I got sick of getting home or to work finding I'd left my memory stick in the computer back at the other end of the journey. So I put it on my keyring. Then I got bothered by the weight of all my keys hanging on the USB port. So I made USB memory Stick Recoil Keyring.
But that design used a keyring recoil, which was quite strongly sprung. I wanted one that latched... like one of those USB cables for laptops... so I picked up a couple for cheap and started experimenting.
Step 1: Gather Your Materials and Tools
1) two retractable USB cables. Can be USB extension or power or anything. No electrical signals are transmitted. I got a set of 3 for �1 each in Pound Land.
2) a photo-frame style micro memory stick
3) A spare keyring
5) epoxy resin
6) stiff wire for twisting
7) electrical tape
1) couple pairs of pliers
2) wire cutter
3) measuring calipers
4) Sharp craft knife or set of knives
Step 2: Version II
I extended the USB cable and was able to draw the cable through the central drum far enough to tie a knot in it. I pulled the knot tight then melted it with a cigarette lighter to encourage the knot to stay. Then I clipped off the spare cable and pulled the cable back until the knot stopped it slipping.
Then on the remaining end, I clipped off the plug and tied the micro usb stick to the end.
Version II works but isn't very satisfactory.
Step 3: Interlude
As an aside, here's how those cables are cnostructed (though you don't need to take them apart to do this project).
The drum has a large coiled spring inside. The cable enters and goes around a channel at the side, which keeps it out of the way of the spring.
The other side of the drum has a complex pattern of channels cut in it, and there's a small ballbearing that runs in those channels to provide the latching effect.
Step 4: The Fun Bit Begins
Fitting a micro flash drive into a USB plug. This flash drive could be prized gently apart quite easily.
The USB plug was not so cooperative. I had to destroy two of them to save the two parts I needed: the metal shielding and the plastic/rubber body. The innards I threw away because they are getting replaced by the micro USB drive.
The second picture shows the innards, and the flash drive inserted into the shielding for a test.
Step 5: Measure Twice, Cut Once!
Before I glued the micro USB drive into the plug shield I plugged it into the computer to check it worked. It didn't so I got out the calipers.
The original innards were 1.7 mm thick, whereas the strpped-down flash drive was only 1.3 mm. So I needed 0.4 mm of padding. As it turned out, three thicknesses of electrical tape did the job. I stuck them on the back of the flashdrive and trimmed them carefully with scissors.
Also in this shot are the cable end and the body of the other plug, which I cut in half in order to hollow out to accommodate the flash drive.
Step 6: Assembly
I put superglue on the electrical tape (white in the picture) and carefully placed it inside the metal shield. Using the calipers and a very sharp craft knife I hollowed out the plastic/rubber plug body to accommodate the new plug.
To attach the cable, I got a small length of stiff wire and twisted it around the end of the cable, just to make an "anchor", and hollowed out a bit of the body to accommodate it.
Then mixed up some expoxy and set everything in position.
Step 7: Enjoy!
Finally, I attached the keyring and the job's done! We have a usb stick that can stay on your keys, but your keys don't have to hang off the computer!