# Design forces for a home built trailer structure (tiny home or camper)?

I am going to purchase a steel trailer frame, and then I want to build a camper on top of that. This will be full height teardrop which is likely wood framed but I am also considering aluminum framing. So some of the questions I have relate to choosing the right size of aluminum tubing.

Most small teardrops I have seen use plywood framed sides, and some use wood framing which looks similar to how you might frame a stationary structure. Likewise for tiny homes, most of the designs I have seen use what looks like traditional house framing. One of the concerns that I have is that I have sufficient strength in the structure to keep it safe but also keep it in tact while driving. For example, in a car accident, I do not want the camper to disintegrate and become an additional safety hazard. But more typically, the structure also needs to withstand rapid acceleration, braking, cornering, etc.

Load I think the structure will want to sheer against the steel trailer frame (for example, as the trailer comes to a stop). So I want to know the lateral force so that I have the right number and size of connectors. I also want to determine a lateral design force to keep the structure from collapsing over.

Method My thinking was that if I fix the weight of the structure, and I have a design value for acceleration, then I can calculate the sheer and lateral forces on the structure using F = m x a. For example, my initial estimate is 1000 lbs of framing and wall coverings, and if the acceleration is 20g, then the force would be 20,000 lb. I can then use that to calculate the correct connectors and size of the vertical framing.

Acceleration I think typical braking would produce something like 1g of acceleration, and some car accident references I found put the g's in 100+ range. My suspicion is that this car accident values reflect hitting a stationary object, but is that really what I should be designing around?

Many one off car designs have been built to 3-2-1 loading, but I'd prefer 5-3-2 for road use. That is, if the weight on one wheel is 1000 lbf, design the suspension and mounting points for 5000 lbf vertical, 3000 lbf longitudinal (potholes) and 2000 lbf laterally into curbs etc. Your bodywork does not need to be as heavily designed as that if the suspension is doing its job, after all you don't experience 5g in a car other than in a crash.

The formula F = ma is an over-kill or an oversimplification for designing a vehicle/vehicle parts to endure wind pressure at speed. The correct equation to use is "$$F_D = C_DA(\rho U^2/2)$$". In which,

$$F_D =$$ Drag Force

$$C_D =$$ Drag Coefficient

$$A =$$ The effective (exposing) body area

$$\rho =$$ Air Density

$$U =$$ Relative Speed (The flow velocity relative to the object)

See this article for the introduction and estimate of the "drag coefficient" for various types of vehicles.