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:
- Yes or No Are you concerned about drones flying around Children?
- Yes or No Do you have a concern about your personal safety when flying a drone?
- Yes or No If a safety device was available would you consider purchasing it?
- What would a safety device look like to you if you could design one?
- 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.
bob
Replies
OwlPic,
Seen them all before. What is your point?
bob
Your effort is very noble, here is my view:
Market
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.
Physics
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.
IMHO
OwlPic,
1) 50 percent of the market is the DJI Phantom line. I believe they have placed over 400K units on the market. I'll take 20% of that industry and do just fine.
2)Okay a screen for a house fan. Fans were first make without a safety screen or enclosure. That was the dark ages of technology. Today no one would even think of having a house fan without adequate protection. It is just the norm. Just because drones are in the dark age of their technology, doesn't mean we can assume safety from propellers is not an issue. There are plenty of examples of injuries, accidents and multiple lacerations from drone propellers. Oh by the way, provisional $3,100. Non-provisional priceless.
3) Physics - Sam Worthington has the math that makes this statement incorrect.
Sorry? When an average Joe is actually cut enough times by some young user, I won't have to do anything. The FAA or US Congress will make it mandatory. Besides, why should we not consider safety as an issue for "young emerging technology under fire from so many"? I know it goes against the grain, but the discussion is valid and needs to be discussed here and in other forums.
I can totally agree with the comments about the patent. We've recently had a UK and US patent granted and the costs to get this far have been about 10x what we originally expected. It's an expensive and very painful process.
On the physics side of things, the above post is not correct. I designed a VTOL UAV for my master's degree and have designed shrouded rotor ducted fans since so have battled with this problem a few times. There is certainly no "vacuum" at the inlet, and the rotor disk does in fact raise the pressure. If it didn't there would be no resultant force and (if Newton got his second law correct) anything with a ducted fan (such as a hovercraft) couldn't accelerate.
This applies both to a open propeller and a ducted fan or shrouded rotor. Here are the calcs for an open propellor and I'll upload the details for a ducted fan when I get time.
A correctly designed ducted fan does have an increased static (have a look a this paper from Rutkowski and Krusz) over an open rotor but you've got to think about tip clearances, inlet diameter, duct weight and other potential problems.
Sam
Worthington Sharpe
This is not the place to have this discussion ... but your reference article and your assumptions assume there is a constant source of fresh air. Suppose I put the propeller several feet into a duct, would you agree then that just above the propeller is a vacuum as long as the prop rpm speed is greater than the ability of the air to flow into the 14.7 psi (STP) vacuum?
Have you wondered why the efficiency of a hover falls off with RPM? It is because the fresh air, only driven by atmospheric pressure, hasn't had time to refill the vacuum left by the prop's rpm.
If so, there is some point down in the duct, depending on prop's RPMs that the hovering prop removes all the air in one sweep and has to wait for 14.7 psi to push 0.07lbs/ft^3 of mass into the propeller area. (also Newton's second).
I'm afraid "no "vacuum" at the inlet" would be tough to convince a vacuum cleaner or leaf blower designer. I do admit this level of detail is above a master's degree. Please PM me and we can take this off line and I will explain who I am and my experience. Thank You (my apologies to Bob Cooper)
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.
Ian,
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.
bob
Scott,
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?
bob
Bob,
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.
Sam
Worthington Sharpe
Sam,
You are obviously a noted scholar on the subject. It may be that the open rotor is a reason for popularity, but as we move forward in the industry no one in their right mind would allow any commercial vehicle such a lapse in safety. I'm certainly not a engineer or aerospace type, but I'm certain the "math" of the situation is really just thrust vs. weight. I know that is way to simple, but if the motor can create a variable of rpm's from 0 to 40,000 rpm and hovers with just 30% of power, than I'm certain as the industry grows, thrust will not be a problem.
I get that it is not a trivial problem, but if it was easy everyone would have done it.
I do thank you for your excellent thoughts and understanding of the issues. Thank you for the math reference.
bob
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