Tag Archives: drone

Let’s recap. My Altoids Drone recently underwent a huge redesign; dropping the bottom half of the tin to create an integrated underbelly with rotor arms and battery compartment etc. The next step was to construct the new design in metal.

Metal prototype of single-piece under-body design

Using a single hole-punched sheet to mount the motors proved very flimsy. The motors would be stable but likely the metal would bend and shear off in a crash; not good if you have to build a whole new undercarriage every time. With that in mind, I revisited some of my original motor-mounting ideas, as well as a few elaborate new ones.

Motor mount test pieces with drilled (left), wrap-around (centre) and enclosing (right)

With a CNC router for easier, more accurate cutting, a wrap-round approach could work very well. However, hand-cutting is too inaccurate to reliably grip the motor with some form of locking part (bear in mind thin metal tears). Additionally, any design could easily bend open or deform so this approach was not practical. The final nail in the coffin was that the design with motors was of similar weight to the wooden frame trial; my motors are too heavy so we know from the outset it won’t take off.

The wonder of crash-kits

Try as I might, I was unable to find the motor’s specs. Good drone and helicopter motors give you the lift they can produce in the specs, so you know these are meant for flight. Any specs of motors comparable to mine did not have lift specified. In short, these motors are meant to produce torque under load, not high speed and weight efficiency.

Finally, I bit the bullet and went back to the shop with the crash-kits from whence my rotors came and bought the motors too. Now my motors, rotors and battery come from a G-Force Hubsan X4 drone. The X4 weighs just under 400g, so I now also know my own weight goal is the same 400g. Thankfully these new motors are cylindrical and so could be mounted into a rubber washer. As such, my new arm design simply had to crimp the washer, not the motor.

Quadcopter Frame with G-Force Hubsan X4 motors and rotors

I also added legs to the arms to protect the motor wires and stand the drone a bit higher. The bridge under the base of the arm is now moved forward to allow it to be crimped rather than fixed with adhesive, making the join structurally strong. Here’s the shiny new drone with the tin lid on.

New chassis with tin and motors mounted

New challenges

Wiring the motors – My motor wires are now considerably shorter, only reaching to the their respective corners. But, this has an upside. It’s important that if anything happens I can replace the motors without re-soldering my Arduino every time. Keeping weight low, the plan is to use female connector contacts crimped to the motor wires (these wires are tiny so need crimping). That way, the Arduino wires can simply be plugged in rather than soldered.

Space – At this point the total depth I have to house everything (apart from the battery) is the depth of the tin lid, approximately 8mm. It’s going to be cosy!

In the next post, I’ll start to plan my electronics and look at how it’s all going to wire together.

The last post covered a one-day build of a prototype quadcopter using a wooden chopstick frame, a battery and motors. It achieved a hover above the table but nowhere near lift. Since then, I’ve been doing some research about calculating how much lift I need and what types of motors or rotors etc. You may have seen this video, which I highly recommend looking into anyway. After watching it, I realised I don’t have the motors’ specs, make or model (remember, I salvaged them from servos) and as they are generic, finding the specs to do any real calculations is guesswork at best.

So, where next?

Thus far, the factors I have been toying with are:

• Upgrading my motors
• Going for bigger rotors
• More powerful versus less powerful, smaller and lighter battery.

Basically, I focused on what I could electronically manipulate to improve performance. Additionally, my new design sketches focused on building a surround for my tin, so as to be minimally invasive to it, as shown below.

1:1 scale concept sketches for an Altoids Smalls quadcopter

There are lots of practical considerations like how do I mount my components inside? Do I leave it opening or cut a hole for replacing the battery? Do I construct a frame with arms, or four separate arms? If separate, how do I ensure everything is secure and flush? All these considerations play off against space, weight and complexity so in short, too many questions and not enough answers. To escalate the situation, I searched lots of drone manufacturers and hobbyists to see what motors, rotors and batteries they use etc. Finding that my motors simply aren’t used, the possibilities of buying lots of new parts opened up.

The answer

After a good step back and a deep breath, I realised that my problem is indeed weight. Everyone else uses plastic; I’m working with metal. So, time to think outside the box, or at least with half the box. The lower half of the tin is the heavier by far. Removing that bottom half and using the hinges / clasp as a mount-point means that once again the world is my oyster.

Back to the drawing board

Without a bottom to work around, it was now possible to have a single frame unit based upon a flat sheet, providing both rotor arms and the main chassis. A battery compartment or sleeve could be incorporated by design as well as using the original tin hinges to mount the lid. Back to Excel (yes, it is my drawing platform of choice and I know it’s weird) to put together some more paper concepts. This was the result.

1:1 scale concept for an Altoids Smalls Drone under-body and rotor arms

The new version incorporates the Mk III arms shown in the preliminary designs post, with additional flaps to join the lower edges, increasing rigidity. When folded, the centre plate forms a battery slot underneath the drone. A plastic layer will be fixed on top, covering the battery slot and insulating the chassis for mounting components. The design needs access for wiring the battery and rotors so that the tin lid will lie flat, but it sufficiently demonstrated the concept.

Altoids Smalls drone schematic with battery placed

With the battery dimensions checked and a few fine adjustments made to the hinges, the tin lid could then be fit to see how the overall design worked.

Altoids Drone bottom assembled with battery and tin

The new design gives me a number of options to explore:

• Different metal thicknesses (an aluminium tin will be used for the next stage)
• Recycling the metal from the original tin bottom
• Using plastic, such as a 3D printed solution
• Using a one-piece design or making removable arms and battery compartment

If I do end up using a 3D printed base, it will be done by a print shop nearby so a quote may be a determining factor here. There are some advantages, such as low weight and making clip-on motor mountings rather than using screws or glue.

In the last post, I had the bulk of my parts ready and talked about giving them a quick go. With that in mind, today’s mission was to build as basic a quadcopter as possible and see how well it performed!

How it works

This model is as basic as you can get; all I want to do is wire the motors to a battery, with not even a switch, and see if it achieves lift. It won’t be pretty, it won’t be stable. But it will tell me if the battery, motors and rotors will get the whole kit-and-caboodle off the ground.

Constructing the frame

My first objective was to make a static frame that could hold the motors (and rotors) still. A set of disposable chopsticks proved ideal; I marked out the half lengths of the rotor, then a 1cm space, the diagonal length of the Altoids Smalls and then another 1cm space and other rotor halves on each chopstick. I then chopped the chopsticks down to end at each rotor mid-point, as shown below.

Chopsticks cut to length to form a cross frame

I angled the chopsticks to match the corners of my Altoids tin and marked where they crossed. This allowed me to file away the marked areas, enabling the chopsticks to cross one another flush. These were stuck together and then taped to make them sturdy. Next, I stacked the ends I had cut off onto the ends of the cross, stuck them together with an adhesive roller (like a sticky tippex) and then wrapped them in sellotape. The sellotape would provide a flat, vertical surface on which to stick the motors.

Wiring

The wiring assembled was very, very simple; one end of the battery connected to one terminal of each motor, while the other end of the battery connected to the other terminals. To do this, I cut 5 yellow lengths of wire and 5 black lengths of wire, all of roughly equal length. I essentially needed a star configuration as shown by the yellow wires.

Fan of wires twisted together to give 5 connected ends

The ends were stripped, with one end stripped twice as far as the other on each wire (extra contact for twisting together). I twisted the wires into pairs, then weaved the pairs together along with the fifth wire and twisted the lot together. If you try this, soldering the wires shouldn’t be necessary as long as you twist the wires really tight with pliers. My wire of choice is single-core, because it retains its shape after you twist it.

Assembly

You can see here all the parts ready for assembly. I stripped down my servos for the motors but left the connectors on for now. That way I can just push the wires into the sockets.

Quadcopter parts ready for assembly

The first step was to arrange the wires onto the frame. Each fan of wires was arranged into a cross with one wire stuck up. Then the two were placed onto the frame in the middle and stuck down. VERY IMPORTANTLY, I made sure that the yellow and black wires DID NOT TOUCH, because that would directly short out my battery and probably catch fire.

Chopstick quadcopter frame with wires taped on

To wire the motors to the wires, I simply inserted a yellow wire and a black wire into the terminals of each motor, taping them if they refused to stay put. Because one pair of my rotors is the reverse of the other, I connected the yellow to yellow at the front, but then yellow to blue at the back. That way the back motors spin in the opposite direction to the front, making all the rotors push air downwards. Here are the motors wired.

Quadcopter frame with motors wired in

To stick them in place I first stuck them to the sellotape with the adhesive roller tippex thingy, further securing them with sellotape wrapped around the sides.

Finally, the battery was taped under the middle of the frame to secure it. Before connecting it, I shortened the exposed sections of the wires as much as possible to minimise them touching when plugged into the battery, thus minimising big boom later. Here is the finished result.

Quadcopter assembled with motors wired directly to the battery

P.S. – Upon revision I would definitely place my battery wires down to save my fingers from the wrath of the rotors, so just keep that in mind. I know I will.

The result

Well, it didn’t fly but I had great fun and in one day got a real feel for how the drone needs reworking. I now appreciate how heavy my motors and battery are combined. I’ve learned that quadcopter is the way to go; I’ll need all that thrust, plus it easily solves the issues of steering without adding excess weight and not spinning from an imbalance of momentum in the rotors. It did make a good hover above the table, so I know that I’m not far off what I need, but alas I either need bigger rotors and either a more powerful or lighter battery.

Have fun with your build and let me know how your trials and tribulations go, or what you think of this build.