Hey!
This is my first post ever over here. I'll be honest I'm not a lot into making quads or anything of this sort but my professor asked me if I could do it and I said yes, as I need this project to graduate.
So now I'm stuck with poor knowledge about quads.
The task that I'm stuck on is that there are four engines that my professor ordered. They're JC120 EVO, 12.5hp gas engines. I want make/order a variable pitch propeller for it. Can you help me find exact dimensions and where should I order it from?
The JC120 EVO detailed specifications can be seen here. http://www.hobbyking.com/hobbyking/store/__33546__jc120_evo_gas_engine_version_2_w_cd_ignition_120cc_12_5hp_8_000rpm.html
Also the quad is being designed to carry a load of at least a 100lb. Does the assembly of the variable pitch and the propellers have to do anything with the weight? Do they have to be stronger than the usual? He asked me to machine it. But honestly I think doing it in 2 weeks will be not be easy for me.
Any help will be greatly appreciated!! I can not graduate until I complete this task =(.
Replies
One single central engine would eliminate the need and complexity of keeping them all at the same rpm.
As mentioned, there is no problem at all control a quad via collective pitch props. In fact, many times plugging up the pitch servo with where an ESC'S would normally connect on a FC works just fine (tuning required of course). Rarely do y out actually need any specific code. Unless of course you have extreme vibrations etc...
Vibrations and harmonics are another problem with 4 multiple gas engines. They will wreak havoc with the harmonics at certain rpm.
Shenhyar,
I think this is possible to get flying but I don't think direct drive props are the way to go. I just don't know where you will find 26-28 inch variable pitch props. I would look at using 4-800mm size flybarless helicopter heads. Use symmetrical 800 mm blade because 2 will be cw and 2 will be ccw. I would look at a 5:1 reduction of head speed from the engine. a good head speed is probably 1600 to 1750 rpm. Make sure everything is balanced. You will want all the engines to be running at the same rpm so I would look at using an electronic governor for each one. I think any flight controller for a quad should work. Instead of increasing RPM you increase pitch and it should have the same effect as thrust and rotation.
However, I also agree with Rob Lefebvre regarding safety. A young man was recently killed in New York flying his helicopter with a smaller blade size than what I recommend.
Shehryar, I'll be totally frank... this is hopeless. Moreover, it's dangerous.
I have been heavily involved in the Arducopter project for 3 years. I'm quite knowledgeable about both multirotors and helicopters. I am a degreed mechanical engineer who likes to get his hands dirty, I have a small machine shop and can TIG weld. And I would love to take on a project like this.
But my timeline for something like this would be on the order of a year. It's a significant undertaking.
If your professor persists in this endeavour with this kind of cheap and fast approach, he's going to get somebody killed and/or the project will fail and be a colossal waste of time and money.
I believe it was him and his dad who designed the flight controller also for his electric system. Im not sure about his gas system...hes also a very skilled pilot.
Please tell your professor that his demand is pure Science Fiction...
O yes it can be done, but if you can achieve that I suggest you go directly to DARPA..
http://www.personal-drones.net/peeking-into-our-future-the-black-kn...
https://www.advancedtacticsinc.com/technology/black-knight/
4 years and still not finished, maybe your professor can help them...
OK, I'll say it.....if it looks like a duck and quacks like a duck....and it's yellow and it has webbed feet and it floats on water and it swims...and it's name is Donald..But let's assume for a second this is legit..
Counter rotation - you may actually be able to change the timing so that the engine can run in the opposite direction - or, you may be able to mount two of the motors upside down (does that work?) or - servos for yaw.
Problem 2 - What risk assessment would let you start the last motor with the spinning propellers of death right next to you - electric starter? wires, entanglement? Nah.
Vibration - hard to know how you would even approach isolating the IMU from frequencies and amplitudes associated with these engines - mount it on 5kgs of vibration damped steel?
Constant speed - IF you could have two of the motors in counter rotation, and IF you could come up with a variable pitch prop, you could achieve yaw. However, this would rely on fine, fast response control of RPM. not sure how you do that on a petrol engine.
The other option would be to have a single engine driving four variable pitch props with two geared for counter rotation. OR, you could have one big engine driving one big prop with individual variable pitch blades (for pitch and roll) with a smaller variable pitch prop controlling yaw.
Hi Shehryar,
Either your professor has a really sick sense of humor or hes a sadist or he has no idea at all what he is asking you to do.
From my own experiences with professors it's most likely to be the middle one.
It is extremely difficult to get this to work at all satisfactorily with 4 independent gasoline engines, keeping stabilization actions working in a timely manner is unlikely (with fixed props)
As you seem to be heading towards variable pitch that probably is at least possible because you can over power the motors and use the pitch for control, but I think variable pitch props in this size either don't exist or would not be in your budget if they did.
Machining sufficiently functional variable pitch hubs may be possible, but it is a considerably major project by itself.
And the time frame you have mentioned is ludicrous, a small team experienced in multicopters working on this for a full semester (or year) maybe (although I would prefer to stand a considerable distance from the test flight.)
I have some beginner level design information on my quadcoptersarefun,com site: http://quadcoptersarefun.com/QuadcopterDesign.html
And the DIYDrones wiki has a little too: http://copter.ardupilot.com/wiki/what-is-a-multicopter-and-how-does...
But basically I think you need to go back and talk with your professor about the magnitude of this project and the impractical aspects of implementing it.
If he laughs, you will know my estimate of his character was correct.
A quadcopter using a single gas engine with direct drive of all 4 variable pitch propellers was completed (more or less successfully) in a California University over a school year by a good sized team of undergraduate students.
The single engine quad with fixed pitch linked to by Spencer is a Curtis Youngblood project, a championship level Traditional heli flyer who put together a single motor variable pitch electric quadcopter he sells that is absolutely amazing.
And he did the gas one as a proof of concept.
He has spent years working on this stuff and is Totally skilled in all aspects of it.
The project you are engaged in is not something I am pretty sure that no one who actually understood what was involved would undertake, certainly not without a lot of time and a lot of money.
Best Regards,
Gary
Most FC's can be adapted to control pitch on collective pitch rotor set ups. Pitch can both control vertical thrust and applied torque. It (as in Constant speed quads) has been done several times.
Before someone calls 'shenanigans', I would be very curious as to who your professor is and what university you're studying at? I'm also curious as to why gas engines over electric and why the 100lb payload requirement.
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