Under the Sea - a K'nex Ball Machine




About: I love building. A mechanical engineering student, most of my instructables involve modeling projects, K'nex ball machines, and Lego creations. I am also a model railroader, and I enjoy science (astronomy is...

For my fifteenth instructable I am proud to present Under the Sea...my latest K'nex ball machine! This ball machine contains four lifts (including a new one), eight paths, and some new/modified elements to match my watery theme. At about four feet tall and five feet wide, this is also my first ball machine with more than one lift network. I have done a lot of cool theming and come across all sorts of similarities to the ocean depths. (For instance, the ball machine has a "seafloor" and a "surface", and the red supports below the floor could represent magma; animals are also placed close to their natural settings, with the shark near the top and the squid near the bottom; etc.) So come along with me and take a tour of Under the Sea!

(Music in video was composed by Frederic Chopin and played by Vladimir Ashkenazy: "Scherzo for piano No. 2 in B flat minor, Op. 31, CT. 198"; and "Etude for piano No. 5 in G flat major ('Black Key') Op. 10-5, B. 57-1", respectively.)

Step 1: Lifts and Path Separators

Since Under the Sea is my first ball machine with two networks, to match my theme I named them "Atlantic" and "Pacific". Network 1 (Atlantic) is actually the shorter of the two, but since it cycles balls much faster I gave it primary status. The Semi-Circle Chain Lift (by Tornado96) is the only lift on this network, but its gentle arch represents the Atlantic Gulf Stream quite well. At the top the balls split four ways using ordinary vertical path separators, although one had to be lengthened to reach the edges of the red rod frame.

Network 2 (Pacific) has two lifts. The first is sandroknexmaster's Falling Arm Lift. I used a different entrance gate because I could not get enough tension in the original string-sprung gate. Since this lift has a lot of sudden motion that reminded me of an eruption, I substituted orange colored gray rods and call it an undersea volcano, since many abound in the Pacific "Ring of Fire". The second lift is brand new, though an expansion of a concept by sandroknexmaster (more specifically, a sort of Spinning Freefall 2). Shaped like a gigantic #4, the Criss Cross Lift has not one freefall, but three! By adding a cross-arm and connecting it to the original arm length, the ball gets raised, falls through, is raised some more, rolls into the second cross-arm, is raised to the top again, falls back through, and one last time is raised to the top to be released. The sequence is an interesting twist on the freefall idea, although it does mean a longer transit time for each ball to end up at the top. For a path separator, I used Shadowman39's Tilting Panel from Citadel. It also splits into four paths.

In addition to the two main networks, the white floor in this machine has a hole, leading to what I call the Seafloor Network. It leads from the hole to a little wheel lift that pushes the ball up with paddles back onto the white floor (I mean, seafloor).

Step 2: Path 1: Anchors Away!

The first path begins with a ride across a length of chain...thus the name of the path. After reversing direction with the help of some protruding rods, the ball drops into the first new element in Under the Sea: Trapdoor Ball Arms! Instead of being dropped down and rolling off, the Trapdoor Ball Arm consists of a basket with a counterweighted floor. When a ball lands in the basket, the whole arm falls forward. But at the same time, the floor of the basket drops down, releasing the ball. After two of these in series, the ball makes its way down a short path back to the seafloor.

Step 3: Path 2: Seaweed

Path 2 begins with Knextreme's panel spiral stairs. After rolling down these, the ball gracefully drops onto a winding section of my Green Flex Path, which for this path is the "seaweed". After rolling along this, the ball is propelled onto a section of rattle path which transitions into a double-wide spiral (also used in Path 3). The ball then rolls down some more rattle path to a classic spiral, dropping off the end onto the Atlantic Network entrance.

Step 4: Path 3: Rip Tide

Watch out for those currents! Balls taking Path 3 quickly find themselves whirled around in the Spinning Basket. After the 270 degree spin, the balls are tipped out onto a rattle path. Pushing aside a path block, balls proceed to roll onto the double-spiral (also on Path 2) and wind down the the finish sharing the rattle path with Path 2.

Step 5: Path 4: Sea Monster

Beware the creatures that lurk near the seafloor...this is a lesson balls that take this path must learn. Path 4 starts with a long piece of blue tube, followed by a hanging curtain. After going through these, a ball will roll onto a ball arm which drops it down onto a yellow curve tunnel with pendulums. At the bottom of this, the ball runs into the giant squid's mouth...literally! The iris diaphragm from Retrograde was re-themed and this time hooked up to the motor that runs the Falling Arm and Paddle lifts. Now the mouth slowly opens and closes, ready to gobble up any balls that come its way! After rolling through, the ball takes a short section of one of Knextreme's custom pavings and rolls out onto the seafloor.

Step 6: Path 5: Shark Attack

SHARK! This path contributes the most to the theme, as the shark up top "swimming" through the water is an eye-catcher. The balls waste no time in facing the menace, either. After leaving the path separator, the ball will roll along a path section straight into the shark's jaws, dropping down onto a panel below. After dropping through another hole, the ball glides down a panel bridge to a Swivel Freefall. Next, my upgraded Zig-Zag comes in. When a ball reaches the bottom of the freefall, it rolls into the counterweight area of the Zig-Zag. When the Zig-Zag is activated (by a ball on Path 6), this ball is raised with the counterweight up one blue rod height before rolling out of the cage onto another path. Having left the Zig-Zag, the ball then enters I_am_Canadian's Elliptica, and drops onto the seafloor.

As an added bonus, the shark can be left to run on its own or be controlled by a viewer. The jaws open and close with one motor, while the body rotates slowly back and forth with another motor. Trying to catch a ball in the jaws is more difficult than it looks!

Step 7: Path 6: Scuba Diving

Path 6 takes a ball first down a long piece of Gray Path (which is ironically enough red). The ball will roll off the end of this onto the Zig-Zag, which will drop down and activate the ball stopped on Path 5. This ball then flies off the end onto a sloped panel area, which funnels the ball onto some Tire Stairs. The ball drops off and back onto the seafloor.

Step 8: Path 7: Ocean Trench

For Path 7, balls fall down an "ocean trench", otherwise known as a Knextreme Panel Drop. After a few back and forth falls, the ball slams through the white curtain at the bottom and transitions onto the second end of the Elliptica. Then the ball goes...yes, right back to the seafloor.

Step 9: Path 8: Whirlpool

Path 8 is the final path, which starts with a set of Knextreme's Panel Stairs. After taking these down the tower a ways, the ball rolls onto a tubing path. It glides into a banked turn to the left, then swoops down to the right...inescapably...into the whirlpool. The ball traverses the spiral bowl, going down and around until it disappears below. A short pathing section deposits the ball onto the Seafloor Network ramp down to the paddle lift.

Step 10: Conclusion

Well, the ball has at last disappeared below the seafloor. Of course, it will soon be lifted back up to the surface to run through again, but our journey through the seas is done. Through both the Atlantic and Pacific (networks) and the various ocean-themed paths, it been a great underwater adventure. Thank you for reading this Instructable; I hope you've enjoyed the time Under the Sea!



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    22 Discussions


    2 years ago

    plz post instructions!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

    1 reply

    Usually ball machines are so large that few people will actually replicate the whole thing, so to save some time I just add enough pictures of each part to get the general idea across. Builders like knexpert#10829476 have proven that it can be done this way quite well, and sometimes it even leads to a few modifications here and there which make the design even better. So no, the machine is already disassembled and no instructions are forthcoming, but I believe being inspired by others' work and then making it your own is the best way to create a ball machine! Have at it and enjoy exploring!


    3 years ago

    Nice ball machine!! You don´t have a instructions? I would like to build it.


    3 years ago

    epic ball machine! this actually inspired me to get back into k'nex! (also I'm your 50th follower :D) check out my first ball machine!

    2 replies

    3 years ago on Introduction

    excellent!!! I've never seen a ball machine so well themed and animated. GREAT JOB (love the shark)

    1 reply

    4 years ago on Introduction

    I really like your ball machine... especially that giant shark! Yipes!! What kind of shark is it? i'm not fond of fish. hope to see your next ball machine (my little brother [ 6 years old])

    This is amazing! The story is so nice to read, and the ball machine looks good.

    That shark is so cool :)

    I like what you did with the Falling Arm Lift entrance, and the Spinning Freefall Lift got a nice upgrade :)

    Definitely deserves a feature!

    1 reply
    Lucas The Boss

    4 years ago

    You might want to enter in the rods and connectors contest btw

    Lucas The Boss

    4 years ago

    I love how you incorporated the guy in the boat on top of the sea and the waves as well. The story is great and so is the ball machine great job


    4 years ago

    Nice build. I never know what to do with my knex.