The RC Pelican challenge

[Upchuk]

ok, how are you going to control the servos, engines, and do it simultaneously? You're operating 4 engines, and 2-4 servos. plus you have to be able to move those independently or together. my wallet is just crying looking at this.

HAHA! Indeed. Like i said, would probably be best to just work with a slow moving hovering version instead of one that can transition to forward flight.

Edit: just thought of something. IF you use a similar model to the one posted above, why not put a single ducted fan in the troop bay for forward motion? Dont technically need it to be video game accurate for it to fly that way. Also, the wings dont fully rotate to vertical to make it hover, it has jets along the bottom for hovering, and the jets at the rear for forward momentum, so an engine in the troop bay would work just as well. Then all you need is a seperate throttle receiver to give it thrust one airborne to move it forward while the 4 VTOL fans give it lift. Now control surfaces might be an issue. Might wanna just get one of those simple 4 fan VTOL rc planes for indoor flight and make a shell for it.

 

[Boba Fett]

that's what I was saying about using differential thrust, but you're still going to need a reciever/transmitter capable of 6 channels... unless you combine them into groupings of forward and back thrust banks. But it's going to be hard to do, plus this thing is NOT going to be very stable in the air.

 

[SpartanM93]

ok, how are you going to control the servos, engines, and do it simultaneously? You're operating 4 engines, and 2-4 servos. plus you have to be able to move those independently or together. my wallet is just crying looking at this.

You think I haven't thought of this already? Boba Fett, come on now.
you have your engines steady on idle or you mod the throttle to whatever speed you need, no controlling them, and your Pelican will fly at a steady speed. just make sure you can hold it when you first start it up and you can catch it.
For the wings, I was merely suggesting if you're super ambitious you could add thrust vectoring. The easiest way to do this would merely be to put the front two wings on a pivot, and then add the servo to the pivot, allowing you to adjust the ships pitch forward and begin straight forward flight

another option, you could buy a circuit board for your set up, I know you're on a budget but i'm sure I'd be willing to donate to the cause if this is something we're all serious about. Using the circuit board, you could adjust which way the servo's would turn depending on your joystick orientation, ie if you point your joystick "northeast" the computer will rotate your wings in the corresponding way. that would allow you to have the thrust vectoring and inredible amounts of control

 

[Upchuk]

Yeah, definatly gonna need gyros or something to automatically stabilize the craft. He might be better off using this
http://nexus404.com/Blog/2008/03/16...-rc-aircraft-you-can-land-on-your-hand-video/

 

[Boba Fett]

Never said you didn't. Just providing a reality check here...

Thing is, on thrust vectoring, you need incredible precision to keep it stable. If you're outdoors, this get's close to impossible because it is so light weight. The best way (I see) is the 4 lift fans, plus 2 more providing differential thrust to move it. But if the budget is tight, it probably won't happen, asn RC stuff get's expensive in a hurry (unless you have something you can cannibalize already o nhand).

also, I'm not an electrical engineer, but programming a circuit board is probably not some small task... though I could be wrong. This is utilizing the same technique as the harrier uses, and even with complex computers pilots have a hard time with it. Good luck, but I forsee problems...

 

[SpartanM93]

Depending on your budget Boba, I think simply buying that plane in the video and building your pelican around it would be ideal.

 

[Rick]

my wallet is just crying looking at this.

RC is not a cheap hobbie. And theres no way to describe the look on some ones face, (especially a teen) when they nose plant all that time and money.

It can be done. they have gryos that may help with keeping it stable. i know you tube has vids on some proto types that might fit.

 

[wiyumishere]

very, very, and i mean very cool idea

 

[OptimusWang]

This might already have been mentioned, but why not take an existing quadricoptor and switch out the body? The blades and whatnot wouldn't be exact, but it would be a heck of a lot easier than reinventing the wheel. Something like this: http://ardrone.parrot.com/parrot-ar-drone/usa/how-does-it-work

 

[Spitfire22V]

Hi guys,

I know I'm new here, but this thread caught my attention as RC airplanes are my primary hobby and I've been at it for years now.

I guess I'll go ahead and be the negative guy that says that unless you have the time, money, and experience for this, it will be a difficult journey that is not likely to end in success. You mention that your budget is struggling to buy some Under Armour. Please consider that quality RC equipment that works well (not those cheap toys you can buy at Walmart or Radio Shack) costs hundreds of dollars. You'd most likely need this type of equipment to properly set up and control up to 4 ducted fans, etc.

If you're really serious about this, I'd definitely recommend taking a look at the forums on RCUniverse.com and/or RCGroups.com. ( You'll get a better understanding at the methods, materials, and experience needed to pull this off successfully). I would say RCGroups would be the best bet here because they have what I think is better forum on scratchbuilding unique electric aircraft like a Pelican

I would personally make the model out of foam. I have made several small, electric foam planes we call "foamies" that are super lightweight, relatively crash-worthy, and cheap. In fact, I use foam board from the Dollar Tree stores, and peel off the paper. $1 a sheet! Can't beat that. Build up the Pelican using the foam, then install the electronics. I think the best bet for control would be thrust control, not thust-vectoring. Thrust vectoring (with the actual ducted fan assemblies tilting) is very difficult to accomplish. Instead, I would set up the radio system to alter thrust to the fans based on what you want to do. Forward flight would be accomplished by increasing thrust to the 2 rear fans, right roll would be increase thrust to the left fans, etc.

You'll need to find the center of gravity of the Pelican, but I suppose that can be done with trial and error once it's built and flight worthy. Just do small hops and move the battery front or back until the necessary balance is achieved.

With that said, I wish you the best, and if you'd like, I'd be happy to answer any question you may have. I'd be happy to point you to great places to purchase cheap, but good equipment. I'll be keeping an eye out on this thread to keep up with your progress!

 

[ForgedReclaimer]

Ok, try this. You have a ducted fan in each engine pod and a ducted fan inside the personnel bay. Remove the cockpit windows and replace them with black painted wire mesh that will allow air flow through the length of the vehicle. Place one servo run rudder behind the internal ducted fan area, much like the steering system of a Hover Craft. use the four down facing fans for up and down thrust and us the rear fan for steering. That way you keep the hover capability and directional movement without a complicated servo system. But as for the battery its going to be big, hopefully the four down facing fans can counteract this weight.

As for stability, facing them straight down may be noneffective. But try pointing the fans outward to a degree in a sort of V shaped thrust, that should yield more stability.

 

[Boba Fett]

I was mainly talking to Chitwood. He was saying that he doesn't want to spend a lot of money... I forsee this costing a LOT more money than it's worth. That's all I'm saying. I fly electric RC's as a casual hobby, and even then I dump a lot of cash into it. an ESC cost me $70. Battery, $50 for a used one (thought it is a BEAST of a pack so it was a decent deal) and so on. And I have planted my plane on it's nose, around 40-50mph. whichever way you go, it ain't gonna be cheap, or without a lot of engineering put into it. I'm not trying to crap the idea, I'm just trying to figure out how to do it in a somewhat affordable way. I'm thinking $300, min. about $30 for each fan setup (and that's low numbers) costing $120 for the engines, receiver/transmitter adds another $100 at LEAST, then battery, ESC, servos, etc.

attaching the body to another plane might work, but I'm not sure that it will work all that well. Especially considering the pelican's shape, which isn't the pinnacle of aerodynamic design.

 

[chitwood1775]

here is an idea that i think might work. take a look at this picture (sorry it's sideways)...

http://s1183.photobucket.com/albums/x478/chitwood1775/Pelican/?action=view&current=eb85bd93.jpg

the red dots represent the duct fans that will be fixed in place facing down to generate lift.
the blue dot represents the fan that will provide the forward motion
the green rectangle represents a rudder that (unless i know even less then i think i do) will cause it to turn.

 

[ForgedReclaimer]

I remember crashing my RC, it went from e rear engine to a front engine lol. Lost the thing in the sun and went 40 right into the ground.


The diagram looks good, maybe the rudder could be placed into the compartment with the fan. The closer the rudder the better the response time and sharper the turn. As long as the rigid sides don't constrict the air flow too much but putting the rudder that close should compensate, that and it would hid it as well as providing another anchor point for the base of the rudder to hold too. Or just try putting the whole fan on a servo, that may be risky.


You know, one thing is though having the foreword thrust engine so close to its center might not steer well, i guess having the rudder further back might be better.

 

[Boba Fett]

I still say differential thrust is a better idea, using 2 motors to provide rotation.

 

[Dreadnaught]

Forged Reclaimer has given about the best suggestion yet for ways to get this to work. The limiting factor here, though is flow-through. You'll need more than just the cockpit windows being made out of mesh to supply enough air to the fan to get any real movement.

Fett is also right. Differential thrust is going to be needed to get any real controllability out of this, even with a rudder set up at the aft end of the troopbay. I think he's less right about the significance in the fans' RPM being different enough to cause an issue, but that may well be my own lack of familiarity with the R/C aircraft world.

Spitfire also mentioned weight and balance. You have to remember that for every item you put into this model, you have to have that much more power to lift it. You're talking about very heavy model with 5 fans and the power and controls to run it. In order to get fans that are powerful enough to lift that weight, you're just about looking at either working three jobs for a while or else knocking over a bank. I don't recommend the bank thing, by the way. ..

Someone mentioned alumium. Avoid that like the plague until you get your model working reliably, and even then... I'd hesitate to use it. It's expensive for the weight and strength, and it will deform when it hits the ground. Straightening that will be a useless endeavour, so you'll be out the cost of a whole new frame. However, if you use balsa or some other light weight wood or even foam or plastic, you stand a good chance of having entire salvageable sections to re-use after you turn your model into a lawn dart.

Someone else mentioned gyros. I've seen them used in R/C planes and helicopters, but, other than agreeing that they are very useful for maintaining control, I know very little about how they would function in a set up like you're talking about. R/C planes use control surfaces, and the gyros will move them to regain level flight. I'm assuming the helicopter gyros function much the same way with swash-plate inputs to the main and tail rotor. As for differential and variable thrust inputs... I just don't know enough to make a guess.

Again, I recommend browsing through Flea-bay to find good deals. They are there to be had, but you will likely get exactly what you pay for.

 

[ForgedReclaimer]

BTW, recommended you don't use a standard helicopter rotor. A rotor is used to push air down to create lift and with the pelicans large flat top, or at least compared to a helicopter. Not enough air will be able to pass down to create sufficient lift unless you use a big rotor able to reach beyond the surface of the pelican. While using the rotor, or even a bigger one, it may be more cost efficient and a bit easier but it also removes the realism of the machine to its game counterpart.

But than again, it is easier and cost efficient compared to 4-5 duct fans and servo's.

 

[Boba Fett]

well, the RPM difference isn't going to be much of an issue, but it will probably require ballasting to even it out. Forged also had a good idea, splay the vectors of the thrust out, so it auto-stabilizes. not much, but it should do it.

 

[Santicity]

Just lurking in this thread, but seems really interesting what you guys are trying to do