Trailer ramps

[Frank S]

No the ramp s were tested at full length the blocks placed with in the span were there to serve as crush safeties in the event the weight of the SD F250 had proved to be more than they could handle within the amount of deflection I was willing to accept.
6061T1 extruded aluminum has an amazing spring back memory as long as it is not stressed beyond its yield point. The planking manufacture has a chart graph that shows they allow up to 1.75" deflection in 8 feet with a concentrated load of 653LBs per 12" width, this would mean without our side rails only 1306 lbs could be supported on a 96" span, their chart stops at 96" span where as we have 120" span. The side rails I designed for our project are an upside down TFJ design. We own the dies and I have the only 2500 feet of this railing in existence. I had it calculated that the railing if properly fixed to prevent it from rolling over that it could support 1000lbs in 6 feet with only 0.5" deflection with a maximum allowable deflection in 6 feet to be 1 inch or 0.166" deflection per foot length. since the ramps are 120" long with 4 rails and 2 ft width of planking and we needed to be able to have a 3600 lb load at center point and knowing that 2" would be the maximum allowed deflection on the planking and our rails this was the reasons for placing the safety blocks under the ramps there to insure the deflection could not exceed the design parameters I am more than satisfied with a 1" total deflection this means our ramps should be capable of an additional 50% load without the need for safety blocks placed under them to shorten the span