What makes up a GVWR rating?
I am wondering what it is in the design of a trailer's frame and suspension or otherwise that gives it a particular GVWR rating. Is it the axles primarily? We have a trailer with a GVWR of 6800 lb...
Forum Discussion
Ron,
The tires are 4 x 1820 lbs = 7280 lbs. The axles are 2 x 3500 lbs. The GVWR is 6800 lbs. Actual tongue weight is 960 and trailer weighs 6600 lbs. leaving 5640 lbs directly on the axles. A 6800 lb assigned figure makes sense, I guess. Tires are Freestar and don't know how long they will last before they explode. They seem close to the GVWR, but then the actual weight on the axles is under 6K lbs.
I am really wondering from a technical materials and construction detail perspective what gives a frame its strength and GVWR. Obviously, axle rating is one factor. But what metal thickness, beam height, flange width, and frame length affect GVWR ratings? What about spring hanger brackets and spring strength? What about cross-bracing from left to right side, and what spacing should they be on? What about weld details? Are welds continuous for the entire length of the joint or are they stitched together in only a couple of sides? What about the A-frame and also how it attaches to the I-beams? What about the grade of steel used? Is the frame strengthened where the tanks are? In any other industry I can think of, from building construction to automobiles, there are various standards spelling out how things must be done and anyone would have access to them. So - there are none in the RV industry? And a frame manufacturer can design and build to their own specs?? I also wonder what quality control methods they actually do have in place.
The tires are 4 x 1820 lbs = 7280 lbs. The axles are 2 x 3500 lbs. The GVWR is 6800 lbs. Actual tongue weight is 960 and trailer weighs 6600 lbs. leaving 5640 lbs directly on the axles. A 6800 lb assigned figure makes sense, I guess. Tires are Freestar and don't know how long they will last before they explode. They seem close to the GVWR, but then the actual weight on the axles is under 6K lbs.
I am really wondering from a technical materials and construction detail perspective what gives a frame its strength and GVWR. Obviously, axle rating is one factor. But what metal thickness, beam height, flange width, and frame length affect GVWR ratings? What about spring hanger brackets and spring strength? What about cross-bracing from left to right side, and what spacing should they be on? What about weld details? Are welds continuous for the entire length of the joint or are they stitched together in only a couple of sides? What about the A-frame and also how it attaches to the I-beams? What about the grade of steel used? Is the frame strengthened where the tanks are? In any other industry I can think of, from building construction to automobiles, there are various standards spelling out how things must be done and anyone would have access to them. So - there are none in the RV industry? And a frame manufacturer can design and build to their own specs?? I also wonder what quality control methods they actually do have in place.
