a while as there must be a correlation between mg and the amount of imbalance weight applied.

This is the exact process the Propshaft Balancing software uses to determine the amount and position of weight to be applied to a shaft in order to reduce the vibration level (measured in mg)

Just going back to your posts Mark, 1 mg = 0.0098 m/s2 and the Gal unit is used to measure the amplitude of vibration. Both these statements are correct (1 Gal = 0.01 m/s2)

Using the NVH software we choose the mg unit to denote the amplitude level but you can alter this by selecting Option > Advanced Options > Accelerometer Units where you can switch between mg, m/s2 and dBg

Coming back to the original question re the correlation between mg and weight:

The Prop-shaft Balancing software initially measures the level of vibration in mg (Initial Run)

We are then asked to apply weight a 3 strategic point about the circumference of the shaft (Test Runs)

Here we introduce a deliberate 3 point imbalance allowing the software to calculate the relative position and mass of our correcting weight in order to reduce the vibration level.

We then confirm the reduced vibration during the Verification Run where we aim for less than 20.0 g.cm

What I am getting at here is we are using mg (vibration level) as one of the essential units in the formula to determine the weight (grams) to minimise vibration

Within this formula we also require the Propshaft Speed and Circumference as both these fundamentals will have a dramatic effect on vibration.

I will dig a little deeper here Mark and look at the formula to see how mg and weight correlate.

Whilst I was looking into the above Wikipedia has a great description of Rotating Unbalance which helps to visualize why we experience vibration.

Rotating unbalance is the uneven distribution of mass around an axis of rotation. A rotating mass, or rotor, is said to be out of balance when its center of mass (inertia axis) is out of alignment with the center of rotation (geometric axis). Unbalance causes a moment which gives the rotor a wobbling movement characteristic of vibration of rotating structures.

I hope this helps, take care.......Steve