Jim,
I'm making the outside width 60 inches (5 foot) because that is the widest AVAILABLE aluminum around here. The interior will be about 58 1/2 inches minus any trim as around the doors.
The Torqflex axles are built to order, and the dimention they work from is outside frame width. Mine is being built 60 inches. Don't know what the flange dimention is, but it's wider...whatever the spindles stick out from the axel.
The main reason I'm doubling the frame rails is for convient attachment of the axel. By doubleing the angle iron in that area I'm effectively making it a section of square tubing for the axel to bolt up to. The way I see it is, the strongest part of the frame needs to be the side rails above the axel because the weight of the trailer is applied to one point about 6-8 inches wide with the Torqflex axel....right were it attaches.
With a typical leaf spring suspension trailer, the weight is spread along the side rail at the two attachment points for the spring, or the length of the spring.
So those are the two reasons I plan to build the frame by doubling a section of the side rails, for mounting convience, and frame strength.
The reason I'm using angle iron as apposed to square tubing is first it is cheaper, second I believe it is strong enough for the weight of the Teardrop I'm building, and third, it's easier.
I won't have to weld on any special brackets or plates to use to attach the body to the frame because the angle iron itself will be the bracket....just drill the hole thru the angle and floor and install the elevator bolts. You see, I' basically lazy and don't want to work any harder than I have to.
Unless of course, someone has a better way to suggest to me?