OK, so the Tune M1 uses bolted together extrusion frames? While extrusion frames with composite panels which are bonded together are a more durable design? And something like the OEV Backcountry does not use a bolted together extrusion frame?
Yes
Yes, if done correctly, which is probably safe to assume for most mainstream companies.
Correct.
Think of the camper frame (not the doors/windows, or how it pops up, but the main 'square/rectangular' bit that gets bolted to the truck bed) as a little structure.
Simplify it in your mind by thinking about it in terms of pieces of wood, if you will. You know that if you simply take 4 pieces of wood (say pieces of 1x2 or 2x4), lay them down and arrange them in a square, and put one nail through each corner, that this little frame will be very easy to 'squish' or misalign by pushing on a corner.
Now take that same frame idea, 1 nail in each corner, and then screw down a piece of plywood to the frame, nailing/screwing it at 6" or 12" on center, around the perimeter.
All of a sudden these 4 pieces of wood can not be misaligned by the human hand. It has been stiffened. Congrats, you now know why your house (wood construction at least) does not blow over in the wind. The sheathing creates
all of the lateral stability.
Now, step back into the realms of the campers we are discussing. The simple 4 pieces of wood, without the plywood, are these less sophisticated camper frame designs, with the bolted connections at the corners. Aluminum is more competent than wood, and there is a bit more going on with the camper, but suffice to say that this simple relationship works for our simplified discussion.
The 4 pieces of wood with the plywood are like the composite framed campers that have a more sophisticated design methodology. These are much more rigid, as we previously discussed, and are likely to last much much longer, and handle more abuse (think vibrations caused by washboard roads), than these simpler designs.
In my professional experience as a structural engineer here is my simplified list of pop-up camper construction categories, rated from worst to best in terms of strength and longevity:
- Simple bolted together aluminum extrusion camper moment frames: Lonepeak, Tune M1, Harker EDC (even worse design, as it has no rear top crossmember, such a terrible idea). These suffer from the issues listed above.
- Composite shelled campers: Scout Camper, 4WC's, OEV Backcountry, etc. These are tough, as I stated above, but lasting a long time is not guaranteed. Exposure to sunlight can degrade the composite/frame interaction (talking a long time here, not a year or two). They are also more likely to suffer a brittle failure of their components, which is the type of failure that we like to avoid (i.e. think about taking a small wooden dowel (thickness of a No. 2 pencil for example) and bending it between your hands. It is strained, but you can't tell. Continue to apply more force and it violently snaps. This is generally not good).
The next category is split into two subsections. Though similar, their one difference is very important:
- Welded/riveted together aluminum camper moment frames with traditional rear door/hatch: Super Pacific X1, etc. These are better than the simple bolted campers above, due to the way that they disperse the load into the corners, and are likely to outlast the composite campers over time. They are also more likely to suffer from a ductile failure, which is the type of failure that will show signs of distress before breaking, potentially allowing you to fix it before it truly falls apart.
- Welded/riveted together aluminum camper moment frames with rear shear wall: Alu-Cab Canopy Camper and Cabin Camper are the only ones afaik. The Alu-cab has a massive advantage over the SP X1 category due to the removal of the tailgate for the full back door of the camper. This basically creates a shear wall (plywood screwed to the 4 pieces of wood from earlier) at the rear end of the camper, down to the bed and frame. This does wonders for overall rigidity and longevity (one of the main reasons I bought an Alu-cab Canopy Camper myself). This design is on par with the most ideal frame design (below) due to this rear shear wall. It solves a massive problem that the other campers have (composite shelled campers also have this idea incorporated into them, most of the time).
- Braced frames: GFC is the only one in this category afaik. This is a more robust frame design at the base level, relative to all of the others on this list, and that is why it is tied at the top with the Alucab. It lacks the rear shear wall that the Alu-cab has, but the triangulated frame design is superior on the other three sides. Its main downside is that it is much less convenient to use (though this isn't a topic of this list) as the triangulated pieces of the frame block your side access into the camper.
All of this can be far more complex and nuanced, but I have neither the time or the desire to spell it all out on the internet. But this is a great basic understanding.
Let me know if you have any questions.
