Introduction: Citadel Knex Ball Machine Elements - Instructions

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Hello everyone! This is a guide to all the elements in Citadel, for those who are looking to add elements in their machine and want instructions. Each element has its own step. Most of these elements are pretty small and compact, as I couldn't use any huge elements in such a compact machine. There are also lots of elements that fit well into red rod towers, so you won't have to have blank towers in your machine. If you'd like to see the video that these elements are in, click here for the Citadel video.

Before you begin: Some of the pictures used in this guide are from Citadel V2. I built onto Citadel after making the official video so I could make the elements and tracks work more reliably. For more information on Citadel V2, here are some links to pictures/video:

Overview video

Citadel V2 Photos

Citadel V2 Construction

Citadel Deconstruction


Here are instructions for the 4-way path separator, made by dododoos!


Note: Throughout this Instructable there are some elements that are more step-by-step than others, as I don't have the time to rebuild all of them. So, I decided to build the more complex ones that require some explanation. You'll also notice that I've put a lot of the picture info in image notes, rather than in a numbered list like I used to. This is so you won't have to leave the full-screen picture mode, read an image's description, and open the next one into full screen. If you're having trouble with a certain element because there aren't enough pictures, leave a comment and I'll rebuild it and make better pictures.

These have not been tested with newer Knex balls, since I use the original balls from Big Ball Factory. You'll have to use your own judgement if you use newer balls, which are slightly larger and lighter than the older ones. Also, lots of the elements have cheap support structures that are meant to be improved (go to Step 21 for an example of these cheap supports).

Let's get building!

Step 1: Curved Maze

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This maze is like a horizontal maze and vertical maze combined, as you can curve it however you like. I thought it looked good as a roof so I put it at the top of the machine. Just make sure it doesn't go too flat or the ball may get stuck. You can make it with white connectors instead of blue, I just did that because I like that blue color.

Step 2: Radial Maze

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This circular maze works like most other mazes, except it's arranged in a circle instead of being just straight. This allows the ball to move an infinite direction in one way (if you have the pieces). When it gets sent down in one place it can end up anywhere once it's at the bottom, which makes it random and cool to watch. It's easy to fit into a red rod tower, but make sure it's reinforced so it'll be nice and strong like in the pictures. Also make sure to either include a floor at the bottom or tracks on all sides. If you'd like to add that curved track that leads into the maze, head on over to Step 23.

Step 3: Altpin Maze

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This strangely-named element is a maze of pins that are weighted and can tilt, like a ball alternator. The ball cascades down very quickly, and it can be made as tall as you want.

Step 4: Zigzag Maze

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Much like a normal maze, this maze makes the ball go back and forth as it travels downward between the pins. This can be made as tall as you want.

Step 5: Tiny Zigzag

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This is similar to the standard grey-rod zigzag where the rods are increasing in distance the longer it gets, causing the ball to roll along towards the wider end, except this version uses yellow rods. The balls move down very fast, and it is very noisy if you make multiple balls go down at once (if you want to do this, a timed release would be a good idea. More info on that is in Step 22). Make sure this is in a sturdy area of your machine, as the vibrations from the balls going back and forth can easily shake the whole zigzag (and maybe even the whole machine itself). You could also arrange each level in a spiral, much like the turnstiles element in the next step.

Step 6: Turnstiles

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The ball will turn through many little turnstiles in this element, like the ones found at parks or airports. It goes in a square spiral, each time going down a level and going through a new turnstile. You can link them up too like I did, but be aware that the friction might build up if you make it linked for too long. I recommend making each linkage no longer than a grey rod, and hooked up to the tower in 2 to 3 places. This will allow the ball to make it through the security check so it can then ride all the coasters in the park, perhaps even Leviathan.

Step 7: Caged Helix

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This is a spin-off (see what I did there?) of an element that was in Wipe Out, and it's not really modified that much except for the top and the cage. If you want, you can make the cage have its sides like in the original, I just made mine with 2 sides since it spins easier (less of a chance of the ball getting stuck at the top). The most difficult part of this element is the top, as you don't want the ball falling out or going to the other helix. If it does go on either helix, you'll need two tracks at the bottom to catch the ball. I got mine to work on just one helix so mine only has one exit track. You might be able to make it taller, but keep in mind it will be harder to spin, and the helix isn't that strong so it might bend too much.

Fun fact: the helix design came from the Power Tower Crane.

Step 8: Spinning Freefall

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This element uses pinwheels along a freefall to make the freefall spin. This one can't be extended due to the friction of the gears. You'll need tracks or floor at the bottom, since it ends up in random places after it's done rotating.

Step 9: Linked Pinwheels

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Closely resembling the spinning freefall, this element uses a freefall with pinwheels that are linked to each other with gears. My version makes each pinwheel move in opposite directions to the one beside it, but you can make them move in the same direction if you want. Make sure to set the pinwheels in the right directions, so the ball will slide past without getting stuck.

Step 10: Zigzag Freefall

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This is a freefall with a twist: it goes back and forth as the ball falls. To do this the whole freefall rotates on an axle toward the back, and there are small pins that the ball passes. Make sure the ball can enter in no matter where the freefall is, though on mine it always reset to the same position (you can do this with guardrails).

Step 11: Twisted Tower

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This is mainly an element for looks. The ball freefalls down it fast, but it does have a slight spiral to it. The inner rods that the ball falls on are in a pattern. When building it from bottom to top, each square rotates counterclockwise.

Step 12: Double Chainsaw Dropper

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A standard chain dropper uses a counterweight and one claw that the ball falls into, resetting when the ball exits. In Cataclysm I made one that has 2 claws and doesn't reset, but it didn't work that well, so I decided to improve it and make this element. It uses 2 chains as well, and the ball transfers from one chain to the other as it descends. The chains are hooked up to a small escapement mechanism, which makes the chains not go down too fast, while still allowing the ball to easily go down. The tricky part of this element is making sure the chains don't go to the side and get stuck. I added some guardrails along some parts to prevent this, as seen in the last two pictures. I wouldn't advise making it taller, as that will just allow the chain to be more loose. If yours still doesn't work with guardrails, make it shorter.

Important: If you make yours a different height than the one in these instructions, the spacing of the red connectors on the chain may be different. For example, The element covered in these instructions has 6 chain links for each red connector, but the one in Citadel had 8 links.

You can mess around with the escapements if you want, the more weight you add the slower the ball will descend. Here's an example video.

Step 13: Mini Spiral Bowl

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These are a very small version of a regular spiral bowl done with flooring instead of track. They can be stacked next to each other, though they have to be staggered so the supports might take up a bit of room. The exit/entrance tracks for these is the ideal location, as the ball will sometimes circle around 3 times before going in the hole. If the tracks are off it will most likely go right in the hole without circling around just once.

Step 14: Square Spiral Bowl

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As with lots of elements, I like to think of ways to modify them, and this one is no exception. If you were to take a spiral bowl and put it in Minecraft, this would likely be the result. It uses a lot of pieces, especially green rods. I'm not sure if it can be made larger, as the ball goes slower the larger you make it, though it would be possible if the levels sloped at a steeper angle.

Step 15: Double Executive Ball Clicker

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This is a modification of the element I made for Wipe Out, except it activates on both sides. The ball coming in should have a decent speed, and railings on the side also help (mine only needed railings on one side). It may require a bit of adjusting to make the tubing just right. My version worked best with 4 balls, but it could be modified to use less balls if you'd like, as long as you adjust the tubing (using less balls will require a deeper middle).

Step 16: Two-way Loop

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This is a small Wipeout loop with a twist: the ball goes through it, and then backwards through it halfway, falling into the middle where the track is wide enough to make a gap. With my loop the ball entered from one side. It would work from both sides if you're willing to modify it a bit, by making the track on the other side slightly more narrow.

Step 17: Vortex

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This combines a spiral bowl, loops, and helix all into one element, the vortex! It uses a lot of pieces, so if you don't have enough you could change the spacing between each orange-tabbed connector. I didn't have enough tubing to make it solid, so I made each orange tabbed connector with 2 blue spacers in between.The more solid it is, the longer the balls will remain in vortex mode. This element was inspired from those funnel-shaped waterslides, except the balls go all the way around instead of just back and forth at the bottom. If you want to make it look cooler you could add a ball collector to the beginning, so all the balls go down at once, or also a timed collector (so they don't run into each other).

Step 18: Green Tunnel

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This tunnel was originally used in Cataclysm, except it was just straight and not very long. This one is curved, and if you have enough green connectors you can make it as long as you want. Keep in mind that, if curving 90 degrees, you'll start to have trouble connecting the green connectors, so it would be better to make it curved like mine rather than spiraling down a tower.

Step 19: Wave Tunnel

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This track element is mainly for looks, as the ball will cause the small pins to raise in a wave pattern. When choosing where to put it, make sure it is angled well so the ball doesn't get stuck along the way. This can be made as long as you want.

Step 20: Boy's Heads

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This is just a 45-degree track that has Knexman heads (or boy's heads) pop up as the ball goes down. You can extend it, but you'll have a lot of headless Knexmen.

Step 21: Portals

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If you build this element, you'll really be thinking with portals. This element is a reference to the popular game Portal. It's one of my favorite games, and since the theme of catwalks and factory was inspired from Portal 2, I decided I wanted some portals in there as well. It may come of surprise, but the pieces aren't actually made of moon rock. A second ball waits behind a wall, and when the first ball activates a small arm it releases this second ball at the right time to make it look like a real portal. You'll have to cut tubing if you want the orange and blue portals, but it looks cool and like the real thing. I made my portals where they are so you can't see what's behind them as easily, like the tracks leading into the back where the second ball is stored. I recommend making a wall so you can't see the second ball.

The version covered in these instructions has the same spacing as the one in Citadel. You can re-arrange them, but the mechanism to release the ball will need to be built different. After you know how this one works it wouldn't be too hard to make different versions.

Step 22: Timed Release Collector

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This is an element seen in many marble machines. Standard ball collectors release the balls at the same time, but this one adds a timed release once they're collected. The balls pile up behind a gate, and when the last ball comes in it goes past the waiting line, using an overflow track much like the ones at the bottom of the machine. It then ends up activating the release gate, which sends the rest of the balls into the exit. This gate is a double gate, much like the one that's motorized before the 4-way path separator for the lower side of the machine. The timing depends on how long you make the track that connects the release gate to the arm. You can make it collect as many balls as you want, and you can also modify the timing by changing the length of the connecting track.

I built two versions in Citadel, one before the vortex that collects 5 balls and one before the yellow zigzag to collect 4 balls. These work best if the last ball is coming in straight on. The smaller one I built had to be more compact, so the balls came in from the side, and sometimes the last ball didn't go into the overflow track. That's why I recommend making the version where the ball comes in straight on from the back (this version worked 100% for me). I'll only cover how to build the better version, and making it shorter is simple; just make the overflow section closer to the release gate.

Step 23: Banked Half Pipe

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This is something interesting that you can add to the exit of a track. This concept is actually pretty old, originally in this ball machine. I just wanted to revive it since I like the idea and no one else was building it. You can play around with the angle of the banking to make the ball stay in longer, and also the speed. I think it goes especially well with a radial maze underneath, as the ball exits randomly out of the curve. I've provided pictures of the track in Citadel, but you can make this element with any track type you desire. Simply make a tight curve and make the middle of it lower than the rest, along with the banking.

Step 24: Tilting Half Pipe

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This element uses a flywheel to make its movement smoother and to allow it to fall slower. I got mine to go back and forth 4 times before the ball falls out, but sometimes it would be 2-3. You'll have to keep that in mind and make a long track to catch the ball wherever it may fall, as seen in the last 3 photographs. I messed around with the counterweight and flywheel for a while, but it's still pretty random.

Step 25: Half Pipe Arm

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Like a half pipe, the ball stays in until a certain point, except this one is in arm form. Make sure it doesn't go straight up when in resting position, as the ball will get stuck at the top, before it even does anything. No one wants that! You can also adjust the platform within the arm that makes the ball exit, if you don't want it to be in there for very long. It actually takes a while to exit, I just edited it in the video so people wouldn't get bored watching it go back and forth a lot (it's fun to watch in person though). These would be cool to put one after the other, in a row down a tower.

Step 26: Double Flipper

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This element is good for the sides of towers, and you can have multiple ones in a row like normal flippers.

Step 27: Zigzag Arm

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This is like a regular arm, except it goes through a zigzag as it it goes down and back up. If the ball falls out on yours, you should make the counterweight heavier so the arm falls slower. Don't make it too heavy though, or else the arm wouldn't move at all, and that would make for a pretty bad arm.

Step 28: Collapsing Arm

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This arm gets smaller as the ball goes into it, making it go all the way around until it un-collapses at the top and resets to normal. This one fits nicely on the side of a flat tower.

Step 29: Multi-Axis Arm

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This arm took a while to complete, since it has to rotate on two axles. First it goes down, and then to the side. It works well being on the edge of a tower, otherwise it would take up a lot of room inside the machine. It bounces back after the ball exits.

Step 30: Rotating Arm

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This arm is a lot like the ones in the Big Ball Factory, except it rotates as it goes down, using gears.

Step 31: Double-sided Arm

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This arm uses 2 balls to operate. On both ends are a holder, and a ball waits at the top. It uses a flywheel inside of a tower to run more smoothly. You don't have to make your flywheel in a tower; I just did that to save space. I do not recommend leaving the flywheel out completely, since the arm will have less control.

Step 32: Scissor Arm

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This is related to a scissor lift, except in arm form. The counterweight takes up a lot of room, but it can fit in a blue-rod-wide space. I decided to encase my arm in white connectors to hide it while it's folded up. Unfortunately, this element cannot cut paper.

Step 33: Crazy Arm

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I call this a crazy arm because it can be made to do many movements, just depending on the counterweights. It's actually 2 arms in one, joined at the top to make a trapezoidal shape. It makes a collapsing motion which sends the ball speeding to the other end, where there's a small piece that pops it off to exit the arm. You can try messing around with the weights, lengths of arms, and where the ball enters/exits to make different variations.

Step 34: Ballbuster

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This isn't really a new element but I decided to include it anyway, in case you have a Knexman that's been getting in trouble taking your builds apart or something. This guy got lazy on the job. He failed to inspect a ball arm, so they put him on the arm instead.

Step 35: Hanging See-saw

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This is a see-saw that's suspended from above. A ball waits in a middle track. When another ball comes, it tilts the element to the side, causing the middle ball to push the outer ball into the exit track. It works on both sides, so it also acts as a path separator.

Step 36: Twisted Track

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If you combine an arm and track, you could get this. It uses a counterweight and twisted track to make it have a smooth return after the ball makes it go down. This is because the ball slowly moves toward the center near the axle, so it has less and less weight on that end.

Step 37: Tilting Tracks

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The first element made for Citadel, this is a platform with tracks on it, and the whole thing tilts sideways when a ball gets to the end. It stays down until the ball leaves the last track.

Step 38: Tilting Tracks 2

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This platform of tracks has two positions as the ball goes through it, resetting itself at the end. It fits well on the edge of a tower. You might have to do some adjustments to make it work, but it's a reliable element once adjusted correctly.

Step 39: Tilted Tower

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This tilted tower has tracks inside which make it rotate 90 degrees, and then back to its original position. It uses a latch at the beginning that the ball activates. Make sure to add little guardrails above the track so the ball won't just skip past the end of a track (the green connector which it should stop at). That way, it will rotate 90 degrees before the ball leaves that track and goes on to the next one. This is important to build because it might get stuck without proper rails.

Step 40: Chopsticks

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No, you won't be eating Chinese food with this element. Its name comes from the two small arms that overlap as a ball goes through. It's a quick and simple element. Be sure to include a bit of a cage around it so the ball doesn't fall out.

Step 41: Rotating Dropper

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This is similar to the standard ball dropper, except the top that the ball is on rotates as it drops. You'll have to tilt it if the ball doesn't roll off on its own, by just pressing down on it while it's in the down position.

Step 42: Wheel With Catcher

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This wheel has a catching device attached, so the ball transfers to that and then exits when it gets pushed off.

Step 43: Quad Ferris Wheel

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I call this one a quadruple ferris wheel since it's a large wheel with 4 smaller ones inside it. The wheels on the inside are more like pinwheel instead of actual ferris wheels but oh well. Since the ball can enter in at any location of the wheel, make sure to add enough guardrails, including a long curved one in the front so the ball won't pop out.

Step 44: Balance Blade

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This blade-like wheel stores 3 balls, and when a ball enters on one side, a ball at the end leaves, which re-balances the wheel for the next time.

Step 45: Disks

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This is a simple small element you can add to places that don't have much room. My version uses 2 disks that rotate, but one that uses more disks would be cool. Make sure to look at the second to last picture, it has an important note.

Step 46: Mini Rotospinners

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I originally made a rotospinner in Cataclysm, but it was large and took up a lot of space so I decided to make a mini version. This one has two of them in a row. It still requires a locking mechanism and exit mechanism like the original. Make sure to add a guardrail where the ball transfers to the second rotospinner.

Step 47: Reversing Arms

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This element is named after the Reverse Arm Lift, as it's like the lift, except the ball goes down each arm rather than up. This uses a see-saw at the bottom to link up two sets of arms (4 arms total). The arms are forced to move when the ball reaches certain points along the way. You could try making it taller, just keep the friction in mind.

Step 48: Zigzag With Linked Pins

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This is just a standard zigzag, except it has pins that are linked to each other that all move when the ball pushes one down. If you make this one taller, expect to be attentive of any friction complications.

Step 49: Zigzag With Linked Rotators

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This zigzag uses pins that rotate to move out of the way, and since they're linked all of them move when a ball triggers just one. This one doesn't have very much friction, so you could make it longer if you so desire.

Step 50: Linked Spiral

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This element uses two seesaws that are inverted with gears. This helps to link all the platforms, which are on 4 corners of the tower. Mine used a flywheel to help with smoother movement, but it's not needed. This should be extendable, but watch out for friction. You can add walls to keep the balls inside, but I had mine without the walls for a long time and never saw a ball fly out of the apparatus.

Step 51: Quad Linked Arms

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This uses 4 arms connected to each other to create an alternating effect as the ball descends. There's too much friction to make it any longer though. It doesn't use any gears, just a crank type mechanism at the bottom. The entrance track (last picture) should make the ball build up some speed to overcome the initial arm friction.

Step 52: Staggered Platforms

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This is a modular element that can be made as high as you want, if you have enough pieces to build the supports. The ball falls through each level of platforms, going down in a spiral pattern. The grey towers that act as supports can be modified to use less pieces. Pay close attention when building this (especially to which corners are which), as a small mistake could cause the ball to get stuck.

Step 53: Collapsing Stairs

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This modular element can have as many stair sections as you want. When the ball goes through these, they collapse down for a time until the ball goes further along and resets them. You certainly wouldn't want to walk up these stairs.

Step 54: Falling Stairs

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This isn't a new element as it was first in Death Trap, but I wanted to share it anyway. These are little stairs that have counterweights, so they tilt and reset as the ball makes its way through. They can be arranged in spirals, zigzags, or a straight stair pattern. This is a simple modular element, good for adding into small spaces.

Step 55: Delayed Stairs

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This element only works with a double-ball path. You can either use a standard 2-ball collector before it, or a path separator like I did. Make sure the timing is right with this one; the middle section should be pressed down as the first ball comes in. In my version the first ball came into the right side, and the second ball went to the left side. This is one of those elements that requires one ball to help the other when it gets stopped. It uses a tilting gate in the middle that's double-sided to achieve this.

I don't recommend making it longer, as friction prevents it from working at such lengths. Mine got stuck once, if yours does that you can remove some of the places that the middle gate section is attached to (like the orange connectors, as seen in the last picture). The main reason mine got stuck was because it hadn't been used for a long time, but a few uses made it more loose and it worked fine after that.

Step 56: Delayed Freefalls

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This requires two balls to operate at a successful rate. It uses 2 freefalls next to each other and some small stoppers that get activated by the ball on the other side. The balls go down at such a speed to make it look like they're bouncing when being released to the next level. This cascading effect also makes a cool sound. You can make this one as tall as you like since it's modular. Like the delayed stairs, this has to have the timing right as well. Go to the last picture to see this.

Step 57: Freefall Clickers

This element is one of the elements from Citadel V2. It's a simple freefall with linked clickers all the way down. You should link them in sets of 3 to 4 so the ball doesn't get stuck.

Step 58: Bonus: Modified From Cataclysm

This element didn't make it into Citadel due to lack of space. This one was originally built in Cataclysm (here's a video of it for reference), but this one is modified to work better. It uses two balls. There are "pushers" on the inside that push the ball on one side out when the ball on the other side falls. This can be made as tall as you want. Note that, like the other 2-ball elements, a ball must first go into the side with the white rods (the pusher). The second ball should then come into the other side (the side with the yellow rods), and the pusher will activate.

Step 59: That's All!

That sure was a lot of steps! I hope you've been able to build whatever elements you wanted. If not, don't hesitate to leave a comment to get help. I could also add more detailed and step-by-step pictures for any particular element if you want.

If you build an element and post pictures, I'll add them as example pictures to the appropriate step.

Thanks for viewing, and have fun building!