Vibratory Plate Amplitude Calculator

Equipment specifications should provide useful information to interested parties. Unfortunately, vibratory plate specifications not only fail in this regard, but mislead those who use the information. Operating Weight is regularly mistaken for Vibratory Mass. Centrifugal Force (CF) is of no practical use as stand alone data and is routinely mistaken for “compaction force”, which CF does not represent. Frequency is usually provided, but like CF lacks context as stand alone data. The problem is complicated by the fact that even when data is available, Frequency, Vibratory Mass and CF must be arithmetically linked to provide useful information. To that end, MBW has long recommended adoption of Vibratory Mass and Theoretical Amplitude (Amplitude) specifications. Vibratory Mass can be thought of as the portion of a vibratory plate’s Operating Weight set in motion to perform compaction work. Amplitude describes the arc or distance through which Vibratory Mass moves during the compaction process. The AMPLITUDE CALCULATOR arithmetically links Vibratory Mass, CF, and Frequency resulting in an Amplitude calculation useful for comparative and/or fitness-for-use analyses.

To use the AMPLITUDE CALCULATOR, enter the CF, Frequency and Operating Weight of any vibratory plate. This information is usually found on manufacturers’ literature or websites. The AMPLITUDE CALCULATOR will apply CF and Frequency values as entered. However, the AMPLITUDE CALCULATOR will automatically adjust Operating Weight to 65% of the entered value to approximate Vibratory Mass. Because the method of approximating Vibratory Mass is applied equally to all plates, the approach demonstrates no particular bias and resulting Amplitude is of relative value for comparative and/or fitness-for-use analyses.

Single Directional Plate Amplitude

Single direction plate Amplitude is higher at the leading edge of the plate, lower at the trailing edge. The AMPLITUDE CALCULATOR provides the average Amplitude.

Reversible Plates

To determine amplitude for a reversible plate, first enter the published CF, Frequency and Operating Weight into the AMPLITUDE CALCULATOR. The result is Amplitude at zero travel or in the “spot compaction” mode. To calculate Amplitude at full travel, enter 70% of published CF. The two results provide an Amplitude range that varies substantially from zero to full travel.

Amplitude Calculator

Footnote: AMPLITUDE CALCULATOR results may differ from Amplitude data provided by some manufacturers. While the Amplitude formula is the same for all parties, some manufacturers factor total Operating Weight into their calculations. Total Operating Weight overstates Vibratory Mass resulting in understated Amplitude. Nevertheless, applied consistently, either approach will provide data of relative value. The AMPLITUDE CALCULATOR, which adjusts Operating Weight to approximate Vibratory Mass, provides a more realistic quantitative representation of Amplitude.

For the amplitude formula and related information, interested parties can read "Beware of Compaction Specifications"