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This FEA analysis simulates a 600lb load on the hitch ball (150lb tongue load with 4X safety factor). As you can see, the stresses are carried from the ball mount through the hitch assembly and into the mounting bolts and frame rails consistently, with the only real stress risers occurring at the high strength mounting bolts. This amount of stress should be well above the dynamic amount seen in normal use, even at the maximum load capacity of 150lb tongue weight and 1500lb trailer weight. The visual distortion of the assembly is greatly exaggerated to show HOW the assembly displaces, and the actual distortion amounts are better quantified later in this report.

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This FEA analysis is similar to the 4X safety factor shown above, except this time the force is multiplied 8X, for a simulated vertical load of 1200lb on the tongue. The increase in stress is apparent throughout the assembly, but the amount of stress is still not indicative of part failure, since the material surrounding the mounting bolts is still not stressed to its failure point.

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Here is a similar, but different, analysis simulating a 1000lb vertical load on the tongue again, but this time the linear displacement of the assembly is quantified. The 1000 lb load means the 150lb tongue weight rating has been grossly ignored in this case. The largest displacement occurs at the ball mount itself, and that amount is even less than the thickness of the ball mount material itself (3/8"). The displacement of the rest of the assembly is barely noticeable, though the Miata's suspension and chassis is surely begging for mercy in this example!!!

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This page shows the same 1000lb vertical load on the tongue again, but this time the material stresses are quantified. As can be seen, the assembly is barely being tested at this point, even with a gross disregard for the 150lb tongue weight limit.

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This is a fun analysis. This particular report simulates a 2500 lb load in a rearward direction. In other words, this model shows what would happen if you actually decided to hang your Miata from this hitch! Again, the graphical distortion is greatly exaggerated, and the actual displacement figures can be seen at the right of the page. If you look at the green area in the center of the main hitch body, it is only being displaced by 1/8", and the largest displacement figure is less than 1/4"!!! This test is by no means recommended, but it should further speak to the robustness of the design.