Odd Balance Question

[Bear_Rider]

I'm trying to design a multipurpose trailer that can serve as a pickup bed for hauling bulky items the 40 miles from town, a support trailer for my living history events, and with the addition of a module or two, serve as a camp trailer for my wife and myself. I have a first approximation of the weights and moments on the frame and the trailer box, and in the cargo/support mode it looks good thus far.

However, I'm not sure where one should assume that the center of load for loose cargo will fall. Should it be on the fore and aft centerline of the cargo box, or should it be forward or aft of that centerline? I did a number of calculations, placing the center of mass anywhere from 20% behind the box centerline to 20% forward of it, and the calculated axle placement varied by almost two feet. Does anyone have any thoughts on this?

[rowerwet]

make the axle adjustable...

[bobhenry]

I have built 4 tiny trailers and could give you 4 answers. There are balance sheets for the very organized who actually know exactly what they are loading ( I never do) and exactly where they are going to place that item (again I never do) I have revisited a couple work sheets based on where my cargo wound up and keep comming back to approx 60% / 40% this means 60 % of the body length in front of the centerline of the axle and 40% to the rear of it.
so if the trailer body (exclude tongue) is 120" then 72" is in front and 48 is behind. A heavily laden galley with water, ice chests, and the cast iron collection from hell may very well make you wish you and gone closer to 70 / 30 But any area in between these 2 numbers seems to be the sweet spot for our style of tiny trailers. Just my opinion I am sure I will be berated for it shortly

[Dale M.]

As long as when you "load" trailer you keep the larger percentage of load, weigh wise forward of axle so trailer is "tongue" heavy you should be ok... Balance sheets are nice IF you are very meticulous and want to work with them... My usually reaction is to watch rear of tow vesicle and see if it is lowering a bit in rear as I load, this indicate tongue weight is probably near right, if rear if tow vehicle is raising it means trailer is tongue light and will tow miserable.... IF you are building trailer put axle slightly behind center line of "box" and just use a little common sense when you load... Always member heavier objects forward....

Dale

[Bear_Rider]

Thanks all for the good advice. The open cargo box mode has been the hardest to figure out, and your suggestions have given me a handle on it.

[angib]

With a simple cargo trailer, it is only the way the trailer is loaded that can control the balance - there isn't an axle placement that will make the balance right, if the trailer hasn't been loaded right.