Campin LI wrote:
Thank you for taking the time to put this utility together. As long as the person reading through it can understand the math, it is a great way to learn what the weights are and what the effect of the weight has on the setup.
The only thing I would add is that it should be used as a learning tool, not as a tool to analyse a setup once to see if you are within limits. If you are concerned about limits, generally it means you are close to them. The reality is, every camping trip, the trailer is loaded differently based on location, duration and number of people. It is also loaded differently on the way to your destination vs the way home. Over the years, you accumulate more things in the trailer and it becomes heavier. Depending on the length of the trip, more or less items will be in the truck, the list goes on. As an example, my V10 Excursion has a 44 gallon fuel tank located behind the rear axle. Dependent on how much gas is in the tank, the dynamics change during the trip.
Usually when engineers design things or analyze them to this degree, there is a 33 1/3% factor of safety involved. That factor of safety usually covers things like uneven load, shifting weights, etc. I never see the factor of safety included in these analysis and that is why some people end up not being happy with their setups. The factor of safety was probably (I don't know for sure) included when the limits analyzed with the utility were set by the manufacturers, so I believe there is some wiggle room either way with respect to weight limits, but the same factor of safety should be used when analyzing your weights. I'm not saying a 1 ton dually is needed to tow a popup, but rest assured, when the owner says he doesn't know it's back there, he's telling the truth (even if it's swaying all over the place):)
Excellent post.
Some industries use a 2:1 safety margin in mfg their products.
As far as using GVWR to determine a payload we have to be careful now that GVWR is almost to the sum of the GAWRs. In fact we've had some members report using GVWR to figure their trucks payload and have over loaded the trucks RAWR/tires while still under GVWR.
Personnaly I prefer using DOTs method for determining any trucks payload. That way I'm not only legal but also safe.
