Lately I helped a friend to design a foldable stool-step. Those brilliant pieces of furniture were very common in Italy in last century, but it seems that lately they are not considered trendy and you don't see them often. In any case they are so suitable that I designed three models with small variations. As you can see the piece is a comfortable bench, but extended it becomes a three-steps little stair, to reach shelves and high spots in the kitchen.
The piece in the photography is my reference, but I will make soon an instructable about the building of one of the three four new models.
Step 1: 1st Version
First version is 70 cm high, and it has a top step of 40 x 26 cm. It's quite sturdy, but very compact. You can add the modification I designed in next step to improve its stability. Indeed I had a request to use these dimensions, but my fear is that the bench is too narrow, so it's better to lock it when opened.
Step 2: Fastening
Adding a sort of lock at the level of the second step lets you locking the stair opened, so that the base will be the full stair depth, and there will not danger that it tips over.
I will design the lock details when I will make the stair, I hope to write soon that instructable.
Step 3: Closed
As you see the small piece rests on the back middle beam when closed, and it's entirely contained in the bigger piece.
Step 4: 1st Version Dimensions
here you can find all the dimensions necessary to build the stair. When you design the connections between beams, boards and wood legs consider them to determine the elements length. For instance if you want to use wood pins, you already have right dimension in my schematics, but if you want to make joints, you have to add the joints length to the element length.
A note about the dimensions, all the wood boards are 4.5 cm thick, and all the beams have 3.5 x 4.5 cm section, disposed with longer inertia in direction of the shorter side of the bench, so to save more space for the inner steps.
Step 5: Operation Principle and Critical Points
You can see in the asnimation how the stair can fold inside the bigger element.
There are some critical points at which you have to pay attention.
Look at the following animations, you see that there could be some interferences between the two parts during the movement. You have to keep those distances the shorter you can, to maximize the efficiency and stability of the stair, but of course you have to check that the parts don't touch one each other.
Step 6: 2nd Version
This version has fewer pieces than the first one, so it a bit easier to make, but the overall dimensions are the same.
Step 7: Folded
Again I show you the first two steps structure folded inside the bench.
Step 8: 2nd Version Dimensions
Here you can extract any information you need to build this version of the stair-bench.
I repeat the note since you could think some measures are missing: all the wood boards are 4.5 cm thick, and all the beams have 3.5 x 4.5 cm section, disposed with longer inertia in direction of the shorter side of the bench, so to save more space for the inner steps.
Step 9: 3rd Version
Last variation has been to enlarge the depth of the all structure, so that it's more stable and safe. So the top step has become 40 x 30 cm. The bench is also a bit taller than before, since I wished to keep the same rise for every step. The only disadvantage is that now the bench is not so compact as before.
Step 10: 3rd Version Folded
This model has the same exact folding principle of the first ones.
Step 11: 3rd Version Schematics
And here the schematics for this bigger version. Again all the wood boards are 4.5 cm thick, and all the beams have 3.5 x 4.5 cm section.
I will write soon the instructable about the building process, but I hope that someone of you readers can build it before, and I'm sure we all can't wait to see your works.
Step 12: [UPDATE] 4th Design
Last but not least an huge 40 x 40 cm bench, with a different support type for the inside moving part. And there are fewer parts to build in this version, but pay attention to make stronger joints, or it will be weak.
Step 13: 4th Design Dimensions
At last the schematics for this bigger square bench.
Add eight rubber feet under this last bench-stair, or it will get struck in the movement against the floor.
Good luck if you decide to build it!
Step 14: 3D Model
If you wish to try making a scale model with your 3D printer here is the .stl file :-)
Step 15: [UPDATE] Reinforcement
after some test I had to improve the stability of the stool step with an additional wood bar in the front of the small piece. then I enlarged the second step and I added a wood small cylindrical bar to help opening the stool.