I would like your help.  Safety is my number one issue with drones. Last year I was learning to fly my  Parrot AR. Drone that I had fitted with carbon fiber blades.  I was doing a simple take off and landing in the living room to impress a friend.  I was hovering and accidentally hit the "Home" button. Instead of a soft landing the AR Drone took off from a distance of about 10' from me and came right at my face.  As I was trying to deflect it, the carbon fiber blade put a gash on my left eye, just missing my eyeball.  I don't know about you, but that really soured my experience and nearly put out my eye. 

I had every intention of taking the money I had saved to start a Real Estate Photography company.  Instead I became afraid of the drone. A friend purchased a Phantom from DJI and had a very similar experience on his very first flight.

Oddly enough I became so fascinated with the industry that started to look for solutions to the danger of any multi-rotor with plastic or carbon fiber blades.  I came up with what I affectionately call DroneKone.  It is complete and substantial propeller protection to help make drones safer.

I started a small company with my limited funds and developed a model of my concept.  I was able to get a provisional patent on my safety device.  Then I had a devastating life event and was out of action for a year.  I have recovered.  I don't have any funding at this point except out of my pocket and started seeking funding. I was told by a potential investor that I needed to survey 100 people to find out if my product is market worthy.

Okay enough story.  Simple Survey for Safety:

  1. Yes or No  Are you concerned about drones flying around Children? 
  2. Yes or No  Do you have a concern about your personal safety when flying a drone?
  3. Yes or No  If a safety device was available would you consider purchasing it?
  4.                  What would a safety device look like to you if you could design one?
  5.                  How much would you pay for a safety cage if one was available when you purchase your drone.

I greatly appreciate you reading this far and ask for help.  If this is just plain stupid, then I would like to know that now, before I spend any money on moving further.

Thank you so much for listening.  I am grateful to be a small part of this awesome community.


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Thank you for your opinion.  I am looking to make a good, reliable, crash resistant, propeller protector.  I have posted a few pictures of our first prototype.



Thank you for filling out my quick survey.  I'm trying to get to the $100 mark.  I too believe it has to be commercially sensitive and under $ 100.00.


I have posted the first prototype images.  This concept will eventually be available for all commercially available copters.  This one is designed for the DJI Flame Wheel F550.  Let me know what you think.


That looks pretty sexy but you should be designing frames with those design skills not prop guards.

Looks like it weighs more then the frame.

Does it allow enough clean air or does the design degrade propeller efficiency?

it looks great but at what cost and I am not talking money.

Can it all be made in that mesh style with black and white hexagons? that would reduce weight, better airflow and could look cool.

looks and function

  1. Are you concerned about drones flying around Children?  Yes but for me, also pets
  2. Do you have a concern about your personal safety when flying a drone?  Yes, I am not a great pilot and do not trust all electronics/mechanics
  3. If a safety device was available would you consider purchasing it?  Yes
  4. What would a safety device look like to you if you could design one?  Similar to yours as long as it allowed room for the parts and didn't restrict airflow too much
  5. How much would you pay for a safety cage if one was available when you purchase your drone.  $100


Thanks for the design kudos!  It doesn't weight more than the frame.  The ducting / manifolds actually add power and efficiency to the thrust.  It also adds a bit of stability.

I really appreciate you taking time to give me a thoughtful critique.



You have all the right answers!  When I have one to sell, I'll let you know.  My target is right around $100.  What copter do you fly?


Yes - But not just Kids. Anybody. If you are filming professionally anything that mitigates the risk of hurting someone is a good thing. Carving up a bride on her wedding day is NOT going to get you an invite to her second wedding! :)

Not really - Having caught many fingers in gas engine props in the early days I'm far, far more careful about working with drones ( 6 or 8 times the threat! )

Yes - If it was reasonably priced. Adding £150 ( $225 ) to the cost of a Hex or £200 on an Octo simply is not going to hack it!

Lightweight, low cost, effective but that having been said I don't need something sturdy enough to be re-useable, something that is sacrificial would also work. Where the device itself is damaged in the process of protecting a person.

A mass produced, lightweight, disposable cage. £10 max.

As an exercise I have designed a shroud that forms around a prop and extends towards the hub, a sort of teardrop plan form device. Given the right design they could be individual units and you buy 4, 6 or 8 and clip them on/off the copter arms. The major advantage is that the airframe is still foldable unlike a one piece unit that needs a van or large vehicle to transport.


Ducts or shrouds can indeed have a beneficial effect on the thrust from a rotor by preventing the airflow from constricting after the rotor disk.

The duct however, they have to be designed correctly. If the duct is too short then it's effect on the rotor slipstream will be limited and the term "shroud" is then more appropriate. You also need to minimise tip clearances, which could be a big problem in trying to get a single unit to fit four or six rotors.

Inlet design is also a concern and a sharp edged duct will cause a lot of turbulence exactly where you don't want it. You really need a large bell mouth on the inlet to stop the flow separating. A mesh or grid will also add turbulence but you might get away with some properly shaped inlet guards. The inlet problem is made more complex with forward flight. The body on your design will also add extra aerodynamic loads.

We stared working in the UAV industry around 20-years ago and I am surprised there aren't more products available with shrouded rotors. Multi-rotors have become so successful due their aerodynamic and mechanical simplicity. I suspect the reason for the popularity of the open rotor is for this reason too. You need to be very careful you don't erode the benefit.

I'm not saying it's a bad idea, just that trying to design a retro-fit rotor rotor shroud that really does increase safety without severely impacting performance is not a trivial problem.


Worthington Sharpe

Bob, I have read elsewhere that duct fans aren't suitable to multicopters due to its tendency to resist against lateral wind, thus making it difficult to move laterally. Your prototype is a kind of ducted fan. Do you think it may suffer the same issue?

Nice layout !! 


Thank you very much for answering the safety survey questions.  I very much appreciate your participation.  I understand you need for protection that is very cost effective and does not add any weight to the air frame.


Your effort is very noble, here is my view:


1) Drones are coming out of 100's of sources including phone, toy and camera manufactures. You cannot compete. A technical consumer product is a difficult way to make a living.

Patents - Have considerable experience in this area:

2) a) A screw over a fan blade is obvious to those skilled in the art (think room fans)  b) A provisional is nothing more than documenting your idea, putting in an envelope and enclosing $130. Don't need a lawyer. Its after one year that it cost mounts up fast. c) A patent is really just a reason to sue, you can sue for anything anyway. d) Patents are impossible to sell.  


Ducted fans for hovering are different than for planes. The hovering blade will suck a vacuum in the inlet, that can only be replished at atmosphere pressure (15psi) Therefore the outlet is 15 psi in your design. Hovering Ducts require wide input funnels with as large acceptance area as possible.

The four letter "S" word.

Machines that kill people are considered acceptably safe. Consider: lawnmowers, chainsaws, weed whackers, step ladders, bikes etc.

Lower your left hand while driving, you not only kill everyone in your car but everyone in the oncoming lane. You should see what my finger looked like when I slammed the car door on it. 

I'm sorry, but my opinion is your pictures and campaign are not healthy for a young emerging technology under fire from so many.

I respectfully suggest you should consider a different use for clearly impressive talent.


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