Try to remember to have adequate ventilation when using contact cement. The fumes can have consequences.
That's good to know because Carl (the Evil Floating Brain) keeps telling me about voices he's hearing but I don't hear them. Must be the fumes. I was afraid this project was making one of us go crazy.
On to the sofa-bed design.
Since you guys kindly showed me your designs it guess it would be rude for me not to show you mine so here goes. I'm not an engineer so my terminology might be all wrong. Hopefully it makes sense.
The sofa-bed will sit length wise in the van and when extended into a bed, what I'll call the "open" position, there won't be much room between it and the cabinets on the other side. That means that trying to open and close it would be a pain, especially in the lower back, so I decided to go with a powered design.
I'll be using an electric actuator to open and close it. Probably this one with the 18" stroke
. Won't need the full 18" but that can be adjusted with an exterior limit switch.
The main problem I'm trying to overcome is that I want the left edge of the bed as close to the wall as possible when in the open position which leaves more room to the right of the sofa-bed.. That's so I can still walk through the van with the bed fully open. I might have to turn sides wise and shuffle to get around it but passage won't be entirely blocked. This turns out to be harder than I originally thought.
Here's the main parts of the design. It uses what I call an "escapement" because it reminds me of one. The yellow squares are the foam padding. The two long blue rectangles I'll call the "back board" and the "seat board" since that's the position they will be in when the sofa-bed is in the sofa, or "closed", position. These two boards are attached with a hinge where they meet. In this diagram the escapement is in it's "rest" position beneath the back board. On the seat board is a "cam" that lines up with the escapement. The escapement is attached to the side of the sofa-bed only at the pivot point.
In this diagram the electric actuator has been energized and the sofa-bed has just started going from the open to the closed position. Actuator, not shown, has pulled the seat board to the left. This causes two different actions. It also pulls the back board to the left but at the same time it pulls the cam into contact with the escapement. This causes the left edge of the escapement to raise pushing the back board upward. Notice the escapements pivot point isn't at the center point but offset to give a leverage "height advantage" so one inch down on the right end of the escapement gives more than an inch rise on the left end
Since the escapement is putting pressure on both the back and seat boards I need a way for the seat board to stay down so only the back board will rise. To hold the seat board down I have it running in a track on each side of the sofa-bed made from metal angle. The edge of the seat board is reinforced with metal u-channel.
As the seat board is pulled to the left the escapement has reached the flat spot on the cam. At this point the escapement has raised the back board to a position where it is now in contact with the "back plane" on the board's left edge. This is actually a ridge that's attached to the sides of the sofa-bed frame.
The upward motion of the back board is now caused by it moving up the back plane as the seat board is pulled to the left. Escapement starts to drop away.
Sofa-bed fully closed. Escapement has returned to a rest position. Because of the "height advantage" the pivot point afforded the cam is able to fit inside the escapement space.
I know of two problem with this design.
1.)The ridges that make up the "back plane" must be large enough to support the back but allow the foam pad to squeeze past them as it rises. I might have to provide extra support using the van wall.
2.)The "height advantage" also means a 2:1 mechanical advantage against the cam. I don't know what kind of weight will be pressing against the cam from the back board and the foam pad but with this leverage setup it will be doubled. I might have to have two escapement/cams. One on each side instead of a single one in the middle. The only way to fully test the weight issue is to go full scale.
A couple more considerations I didn't mention but affected the final design..
My battery bank will located behind the sofa-bed and I need access for maintenance. With this design I can remove the foam pads and fold the back board flat against the seat board for access to the back.
The seat board will have two doors so I can access the storage space underneath.
I know this is a long explanation but trust me it could have been much longer.
I've been thinking (obsessing?) about his for some time.