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Engineering question...

by 3ladybugs
posted 08-24-2016 04:48 PM

13 replies so far

View MadMark's profile


979 posts in 2340 days

#1 posted 08-24-2016 04:52 PM

Angle iron will be fine, 2” tube will hold tons. Old bedframes are a great source of materials.


-- Madmark - [email protected]

View pintodeluxe's profile


6213 posts in 3700 days

#2 posted 08-24-2016 05:13 PM

If you sketch it up, or show us a picture of similar designs… I’m sure many here at LJ will lend a hand with the design work. You could even take a picture of a pencil and paper sketch to get us started.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View Dark_Lightning's profile


4212 posts in 3996 days

#3 posted 08-24-2016 05:29 PM

What is going to be on the platform besides the book case on one edge? That leaves a lot of area unaccounted for.

-- Steven.......Random Orbital Nailer

View bbasiaga's profile


1243 posts in 2882 days

#4 posted 08-24-2016 06:01 PM

Rough sketch please. Sounds like there is both a trundle bed and Murphy bed somehow tied in…having trouble picturing it.


-- Part of engineering is to know when to put your calculator down and pick up your tools.

View bondogaposis's profile


5875 posts in 3238 days

#5 posted 08-24-2016 07:18 PM

I can’t begin to visualize what you are talking about, I need a picture.

-- Bondo Gaposis

View Natobious's profile


49 posts in 1592 days

#6 posted 08-24-2016 07:41 PM

I second the rough sketch request.
Take a look at the queen sized bed I made. Completely disassembles and strong enough for two adults with only wood (except bolts).
I realize a bit different than your description, but gives one idea of what can be done with only wood.

There are many things to consider in furniture design, especially designs for children, but with patience, learning, and questions it can be done. If you are serious about this it may be worth learning google sketch up. This would allow you to see the idea in 3d and get advice from that model.

View 3ladybugs's profile


5 posts in 1527 days

#7 posted 08-24-2016 09:30 PM

This shows what the day (upper) and night (lower) view would be for what I am wanting to do. The mattress that we have right now is only about 3 inches thick. I am thinking that will be good for my baby (he is 3). I am figuring on a piano hinge that would make this mattress essentially sit on the floor (the platform). Blue is for my younger child, green is my older child.

This shows the end view, and the side views. Ideally I would like the desks to be at or about 30 inches, as that seems to be a normal desk height. I would also like to block them from each other as my older son is in 3rd grade right now and my younger one is 3 like I said. However this looks very tall to me, so that part is a bit of a work in progress. I might also switch the sides that the boys shelving is on (reverse them) as there is a window on the wall where this would rest in the short direction. The twin size mattress is 6 inches shorter then the Twin XL. So either my younger child will have a small shelf, or a small walkway. If I switched the sides on the main shelf, I may place another shelf at the end (prior drawing in front) so my younger son will not fall off the platform when at the desk.

My hope is when they are not doing school, and they are not sleeping, that this would become a great place to play. Either on the platform, or on the floor where the older son’s bed would go.

My older son’s bed would be on casters or wheels of some sort so it would slide in and out easily. I will get him a foam mattress that I am hoping is about on par with his brother’s. I don’t want anything that they can’t bounce on as they are prone to do that. Very active boys!

Ideally this whole thing will make it so when I am working with one boy, the other can either play or work depending on what they need.

View 3ladybugs's profile


5 posts in 1527 days

#8 posted 08-24-2016 09:39 PM

I just realized that my sketches don’t show the full view even when you click on them.

I hope these links help. :)

View Natobious's profile


49 posts in 1592 days

#9 posted 08-24-2016 11:40 PM

It is clear you put a lot of thought into your design.
The trundle bed is easy.
For the platform, My recommendation would be a torsion box.
These can be done with tops and bottoms or just tops.

Now a standard step is 7” tall and 11” deep. If you made the platform 14” tall, it would be a one step up design and provide ample clearance to roll the trundle under.

The murphy wall would mount to the wall, but be framed to look like it is resting on the platform.

The book shelf would just sit on the platform, anchored with a few screws for stability.
The desks could either fold out or slide out depending on the design.

For the in floor storage you could make the torsion box with top openings in that area and a walled off section.

Overall, this looks quite doable. The trundle first, then platform to suit, then murphy bed, then shelves.

View 3ladybugs's profile


5 posts in 1527 days

#10 posted 08-25-2016 01:46 AM

So do I use 2 by 4’s for the frame of the platform? Should I put angle iron on that? I have an old full size bed frame in my basement. It isn’t quite long enough to go the whole way across but I suppose we could just screw it in the middle where the most stress would be.

I need to double check I have the height for 4 more inches. This is going in the upstairs of a cape style house so I have ceiling/wall issues.

View Natobious's profile


49 posts in 1592 days

#11 posted 08-25-2016 02:19 AM

The steel may not actually help as much as you would think. I know that sounds strange, but think about a standard bed; the steel frame holds up a box frame. and the box frame holds up the mattress. Because the mattress is flexible it needs closer spaced support.

The same will be true of the platform, the weaker the walking surface is, the closer the supports need to be spaced to reduce the span.

Depending on your level of skill, I would suggest 3/4” plywood (not chip board) with 2×2’s under it. set it up on some blocks at the corners and walk around on it. Kids first, then adults if it is sturdy. if it is too spongy add more 2×2’s or a bottom layer of plywood. If you space the 2×2’s every 18 to 24 inches it should be fine. Also, you could use a couple 2×4’s on their sides (to save height) for the longer span.

There are some online calculators that will predict how much the wood will bend with a certain amount of force applied. They are used for designing bookcases but work well for your application too.

View 3ladybugs's profile


5 posts in 1527 days

#12 posted 08-25-2016 02:39 PM

I am so baffled by this. I live in a library. We have bookshelves from Ikea and some of them are sagging after a few years because of the weight of our books. They are not sagging much, but a bit. Is this a case that real plywood is better then whatever they make bookcases out of at Ikea?

Then again, the bookcases that we have that are solid wood also have this issue. However they are only about a half inch thick for the shelves.

What am I missing?

View Natobious's profile


49 posts in 1592 days

#13 posted 08-27-2016 05:04 PM

Here is a good link for a general introduction to designing shelves.

Often Ikea’s main goal is pretty, affordable, and lightweight. So pound for pound Ikea furniture can have good strength, but they are not designed as bookshelf to actually be filled with books.

Particle board is weaker, harder to make it look decent (paint and such) and it really isn’t that much cheaper than plywood. Solid hardwood on the other hand is even better but much more expensive especially if you are buying from a big box store.

For your platform the most bang for your buck is plywood with a “2×4” support. But the 2×4 will be too deep so that is why I suggested 2×2’s. you could use 2×4’s on the three edges where the trundle bed won’t interfere for added strength. Also don’t be alarmed if the platform is a bit spongy for an adult, domestic flooring is intentionally over strong to prevent spongy, because of aesthetics. This will also be less spongy for the normal kid traffic.

Regarding the 14” maybe you could use two six inch steps to get it down to 12”. One 10” may be too much for kids in the long run.

Hope this all helps, and that you get to see it turn into reality. It is a unique and intriguing design.

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