## How the marble pump works

The marble pump is the heart of the Lego marble machine, as well as the wooden marble machine 1. The pump is always the thing that looks like magic, because the pump itself occupies a very small space. In order to guide the pieces and the marbles, most of the movement and working is hidden from view. All the observer sees is that marbles fall into a hole, and then somehow rise up this stack. The piston (shown in green) is completely hidden.

 The green piston is mounted on a crank at the point shown with the black spot. In the position shown at left, the piston is in its bottom most position of its circular motion, and moving towards the right. As it follows the circle that the crank moves it in, once it is on the right, it moves up. This forces all the marbles above to be pushed up, and the marble above the piston to eventually be pushed into the column as the piston moves towards the top of its circular path. Once the piston is at the top, it moves left again, but this time its top is level with the block shown in red. Thus, as it moves left, it does not take a marble back to the left. Once it is on the left, it starts its downward motion again, allowing for a marble to descend into the hole. The whole mechanism, so long as there is always marbles at the intake, works very smoothly. It gets a bit noisy if the intake runs out of marbles, because the space above the piston will then be empty as it moves right, allowing the column on the right to fall down into the empty space.

Lots of people have difficulty understanding the pump, even with this diagram, so don't feel dumb if you don't get it. However, if this is not intuitively obvious to you, you should definitely not attempt to build your own marble machine. Marble machines are tweaky to debug, and take a lot of intuition about mechanisms to get working smoothly.

I have since produced a video on how to build the marble pump, and have some marble machine plans for sale, which include plans for the marble pump.

 Got email from a guy , Juergen Kintscher, who was inspired by my page to build his own Lego marble pump. With permission I lifted this animated gif.
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