In this inventor interview the Quadshot team talk about inventing their clever remote controlled aircraft.

the quadshot team

Clockwise from upper left: Chris Forrette, Pranay Sinha, Piotr Esden-Tempski, and Jeff Gibboney

Tara: Please could you tell me your names, invention name and website URL?

Quadshot Team: We are Piotr Esden-Tempski, Chris Forrette, Jeff Gibboney, and Pranay Sinha. Our inventions are the Quadshot and its ‘brain,’ called Lisa. The Quadshot’s website is

Tara: Please could you tell me a little bit about where you are based, your background experience how you first started inventing?

Quadshot Team:We are based in Santa Cruz, California. Piotr has a degree in Computer Science and has a lot of experience designing embedded electronics and writing software for Unmanned Aerial Vehicles (UAVs). Chris is an expert remote control (RC) airplane builder and pilot and has an Aerodynamic Engineering background. Jeff has degrees in Computer Science and Mechanical Engineering and experience designing and building bicycles, robotic vehicles, and UAVs. Pranay has degrees in Aerospace Engineering, and experience designing everything from spacecraft to robotic submarines. Piotr and Pranay work for Joby Energy, Inc., which provides their services to us as consultants.

quadshot invention

Tara: Please could you tell me a little bit about your invention, what it is, and how you came up with the idea?

Quadshot Team: The Quadshot is a remote-controlled aircraft that combines the abilities of a helicopter and a fixed-wing or “traditional” airplane, in that it can both fly forward like an airplane and hover like a helicopter – but without many of the complicated, expensive, and fragile moving parts.

In addition to the innovative, lightweight and durable airframe design, the main development that makes this possible is that the Quadshot has a “brain” that we call the Lisa. Like the flight computer on an advanced aircraft or unmanned aerial vehicle (UAV), Lisa is equipped with a sensor suite called an Inertial Measurement Unit (IMU), which contains 3-axis solid-state accelerometers and gyroscopes to keep Lisa up-to-date on which way she, and thus the Quadshot, is pointing and how fast she is rotating.

Lisa combines all of this information with pilot commands and then adjusts the speed of each motor hundreds of times per second, which allows the Quadshot to hover like a helicopter, fly slowly and steadily like a trainer airplane, or allow for high-speed aerobatics – all by flipping a switch on the RC transmitter.

So how did we come up with the idea? Well, we met while working at an airborne wind energy company called Joby Energy, Inc., where we worked on designs for large rigid kites that could generate energy as they flew around. For the small prototype kites, the control electronics had to be small and light so that they didn’t weigh the kites down or take too much space, but still powerful enough to run all the complex control software. We collaborated with the Paparazzi UAV project, developing both software to fly our kites and electronics to run the software. The first result of the collaboration was Lisa/L:

Lisa/L weighs about 35g (about the same as six quarters) and is the size of a business card, compared to other designs on the market that weighed over 500g and were the size of a paperback novel.

The dramatic reduction in size and weight meant we could make a much smaller, lighter and zippier flying machine – all excellent qualities for a hobby aerobatic platform. We started discussing what the design could look like, did some aerodynamic design to make sure it could fly, and the basic Quadshot idea was born!

Quadshot Lisa invention

Tara: What were the first steps you took after having your idea?

Quadshot Team: After we first came up with the idea of an electronically stabilized, highly aerobatic and very capable hobby aircraft, we decided to define these capabilities as well as performance requirements more clearly and in a manner that would set goals we could work towards – just saying that the “airplane needs to be cool” wasn’t enough. So, we talked to friends who were involved with the UAV and controls research fields, as well as the hobby RC community and asked them what they thought a really great aircraft would be capable of doing.

We looked at everything from the easier to fly “trainer” RC systems to high-end UAV and research vehicles costing tens of thousands of dollars to figure out how to go about designing a system that could be used by everyone from novice RC pilots to experts and researchers. After these initial steps, we had a good idea of what our product was going to be and went about creating a company to make it.

The next steps were to try and raise enough money to get into production, and also validate our idea by showing it to a wider group of people. We learned about Kickstarter and thought it would be a perfect way to do both at the same time. We set a goal of raising $25,000 in six weeks, and ended up with $84,000.


Tara: Did you get presentation drawing sheets produced or make a prototype of your invention, how did you go about this?

Quadshot Team: We have access to Joby Energy’s machine shop and experience building RC aircraft, so we were able to design and build the early airframe prototypes ourselves. For the first prototype, called JT1, we used a hot-wire cutter and CNC router to make an airframe out of foam, fiberglass, piano wire, and balsa wood:

Quadshot  wing

We installed a Lisa/L and spent a lot of time hacking, tweaking, and tuning the Paparazzi software to make JT1 able to hover and also fly forward. We also crashed a lot, learned what broke and what didn’t, and tested about a dozen other prototypes of various designs before settling on the Quadshot design. We used a 3D computer-aided design (CAD) software package to model the designs and make drawings, and ordered some parts from a 3D printing company to test part designs we couldn’t make ourselves.

The “brain” electronics in the final Quadshot, called Lisa/M and Lia, are evolutions of the original Lisa/L and even smaller:

Quadshot size

The electronics designs were developed with input and support from the Paparazzi UAV community, which was invaluable as a source of design improvements and helped us make them easier to use, cheaper, more reliable and more power efficient. We laid out the circuit boards in an electronics design package called EAGLE, and had prototype circuit boards made by mail order. We soldered on the chips and other components ourselves, and wrote and modified the low-level code necessary to get the Paparazzi software working on them.

Tara: Did you try and patent or protect your idea in any way and how did you go about it?

Quadshot Team: The “brain” as well as the software making the Quadshot fly are (respectively) Open-Source Hardware and Open-Source Software, which means that the physical design files are available to everyone under a Creative Commons license, and source code is available to everyone under the Gnu Public License (GPL). This is a fairly new approach to the development of innovative products in this area and allowed us to get input from some very smart people who were happy to donate their time, thus lowering our development costs.

We are in the process of patenting some parts of the Quadshot, such as the airframe configuration and some innovative designs and ideas that have gone into making the airframe a user-friendly and high performance product.

We were fortunate to meet and work with a local patent attorney at Joby Energy who is excellent at what he does and also passionate about flying vehicles. The approach we have taken is to write up initial documentation describing our inventions, which has sometimes even been in the form of drafts of papers we are submitting to academic conferences, and then passing it over to our attorney for molding into the application format.

Tara: Did you always intend manufacturing your invention yourself or did you look into licensing the idea?

Quadshot Team: We were interested in going through the manufacturing process ourselves, so we didn’t look extensively into licensing. Furthermore, we weren’t sure how potential licensees would react to our Open-Source approach. Thus, we decided to take care of the initial manufacturing ourselves. This is not meant to imply that we do everything from scratch – we have the electronics assembled at a local vendor here in Santa Cruz, contract with molding companies for the foam and plastic parts, and buy some things off the shelf. Since quality assurance is important to us, we will do final assembly and testing ourselves.

Tara: How did you go about finding a suitable manufacturer for your invention and did you self fund this?

Quadshot Team: For the electronics manufacturing, our experience at Joby Energy proved very valuable. Not only did we know where to source our components, that is, the pieces that go onto the boards, we had also developed a great working relationship with a local PCB assembly company, Dallas Electronics. They proved to be very helpful and provided some great feedback on how to get our electronics assembly costs down. They assemble all the Lisa boards and sensor packages that go into the Quadshot.

A Minnesota-based quick-turn plastics molding company, ProtoLabs, sponsors the Cool Idea contest, where they award mold tooling and small manufacturing runs to help innovative ideas bootstrap their manufacturing process. The Cool Idea organizers found our project on Kickstarter and encouraged us to apply. We were fortunate enough to win support from the contest and received mold tooling for our plastic parts and the first 400 pieces free! In addition, the ProtoLabs engineers gave us some great design support as we got our plastic parts ready for the molding process, and the parts we’ve received have been of great quality.

Finally, one of our investors, JoeBen Bevirt, has extensive experience in manufacturing consumer products – he successfully founded Joby, which makes the Gorillapod line of articulated tripods for cameras. He was able to provide us contacts in Shenzhen, China, which Jeff visited to locate vendors and manufacturers for some of the Quadshot’s components.

Since the initial startup, we have also been able get some revenue from sales of our electronic boards to hobbyists and researchers who want to make their own vehicles. We also offer our services on a consultancy basis through our company, Transition Robotics, Inc..

Tara: In what ways are you looking to promoting your invention?

Quadshot Team: Since we are initially selling Lisas and Quadshots ourselves, we are focusing on the Internet, social media, and direct face-to-face events for promoting our inventions.

Kickstarter was definitely the biggest promotion we have done so far. During our campaign, we sent out press releases to many technology blogs, and got a lot of support from the Paparazzi community as well as from UAV and RC enthusiasts in general. Additionally, we submitted papers to academic conferences and showed off our early prototypes at Defcon, an annual “hacker” convention held in Las Vegas. While there, we met the producers of online TV show called Hak5, who were kind enough to feature us on one of their internet TV episodes. The Cool Idea press release from ProtoLabs has also contributed greatly to our campaign.

We plan on attending Defcon again this year, as well as other events such as Maker Faire in San Mateo and the CCC in Germany.

Tara: What have been the most difficult elements of bringing your invention to market so far?

Quadshot Team: Although we were able to build prototypes relatively quickly, the road towards a mass producible product is much longer and more difficult. We had to learn a lot about plastic and foam molding, and resolve the design to a much higher level than what is needed when building “one offs.”

A big challenge was estimating our ship date. As none of us had experience with mass production, we underestimated lead times, and are learning to manage inventory and cash flow as we go. As many inventors will tell you, it is very difficult to see in advance what problems will emerge, but a good thing to keep in mind is the PI rule: the time to finish a project is the time you predict multiplied by PI, even if you take the PI rule into account!

Tara: How long has it taken from your initial idea to taking it to where you are now?

Lisa/L was designed in mid-2010, and we flew the first Quadshot prototypes in late 2010, so we have been working for over one and a half years.

Quadshot Team: Is there anything you learned developing your invention that you would now do differently if you had to do it all again?

The process of building Quadshot has been a great experience! We’ve learned an incredible amount – there really is no substitute for taking an idea, starting a company, and building something yourself.

One big lesson we’d like to share is that if you are making a product for mass production, it is critical to focus on simplifying and perfecting your concept as much as possible. However, you have to balance that against the risks of taking too much time to get to market.

Lastly – underpromise and overdeliver!

Find out more about the Quadshot at

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