I want to make a construction of two boxes, that by default would be stacked one on top of the other, but linked in a way that would allow the top box to slide off and then move down so that they are lying beside each other.

I want to be able to move the green box between two final positions without having to lift it by much, as it will be quite heavy, so I can't really use a parallelogram and came up with the idea of sliding motion.

In real world execution they will be made of plywood and around 500x800mm, I'm thinking about using some bearings as rollers maybe or aluminium flat bars for linkages, but I'm open for suggestions :)

Oh, and as it's my first post here, welcome and thanks for all the answers and suggestions!

Belowe are some images to explain the situation:

First the green box rests on top of the blue box: Boxes stacked vertically

During motion, the green box slides over: Boxes during sliding

Green box, fully slides off and drops down: Boxes side by side

To add some details: What I intend to use it as is to build a "camper box". You put the box in the trunk of an SUV, that can hold a portable stove, grill, some water tank, extendable table, etc. Then you can fold the back row of seats, and fold out a bed platform from the box.

All the existing designs I've seen just use some flat panels as the extendable bed, but that leaves a lot of space under that part of the bed. With this approach I could have a higher folded box with more space without having the bed be so high that it leaves you little space above to actually sleep. I imagined that the top box would hold lighter things like clothes, so you could still easily move it during conversion.

  • $\begingroup$ I think you are going to need to specify how much modifications to the block is possible and how much room you have around the blocks for mechanisms. Do you need drive mechanisms? Or just a guide mechanism? I don't see the problem with a parallelogram either. Don't you want a parallelogram since it helps one block climb on top of the other on a single smooth motion? $\endgroup$
    – DKNguyen
    Commented Nov 29, 2022 at 20:23
  • $\begingroup$ Hi, to answer your questions: I just want to guide the top box and move it manually. The prallelogram seems to be simple solution but as the box could be pretty heavy, I'd like to avoid having to lift it. I could change the shape of the boxes a bit, like rounding a corner or smth :) I was thinking about combining the parallelogram with some kind of drawer slide, so that the parallelogram would only lower the box at the end of the slide, but I'm sure there are better solutions, I just can't come up with $\endgroup$
    – Mroova
    Commented Nov 29, 2022 at 21:19
  • $\begingroup$ You can edit any details you need to add into your original post. $\endgroup$
    – DKNguyen
    Commented Nov 29, 2022 at 21:20
  • $\begingroup$ @DKNguyen I've also edited the original post to explain what I intend to build $\endgroup$
    – Mroova
    Commented Nov 29, 2022 at 21:29
  • $\begingroup$ I'm not picturing how you plan on avoiding lifting it with this setup since it needs to move either way. Can you not add a lever or something to lever it up just enough to sit on the edge where you can then push it in? Or assistive lift pistons? A four bar linkage where the top sits in slots/grooves so the top can slide would could connect the two. Although the four bar linkage would need to have curved members since the pivot points are inline when the two blocks are unstacked so you need the curve to go around them. $\endgroup$
    – DKNguyen
    Commented Nov 29, 2022 at 21:44

1 Answer 1


Since it is inside a vehicle you could attach a pulley to the roof at a specific point above the boxes so that when you pull on the rope it slides towards where it has to be lifted down, and the balancing motion also helps for reverse action.

It could help to round the contacting edges, and smoothing plywood contacting faces with increasingly fine sand paper, or having a rail between them could help too. It may also require a four point attachement on the green box if what it contains is unbalanced or moves.

enter image description here


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