I set out to create a weight system to close a door without having to be near the door. A string would be attached to the door and go through a series of pulleys to a weight. Once the weight is released, the door closes quickly.

1st- I created a basic prototype out of yarn and cardboard as shown in the first slide. I originally envisioned to have a platform which the weight would rest on. Once activated, the platform would flip and release the weight.

2nd- I changed the way that the weight would be released. Now, as shown in slide 2, there would be a ratcheting mechanism. The string would be wound around a pulley connected to a ratchet wheel. As the door opens, the string would come up, spinning the pulley and allowing the ratchet to move. But once the door stops and the weight pulls the string down, the ratchet arm would engage, preventing any movement. I envisioned a motor wirelessly connected to a remote that would release the ratchet arm when needed.

3rd- In addition to closing the door from anywhere in the room, I wanted to have the system 'prime' itself for the next use. This requires the weight to be halfway up the doorframe even the door is closed. This would make the door easier to open- because you wouldn't have to fight against a weight.   I then made a pulley prototype. What I found was that winding the weight up the doorframe also requires the string above to tighten. Because the upper portion of the string is fixed to a closed door, it gets too tight and could snap.

4th-I then made a double pulley so that two independent strings can be attached, solving the problem of one string affecting the other. However, I found that this wasn't needed.  I tested the weight needed to adequately close the door from about halfway up the door frame. It was about 7 lbs. I then opened the door with the weight attached via string and found it is not difficult to open. I discarded the weight 'priming' idea.

5th- As time was dwindling, I decided that the ratcheting system would not be ready in time. So, I decided to focus on the mechanics of the locking mechanism. As seen in the 5th slide, I decided to use a  hinge and flat surface to hold the string in place. With knots in the string and an upward angled hinge, the string can travel upward as the door is opening. but once it stops, the knots would come back down at which point to the hinge would prevent any movement. Then with a flick of the hinge, the strong travels down, closing the door.

6th- I found that there was too much friction among  the string, the pulley and the door frame. So, I mounted the pulleys angled on the metal door frame.

7th- Halfway down the door frame, I put a 3D printed hinge holder. This is similar to the hinge idea i previously had.

8th- Finally, I moved to a different door and mounted two pulleys on the metal frame.
 

I set out to solve the problem of wanting to close a door even if you’re not near it. This is useful if you are in bed and realize that your bedroom door is open, or if you are teaching a class and want to keep the door open as students enter but want to close the door when the bell rings.  This could also be useful for the elderly and disabled.

The string is connected to the door and goes through the pulley system. These pulleys change the direction of the string so that it goes directly down the doorframe. Halfway down the doorframe is the locking mechanism that holds the string in place, preventing any movement. Then at the bottom is the weight. The locking mechanism consists of a 3D printed holder and a regular hinge. This locking mechanism catches knots in the string as it goes past the hinge. If the string is going up (as in the door is being opened), the door is not affected. But if you want to keep the door open, the knots engage with the hinge, preventing closing.

An Arduino microcontroller is used to connect a remote control to a servo motor, which is in turn attached to the hinge.  If you are somewhere in the room and want to close the door, you can push a button on the remote and the servo will pull the hinge open, allowing the weight to close the door. This allow for hands-off control. 

The door closer in action.