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Hi Everyone. I'd like to show you my GBC Module that I made called "To and Fro". Definition: to and fro /ˌto͞o ən ˈfrəo͝o/ adverb - in a constant movement backward and forward or from side to side. verb - move constantly backward and forward. noun - constant movement backward and forward. I wanted to design a GBC module that I hadn't seen done before. The main feature of this design uses a string and pulley system, with different levels of mechanical advantage implemented to get the timing of the mechanisms just right. This GBC module adheres to Type 1 of the GBC Standards, processing one ball per second on average (http://greatballcontraption.com/wiki/Standard). The main focus of this module is the 'ladder' in the middle which raises and lowers using string and pulleys. You can see this in the video between 1:48 and 2:04, and I'll try to describe what is happening. First of all, the end of the string is attached to the frame, and goes down to the cranks. The exact length of the string can be adjusted, similar to how guitar strings are tightened. The cranks have pulleys on them, so the string actually moves twice as far as the diameter of the cranks as they rotate, but at the same time the force is halved. Next, the string goes up to a pulley fixed on the frame, then down and around another pulley, and back up again. The bottom pulley is attached to the moving part of the 'ladder'. This halves the distance that the 'ladder' moves compared to the string, but also decreases the force required to do so. The string goes over another static pulley at the top, and then back down to the outside edge of the moving part of the 'ladder'. To move the outside edge of the 'ladder' requires the full force of the string to move. Due to the mechanical advantage of the different parts of the pulley system, the 'ladder' wants to move up first since this takes less force, but once it hits a stop at it's upper limit, the string then provides force to the outside edge of the 'ladder' which causes that last little 'kick', which lets the balls roll to the other side. This module can also be broken down into four smaller sections for easier transportation: The motor which is part of my Automatic Motor Shutoff and Alarm System, The 'hopper' and 'ball diverter', The 'ladder', and The 'waterfall'. There is only one M-motor powering this module and that helps ensure the timing of each section is in sync with the next. The motor section is attached to the 'ladder' section with a universal joint, and the 'ladder' section is attached to the 'hopper' section with a CV joint. The 'waterfall' section doesn't need any motor input, so it is attached to the 'ladder' section with a single axle that allows it to be detached easily. Between the 'ladder' section and the 'hopper' section is differential (hidden away underneath), and I can manually adjust the rotation of this differential via a worm gear to get the timing between each section just right. Apart from this one worm gear used to make timing adjustments, I haven't used any other worm gears as I have seen the damage they can do to GBC modules if something gets jammed (although, in theory, my Automatic Motor Shutoff and Alarm System should stop this from happening anyway). There are quite a lot of gears within the drivetrain, but it runs quite smoothly. When I was creating it I thought the weight of the 'ladder' would cause a lot of strain on the motor, but when one side is going up gravity is making the other side go down which cancels out a lot of the strain. Jams sometimes occur in the 'hopper' and 'ball diverter' sections, and are typically caused by too many balls in the hopper, or the timing of 'ball diverter' not being adjusted correctly. I have had this running at a public expo that my LUG held, but I was too busy to baby-sit this module, so it was only running part of the time, but when it was running it ran without issue. This is the first GBC module that I have made, so I spent a lot of time trying to get it working consistently. I hope you like it. Any constructive feedback/comments/questions are welcome. UPDATE: I have created an LDraw/MLCad file of my GBC module. Read more here. Music: