Hi, my name is Nicolai Valenti, I'm 18 and I'm the founder SandwichAero (https://sandwichaero.com/)
It was September 2017 when I decided to build a hybrid drone, I decided so because of the range and the autonomy where too limited, I worked hard trying to build a generator from a brushless motor, a nitro engine and some simple electronics, after trying more times and building a sample prototype I shared my idea on the DIY Drones forum, here my work was really appreciated and I realized that this thing was bigger than I expected, after a few months of publishing posts I received a completely unexpected mail, it was from Phillip Kocmoud and Jordi Munoz (designer of Ardupilot and co-founder of 3D robotics) they decided to help me with some founds and their hardware, just because they liked my project, and I was amazed by this, I will never thank them enough.
After this, I keep working with the Co-founder Giovanni Mastronardo on this project for several months and now after a lot of working and designing we are here with our products. The following contents are the summary of all the working we went through.
I was first inspired by this video to make my first gas generator for drones.
The difficulties that however I faced during the project such as vibration damping, voltage stabilization, engine, and generator cooling were all worsen by the fact that I could not add weight and simply resolve all the problems like the manufacturers of the standard portable generator can do.
The project started inside a garage as most of the projects, we started by connecting a brushless motor to a 26cc gas engine and trying to generate some power by rectifyng the output with a simple circuit and a capacitor.
The first results were not satisfying and we often had troubles to keep the engine running due to the absence of a good flywheel. The power control module was a simple servo connected to Arduino (via PWM) that with a closed loop controlled the whole system to produce just enough power and burn the right amount of fuel.
Here is a little "documentary" about our early prototypes
This drone was using the Pixhawk flight controller which run pretty good on all of our other drones but gave us some navigation problems on this one (I suspect that one of the ESC was not working properly).
Fast forward some months later we finally managed to make an automatic start system wich used the electric generator as a motor during the start-up. This time the generator was running very smoothly despite it was small and was producing only 500W.
All the electronics you can see in the video is today compressed inside one small box.
After this first success, we decided to go big and we worked on 1000W generators and 2000W.
Every time we changed the components a massive work had to be done in order to adapt the rest of the generator.
Most of our engines didn't have a cooling system so we had to design and build also those parts.
In the last months, we had many tests on our hybrid drone which mounts the 2000W hybrid system, achieving fuel consumption of less than 1L per hour.
Today we are working on smaller hybrid drones, to make the thing affordable and easy to use for every drone user.
This last design will soon be our 500W Hybrid drone ptototype with a 1kg payload and more than 2 hours of flight time.
The hope is to be able to sell those drones at affordable prices.
Find more on: https://sandwichaero.com/
Thank you for your time.
MIT is testing hybrid quadcopters that switch between gliding and hovering.
Now we just need to do this: https://www.engadget.com/2019-07-16-mit-is-testing-drones-that-can-switch-between-hovering-and-glid.html
Then slap a solar panel on top across the wing, and combine the solar panel into a circuit that augments battery recharge somehow, and it may fly forever if you program it to act like a bird and catch updrafts properly.