A crane for my keyboard cable! (started 03/08/2021)

So, basically, I wanted a keyboard on my chair, but not wireless. In the past I've had a dangling usb cable running from my keyboard to the computer. But I found it very annoying that I can't move my chair around the room. I couldn't even spin it!

I've decided that the wire should go straight up from the chair, and then there will be a mechanism above that follows the chair.

Dangling usb cable between computer and 3d printed keyboard

Plan

I've been considering different materials, joints and designs. I wanted to find some good hinges to buy, but I couldn't find any that were designed to not be used in pairs. The best option was to use metal profiles that fit perfectly inside each other, so I can make some tight hinged joints.

I'll be using aluminium for everything because it's light (and cheap). I'll try making everything without ball bearings at first, hopefully the wire will be able to pull it around. I made some measurements, plans and 3d printed prototypes!

A desk full of tools, plans and prototypes

Building the crane!

I pretty much followed the last prototype to make the joint. It's a rectangular hole in the side of the bigger profile, it works great!

Originally I wanted to make it without a counterweight, but it soon became clear this is not an option. I can make the middle joint without a counterweight, but not the main axis. I calculated the counterweight and found this block of concrete which is just right. It feels weird to have this brick hanging over my head on a rope, but it'll do for now.

In the image you can see it mid-construction. This is when I realized the counterweight won't fit between the crane and the wood, so I needed to increase the length of the vertical spacer (a radiator pipe).

Crane being built

Finished structure

It's built and it works! This arm is 2.5m long when extended and it reaches all over the room!

I think it looks really cool, and this was one of the reasons I made it! I wanted it to be the centerpiece of the room, the first thing you'd notice when you walk in. Besides the triple screens, hihi

It'll get a wire soon. I already made a 10 meter usb cable and verified it works flawlessly, but in order to run it through the crane, I'll need to cut it and resolder it on the other side.

Folded crane arm

Here you can see my 15% scale Fischertechnik prototype by the real thing. It really is quite big! It looks pretty intimidating irl because it's above your head. But I like it this way!

I'm not done with this yet. I want to put something soft on the ends so it doesn't damage my walls and furniture. And obviously I need to run the wire.

Because of a change in the mounting position, the arm can actually hit the opposite wall of the room. This was not planed, it's a bit unfortunate. But I think it will be fine if the end can't damage the wall.

I somehow managed to drill unmatched holes for the main axis in the long profile, so everything is a bit tilted. This is not visible in the images but the second arm hangs down a bit. I think it'll be fine. If not, I can drill a new pair of holes and fix two problems at once.

Also, I'll be the one to say ... it kinda looks half of it is made of trash. I'll see what I can do about that. Maybe proper weights could help.

Big and small crane, both extended

Finished structure

It's built and it works! This arm is 2.5m long when extended and it reaches all over the room!

I think it looks really cool, and this was one of the reasons I made it! I wanted it to be the centerpiece of the room, the first thing you'd notice when you walk in. Besides the triple screens, hihi

It'll get a wire soon. I already made a 10 meter usb cable and verified it works flawlessly, but in order to run it through the crane, I'll need to cut it and resolder it on the other side.

Folded crane arm

UPDATE 26/08/2021:

New weights! These are 2kg lead weights, the ones you would strap around your belt and go scuba diving. But I'm using them as a counterweight. I was able to attach them firmly by running threaded rods through the holes. If you look carefully, you'll count 6 layers, but there are only 5 weights. One of them is a 3D printed spacer that looks like an extra weight.

There is still a rope, but it's no longer used for attachment, it's just a safety percaution. If the crane breaks and starts falling, the rope will stop the weights. With this particular length of rope, it won't save the TV underneath. And, honestly, in the unlikely event that this goes to pieces, the TV is not important enough to matter. But I am!

Crane with lead counterweight

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