AF-450
This unit is mounted on an IC-45-2rubber tracked crawler. The machine weighs approximately 18,000 lbs but due to its wide tracks it has an extremely low ground pressure of 4 PSI. This is less than a person on foot and much less than wheeled source units. A normal car has a ground pressure of around 30 PSI so you can see how this machine can traverse soft terrain without rutting it up or getting stuck. No-till farmers also love it because it does not cause near the ground compaction of a wheeled vehicle. The AF-450 utilizes a 450 lb. hammer accelerated by compressed nitrogen. The AF-450 is appropriate for targets 12,000' or less. The auto fire mechanism is very simplistic and requires only two hydraulic cylinders to operate. It also has a faster cycle time than a latching source like the XLR8 which increases production rates.
Over time the trend in accelerated weight drop sources has shifted from heavy hammers accelerated slowly to lighter hammers accelerated rapidly. The potential energy of a weight drop source is a result of the mass times the velocity squared. Since the velocity is squared a lighter hammer moving faster can easily output more energy than a larger slower hammer. Our AF-450 surpasses the XLR8 source unit in terms of energy output even though the hammer is roughly 1/3 the weight.
Our AF-450 is equipped with Seismic Source electronics which combined with SourceLink software enables us to record autonomously. A highly accurate GPS unit is mounted on the source and captures the precise time and location of each thump. At the end of the day this information is downloaded from the unit and correlated with the positional surveying information virtually eliminating the possibility of human error in notating the source event on a different station than it occurred at.
XLR8
The XLR8 "Accelerate" is an accelerated weight drop energy source that is mounted on an International 4800 4X4 truck. This unit is reliable, efficient, and can go many places where Vibroseis and Dynamite can not be used. The 1450 lb. hammer is accelerated by compressed nitrogen. The XLR8 is appropriate for targets 12,000' or less. Our XLR8 unit has been resting in the stable since we purchased the AF-450. It is a good unit and we have thumped hundreds of thousands of times with it over the years but the tracked AF-450 offers many advantages over the truck mounted unit so the XLR8 does not get much use anymore.