All right, here's a tough one for ya'll. How can I built a marble pump out of LEGO bricks? What would the mechanism which pushes the marbles up need to look like? Here's an example in this video: Unfortunately, one cannot see the mechanism which pushes the marbles upward very well. I couldn't determine what pieces he was using - I think there was a slope, but I'm not sure as to how it moves the marbles up the pipe. A pump is one of the most classic GBC (Great Ball Contraption) modules but is indeed difficult to get right. One of the best illustrations I know is on this site: Unfortunately, most of the site is in German, but the pictures are usually illustrative enough and I think it's a good source of information for ball machines in general, not only LEGO ones. The best is of course to get in touch with one GBC builder at events and ask for information. Here is a picture based on the model at aforementioned site: Here is a video showing the mechanism in action.
Marbles weigh more than LEGO soccer balls but there is a thriving community of avid "Great Ball Contraption" builders... these move soccer balls from their (standardized) input to their (standardized) output. They use various techniques including stairstep, conveyor, helix, scoops, and every other motion technique imaginable. I think looking through their designs will give you lots of ideas This great site by Phillipe Hurbain ("Philo") should get you started, In particular look at the Ball Pump and Jigsaw module, which has instructions included I found this question and used Joubarc's and Peter's answer to guide my pump build: The video of it's operation is here. As per Joubarc, it was very tricky to get right. Here are some subtle things I learnt/did during the build: The blue down wedges in the ball feed are not symmetric horizontally. Putting them on alternate layers helps stop the 14mm beads getting jammed. The ball feed needs to be narrow at the bottom (beams with a 2 stud gap, no wedges) to avoid ball jams and ensure the balls drop down with gravity into the intake.
Needed a gradual ramp in the slider/feed section (yellow) to prevent ball jams and ensure the balls would drop into the intake Older bricks that have been nicked from drops, rough play tend to jam the slide mechanism as they brush past each other. Use newer/non nicked bricks. Use longer horizontal beams in the slide mechanism and adjacent walls. Every vertical vertice is an opportunity for the slider to jam. Long horizontals reduce this. Use window pieces in the slider to reduce slide contact and friction (see white slider section) Needed a long slide (white section) to increase clutch power holding it on to the bottom plate. With a smaller slide section it didn't take long for it to pop off due to push/pull action from the piston. a 2x1 beam with two holes was used to mount the piston. This aligned the piston just right to not jam during rotation. A single hole 2x1 beam didn't work for me. Needed to bias the balls at the top of the chimney to pop them out into the race section.
Did this with the mini cheese wedges mounted vertically. Sign up or log in Sign up using Google Sign up using Email and Password Post as a guest By posting your answer, you agree to the privacy policy and terms of service.Browse other questions tagged building or ask your own question.Today I would like to show you my latest GBC module, a Quincunx also known as a Galton Board, named after its inventor Sir Francis Galton who used it to demonstrate the central limit theorem in 1894. The balls are being transported up with a conveyer belt and a light sensor counts how many balls have passed. The balls then roll down the board and at each peg they can either bounce left or right. After the last peg the ball is caught in a repository. Once 100 balls made their way down, the gate opens and releases all the balls. Probably no GBC module could deal with 100 balls at a time, so I queued them up and deliver them one at a time. The chances of the ball going left or right at each peg are even.
So you might conclude that the balls should be evenly distributed amongst all repositories. But that is not the case and it takes a little bit of math to understand why. Lets assume we only had three rows of pegs. That means that a ball would have to make only three decisions to either turn left or right. This means the number of total possibilities is 2x2x2=8. We can also write this shorter more generally as 2 to the power of n, where n is the number of rows on the board. We can list all eight possible paths for this board: What we observe is that the sequence of decision does not matter. A ball that the goes the path LRR will end up in the same repository as the ball that went RRL. We can add up the number of paths to a repository and divide it by the total number of possibilities to calculate the probability of a ball landing in a specific repository. We can even consider the index number of the repository as the number of right turns the ball took. The chances for balls to end up in repository are unevenly distributed because a different number of paths lead to them.
If we would let 1000 balls flow down this board then 125 are likely to end up in R0, 375 in R1 and R2 and 125 in R3. The reason for this is that there are more paths to R1 and R2 than to R0 and R3. In math we like to generalize our results to any number of pegs, repositories and balls. First we need to find out how many different paths exist for a ball to end up in an arbitrary repository, which is equivalent to the number of right turns. The formula is this: Where n is the number of decision, which in our case is 3, and k is the number right turns. For a ball to get into R2 it needs two 2 right turns. This means that the number of paths to get there is : There are 3 ways and hence the probability of a ball to go to repository 2 is 3/8. This Quincunx GBC module has 32 repositories which means that the balls have to make 31 decisions to either turn left or right. Using the formula above we can calculate that the probability for each repository and show it in a graph. This graph is fundamentally a binominal distribution.