Weight Drop Theory

The Accelerated weight drops have been successfully used over the years in many areas and applications that preclude the use Vibroseis or dynamite for exploration. Most AWD systems are smaller, less environmentally abusive, and operate at a higher efficiency than other sources, with excellent data quality.

AWD systems rely on a means of accelerating a mass at a much greater rate than that due to gravity, in order to increase energy output while keeping overall height, and therefore cycle time, to a minimum. United Service Alliance is pleased to hold the patent for the use of nitrogen springs to accelerate our AWD’s. Nitrogen is an inert gas, easily controlled, adjusted, and recorded that is used to tailor the energy output based on vehicular and environmental conditions. As the hammer is raised to the ‘fire’ (cocked) position through the stroking of hydraulic cylinders, nitrogen spring(s) are compressed above the hammer, increasing ‘cocked’ force. When triggered to fire (released by latches, brakes, or an autofire), the gas inside the nitrogen spring expands, causing the piston and rod to accelerate, thereby accelerating the hammer, until the hammer strikes the baseplate, transferring the kinetic energy into the baseplate and ground…

Over the years, several manufacturers (including us!) have struggled in attempts to quantify accelerated-weight drop performance. Many attempts have been made to quantify output, with mixed results (and units) with very few that are repeatable, predictable, and comparable. Peak force is an instantaneous expression given over a very short period of time, achieved ‘normally’ through the use of accelerometers mounted on the hammer and/or baseplate. While this approach can be accurate, and provides data for true output, it does so in that state, condition, and shot –only-. After the first impact, soil dynamics have changed (affecting spring rate), and the imparted compaction changes the flight time. From a mechanical system stand-point, hammer release mechanism conditions, wear on flights and guides, friction, hammer and striker deformation, and fluctuations in accelerating media pressures all affect the final output of the system; none of which are easy to quantify and predict…

After reviewing both internal and external data, we have decided the most effective, understandable, quantifiable means of describing/defining our hammers is to rate them in terms potential energy, based on the acceleration of the mass over a given distance. Hammer acceleration is calculated by applying the average external force applied by the accelerants divided by the known hammer weight; with a known flight distance, flight time is then calculated. The velocity at impact is then calculated, and potential energy is a result of mass times the velocity squared…

So, the system is now defined by irrefutable physic principals…

F = ma (a = F / m)

S = ½ (at^2) (t = sqrt (2 * S) / a)

KE = ½ (mv^2)

This simple analysis allows the end user to review and compare competitor’s products on like terms, without the obfuscation of system and conditional issues…

Predictions, assumptions, theory, and speculation...

U.S. and International Patents granted.

United Service Alliance is dedicated to obtaining true, accurate, and predictable output (both energy and spectrum), and is currently working with well-known leaders in the industry to assist us in achieving our objectives. USAI has in the works plans to build a dedicated test site with soil pressure gauges and proper instrumentation in hopes of correlating theory with empirical data...