06-07-2015, 05:33 AM
It's the shock load that works on bridges - the jarring, bouncing ect which is a direct result of the suspension ( or lack of ). Same effect when the 150 lb teenager "plops" down on the step of the coach - the step is feeling more the effect of 300lbs.
marc & shari popejoy
western Oklahoma
1987 Newell #135