Magic Opening Doll Box

[Herr_Sprecker]

Greetings all. I was wondering if anyone has had experience in creating a 'magic' opening door without using any manner of electronics or such.

Here's the situation. We're gearing up for a production of Nutcracker, one that we remount every few years. One of the dancing toy dolls is removed from a human-sized decorative box, looks a bit like a wardrobe. It's a little over 7 feet tall, 2 feet thick and 4 feet wide. The back is a piece of fabric that can be lifted so the dancer can get into the box, and the fabric fills the back when it is opened. The doors are shorter than the overall frame of the box. Each door has a couple springs (visible when you get up close to the box) that do the pulling tension, and there is a crossing cable across the door tops tied to a bar located on the back. The operator can pull the bar down from its locking point and then ease it up to allow the springs to open the door by themselves. Then the operator can pull down on the bar to close the doors by themselves. When it is first used, when Drosselmeyer goes to get the doll out, the operator is given instructions to loosen the clamp bar so that the dancer can pull the doors open manually, and then manually close them after the dance when the doll is put away in the box. At night, the doors are to open magically by themselves when the dancer emerges.

We are rebuilding this particular unit, and I would very much like to improve upon the effect. I would like to avoid using any kind of electrical device or control for this particular mechanism, it doesn't need to be terribly sophisticated. I would just like something that looks a little more magical without obvious tension cables stretching across the tops of the doors. Might anyone have any thoughts or ideas?

Thank you in advance!

 

[QuealeTeam6]

Might be worth trying to building some of the mechanics inside the floor/ceiling/walls of the unit to make it more "magical".

I think you can probably use some linkages that would give full control over the range of motion. Some inspirations:

• A mechanical gripper where a central actuator causes a rotation about a pivot. Rearranging the geometry of one of these could get what you're looking for:
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• I know this is electrical, but you can make this human operated: https://www.amazon.com/dp/B0CCTPGQDW/?tag=controlbooth-20
• Have the doors mounted to a shaft that runs from the height of the unit. Then use a sprocket with some chain to control the motion.
• Similar to above, but with a rack & pinion system at the top/bottom

A lot comes down to parameters: time, money, and final quality. But hope that's a start!

 

[Dover]

If you only need it to open on its own and can reset it manually, I would try some gas springs. They would give it that slow magical opening. The tiny ones that are used on tool box lids might be just enough if the doors move easy.

 

[Van]

Taking a que from @QuealeTeam6 above:

Assuming the bottom of the box is a couple inches tall, so it can roll on casters, you might want to pull a modified trick from Heron of Alexandria (old tricks are the best) tricks. as the bottom hinge of the door run a shaft through the flooring material so it sticks out a couple inches below. Attach either two sprockets or pullys, sprockets would probably be better, sprocket to a much smaller sprocket either driven directly by a gear motor, or build your own gearing setup. The other sprocket runs to the shaft on the other door with a cross-over so it drives in the right direction <imagine a figure eight one sprocket resting in the loop of each half.> You could easily power this with either a wound spring (that's wound not wound), like a clockwork, or a gas cylinder, though that would be difficult to close, or a small electric gear motor driven by,say a 12 or 20 volt Gell cell battery (like from a safety light or a UPS, or even a 12 or 20 volt cordless tool battery. Yout could rig the whole thing to a small push button in the floor that the Ballerina could step on, on cue to open the door, or whatever.
If you've never heard of Heron, look him up. In my opinion anyone who builds or rigs "tricks" on stage should be intimate familiar with the trick he was performing, on stage and for temples in 2000 years ago.