In this tutorial you will learn how to make a rubber band Gatling gun (a.k.a "minigun") out of K'NEX.
The gun features 8 barrels that can each hold about 4 rubber bands for a total of about 32 rounds of ammunition. The gun can be driven by an electric motor (specifically the K'NEX plug-in motor), or with a flip of a lever it can be converted to a manually-cranked mode for those times when an outlet isn't available.
The gun is quite large as it is designed to fire 7-inch rubber bands. I particularly like using Alliance brand "Pale Crepe Gold" size 117B rubber bands, although the gun should work with most 7-inch bands. When loaded properly, the gun should fire accurately up to or beyond 20 feet.
This is a design I had developed over a year ago. You can find a short video of me test-firing the gun at some paper targets are varying distances here (link will open a new tab). The design in this Instructables actually features a slimmer barrel design than the one shown in the video.
Not enough pieces to build this gun? Try my Semi-Automatic Rubber Band Pistol (link will open in new tab).
Step 1: Some Notes Before We Start
Throughout the instructions I will refer to certain pieces, mainly the rods and connectors, by a color in order to specify their size or shape. The colors I refer to will usually be the original colors used by K'NEX for these pieces (see labeled photo above). However, keep in mind that a given piece will often be available in more than one color, and that the photos in my instructions will often feature these multiple colors. So, for example, if I refer to a "yellow" rod in the instructions, keep in mind that the rod in the photo may actually be gold. I may or may not make note of the color difference in the text. I may also refer to the shape (e.g. a "circle" connector = a "white" connector) In general, the color that you use won't matter as long as the part is the same size or shape, unless I explicitly say otherwise.
I will also refer to "3D" connectors. These are the combinations of purple and blue connectors that allow you to build out in three dimensions. I will refer to these combinations as purple/purple, purple/blue, or blue/blue. Again, keep in mind that the actual colors may vary in the photos.
There may be instances where you don't have an exact part that I call for in the instructions. If this is the case, use substitutions as appropriate. I will try to provide some guidance for certain aspects of the build, but I can't accommodate every unique situation you may face, and so I will trust that your common sense will guide you through the rest.
I use a lot of spacers (e.g. blue spacers and silver spacers) in this build. Following from the discussion on substitution, keep in mind that one silver spacer equals three blue spacers, so you can always make that substitution if needed. If you don't have enough spacers, you can try to use something like a small grey connector to replace two blue spacers, as long as the size of the connector doesn't get in the way of something else. However, there are places where you will need at least some blue spacers, so if you don't have any, you may be out of luck unless you are willing to cut some connectors in half. If you have none, I would highly recommend buying at least several dozen before starting.
I suppose I should also throw in the obligatory "don't use the rubber band gun on people or animals" statement. However, let's be realistic here - you're going to want to shoot rubber bands at your friends, your parents, your little sister, and pretty much anyone that walks through the front door, right? Just use common sense if you do - don't aim for the face, make sure your targets are willing participants, and it helps if you all wear some safety goggles. And leave your pets out of it. I won't be held responsible for any damage you cause with this thing.
Now, if you're ready, let's get started.
Step 2: Making the Barrels
We'll start by making the barrel assembly, which starts with making 8 individual barrels as shown.
Each barrel has a front portion, a "bridge", and a rear portion which contains a spoke and cam lever. The front portion acts as the front hook that holds the rubber bands. The rubber bands are stretched back, over the bridge, and hooked into an empty notch in the spoke. The spoke and cam lever assembly acts as an escapement which allows semi-automatic fire of the rubber bands. Several rubber bands may be loaded on each barrel by cocking the spoke back between each loaded rubber band. The cam lever rides over a cam ramp, lifts upward, and fires a rubber band.
The spoke is made from a white (circle) connector with 4 green rods to make an "X" shape. It is then inserted over a blue rod axle with a silver spacer on either side.
The cam lever uses the parts shown. The lower lever half in the detail image is connected to the empty ends of the white rods of the upper lever half so that the halves are parallel, trapping the x2 blue spacers between them. The blue rod is inserted through the white (circle) connectors as an axle. 2 blue spacers are on the axle between the white connectors, and one blue spacer is on each outer side of the white connectors.
Further notes are included in the photos regarding the numbers of spacers used at each blue rod along the length of the barrel.
Again, make 8 of these barrels.
Step 3: Making the Barrel Core
The barrel core is the central structure around which the barrels are mounted.
Start by making 4 of the side segments as shown in the photo. The rearmost 3D connector is a purple/blue combo. The remaining 3D connectors are blue/blue. Note the orientation of the front most blue/blue connector (marked by *), which is perpendicular to the others. You will know if you got this wrong since the yellow rods won't be able to follow the zigzag pattern properly if the 3D connectors aren't oriented properly.
Step 4: Making the Barrel Core (Cont'd)
Once you have 4 of the side segments from the previous step, begin connecting them together as shown to form a square tube. The sides are all oriented in the same direction around the tube. The photos show the first 2 side segments connected to each other, followed by all four to form the tube. The resulting tube should be quite rigid and strong.
Step 5: Making the Barrel Core (Cont'd)
Next, make six "x" shaped pieces as shown (a white connector with four white rods), and insert them within each of the six 3D connector squares of the tube. These further strengthen the tube and provide central holes for the axle around which the entire barrel assembly turns.
Step 6: Making the Barrel Core (Cont'd)
Next, make the part shown above and attach it to the front end of the barrel core. This spaces the front end of the barrel core from the tips of the barrels and prevents interference between the tips and the support frame when the barrel assembly turns.
Step 7: Making the Barrel Core (Cont'd)
Next, make the parts shown above (green connectors with white rods). Each group contains 8 pieces, and you will need 6 of these groups (48 pieces total). Attach each group around each 3D connector square to form an octagonal pattern.
Step 8: Attaching the Barrels to the Core
The spaces between the green connectors, arranged in the six octagons along the lengths of the cores, will accept the free ends of the blue rods of the barrels (except for the spoke axles). Attach all 8 barrels between the green connectors around the core by these blue rods. As shown above in the second photo, you will notice that the blue rods forming the spoke axles are not yet capped off at their ends. Do so by adding a green connector between each adjacent pair of spoke axle ends (not shown - note that I only show one barrel being attached as the rest of the barrels are attached in exactly the same way).
Step 9: Finishing the Barrel Assembly
The barrel assembly is essentially complete, but just needs some finishing touches. First, wrap a couple of rubber bands around the front end of the barrel assembly over the orange connectors, near the barrel tips. The purpose of this is to prevent the ammunition rubber bands from wedging themselves between the orange connectors when they are loaded. Second, place another rubber band around the circle of cam levers as shown in the photo. This biases the cam levers inward and allows each one to return to that position after being triggered.
Step 10: Barrel Assembly Complete - Loading and Test Fire
Congratulations, you've just completed the barrel assembly. At this point the barrels are functional, and you might want to conduct a test fire to make sure everything is working properly.
Place a rubber band over the tip of the barrel, then stretch it over the bridge and into the empty slot of the spoke. To load another rubber band, first cock the spoke back until the cam lever catches and the next slot is presented. Repeat this loading procedure until you have the desired number of rubber bands on the spoke. I usually stop at four to avoid over-loading the barrel, although you can theoretically continue beyond four.
To test fire, lift the cam firmly upward until the spoke rotates forward under the tension of the rubber band. Letting go of the cam should then fire the rubber band. Keep in mind that the rubber band(s) may fire uncontrollably if you don't keep a firm grip on the cam lever, especially with several rubber bands loaded.
Note: A tip when loading the gun, or when shooting a rubber band in general, is to place slightly more tension on one side of the rubber band than on the other side. This asymmetrical tension creates a sort of rotational effect when the band is fired. A band fired in this way will maintain a tight configuration and travel much faster, farther, and more accurately than with standard symmetrical tension. You can easily try this by hand-firing a rubber band using both techniques and noting the difference. It may take some practice to get a feel for the right tension ratio, but it's definitely worth it. When loaded in this way, the gun should be capable of shooting rubber bands accurately up to around 20 feet or more.
Step 11: Starting the Support Frame
The support frame provides a rigid framework that holds up both ends of the barrel assembly as it rotates. This design might seem overkill, but I find that it works better than some other options. For example, you might be tempted to simply make a square tube using purple/purple 3D connectors along the corner edges. However, this frame will be under tension along the top side, and the 3D connectors have a tendency to pull apart under tension. They also have more compliance than normal connectors which would keep the frame from being rigid enough, which is why I went with this design.
We'll start at the front of the frame, which holds up the front end of the barrel assembly you just finished. The front end forms a riser that supports the front axle of the barrel assembly. The photos show several views of the parts of the front end, as well as the completed piece.
Step 12: Support Frame (cont'd)
Next, we'll start building the length of the support frame. The frame is basically made from a series of segments like the one shown above, with some variations later on. For now, make four of the segments shown above. The front side of the first segment gets connected to the rear side of the front end built in the previous step. The remaining three frame segments are connected in series behind the first segment to begin a square tube.
The first and third frame segments in the series should be built as shown above. The second and fourth segments should have the diagonal yellow (gold shown) rods reversed so that they form a zigzag pattern down the length of the frame.
Step 13: Support Frame (cont'd)
Let's try to do the next frame segment in one step. This shouldn't be too difficult based on the previous steps.
This next frame segment essentially follows a similar pattern as the previous segments. The major difference is the addition of an extra layer (the one with the green connectors) on the top to build extra height at this part of the frame. To do this, replace some of the yellow (semi-circle) connectors that would normally be on top with white (circle) connectors instead. Then add the green-connector layer as shown. Be sure to maintain the zigzag pattern of the yellow rods as before.
Also note the white (circle) connector (black shown) added to the bottom side. This will eventually be attached to the multi-axis swivel platform which allows the gun to be freely aimed. The extra height of the frame in this area helps keep the frame from bending in the area directly over the swivel platform.
Attach the front of this piece to the rear of the rest of the frame built in the previous steps.
Step 14: Starting the Drive Housing - the Outer Walls
This next part of the build will be the most challenging. The drive housing contains all of the mechanisms that drive and control the gun. We'll start by building the outer side walls, and then building the inside parts from the bottom up.
The two side walls are shown in the photos above. The inner surfaces of the side walls are facing the camera. Note that all 3D connectors are either purple/purple or purple/blue (i.e. no blue/blue). The outer face (away from the camera) is smooth and has no protruding connector portions.
Also note the three yellow connectors located where blue rods would otherwise fit (labeled in the photo of the right side, one of them is actually light grey in color). The left side mirrors these yellow connectors. These will be needed for connecting some of the inner parts later.
Step 15: Drive Housing (cont'd) - Add the Motor
Next, acquire the AC motor and other parts shown in the photo and assemble them to the right-side wall as shown.
Note: I chose to use the K'NEX AC plug-in motor for my gun because I like the power it offers, although being limited to the length of the power cord is sometimes inconvenient. If you have a different motor that you would prefer to use, then I will let you figure out how to best install it into the drive housing. Just make sure that all other gears are in the same locations as shown in these instructions, and that the gear ratios remain the same. Don't worry about the spin direction of the motor right now. If the barrels end up spinning in the wrong direction, you can simply switch the direction of the cam ramp (described in later steps).
Step 16: Drive Housing (cont'd)
Now, attach the left side wall (on the right in the photo) to the free ends of the blue and white rods added in the previous step. The left and right walls should mirror each other.
Step 17: Drive Housing (cont'd)
Next, assemble the first gear axle as shown in the photo. Then attach it above the AC motor as shown. The white gear should mate with the worm gear on the motor shaft, and the small blue gear should be toward the rear end of the drive housing.
Note: If you are using a different motor, then the white gear is unnecessary as it is specifically designed for use with the AC motor. You may choose to attach your different motor directly to this axle, adjacent to the blue gear, if possible. Just be sure that you have convenient access to the on/off switch, and that the blue gear is in the same location along the shaft as shown. The motor also needs to be out of the way of the gears and mechanisms that are added in the next steps. Perhaps some additional gears to link your motor to this axle would be better.
Step 18: Drive Housing (cont'd)
Next, assemble the second gear axle as shown. Then attach it above the previous axle, similar to before. The red gear should mesh with the blue gear of the previous axle.
Step 19: Drive Housing (cont'd) - First Clutch
This next component is a clutch which transfers motion from the lower gears to the drive axle of the barrel assembly. The part enclosing the gold gear is intended to slide the gold gear along the red rod into and out of engagement with the red gear beneath it, so don't be tempted to fill in the gaps with more spacers on this one.
Start by building the component as shown. We'll add some more to it in the next step.
Note: It is preferable to use a small gold gear as shown, rather than a small dark blue gear or small grey gear. The gold gear is able to rotate and slide freely on the rod, while the other kinds of small gears are tighter and do not rotate or slide as freely. If you do not have a gold gear as shown (or something equivalent, maybe in another color that I'm not aware of), then you might be able to get away with a small blue one (just test it to make sure if slides nicely), or you could potentially ream the hole of a tighter small gear if you're willing to modify your K'NEX slightly.
Step 20: Drive Housing (cont'd)
Now assemble the small parts as shown in the photo and add them to the clutch component from the previous step. The clutch should now have a sort of "bow tie" shape. Note the orientation of the tan lock portion.
Step 21: Drive Housing (cont'd) - Install the First Clutch
Now, install the clutch assembly above the previous gear axle. The photos show the location and orientation of the clutch assembly.
You will need to temporarily disconnect the blue rods of the housing side walls to get the light-grey triangular connectors over them as shown. Once connected, the clutch should be able to slide the gold gear into and out of engagement with the red gear beneath it. The bow-tie portion should slide along the four blue rods.
Make sure that the white/silver rod with the x2 blue spacers and tan lock connector is oriented on the top.
Step 22: Drive Housing (cont'd)
Next, make the part shown and add it to the front end of the drive housing.
Step 23: Drive Housing (cont'd)
Next, we'll make the drive axle for the barrel assembly. This is the business end of the drive housing that transfers rotation from the previously assembled gear train to to the barrel. This axle needs to be long, so we'll make it in two parts. The rear part is shown in the photos above.
Note the "brake spoke", which is made from a circle connector surrounded by eight green (black shown) rods. You'll see how this works after the drive axle is installed.
Step 24: Drive Housing (cont'd) - Drive Axle
Next, build the second part of the drive axle as shown. Note the use of a black rod here instead of a grey rod. You may have noticed before that black rods are a little heavier and stiffer than grey rods. Their stiffness means they make good load-bearing axles, and this one will have to hold up the rear end of the barrel assembly. You could get away with a grey rod, but the black one is preferable.
Step 25: Drive Housing (cont'd)
Now complete the axle by connecting the two axle parts. The end of the second part with the two red connectors gets attached to the first part between the two grey connectors.
Note: You'll notice that the brake spoke in these photos only has 4 rods. That's my mistake. I had forgotten to put all eight on the spoke before taking these photos. I replaced some earlier photos with the same mistake, but forgot to fix these too. Oh well, you get the idea.
Step 26: Drive Housing (cont'd)
Now the drive axle goes into the drive housing as shown in the above photos. Make sure the black rod faces the front end. The red gear should mesh with the gold gear below (when the clutch assembly is in its rearmost position).
You might be able to see the purpose of the brake spoke now. When the clutch assembly is in the rear position, it links the bottom red gear to the top red gear, thus completing the drive train from the motor to the drive axle and ultimately allowing the motor to turn the barrel assembly. However, when the clutch is in the the front most position, the motor drive train is disconnected and the little end of the white (silver shown) rod (in the center nook of the bow tie) should engage between the rods of the brake spoke. This stops the barrel assembly from rotating under its own momentum when the trigger (not yet added) is released.
Step 27: Drive Housing (cont'd) - Second Clutch
Next, make the gear axle shown in the photos above. Like in the previous clutch assembly, the part surrounding the gold gear on this axle is intended to slide along the black rod.
Note: Unlike the gold gear in the previous clutch, this one is connected to a tan lock. The tan lock slides with the gold gear, so there will actually be some sliding friction this time. This friction is desirable though since it will help keep this gold gear in place as it gets switched back and forth (you'll see later). The gear still needs to spin freely though, so the gold gear (as opposed to a different kind) is still preferable.
Step 28: Drive Housing (cont'd) - Install the Second Clutch
Now, install the previously built gear axle into the drive housing above the red gear. The gold gear should mesh with the red gear (when the gold gear is in its rearmost position). For now, the end of the axle with the yellow gear and orange connector will hang off the back end as shown.
The grey connectors on the ends of the V-shaped section slide over the blue rods. Like with the first clutch, you'll need to temporarily remove the blue rods to get the grey connectors over them.
Step 29: Drive Housing (cont'd)
Next, gather/assemble the pieces as shown. Attach them to the rear of the drive housing in the area of the yellow gear. The end of the axle with the yellow gear is now supported. The yellow connectors go on each end of the red rods.
Step 30: Drive Housing (cont'd) - the Crank
Next, make the crank assembly shown (or at least gather the parts for it). Then, assemble/install it onto the right side of the rear assembly from the previous step. The crank axle goes through the yellow and white connectors, with three of the blue spacers between those two connectors. The small gear should mesh with the yellow gear, and the tip of the yellow rod of the crank should barely graze the yellow gear axle.
Note: If you are left-handed and would rather have the crank on the left side, you could do that since the rear portion of the drive housing is symmetrical. However, you would either have to use the crank backwards, or use the crank forwards but also turn the motor around 180 degrees to drive the barrels in the opposite direction. In other words, the motor and the crank have to be able to turn the barrels in the same direction. Just keep this in mind if you choose to deviate from the instructions at all.
Step 31: Drive Housing (cont'd) - the Lever
Next, make the part shown and grab a red rod, along with four blue spacers (not shown). The red rod and blue spacers go through the yellow connectors that are above and in front of the yellow gear. The grey connector of the part shown is connected to the front end of the blue rod on the upper clutch member. The length of orange connectors then doubles back toward the rear end, where the red connector end gets attached to the center of the red rod. Then, fill in the gaps on the red rod with some grey connectors as shown (you could also use more spacers - I just didn't feel like it at the time).
Step 32: Drive Housing (cont'd)
I like to cap off the red connector end with this little grey gear, but you can do whatever you like with it. This completed assembly makes a lever which moves the gold gear of the upper clutch back and forth, into and out of engagement with the red gear it meshes with. Go ahead and try rotating the red connector end forward and backwards like a lever to make sure it works. Remember when I mentioned the extra friction caused by the tan lock with the gold gear? That friction helps keep the lever in the position you want it, either forward or backward.
Step 33: Drive Housing (cont'd) - the Handle
Assemble the parts shown, and then connect them to each other to form the handle.
Step 34: Drive Housing (cont'd) - Trigger Axle
Now make the axle part shown, and attach it to the rear of the drive housing as shown. The red rod goes through the red connectors on the back end of the housing. Once installed, cap off the free ends of the red rod with a silver spacer and grey connector on each end as shown.
Step 35: Drive Housing (cont'd)
Next, thread a blue rod through the three grey connectors on the lower back end of the drive housing (these grey connectors were added near the beginning the the drive housing construction). Also include the two blue spacers as shown on that blue rod.
Step 36: Drive Housing (cont'd) - Attach the Handle
The handle now gets attached as shown between the trigger axle and the blue rod added in the previous steps.
Step 37: Drive Housing (cont'd) - the Trigger
Now, build the trigger assembly as shown, and attach it to the trigger axle. The green rods on the trigger assembly are attached to the remaining free spaces of the grey connectors on the trigger axle. You can now see how it forms a trigger in front of the handle. For now, the yellow rods will hang freely below the trigger assembly.
Step 38: Drive Housing (cont'd)
Now, make the small parts shown, and attach them to the right side of the drive housing in the locations shown. Note the location of the red rod assembly in relation to the two white rod assemblies. The other end of the red rod assembly gets attached to the left side of the housing in the same area - you can see how the red rod passes through the housing to the other side. The blue/purple 3D connector it is attached to is part of the first clutch assembly, and so it will also slide back and forth with that clutch.
Step 39: Drive Housing (cont'd)
Now you can attach the free ends of those yellow rods on the trigger assembly to the grey connectors on the red rod assembly from the previous step. This links the trigger to the clutch. Go ahead and move the trigger to make sure the clutch moves with it.
Step 40: Drive Housing (cont'd)
Now make the small parts shown and attach them to the left side of the drive housing. They are placed in the same area (just on the opposite side) as the first set of small parts (white rods with grey connectors) that were attached to the right side. Be careful to make sure these parts line up exactly as shown. For now, keep the little pin on the tan lock facing outward. It should be able to slide past that black piece.
Step 41: Drive Housing (cont'd)
Now, get a couple of nice, thick rubber bands. The ones in the photos are the kind you would get on a bunch of asparagus at the grocery store. If you don't have something like these, you could double-up on some smaller rubber bands.
Place them over the blue spacers on the small parts we just added to each side of the drive housing. These rubber bands bias the clutch toward the forward position. The trigger should now be biased forward as well, so that when you pull it backwards it will return forward after it is released. Use rubber bands that result in a nice trigger pull force - not too wimpy, but not too heavy either.
Step 42: Drive Housing (cont'd)
Now, just add three blue rods in the locations shown to finish connecting the two sides of the drive housing.
Step 43: Drive Housing (cont'd) - Cam Ramp
Now, make the cam ramp as shown in the multiple views. Note the use of a blue connector in the front-middle location. It is important to use this here because it creates a sharp inside corner that does not interfere with the cam levers of the barrels as they drop off the top of the ramp. The yellow connector in the rear-middle position will not interfere with the cam ramps because they do not reach that far back. You'll see what I'm talking about when the gun is assembled.
Note: In some previous steps, I had mentioned the possibility of changing the crank and/or motor direction from what is in these instructions. If any changes you have made will result in the barrel assembly turning in the opposite direction, you will need to build your cam ramp to mirror the one shown in the figures. In other words, everything on the left side of the ramp should be mirrored to the right side, and vice-verse. Make sure the front/rear orientations do not change, however. For example, anything that is in the front should stay in the front. It will just be mirrored to the opposite side (left or right).
Step 44: Drive Housing (cont'd) - Attaching the Cam Ramp
Take the cam ramp you just completed, and attach it to the blue rods near the top-front of the drive housing as shown. Then fill in the gaps of the blue rods with some grey connectors. Make sure the ramp faces toward the right side of the drive housing, unless you have decided to change the motor and crank direction (see note in previous step).
Step 45: Drive Housing (cont'd) - Adding Sights
The top of the drive housing provides a location for adding sights or a scope to the gun if you want to. I show the one I use in the photos above, but you could use a different design of your choice. Or, you can leave the sights off completely if you prefer.
Step 46: Assembling the Gun
Now it's time to assemble all of the components that you've just finished building.
Start by attaching the rear end of the support frame to the lower front end of the drive housing as shown. Make sure the front portion of the support frame is pointing up.
Note: You may notice that some of the part colors in the next few steps don't match up with the ones shown in previous steps. This is because I had taken apart my original gun for some photos, but built some new separate parts for other photos. The next few steps show my original gun being re-assembled.
Step 47: Assembling the Gun (cont'd)
Now, slide the rear portion of the barrel assembly over the drive axle of the drive housing. The black rod should pass through the two rearmost circle connectors in the center of the barrel core. The tan lock on the drive axle should engage the rearmost white circle so that the barrel assembly will turn with the axle.
Note: It will probably be much easier to temporarily remove the front portion of the support frame prior to sliding the barrel assembly onto the drive axle. Re-attach the front portion once the barrel assembly is on.
Step 48: Assembling the Gun (cont'd)
Next, make sure the black rod is pushed back (to the right in the photo) about as far as it will go, and cap it off with a silver spacer, two blue spacers, and a grey connector as shown.
Step 49: Assembling the Gun (cont'd)
Next, slide a red rod (I used a tan-colored one in the photo) through the front end of the support frame and into the two front circle connectors of the barrel assembly. Add a silver spacer between the front portion and the barrel assembly as you slide in the rod. Cap off the rear end of the red rod (the end within the barrel assembly) with a blue spacer and a connector (I used a small metallic blue connector). Cap of the front with just a connector.
Step 50: Gun Assembly Completed...But Wait, There's More!
Congratulations! The gun is now essentially completed and fully functional, and you could choose to stop here and use the gun like this. However, you may find that it is very large and difficult to pick up and aim. That's why in the next steps we'll be making a multi-axis swivel platform to help you support and aim the gun.
Step 51: Multi-Axis Swivel Platform
Start the platform by making the base plate as shown in the multiple views above.
Step 52: Multi-Axis Swivel Platform (cont'd)
Now add red rods to the corner purple/purple connectors and add some upright yellow rods to the remaining connectors as shown.
Step 53: Multi-Axis Swivel Platform (cont'd)
Next, set the base plate aside and build the wheel plate as shown in the multiple views above. All four wheel axles projecting to the corners of the square are identical, and all four wheel axles projecting to the sides of the square are identical.
Step 54: Multi-Axis Swivel Platform (cont'd)
Now, connect the bottom of the wheel plate to the ends of the upright rods of the base plate as shown.
Step 55: Multi-Axis Swivel Platform (cont'd)
Next, assemble the component shown in the multiple views above.
Step 56: Multi-Axis Swivel Platform (cont'd)
Then, assemble the large gear axle as shown in the multiple views above.
Step 57: Multi-Axis Swivel Platform (cont'd)
Now, connect the white/circle (black shown) connector of the large gear axle to the free ends of the blue rods of the previous component. The tip of the black rod with the grey (x2) and blue (x1) spacers gets connected to the hanging grey connector as shown.
Step 58: Multi-Axis Swivel Platform (cont'd)
Slide the long end of the black rod from the previous large gear assembly through the top-center white/circle connector of the base assembly and through the bottom-center white/circle connector of the base plate. The end of the black rod will protrude through the bottom of the base plate. Cap it of with a short connector (like the metallic blue one shown, or a tan lock).
The teeth of the large gear should now ride within the grooves of all eight small grey wheels. The large gear assembly should easily spin around, supported by the wheels.
Step 59: Attaching the Swivel Platform
Now, simply drop the gun onto the swivel platform so that the two circle connectors on the bottom side of the support frame line up with the horizontal red rod at the top of the swivel platform. One silver spacer should be on each outer side of the support frame, with the rest being between the circle connectors. Once everything is lined up as shown, snap the circle connectors onto the swivel platform.
Step 60: Gun Complete!
Congratulations, the gun is now complete! In the next steps, I'll explain how to operate the gun.
Step 61: Clutch Positions
First, I'll explain the different clutch positions.
As explained in an earlier step, when the trigger is not pressed, the clutch is in its forward position. Here it engages the brake spoke of the drive axle to keep the barrel assembly from rotating. We can call this the "park" position. When the trigger is fully depressed, the clutch is in its rear position and engages the gold gear to the red gears, which completes the drive chain between the motor and the drive axle. we can call this the "drive" position. However, in both of these positions, the crank will not work since the drive axle is either kept from rotating by the brake spoke or the motor (which is off and unable to be rotated by an outside influence).
There is a third position - we can call it "neutral" - where the clutch is right in between park and drive and isn't held back by either the brake spoke or motor. To put the gun in crank mode, we must first put the lower clutch into "neutral".
The upper clutch is operated by the lever on the top of the drive housing. The lever slides the gold gear into (rear position) and out of (forward position) engagement with the red gear of the drive housing.
We'll put the gun into crank mode in the next step.
Step 62: Crank Mode
Crank mode will give you more control over the rotation of the barrel assembly while you get a feel for the operation of the gun, so we'll start there.
On the left side of the drive housing, at the level of the lower clutch, you should remember the small pieces wrapped by the rubber bands. When we attached these pieces, I specified that the pin of the tan lock should be facing outward. Now, turn the tan lock around 180 degrees so that the pin faces inward. Use the trigger to pull back the clutch a little to line up the hole of the black piece with the pin on the tan lock, and insert the pin into the hole. This will keep the lower clutch in the "neutral" position.
Then, move the top clutch lever into its rear position to engage the gold gear with the drive axle. The gun is now in crank mode.
To rotate the barrel assembly, rotate the crank forward (unless you reconfigured the controls in the previous steps). The cam levers should move smoothly over the cam ramp, lifting up fully and then dropping as they pass by. If the cam levers get stuck, try moving the spokes a little bit. Sometimes they get jammed when they are unloaded.
Step 63: Motor Mode
Now that you're more familiar with the operation of the gun, it's time to test the motor mode.
Essentially you'll want to perform the opposite steps from what you did to put the gun in crank mode. Pull the pin of the tan lock back out of the hole in the black piece and turn the tan lock back around so that it can slide against the black piece. The clutch should spring back into the "park" position. Then, push the lever into the forward position to disengage the gold gear from the drive axle. The gun is now in motor mode.
Plug in the motor (or otherwise turn it on if you used a different motor). The motor will run continuously but the barrel assembly will not yet spin. To rotate the barrel, pull the trigger to put the lower clutch into the "drive" position. When you let go of the trigger, the clutch will move forward back into "park", where the brake spoke will stop the barrel assembly.
Step 64: Loading and Firing the Gun
To load the gun, first put the lower clutch into "neutral". However, keep the top clutch lever in the forward, disengaged position so that the crank won't spin.
Start with the first barrel past the cam ramp (see photo). Refer to step 10 for instructions on how to load rubber bands onto the barrel. Fully load this first barrel before proceeding to the next one. I would load about 4 rubber bands on each barrel.
Once the first barrel is loaded, manually rotate the barrel assembly to index the next barrel. The next barrel should pass over the cam ramp and into the original position of the first barrel like in the photo. Repeat this loading procedure until all eight barrels are loaded.
Once the gun is fully loaded, put the gun into your desired firing mode. Make sure you're not aiming at anything or anyone that you shouldn't be, and then let it rip!
Step 65: Conclusion
By now, if I've done my job correctly, you should now be the proud owner of K'NEX rubber band Gatling gun.
This gun was a lot of fun for me to build, and I hope that you've had fun building yours. This gun is an impressive piece of machinery, and it will make a great conversation piece.
Anyway, thanks for following along, and enjoy your new equipment!