COG educational thread

Kayteg1 wrote:
The topic about COG got closed for reasons I don't have to understand, but IMHO it shows how little owners understand the technical issues.
So big TC owners are between truck manufacturers who recommend camper COG in front of rear axle and camper manufacturers who build big campers with COG behind rear axle.
I am pretty observant with loading and even with all heavy tools, water and other heavy stuff in truck cabin, having only light cloths in camper rear cabinets, my COG still comes behind rear axle.

COG for the vehicle is NOT a single point. COG is usually expressed as an envelope. COG markings on a camper are placed on one spot (by the manufacturer) based on empty weight, as equipped. We really don't know what the camper COG is with full water and full tanks (black and gray) or worse with partial fresh full gray/black, etc. Then there's really no control where an owner places additional loads, how heavy the loads, etc.

My RAM 3500 has a manufacturers camper COG envelope expressed by measuring from the rear of the truck bed (seems backwards but I can subtract). For my particular truck, the COG of the camper can be placed anywhere from 13.7 inches from the front of the bed to 47.7 inches from the front of the bed. The COG marking on my new Arctic Fox 811 is 43 inches back from the front of the rubber bed bumpers to the COG mark. Based on that, my empty AF811 is within the manufacturers recommended envelope (approximately 4 inches forward of the rear limit of the envelope).

My RAM 3500 is a short box model and all (newer) RAM short boxes are 6'4" (76 inches) from the front wall to the rear end of the bed. The rear axle center-line is roughly 41 inches from the front of the bed. That puts the manufacturers recommended camper COG anywhere from 27 inches in front of the axle to almost 7 inches behind the rear axle (a total COG envelope of 34 inches front to rear).

Insisting that COG ALWAYS be over or in front of the rear axle is mis-information as manufacturers (and design engineers) likely will tell you it is a function of total weight and balance(COG). They'll also likely tell you that there is an acceptable envelope (like RAM does in published consumer data) at the maximum recommended load. Lighter loads can move further out of the envelope, heavier loads are never recommended (by the manufacturer) but should be closer to the center of the envelope.

You're right on one thing - most people don't understand COG.