DIY Frame and Mattress

Phoenix,

It is interesting that the Poisson ratio is high for wood. Another thing you can study in Wikepedia is orthotropic. I did not model it but the elastic properties of wood are different with the grain compared to perpendicular to the grain. In general, the deflection of the frame is relatively insignificant compared to the body and the foam.

The Poisson ratio of foam is close to zero. If you compress it in the vertical direction, it expanse very little in the lateral directions. It would be interesting to model the contour of the human body and spine alignment laying on layers of foam. Develop models for women with bigger hips and men with bigger shoulders laying on foam in different positions and quantify spine alignment and pressure points. This must be already done, but I could not find anything on the web after looking 30 minutes.

The spine alignment would depend on the muscular structure, mass distribution, and the body contours along the spine.

goldfreaz

Hi goldfrreaz,

There are some interesting books I’ve read that go into all of this in much more detail (including mathematical models and specifically designed testing systems that take into account the different response of each of the body tissue layers). Back and Bed … Ergonomic Aspects of Sleeping is one of them (which has a fair bit of higher level math but is still generally inside my range of understanding) and another one is Preventative Biomechanics … Optimizing Support Systems for the Human Body in the Lying and Sitting Position which is also very interesting reading but is much more difficult to read and includes some math that I have some difficulty with.

Phoenix

Hi Goldfreaz,

I am planning on building a platform bed frame for my new latex queen sized mattress. I have never done something like this before. I was wondering if you had any more pictures and if you could go into more details on your plans or some resources you used for your plans.

Thanks!

Pheonix,
Thanks for the book references. I read some of the first one on Amazon preview. It was packed with information.

Sleepy,
The wood was free and I own many power tools. Even with all these resources, this bed frame took 60-80 hours of work. The most important design features are (1) a split frame so it can be move, and (2) 1" thick slats that are supported well in the center as while as both sides of the bed. Gluing the frame together requires a thickness planar and table saw. You may be better off looking at other designs on this board that use 2x4, 2x6, 4x4, deck brackets, and deck screws.

Thanks for the reply goldfreaz. Would you mind posting any resources/threads you found useful. I only found the “king size deck” thread regarding DIY frames. I have plenty of tools at my disposal just need a good set of plans and a list of materials/wood I’ll need. I haven’t built much before and certainly no project like this, so I would need plans that are fairly detailed. Thanks for your help.

Hi sleepypeepy,

I’m not goldfreaz of course but the foundation post here has some DIY foundations and platform bed designs contributed by some of the members here that include instructions, pictures, and material lists. There are links to two of them at the end of the KD foundation section and one at the beginning of the slatted platform bed section.

Phoenix

Thanks for those links Phoenix.

I definitely like the idea of a split frame since I am in an apartment and will likely be moving in a year.
Goldfreaz, how are the two sides held together and how easy to take them apart? It looks like there only 2 legs in the middle. Do these detach when you take apart the two sides? Any additional pictures of the frame?

That .015" is going to look pretty small once you see your latex “oozing” out between the slats.

Very I formative stuff , I am a structures specialist who works in collapse zones and the study of the elasticity of wood and running grains are very fascinating . I thought it in our studies to look at the time of yr a piece of wood is harvested contributes to these measures. Sometimes I don’t think engineers have anything better to do! Except build cool beds! Nice work!

Interesting to know about the timing the wood is harvested. I was of course aware of how important grain orientation was but had never heard about harvesting and its affects.

I have added more detail to my bed frame illustrations. Also, the stiffness of two mattresses are compared. I much prefer the King size mattress, although the queen size mattress from Spindle is still very good. More importantly, my wife likes them both.

Details:

Hi goldfreaz,

ILD is a little less precise than you seem to have documented it, although you have basically the correct info. One example of this is that Ild is usually measured with a 4" layer for polyfoam, and a 6" layer with latex foam. Each is measured to 25% compression, however that means that there is 1" deflection with a 4" layer and 1.25" with a 6" layer - the impact this has is that it’s easier to compress a material by 1" than 1.25" and therefore if ild is compared between the two is such that the polyfoam ild would be higher were it tested in the same way as latex.

Hi goldfreaz,

That’s an interesting spreadsheet :slight_smile:

How did you calculate the spread column? Did you factor in the estimated compression modulus of the material (different materials have a different compression modulus which is the ratio between 65% ILD divided by 25% ILD) which can also affect how much a material compresses under load.

Different materials will also affect how the load spreads relative to depth (a cylinder in the case of a spring and more conical in the case of different foams).

How did you calculate the surface area and weight distribution for each part of the body (shoulder, torso, hips) to calculate the stress on the material under each part of the body?

Is there any simple way to calculate the continuously changing surface contact area that comes in contact with the mattress as you sink in deeper or to account for different body shapes, weight distributions, or with different sleeping positions (moving the arm for example from under the body to an arm forward position will change the surface area in contact with the mattress and affect the load)?

I’m assuming the numbers are designed to reflect side sleeping?

This is interesting (and complex) stuff … and thanks for sharing the results of your work :slight_smile:

Phoenix

Pheonix,
How did you calculate the spread column?
The load is assumed to spread x% per inch of compressed material (x=12%, guessed). If the layer is compressed 50% from 3" to 1.5", then the load would decease by 1.5x when applied to the next layer. This is not quite conical but close enough for me. This helps model the fact that bottom layers affect the feel less. As you can see though, the bottom layers are still important.

How did you calculate the surface area and weight distribution for each part of the body ?
I guessed at these values. I do not think these add much to the comparsion. I did not model the shape of the body either. It is interesting that the guessed load values closely produce the deflections that I personnelly experience.


I’m assuming the numbers are designed to reflect side sleeping?

Yes, I was trying to calculate the deflection at the shoulders, torso and hips of a person in the side position. I think this part of the spread sheet is over-simplified and not useful. I would like to add body shape and weight distribution, but I am running out of motivation.

goldfreaz

Hi goldfreaz,

I can certainly understand this and there are many cases where my own more technical research can lead to more avenues to be explored than it leads to answers and the process can seem to be never ending :slight_smile:

As you know … for some people (such as the authors of the books I linked before) this whole area of investigation is the subject of a lifetime of research that involves some very complex math and some specialized testing equipment and it can be daunting for a layman (such as myself) to try and understand all the variables and even more difficult to “translate” it into meaningful results that can be easily used to predict the experience of individual people on different mattress designs and materials.

Having said that … I think that the fact that your numbers are such a good reflection of your actual experience and the fact that you had already considered much of what I mentioned and factored it in says a lot about your methodology and knowledge.

If there was one additional set of numbers that I think would be particularly relevant and interesting it would be adding a 4th section for how the lower back that includes the inward curve of the lumbar compares to the shoulders, torso, and hips since this is a fairly critical area that can be important … particularly for some body types that either carry more weight there, have a more athletic build, or that have a wider differential between their hips and waist or their shoulders and waist.

Phoenix

I removed the crappy box springs (cardboard/ wide slates) and replace them with a home made frame. The mattress came to life and feels flatter. A noticeable improvement. The mattress is a Queen Spindle Abscond with two firm layers on top of a medium.

goldfreaz


:woohoo:

Details:

Hi goldfreaz,

Thanks for another update and the pictures.

Your new frame is certainly a huge improvement compared to the foundation you had and it’s not surprising that it made such a difference.

Nice work :slight_smile:

Phoenix

After sleeping on the Spindle Abscond for three months, I have decided that it was not firm enough for me. Initially, this bed started off with a medium layer on top and two firm layers as support. The medium layer was quickly moved to the bottom. A few days ago, I called the KTT Enterprises and had them cut the medium layer in half and purchased a 2" layer of 40-44 ild blended talalay to place on the bottom. I noticed that the firm layers (dunlop) were firmer on the bottom with larger holes. I placed these on the talalay with the bottom side up. The medium layer seamed more consistent (top to bottom) so I used the top half of this layer as the final comfort layer. The result was a bed with more support and softer comfort layer. If more support is needed, I will move the talalay up.

Thanks again to KTT for there great customer service and this board for all its ideas.

Goldfreaz

More info:
Link

Hi Goldfreaz,

Thanks for the update on your configuration … I appreciate it :slight_smile:

It sure is handy to have KTT so close to you and that they have a slitter.

Phoenix

I am jealous of your beautiful mattress and bed frame. just beautiful.

Cheers