thanks Will, very helpful info. I like the idea of using angle to create my frame, then building the floor and sides out of wood. I can use the dump trailer as a flat bed for hauling drywall etc., and i will be using it for clean fill from excavating. the removable sides is definitely a plus. basically 2 trailers in 1!
my questions i have is a) what is a full-float axle, and what/where do i look for one b) i understand how electric brakes work, but how does one set them up using existing brakes?
i think maybe targeting a 7'-8' is reasonable. assuming the dimensions are 7' long by 4' wide and 3' deep, thats 84 level cubic feet. that is my goal! this could turn into a pretty cool build thread!
BrakeRite is the electric over hydraulic setup. It takes your electric controller and has a motor that activates the hydraulic brakes. It's expensive.
A surge brake actuator is cheaper, but you'll have to have the tongue end in a 3" square tube. I like surge brakes and that's probably a better choice--no wiring in the truck.
Using a trailer axle might be okay, but it's also an expensive proposition if you want a 6,000# + axle and brakes. One of the benefits of using a pickup is that you have an axle and frame.
A full-size pickup bed is larger than your assumed dimensions. It's 80" wide to the outside of the box so you have about 6.5' inside and 50" between the wheel wells. The stake pockets will let you make the height whatever you want.
It's typical for a 2 axle trailer to have a pair of 3,500# axles. Depending on what you carry, you will want a 250/2500HD and above. A 14-bolt full-floater is a 7,500# axle, for instance. You aren't going to hurt it. With a full-float you can pull the axle shafts and pack the bearings with grease. You need to make caps to seal the ends, but anything would work for that.
A 1/2-ton axle is generally 4,000# max capacity. A load of oak stacked as high as the cab can reach 5,000#-- + the weight of the trailer. I have a video of an F150 with a broken axle being helped home by a loader. A semi-float axle has one little bearing directly under the wheel and a full-float has 2 large ones. A trailer axle has 2 bearings instead of one little bearing so even a 3,500# trailer axle stacks up well against a 1/2 truck axle, though each of the trailer bearings is smaller. A 6,000# trailer axle has decent bearings in it, but it's going to be expensive and not worth putting one in a pickup-bed trailer. Also, that size of axle is going to be much wider than a truck bed if you get one off the shelf.
Cheapest way to get a dump trailer is to cut a suitable 3/4-1-ton pickup frame, make the hinge like I did, use a High-Lift and make the tongue end in the 3" rectangle so you can use an
8,000" surge coupler.