Monday, 17 June 2013

Designing a Traditional Futon Sofa Bed

We have a double futon that we don't usually use and it's kind of tricky to find somewhere to put away. So at the moment it's folded into three and sitting in the kids room doing a rather poor impression of a couch. It's doing a very good job collecting toys and dust, since it's directly on the floor, and is creeping, gracelessly and lopsidedly, away from the wall.

What we really need is a base for it that will convert from a couch into a bed. So I'm in Japan, and you'd think that it would be really easy to get one. This is the land of futons, right? Everyone must have one. 

Well, actually... 

Traditional Japanese futons go on tatami mats. These are traditional Japanese floors. If Japanese people get rid of the tatami mats or build houses with wooden floorboards or carpets, as they increasingly do, they get beds. If they want to sit on something other than the floor, they get sofas and couches. 

There is no such thing as a traditional futon sofa bed. Futons, sofas and beds are from different traditions. 

So, to the drawing board and then to the shop to get some wood. As usual, I start the design process with bits of paper and crazy ideas, then, a few sheets later, I start looking on the internet to see what there is and how they make it, and find nothing ideal but many things inspirational. Then, several sheets later, the ideas become more detailed, and the designs become more simple as solutions to problems take away the causes of the problems.

Like the legs, for example. The problem with having the futon on the floor is that you can't sweep under them. So this means the frame needs legs.

There are two basic designs of futon sofa beds: bi-fold and tri-fold. In the bifold, the length of the futon is the width of the couch, and the back basically falls back horizontal to make the bed. This is good if you want the couch to be as wide as possible. We don't, so we're going for the trifold, in which the width of the couch is the width of the bed, and frame and futon are both kind of folded into three to make the couch. 

The back of the couch is made up of two of the parts, in a kind of A frame, with the other part sticking out to sit on. It looks something like the picture below.

So I started with some legs at the front, then the legs of the back part tucking underneath it, and some legs under the middle hinge, the one opening upwards. It seemed like a good idea to have a leg under this hinge, to stop the bed collapsing at that point. The other hinge opens downwards, so if there is an adequate stopper on it, once it opens to 180 degrees it won't go any further, even if you put weight on it. This all means that when the bed is open, there are three sets of legs along its length, one set at each end, and one a third of the way along. Not ideally balanced, but it should work. 

When it turns into a chair, the legs at the front of the chair are still active. The ones at the back are now sticking in from the back at around  horizontal, hopefully not getting in the way. The middle legs are sticking towards them, the back of the seat now being held off the ground by an extension of the middle span. 

But why not get rid of those two legs, and have the existing legs swing out of the way when it's bed time? Then there are less legs to worry about, it doesn't matter which way the hinges go since the whole of the frame is lying along the floor. Functionally, this is going to spend most of its time as a couch rather than a bed, so being able to clean under the bed is not a problem. 

Simple is best. As Antoine de Saint-Exupery said, "A designer knows he has achieved perfection not when there is nothing left to add, but when there is nothing left to take away." 

And yes, I could have just followed 
Bored Guy's excellent instructions here. Or bought something online for slightly higher cost. But actually it's the design part that I enjoy. 

In fact rather than making my traditional futon sofa bed, I may just design a few more. 
How to design a chair: ergonomic data from Cornell.