Side Rail Spec's
I want to fabricate a rack that holds both of my ATV's. This rack will sit on the side "rails". I'm not sure where to post this so I will try other areas of subject matter.
Thanks . . . Monte
I would build the rack so it goes on down to the floor and, against the front bedwall on the floor, weld it to a thick angle that crosses the whole bed floor, bolt it in where the bed bolts to the frame. That way at least you know the front is being supported by the frame.
On the rear, I would bolt it to the floor over one of the factory sheetmetal crossmembers of the bed floor. The one the bed bolts through to the frame would be a good choice. It doesn't really involve that much more steel to go all the way down and should be plenty strong for what you're doing.
I remember seeing a post in here a while back about someone's SD bed sheetmetal cracking due to a lumber rack. For the weight of quads, that sucker needs to be attached to the frame through the bed.
To be removeable, take a look at fifth-wheel hitches.



