Hello I am Kelkschiz. Welcome to this video about automatic LEGO
shooting mechanisms. In this video I will do two things. I will begin with explaining
some of the basic principles involved in designing a LEGO shooting mechanism. After that I will
show you some popular and interesting mechanisms. As you can see, I have build these seven models
to show you how they work. Three of these are my own design. As this will be a long
video, I have added a table of contents in the description. So lets start with the basics!
First off all it is important to notice that many different forms of energy are used in
a creation like a shooting mechanism. This start with the equipment you use to power
your mechanism, most likely this will be either the LEGO Power Functions or LEGO Mindstorms.
Those systems both transform electric power to rotational mechanical power. Shooting mechanisms
all rely on elastic power, so one challenge is to find a way to transform rotational mechanic
power to elastic power. The elastic power in turn is imparted to the projectile turning
it into kinetic energy. The storage of elastic energy is central to
building a shooting mechanism, lets focus on that first. In the examples you are about
to see, three types of elements are used to store elastic energy, namely: rubber bands,
LEGO springs and LEGO axles. Of course this last type of storage was not designed to store
elastic energy and that may cause problems. But those are only the very basic forms of
elastic energy storage, it is also possible to make more complex mechanisms with them,
like crossbows or ballistas. Those types of devices are much better suited to transfer
elastic energy to kinetic energy. Another thing that I should mention is that all these
forms of elastic energy storage rely on linear motion to storing the elastic energy. But
LEGO Power Functions and Mindstorms only offers rotational motion.
So we also need to find a way to transform rotational mechanical power to linear mechanical
power before we can store it as elastic power. Fortunately, we are not the first who try
to solve this problem. Here are some examples: The first one was the Scotch yoke mechanism,
followed by a single knob and a gear, a long line of teeth and a gear, and finally a linear
actuator. And of course there are many more. If you watch carefully you may recognize one
or more of these mechanisms in this video. Now on to the actual shooting mechanisms!
I would like to begin this segment by saying that I do not aim to present one mechanism
to be better than the others. I have selected these mechanism because I feel they each have
a valuable lesson to teach, or inspiration to give. The first automatic LEGO shooting mechanism
I ever saw was the one in Gyuta97’s Autoload Tank – by the way, you will find links to
all the discussed MOC’s in the description below. It was the first time I saw a mechanism
like that in a LEGO tank and I was quite amazed by it. So much so that I wanted to see if
I could recreate it. So how does it work? I have build this model
to show you. Lets start of with the storage of elastic energy. The elastic energy in this
shooting mechanism is stored in the most basic form possible, a simple rubber band. The rubber
band in turn is connected to a shaft. The shaft is pulled back and released. When it
is release it’s accelerated by the rubber band and the shaft hits the projectile and
launches it from the barrel. But that leave two things undiscussed. One
of those is the magazine. In Gyuta’s design the magazine is attached to the side of the
barrel. On the other side of the magazine is a follower with a rubber band attached
to it, which pushes the projectiles towards the barrel. Each time a projectile is launch,
a new projectile will be pushed into the barrel. Finally we have the mechanism that pulls back
the shaft and releases it. This is perhaps the most intricate part of the mechanism,
it’s task is converting the rotational motion to a linear motion. You may recognize that
this part is very similar to the Scotch and yoke mechanism. Now some thought on this mechanism.
In one respect Gyuta’s mechanism is very different from the others that you are about to see.
And that is because it consists of two separate parts. At the front there are the barrel and
the magazine which are able to pivot. And in the back is the pullback mechanism which
is fixed to the turret. This creates a problem when moving the barrel up or down by a certain
degree. Because the pullback mechanism is designed to only work with the barrel being
horizontal. Once the angle deviates too much, the mechanism stops working. So why did Gyuta
design his mechanism like this? The answer is probably that he had to make a compromise.
He probably wanted to be able to elevate the barrel. But the size of the pullback mechanism
prevented him from attaching it to the rest of the shooting mechanism. This brings up an interesting point, not only
is the size of the shooting mechanism is important, the shape is as well. Ideally the mechanism
is shaped somewhat like a triangle on it’s side, with the bulkiest part near the pivot-point.
Like this the barrel is free to move up or down. However if the mechanism has the most
bulk in the rear, the barrel can hardly move at all. This is probably the reason why Gyuta
chose to cut his mechanism in two parts. The mechanism shown here, not including the
barrel, is 13 studs long, 15 studs wide and 11 studs high, this makes it about average
in size compared to the other mechanisms. Finally I would like to say a few words about
reliability. Every automatic mechanisms fails at some point. Some fail every few shots,
some fail once in about thirty shots, and some fail almost never. In my experience the
reliability of Gyuta’s mechanism is very good. Misfires are very rare. The next mechanism I want to show you was
designed by ats1995 and Dacke93 was kind enough to make building instructions for it. Not
including the barrel, it measures 27 studs in length by 32 studs in width and 13 studs
in height. It is by far the largest mechanism of this line-up. To be fair this mechanism
was never designed to go inside a tank, and as a consequence it is very large. Too large
to consider for anything be the very largest of LEGO tanks. So how does it work?
Lets start again with the storage of elastic energy. As you can see the energy is stored
in a bowlike mechanism near the front. In general bow-like mechanisms are better at
propelling projectiles than a simple rubber band or spring is. That being said, it is
high time to caution you from construction a bow like this. Both ats1995 and dacke93’s
design are based upon distorting LEGO elements that are NOT meant to be distorted. Using
LEGO in this way is almost sure to damage it. There is no need to make a bow like this,
as we shall see later on in the video. Lets move on to the magazine. The magazine
is placed above the barrel. Once a shot is fired a new projectile will simply drop into
place. Many shooting mechanism make use of a magazine like this. It is very easy to make.
The force of gravity is usually just enough to keep the projectiles in place.
The last part of this build is the pullback and release mechanism. This part is powered
by a Power Functions M-motor. The force is geared down and connected to this pullback
element here. This element is connected with a wire to the bowstring. And with it the bowstring
is pulled back, where it is held back behind two LEGO studs. The pullback mechanism is
designed to work in sync with a release mechanism that is powered by the same rotation. The
rotation is transferred through a set of gears here, to a release mechanism here. The release
mechanism is a simple knob the that lifts a beam which in turn pushes the bowstring
up, releasing the bowstring from the LEGO studs. The release mechanism fires when the
pullback mechanism has had time to slacken the pullback wire. Time for some concluding thoughts on this
mechanism. It’s size is probably also it’s biggest drawback.
Clearly, it was not designed the be put in a small tank. Yet I do feel that given the
effort it is possible to reduce it’s size significantly. It was just not build to be
small which doesn’t mean that it can’t. The main reason for including this mechanism
is because this mechanism has inspired me like no other. Build it, and you may see why.
It works very well, the mechanism functions smoothly, it is powerful and still reliable.
It can shoot projectiles about up to about 8 meters of 25 feet before they hit the ground.
However that power comes at a price, the construction of the bow is likely to damage your LEGO.
But even that may be fix by replacing the bow with something like you will see in the
next creation. This next creation is the one that I have
designed myself. In the information card at the top right of the screens you will find
some build videos. My main goal was to make a powerful and reliable shooting mechanism.
The most powerful version, is rather large. It’s 15 studs long 21 studs wide and 10 studs
high. While the smallest measures 11 studs long 15 studs wide and 10 studs high. Let me show you how they work.
Lets start of with the storage of elastic energy again. I have two big models here,
both use a ballista-like mechanism. One uses rubber bands to store the elastic energy while
the other uses LEGO springs. The one with LEGO springs is a little bit more compact
but the one using rubber bands is the most powerful. It’s projectiles have a flight range
of about 8 meters or 25 feet. I also have a smaller mechanism, designed for smaller
tanks. The smaller mechanism can only use rubber bands and it has a shorter range of
about 3-4 meters. The two bigger mechanisms use a detachable
magazine, that is attached to the bottom of the shooting mechanism. They are powered by
a rubber band that keeps the projectiles in place, and pushes up a new projectile when
the one in the barrel is launched. With the smaller mechanism I couldn’t find the space
for a bottom fed magazine so I made a simple gravity powered magazine on top.
The pullback and release mechanism is the same in all three of my models. The pullback
mechanism is also somewhat similar to ats1995’s pullback mechanism. But in my shooting mechanism
the pullback mechanism doubles as a release mechanism.
The bowstring is pulled back and fixed behind adjustable axles. Then the pullback mechanism
continues it’s circle back to the beginning, so that the pullback wire slackens. When the
pullback mechanism is back at it’s starting point, it lifts the bowstring off the axles
which is then free to shoots forward. Hitting the projectile which is then launched from
the barrel. Now some concluding thoughts on the mechanisms
The bigger mechanisms are both very reliable and powerful, but they aren’t small enough
for most MOCs. The smaller mechanism is not as reliable nor as powerful. I am planning
to improve it further. If you want something small and reliable, the next mechanism may
be something for you. If you want to see some additional footage of these shooting mechanisms
please check my Flickr page. By far the most popular mechanism out there
is the spring powered shooter. As far as I was able to dig up, Sariel was the first designer
of this mechanism, back in 2008. But I could be wrong, it may be the case that several
people, designed a similar system independently of each other. Several other builders have
used the same basic mechanism but put a different spin on it. Some notable creations are fr3dpivo’s
25-shot tank, which has an interesting magazine and reload system. And recently Samolot made
an inspiring massive launch system for his Drone Tank.
It’s not hard to explain the popularity of this mechanism, it is easy to build, reliable
and very small. Sariel’s mechanism measures 18x7x5 studs, making it by far the smallest
mechanism in this line-up. Sariel has some very easy to follow building instructions
up on his website. But I would also recommend taking a look at the other builders I mentioned. The mechanism itself is very simple, explaining
it won’t take long. The elastic energy is stored in a large LEGO
spring. It is compressed by letting a 3-knob gear revolve against the the knob on the LEGO
spring. The knob on the gear then moves out of the way and the spring is released. An
axle passes the force of the spring to a projectile which shoots out the barrel.
The magazine is just a simple liftarm with small axles in it that are the projectiles. In conclusion.
It’s a really brilliantly little mechanism. It is small, reliable, and easy to build.
And I think Sariel’s mechanism is quite beautiful as well, because it’s so simple . If you have
no clue where to start, I would recommend you to start here. Just get the building instructions
from Sariel’s website and start building. I would however like to caution you. Because
there is quite a lot of force being exerted on the gears and motor in this mechanism.
Especially if you use the stronger type springs. If you want to use stronger springs please
consider using a stronger motor, and gear down the mechanism. I would like to close off with something special.
This is the shooting mechanism of Tommy Styrvoky’s ISU-152. It is beautiful not because it’s
simple but because it is original and quite complex. In fact it was the only mechanism,
I had some difficulty with putting together. But at the same time it was a very satisfying
build. While this mechanism is not the smallest, it measures 20x12x9, it’s shape does somewhat
resembles a triangle. Most of it’s bulk is near the pivot point, which is ideal. I think you will be interested to see how
it functions. There is not a lot to say about the storage
of elastic energy and the magazine. The elastic energy is stored in a simple rubber band,
and the magazine is one that is attached to the side of the barrel, also powered by a
rubber band. You may notice that this part of Tommy’s mechanism is nearly identical to
Gyuta’s mechanism. Now to the interesting part, the pullback
and release mechanism. The release mechanism is activated by a clutch. The mechanical force
is geared down and then it passes through the clutch, which is normally engaged. With
the clutch engaged, a gear is pulling back a toothed shaft, like so. Attached to the
shaft are two bionicle teeth. When the shaft is pulled all the way back, one of the teeth
hits a knob which rotates this central axle. The rotation of this axle releases the clutch.
When the clutch releases the shaft shoots forward, ramming into the projectile. But
also ramming the second bionicle tooth into a knob which reengaging the clutch. And immediately
the shaft starts moving back again. It’s quite fascinating to see it in action. some concluding thoughts on the mechanism.
This mechanism is pretty difficult to build, and it is not the most powerful nor the most
reliable. So why did I include it? I included it because I think the mechanism is both original
and inspirational. I consider this mechanism a work in progress. The fact that it is not
reliable or powerful yet, doesn’t mean that it can’t be. If you like tinkering with complex
mechanisms and if you are up for a challenge then don’t overlook this one, because it’s
a diamond in the rough; it offers new thinking and lots of potential. That was the last mechanism of the line-up.
Here you can see a small overview of all the mechanisms. I wasn’t sure if I should include
such an overview, because these characteristics depend on a lot of variables, which can easily
change. Also they aim of this video was not to thoroughly test and compare the mechanisms.
But instead to show you how they work, and to inspire you to build your own. So please
take this overview as nothing more than a rough estimation of the properties of these
mechanisms. If you feel that I have overlooked something,
or if want to share your own thoughts on these mechanisms, then please leave a comment. If
you liked this video, and would like to see more like it, please consider pressing the
like and subscribe. Finally I would also like to thank: ats1995,
dacke93, fr3dpivo, Gyuta97, Samolot, Sariel and Tommy Styrvoky for inspiring me with their