Mini-copter Toy

This instructable will teach you how to make, and more importantly, design your own mini-copter. The idea is very simple, our copter will fly by spinning up a propeller as fast as possible. To drive our helicopter propeller, we use a cord that you can pull to spin the stick to which the propellor is attached.

In this instructable, I'll show you the design process of the 3d printed propeller in Tinkercad. My ultimate goal is to reach the longest flight time. I'll try to explain some of my design ideas and concepts. With this information, you too are able to design your own mini-copter, and I challenge you to design an even better propeller and beat my flight-time record with it.

In order to make the mini-copter, you'll need:

1. a cocktail pick
2. a piece of cord
3. gum (or glue)
4. a 3d printer
   (Since most people don't own a 3D printer: You can also make this by cutting the propeller out of a carton. It requires a bit more creativity, but you can make it work!)

The middle of the propeller has to be attached to the rod after printing.

In tinkercad, we'll start with an empty new 3D design.
The first shape we add is a simple cylinder, which will be the middle of the mini-copter. The cylinder has to have a hole for the cocktail pick and has to be sturdy enough to hold all of the propeller blades

I use a cylinder with a radius of 4mm (diameter = 8), and a height for the two of 8 mm.
After The cylinder has been put in, you can select a hole in a cylindrical shape by selecting the grey cylinder. A hole Put it exactly in the middle, so there will be no imbalance. You can do this easily by switching to "bottom view" by clicking the cube in the top left of the screen. The hole has a radius of 2mm (diameter = 4), and also a height of 8 mm.

In this part you want to have as little mass as possible, the heavier the middle is the faster the mini-copter will drop to the ground. So I recommend only make the middle as small as you absolutely have to.

Next up is the "engine" of the mini copter. The blades push the air downwards, and as a result, also push the minicopter upwards.
I start by adding a cube in tinkercad, by decreasing the height and increasing the length you get a nice flat rectangle that will be an ideal start for a blade.

Make sure the blade touches the middle by dragging the rectangle. Note that you don't have to worry the rectangle will cover up the hole you made for the cocktail pick, it will automatically make a hole in the rectangle aswell.

The next step is to determine a nice angle for the blade. The higher the angle, the better the blades push away the air. But if you lower the angle, the air resistance decreases and the minicopter can spin longer. I therefore choose an angle of 45 degrees.

You can easily apply the angle by clicking the cube in the top left, and view the blade from the side.

The next step is to duplicate the blade, so you can have as many blades as you want. I choose 4 blades, which I think is a nice balance between construction strength, having enough blades to fly, and being light enough.

You can copy and paste the first blade you made. By tilting the copied blade to the desired angle, and dragging it to the correct place.

Make sure to check if all blades are perfectly symmetrical by looking at your propeller from the bottom view. Otherwise the mini-copter will not fly stable.

You can try changing the number of blades, the angle, the length, width and the thickness of the blades.

In order to make sure the propeller is less prone to breaking, and to make a sturdier connection, will add a tube around de blades.

Start by selecting a tube from the shape menu. Place it exactly in the middle. By altering the radius and wall thickness you can place the ring at the right position.

In addition to construction strength, the ring also adds inertia to the mini-copter. The larger the inertia, the more energy the mini-copter has, and the slower the propeller will stop spinning. Making the ring heavier therefore could result in a larger flight time.
In opposition to the middle, where extra weight results in very little extra inertia, the extra weight in the ring could improve the performance.

Be very carefull to not make the ring too heavy, the mini-copter will fall straight down...

The handle makes sure you can hold the mini-copter while spinning the propeller up.

The design is quite simple. A cylinder with a radius of 5mm, and a hole with a radius of 3mm (slightly bigger than the middle of the propeller, to ensure there is little friction) the height is 55mm which fits nicely in your hand.

The next step is to print the blades. I use the software cura to set up the print, and a ender 3v2 to print the blades.
The settings I use in cura are: PLA, low quality (faster printing), 2 walls, 3 top layers, and 40% infill. Printing takes about 40 minutes.

We will attach the cocktail pick to the propeller with gum. If you have chewed the gum for a while, it's perfect to firmly attach the propeller. The reason I use gum, is because the cocktail pick might break. With gum it is easy to replace it!

It is important to make sure the rope is not attached to the mini-copter. The rope should namely come off after you are done spinning. Otherwise, the extra weight of the rope is far to big.

To ensure this, you start by laying a short endpiece of the cord alongside the cocktail pick. You can then wrap the cord around it so it is won't come loose.

After you've done this first piece, you can wrap the remainder of the cord around and around. I use a cord length of about 90cm.

Then finally you are able to fly!

Put the mini-copter in the holder, after winding the cord around it. Once you pull the cord as hard as you can, the mini-copter will fly up.

It takes some time to master, but once you get the hang of it, but after a while, I was able to get a flight time of about 3.6 seconds from a starting height of about 1.5m. Are you able to beat this time by altering the design?? Good luck, and let me know in the comments!

edit - aeinsignares noted that the rope can be wound under the handle instead of above. This really helps with the minicopter flying straight up.