ALSI: a Lovely Small Ingenuity

I have been a fan of space exploration for as long as I can remember.

I still remember getting lost in the pages of an old Space Atlas that I was given when I was 5, where the details of the "upcoming" Huygens/Cassini mission were described. Or being amazed by that poster included in a certain National Geographic issue with the first red and blue "3D pictures" taken by Sojourner in 1997.

Almost 25 years later, I was fortunate enough to watch (almost online!) humanity's first drone hovering over the surface of Mars. However, this time I decided to celebrate this event in a more appropriate way for my "maker" soul, and so it was that I went for the tasks of creating a fairly accurate but functional reproduction of Ingenuity in the most simple and economical way possible.

The basic idea was to use the cheapest vertical coaxial gyro/chopper available on the market, some PLA, Blender, some bolts and the eventual addition of some carbon fiber blades compatible with a DJI drone. (Yeah, yeah, I know, it was supposed to be cheap... but more on that, later!).

I've used the Ingenuity 3D model that NASA released for free as my basic reference for measurements and proportions.

Soon I discovered that the design was not such an easy task as first thought. However, after 4 iterations over it, I think I finally reached a fully functional prototype. We can consider it a Beta version, but as by now I'm seriously considering moving into a fully functional flyable version -maybe grabbing the internals parts of a 2.4Ghz chopper, or just creating a functional diorama version that would be controlled by an Arduino-, I'm sure I will not work into making improvements over this version anymore, and thus I would like to release it for the community.

PS: I've made a not so serious video about the whole design process. It is not related to the Instructable per se (and it was made in portrait mode, shame on me!) but some of you may find it interesting :).

• A 3D printer, of course.

Any printer should do the job. No fancy specs, no weird filament. But considering your chopper will be prone to crashes, a nice elastic PLA+ filament would be welcome.

• Some .stl files that are listed here.
• 4 x M3*8 bolts
• 1 x M3*25 bolt
• 3 x M3 nuts
• 4 x M3*8 inserts
• 4 x Mini screws (M1, M1.4, even M1.7 could work)
• 1 x 1/8'' sheet metal screw
• 4 x metal rods (L x D) 7.5 cm x 2 mm
• A donor for the mechanics and electronics.

The 3D pieces have been designed considering the PCB used in this flying sphere.

However, with small modifications on the mounting points, you could adapt it for any other 2 bladed gyro or small chopper

• 2 x DJI Carbon Fiber replacement blades.

The only way to keep the proportions of Ingenuity and deal with the extra weight through improving the donor aerodynamic efficiency, is by using these bad boys. They are not cheap, but they are worth it.

• Tin foil (Optional)

Even though the model in the pics is not covered in tin foil, Ingenuity's main body is. In my case, I've decided not to cover it because I like to see the internals and because it is very common for this gyro to crash. In fact, it is designed to crash and survive most of the impacts. And replacing the cover becomes annoying very fast. So I strongly suggest not to do it, or maybe try with the aluminum foil that comes with some 1st Aid Boxes and remove the case before each flight.

• Some kind of saw/rotatory tool for cutting the metal rods.
• Soldering iron. An M3 heat set insert is desirable too.
• Superglue.
• Screwdrivers.
• A set of 2 pliers.
• A small, low speed or manual drill.

In my particular case (and after a multitude of iterations!), I printed all the pieces at once. You will find attached the gcode -including the config- that I've used.

Nonetheless, if you are doing it for the first time with your own 3D printer, I suggest printing the pieces separately, making small adjustments to improve the quality of the prints.

Printing the frame is very straight forward. To make assembling easier, I've decided to split it into two pieces that can be superglued later.

After printing, it's very important to review all the guides and holes. Check and make sure there are no cracks on the pins and that they slide fairly easily into the holes. If it doesn't, there are some tips hovering over the pictures.

Print these pieces separately, so you can try different support structures or infills to increase strength and look. Let yourself be creative!

You will need to print 4 of these.

Another batch of tricky pieces. In this case, I had to rework them with my pen-drill to improve the holes because the resolution of my Ender wasn't enough to print the blade spacers' guides for the M1-ish bolts.

You will need to print 4 of these pieces (4 feet and 4 spacers).

Once printed, with the help of a soldering iron (and an M3 heat set insert if you have one, otherwise, the standard tip and some care will also do the job), introduce the M3 inserts into each corner of the top of the upper part of the frame. Be very careful not to heat the plastic too much while doing it, otherwise the frame can deform. Try to put the insert straight as you can, otherwise you might experience issues later while screwing the legs.

Cutting the rods for the legs will require taking some measurements, patience and care. The length I've chosen for them is 7.5 cm, based on the proportions and the scale. AFAIK, standard post-its side length can be used as a basic reference (I've found by sheer luck that they have circa 7.5 cm too!) and after the cutting, you can sand down the borders to make all the length of all the legs match.

I can also recommend cutting some extra legs that could be used as spares in the future.

Assembling the legs is very straight forward:

1. Take the metallic rod and insert it into the foot.
2. If it doesn't fit easily, don't force it! Use the drill bit to open the foot mounting point a little.
3. Once both pieces join together smoothly, you can superglue them.
4. After the glue dries, mount the other side of the rod inside the leg holder. Bear in mind that you need to push the rod up until the top of the holder, crossing the -simulated- arc joint. This piece should not require superglue to keep the leg in place, the "double ring" should do the work quite well.
5. Test one M3*8 in the hole on top of the leg holder. Make sure that the bolt have some extra room to allow screwing, their fit should not be tight.
6. Repeat until you get 4 fully assembled legs.

This is a good moment to also glue the top of the chassis on the lower side and present the legs, just to check that everything goes according to the plan and no leg is longer than the rest... been there, done that :P.

If everything is ok, remove the legs and continue to the next step.

Time to open up the sphere that encapsulates all the electronics inside the donor! Depending on the model of gyro that you got, the disassembly process could be more or less easy (In my case, I had to destroy half of the carcass... not proud of it).

The donor that I suggested to use has a battery charger, proximity sensor and power on button integrated. It also included an IR controller. But it also has a curved shaped PCB that was slightly annoying to adapt to the cube shaped chassis.

As a side note, bear in mind that there are other models of these chopper/gyros. You could build your ALSI with any of those other donors too! Just be aware that some rework on the .stl file of the lower chassis mounting will be needed. Any remix is welcome!

This is probably the most critical and hardest step of the whole project. To make things worse, because of how hard it was for me to make it work, I cannot provide additional documentation of the process (taking pictures while keeping the piece in place was nearly impossible for my clumsy hands!).

For this step, following the pictures above in order is very important.

As you will notice, the height of the mounting points for the new carbon fiber blades are bigger than the original ones. This is far from ideal, because the blades will spin very fast and securing the blades is not only important for the flight, but also for our own security.

The solution that I've found was using the blade spacers and add 2 extra bolts per rotor assembly to keep the blades in place.

The sub-steps for this assembly are:

1. Remove the 2 screws from the rotor assembly and get rid of the original blades.
2. After reworking the holes on the blade spacers, they should fit in place in the space highlighted on picture 2 (the top view of the rotor assembly, remember to open the image to read the notation). Superglue the pieces there! Even if the mounting fits, the only way to keep them in place is by gluing them. Don't rush the process, leave it to dry and don't spare in superglue here. Bear in mind that you have to do this on both sides of the rotor axis (2 spacers per rotor assembly).
3. While the glued pieces dry, take measurements of where the internal hole of the mounting point of the new blade will be in relation to the top piece of the rotor assembly and make a small hole to allow screwing one M1-ish bolt on it. This bolt should fit inside the carbon fiber blade's internal hole on the mounting point and keep it in place. Repeat on the other extreme of the top piece.
4. Mount the whole assembly. It should look like the last picture of this collection. The blades should have some free space to fold in case of a crash, but not too much. Also, keep in mind that the vertical movement should be minimum! Otherwise, in case of a crash, the lever movement of the blades could break the rotor assembly plastics.

And now it's time to finally start to put everything together!

The first step of the reassembly is to fit the green PCB with the electronics into the lower part of the chassis. In order to do that, we should match the notch of one of the sides with the power on button, and slide the PCB into the guides. Press the board until it fits tightly into position.

To attach the motor/battery/rotor assembly into the chassis, two screws will be used: the M3*25 and the 1/8'' sheet metal screw.

The idea is to use the 1/8'' screw to fix the engine using the assembly side mount (a can be seen in picture 1), then use the M3*25 to anchor the upper part of the motor assembly and fix it into a centered position (working as an alignment system). This will help us to easily fix the rotor in a position perpendicular to the floor later.

Extra note: There is a chance that some donors could have the upper fixing point removed. In those unfortunate cases, the solution could be to just solder/glue a M3 nut to the side of the rotor axis. Although it is not an ideal solution, if done right it should work.

For this step, my suggestion is to introduce the 1/8'' screw into the motor assembly hole, but not to try to screw it into the mounting point immediately (picture 2). Instead, try to pass the M3 bolt through the designated fixing point. It is also very important to put two of the three M3 nuts between the fixing point and the chassis side hole that is being used by the M3*25 bolt. Those nuts will be used later to fix the rotor axis.

After doing this, the motor assembly will be already in a comfortable position to allow screwing the 1/8'' bolt into the plastic far more easily, reducing significantly the risk of breaking the plastic by screwing a misaligned bolt.

After putting the side bolt into the fixing point, it will become evident that the axis rotor will be displaced, like is shown in picture 1. Here is when the alignment system comes into play.

By using the set of pliers, first adjust the nut that is closer to the bolt head to fix the bolt against the chassis. Then, add the third nut on the other side of the fixing point and use the nut to move the axis until it is perpendicular to the floor. Then, using the 2 pliers, screw the nuts on each side of the fixing point in opposite directions to create some torque and force the fixing point to stay in place. This is a tricky move, so do it with care and patience.

Now, it is all set to screw the four legs on each corner of the chassis with the M3*8 and the inserts previously done in the chassis -like we did during the preliminary assembly at the end of step 7-.

This is the moment to add the tin foil wrapping or to just leave it without it. And that's it!

Now go to an open space, place your ALSI on the floor, turn it on and enjoy watching it fly!

And remember that this is not a toy meant to be used by children. It is dangerous and even if the blades will stop immediately after crashing, the carbon fiber blades hit could be very harmful. Be responsible while operating your ALSI.