Originally Posted by MJAB
Other details can be found in some videos, are shown different models vans, motorhomes bases, cutaway, cowl
There is a version for motorhome manufacturers that doesn't have the top reinforcement frame, it is the "light frame" version (note: rear track is wider in motorhome versions).
Thanks for the pictures and videos. By stopping and starting the videos, I got some good views of the internal construction. It was interesting to see that the rear frame is initially constructed as a separate unit from the front, then welded together. I still would like to see some clear detail pictures of that joint, but I doubt that I will find that. Anyway, your pictures helped!
I am glad to learn that the RV "chassis cab" is different from the vehicle sold as a chassis cab. I had been thinking that a wrecked RV might be a good candidate for conversion to a flatbed, but it apparently would not be very different structurally from a stripped van. It would still need an additional frame rail on top of the lower rail. Apparently, RV's are engineered as unibody (or semi-unibody) vehicles, like the vans. In any case, I noticed that the RV "chassis cab" is strong enough, in its stripped condition, to drive within the factory.
The last picture you posted, while it looks like a flatbed, also appears to be engineered with the expectation that a box body will be added, and that box will become part of the structural integrity.