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DIY Frame and Mattress 05 Jan 2014 07:00 #1

Below is a link to pictures of a king bed frame and mattress I am assebling with the knowledge gained from this site. I am waiting for the cover but everything else is ready to test. Living in Connecticut, I was able to meet the friendly people at KTT.
goldfreaz.weebly.com

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DIY Frame and Mattress 05 Jan 2014 12:40 #2

Hi goldfreaz,

Thanks for the pictures and the description of your new sleeping system ... I appreciate it!

Your bedframe looks very strong and very suitable for a latex mattress. I'm curious ... how did you measure the deflection so accurately?

Your mattress components also sound great and I'm looking forward to your feedback when everything is put together.

Thanks again for sharing all the parts of your design ... and congratulations on your new sleeping system :)

Phoenix
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DIY Frame and Mattress 05 Jan 2014 13:45 #3

I can help answer one of your questions Phoenix as to how he came up with the deflection data. By the looks of his #'s and the screenshot of Ansys it appears this guy may be an engineer(like myself). Ansys is a Finite Element Analysis program that is used to analyze the stress/strain of a particular component or a system of components. To put it simply you enter in some properties of the material and apply a load/loads to a component or assembly and it will tell you what the deflection is and what the resulting stress and strain is among other things.

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DIY Frame and Mattress 05 Jan 2014 13:59 #4

0.015" deflection @ 400 lbs seems a bit flimsy to me... Maybe it needs some ceramics or carbon fiber? ;) ;) ;) ;)













(..seriously, it looks amazing!)

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Last edit: by dn.

DIY Frame and Mattress 05 Jan 2014 14:22 #5

Hi Pist0lpete,

I can help answer one of your questions Phoenix as to how he came up with the deflection data. By the looks of his #'s and the screenshot of Ansys it appears this guy may be an engineer(like myself). Ansys is a Finite Element Analysis program that is used to analyze the stress/strain of a particular component or a system of components. To put it simply you enter in some properties of the material and apply a load/loads to a component or assembly and it will tell you what the deflection is and what the resulting stress and strain is among other things.


That's very interesting ... thanks :)

So as long as you know the properties of different species of wood ... I'm guessing primarily the modulus of elasticity ( such as here ) and you enter them into the application along with the dimensions of the assembly and slats and the span lengths then you can just input the stress and it will provide the expected deflection? That's very cool!

Phoenix
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DIY Frame and Mattress 05 Jan 2014 14:59 #6

Pheonix,
The model uses a modulus of 1.5e6 psi and a poisson ratio 0f .42 for all the various woods. The value for soft woods like spuce is 40% lower and for hard woods like oak ~30% higher. The deflections would be porportional to the modulus for the same geometry. All contacts between pieces of wood are assumed to be perfectly bonded. This is not true for the slats which are not screwed down. All other joints were screwed and glued. In fact the frame was so rigid that I could not pull the diagonals to be equal with large clamps. One diagonal is about 0.5" longer than the other.

I thought this was over kill (even for a life time engineer) but the weight and rigidity of the frame is noticeable better than the standard steel bed frame with wheels and box springs.

The software is Autodesk Inventor, though I use Ansys Mechanical at work.

goldfreaz

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DIY Frame and Mattress 05 Jan 2014 15:43 #7

All good info to know.. It appears you created a very solid bed and foundation that will last for many many years. I am anxious to hear on how your DIY mattress works out comfort wise. Keep us posted.

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DIY Frame and Mattress 05 Jan 2014 16:51 #8

Hi goldfreaz,

Thanks for the additional info. This is really interesting stuff to me :)

The model uses a modulus of 1.5e6 psi and a poisson ratio 0f .42 for all the various woods.


While I'm certainly not an engineer so this would be at the edge of my understanding ... I'm not clear on how poisson's ratio would apply to a foundation (although I understand how it would apply to a mattress that was subject to compression forces). Is this because a lower poissons ratio would mean the wood was more elastic which in turn would allow for more bending under stress across the same span?

Of course this isn't something that I "need to know" and my knowledge of all of this is limited but I'm curious about how it factors in.

Phoenix
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Last edit: by phoenix.

DIY Frame and Mattress 05 Jan 2014 19:23 #9

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

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DIY Frame and Mattress 05 Jan 2014 19:52 #10

Hi goldfrreaz,

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.


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
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