Big magic arm

An open-hardware robust adjustable strong arm to hold laptops and books in space in any orientation.

Subir Bhaduri

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Description

A client that i design for has spinal injury and thus must often work lying in bed. But currently struggles with laptop screen orientation which is at the best slanted to the exactly horizontal needs of the client.

My solution is to scale up the Manfrotto's Magic arm system to hold laptops or other gadgets in any orientation as needed.

Details

The key idea here is to have a ball on both ends of the device and a linking arm structure with adjustable friction mechanism. One of the balls must be fixed to the ground and the other to the laptop. The idea has been inspired from Manfrotto's Magic Arm camera positioning jig.

But instead of the complicated inner mechanism used in the Magic Arm, i devised a simpler design (Manfrotto, you are welcome), inspired by the usual prongs or pliers.

The tightening of the knob in the center can result in increase in the frictions on the 3 moving parts, the ball at the bottom, the hinge in the center as well as the ball on the top holding the laptop. The challenge is - will the clamping be good enough to hold a heavy 3-4 kg laptop in the cantilever form we desire? There is only one way to know - to make it.

Here's an interesting video to show that the bigger the ball, the more the holding force can be achieved.

See my failed prototype #1 update in the project logs.

Project Logs

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Prorotype #1 (failed)
Subir Bhaduri • 08/10/2021 at 09:37 • 0 comments

I made the first prototype, but it didn't work so well :(

The idea was to make something like this:

A central knob when turned presses the bottom and top pincer arms together, clamping the balls attached respectively to the ground and to a laptop. This should fix both the ends as well as the hinge.

Here's a video of my first prototype and some images of how i built one of the arms of the above mechanism.

But as you can see, it hardly holds. Thinking of another prototype with stronger gripping action.