Engineering question

Elothar

Hi there,

I'm not quite sure if this is the right forum for this question but I couldn't think where else to put it.
I'm hoping to build a murphy/wall bed in my spare room. The mechanism's you can buy all are extremely expensive. I'd like to make my own "spring assisted" mechanism but I am unsure just how to make that happen. From what I can see I'd need two anchors, one on the wall/frame and the other on the movable part of the bed and attach the two with springs. What I need to know is how many springs and what strength they'd need to be?
I understand that the strength of the springs will be dependant on the weight of the movable bed part. I aim to make it roughly double bed sized and construct it out of MDF or plywood. The mattress will be an IKEA thin mattress to keep the width of the bed as small as possible. Even a ballpark figure would be good and an opinion on whether I'm mad out of my head for even contemplating making my own mechanism.
If you're feeling particularly creative and generous and can design/describe such a mechanism with parts from a DIY store then please feel free.
Thanks for reading.

mawk

You could make it counter weighted instead of spring assisted. Hinge the bed at the wall, and put a washing line pully up higher. Put some aircraft cable or 550 paracord to the outside corners of the bed, through the pully and down to a weight below the hinge.
Pulling the bed down lifts the weight, the weight dropping lifts the bed. Adding more weight is easier than calculating springs for diy

Elothar

Thanks for the reply mawk.
Hadn't thought of doing it that way, thanks for the suggestion. As you say it'd be easier to work out the optimum setup by either adding or subtracting weight. I'm not sure how aesthetically pleasing it'd look though having cord/cable running out to the bed part.

mawk

I dunno, it looks nice enough in my head. But we're probably envisioning it pretty differently.

Something like
http://ana-white.com/2010/08/easiest-hanging-daybed.html

You could also make more of a suspended feature of it. Wrought iron rings on the wall and a halfway ornate chain instead of cord and pully


Or if there is an Attic above, rope vanishing into the ceiling and the pully and weight in the attic out of sight

Elothar

Yeah the link you provided showed the same image I had in my head from your description.
I'd prefer the mechanism to be less obtrusive. I can see the cable causing problems for anyone using the bed, especially if they're movers while they sleep.
I might just have to do what I usually do which is muck about until I find something that works.
Again thanks for taking the time to reply.