Although our original ground anchor was very popular, we found that we could further increase the resistance by adding a second plate to the anchor to lock all three spikes in position, thus preventing any of the spikes from working loose independently. The result is a substantial increase in pull-out resistance.
Tested in a mature lawn with loamy soil and partial sunlight, the Model II anchor showed resistance values of 700 lb in a vertical pull, 1500 lb in a 45° pull, and 2,000 lb for a pull parallel to the ground. The anchor has greatest pull-out resistance in hard packed soil but is most commonly used in mature lawns like the one we used for testing.
The anchor can be used in loosely-tilled soil or in sandy soil that has minimal grass root structure but both will have reduced pull-out resistance for obvious reasons. The level of ground moisture can also alter pull-out forces. For example, if the soil is oversaturated due to spring run-off or heavy rainfall, it will lower the pull-out resistance but if the soil is dry and hard-baked by a hot summer sun, it will raise the resistance.
All components of the anchor are made of galvanized steel.