Here is probably the worst useless machine ever made. It started out as a Chinese DIY PVC kit that I couldn't get working right so threw out the geared motor mechanism and used a servo and it works great - just looks bad.
This is probably one of the thinnest useless machines you will ever see though.
Video shows my machine working.
First picture shows what it is supposed to look llike
Second picture shows how the arm and switches work.
Third picture is the schematic which is pretty informative even though I don't read Chinese.
Fourth picture is my abominable useless machine with ill fitting lid. The two wires are the kill switch in case the bumper switch does not shut off the servo but that hasn't happened so the kill switch is really not necessary.
Fifth picture is inside guts of my useless machine using servo rather than the kit supplied motor and gears.
Finally the last picture in blue is the kits gears that you have to assemble yourself. Mine worked fine at first but then the arm started slipping on the axle and then there was no fixing it so I used a servo which works great.
I took a microservo and made a geared motor out of it by snipping the little stop peg on the top gear, removing the circuit board and soldering two of the servo leads directly to the motor. Works great.
The bumper switch inside the box is just placed in a bunch of hot glue, the servo is zip tied to the inside of the box, the arm is a piece of wooden spoon with a bit of fishing pole hot glued on. Love hot glue and zip ties and duct tape.
This one uses a slide switch rather than the usual toggle switch.
I feel sorry for whoever bought this kit because only a craftsman could put it together and get it working the way it is supposed to. As you can tell, I am no craftsman. Even though it only cost 4 bucks - it is the 4 hours you put into it that you lose. The kit supplier shows a video of it working but even theirs got stuck. Mine doesn't get stuck.