troubleScottie wrote:Just wondering, can a wooden/foam teardrop handle the forces needed to support the two vertical columns? And what about the down force on the floor -- guessing 100 to 200 lb for just the bed/mattress/frame over 32 sq inches ( 2 - 4"x4" brackets at floor ) Obviously more with people in it. What about jumping up and down children?
Here’s the force calculations. I went to the bed website and found these dimensions:
Total width 48 inches
Distance hinge from wall 10 inches
Far edge to hinge is therefore 38 inches (48 – 10 = 38)
I weigh 180 pounds. Lets assume I sit on the edge to take off my shoes.
I don't see exactly how the rotation stop is made for the open position - I see a moving steel angle bracket near the hinge attached to the vertical steel post, perhaps that's how it stops rotation. To get a sense for the forces, lets just presume we have a pin in the wall to stop the edge rotating.
We need a couple variables to solve this
Let the down force near wall = Fw
Let the up force on hinge = Fh
Now lets look at moments about the hinge, with the classic sum of moments equals zero. That will give us the down force at the wall.
0 = 38 inches x 180 lb – (10 inches x Fw pounds)
0 = 6840 in lb – 10 (Fw) in lb
-10 FW = 6840
Fw = 684 pounds
Now we can use the classic sum of vertical forces equals zero to find force at hinge.
0 = 180 + 680 – Fh
Fh = 860 pounds
To be fair, there are two ends on this bed, so these forces get divided in two.
Even so, that's 342 pounds at the wall pins and 430 pounds on each hinge
I suppose that's why the bed frame is made out of stout steel.
But it shows that it would not be wise to try to cobble up a wooden frame that looks just the same.
The forces can get into hundreds of pounds pretty easily.
No big deal for pairs of 14 gage steel brackets, but probably no good for wood.
The fancy euro bed is more like a giant pair of pliars than like furniture.
Simple chains at far edge with wall hinges might work.
Something like this
If the chain angle is 45 degrees, the tension in the chain is 254 pounds for me sitting on the edge of a 48 inch bunk. Again, divide by two so each chain has 125 pound tension.
That's no problem for breaking chains or pulling out the screws at the wall, but its a pretty good bending load on the wall. If I sit down hard the forces spike upwards.
Lots of trailers have fold up beds, but they have vertical supports under the bed at the moving end.
It's probably the best approach, hence the popularity. No angles to increase chain tensions and no lever arms to increase forces.
Just support the plain weight with no multipliers.
by hankaye » Thu Apr 06, 2017 10:13 am 
