Idea !!!!

[x-boy]

Ok so i just came up with a concept for a car cum plane....

Well a basic diagram is....

http://img340.imageshack.us/my.php?image=ideamr5.png

Ok the platform is the rectangle onto which the body will be built...

The small tube in the middle is a motor housing hinged on an axis.

The prop with the motor goes here.

A servo will be used to tilt the motor.

Ok so since i have no EDF's im going to use a tube and use a sp600 with 3:1 gearing or so....or maybe 2 sp400's.

Around 20-30 ounces outta the sp400's or maybe more with a sp600....

Now will this work ???

The idea is to have wheels so the engine can be tilted horizontal and the vehicle can move forward....if i had a car esc then maybe braking could be possible by running in reverse.

Or to take off i could either have a running start by running the motor horizontal and then tilting it....Or with enough power a vertical takeoff...

There will be short wings on the side for flying.....well if i had the equipment i could also make retractable wings....

But for testing it's not going be all that fancy...

So what say all the smarties ??? GO AHEAD or GET LOST ??? :o

[jkettu]

I can see some potential problems with stability and control while flying, but go ahead, do it and report your results here. Nothing tried, nothing learned.

[BMatthews]

The tilting of the motor and shroud would not be enough to provide in flight control. All your thrust angling is far too close to the center of mass.

You need something similar to the reaction jets that the Harrier uses at the tail and wingtips to get what you want. This is also why those X or Y style multi motor helicopters use separate motors and props out at the periphery of the craft so that the differential thrust and torque effects are at the outsides where they have a proper moment arm from the center of mass so that their effect will provide the control torques needed.

[x-boy]

Huh.....what ??? Couldn't understand you matthews...sorry


And yeah it is an idea....could be the next breakthrough you never know :D

And for the torque problem....Well 2 motors would solve it wouldn't it....and well at this stage as long as it lifts off i am happy.

This is what is going to be my science project....my dream....my idea.

And hints and or snags you can see ??

And would it have to be a 3D plane ??? As in thrust greater than weight to take off ??


Oh and the tilting is basically not for in-flight control....

Well i wanted it to be but since i'm low on cash and parts, i'm gonna go with elevons....you know flying wing style.....

The tiliting is basically for the height control.

[BMatthews]

OK let's try this. A center mounted motor like you showed will crash.

You showed no way to control the platform in a hover and didn't mention any other than tilting the motor. That is what is missing. Also for a center mounted motor to be able to lift vertically the CG needs to be in the center at the thrust axis. But if you try to shift to forward flight the CG will need to be forward around the 20% point back from the leading edge or it will be unstable and tumble.

Basically you need to stop and do some more homework on the concept and how it is intended to be controlled in hover and how it will change to a stable forward flight mode.

Right off the bat the motor needs to shift so that it is located at the 20% chord point where the Center of Gravity will want to be located for normal forward flight.

Standard contol surfaces don't work at very low speeds unless they are in the air blast from the prop or fan like you see on a 3D model. So you need to figure out some way to make that happen or arrange for some other method for contol in hover or very low speed forward flight.

And this is what I meant about the peripheral motor helicopter...
http://www.seattlerobotics.org/encoder/200311/weimer/bxflyer.html

In that setup the balance of the power to the motors can control all the flying functions. Note how two rotate one way and the other two the other way. By controlling the balance of power to the 4 motors you can get all the 3 axes of control you need.

[x-boy]

Ok....

So what if i had the two motors one placed at the 20% chord point where the Center of Gravity will want to be located for normal forward flight and one placed at the same point in the back...some what like this.

motor----------CG----------motor

Then would it work ??

[JetPlaneFlyer]

This 'may' be enough to control it in pitch but what about roll ?.. i think you would need at least 3 fans, or have cyclic pitch like a helicopter.

[BMatthews]

You're missing the point here. I'm trying to point out that there's a whole heap of factors to consider before you place you motor/thruster

If the model will need to fly stably in forward flight you need to deal with that design first. Within the overall look of your "Aerocar" try to arrange for thrust and controls to deal with that. Don't forget your vertical tail area.

Once you nail that configuration down then it's time to see how best to adapt it for vertical flight and transitions. Now comes the hard part. The forward flight mode sets where the CG will have to be located. At that point your thrust needs to be centered on or balanced around that point. If the CG is located at the 20% mark and you want thrusters in front and behind then the thrusters will need to be equally spaced in front and behind that 20% location or the thrusters will tumble the model.

You'd probably find that it's easier to arrange for the thrusters to be on either side of the balance point.

You also need to figure out a way to use thrust throttling or thrust diverting to control all three axis while in hover or transitional flying (very slow hovering like motion). This means doing more homework to figure out how to get that. The wind will often be blowing on the model and while it's in hover you need to be able to counteract that disturbance by using control inputs for lift, roll, pitch and yaw. Just like a helicopter. If you don't have a strong enough controlling force in any of those directions then the model will not be able to recover when disturbed and it'll crash.

There's no point in thinking about how you do one thing without thinking about how that one thing will affect ALL the other aspects of such a model. Your thruster placement and other choices all need to work together or it'll never get off the ground and fly for long.

It's possible that you will get something to work but you've got a lot of homework to do on it before it'll fly. THis is why you don't see setups like you're describing. No one has taken the time to make it work or some performance factor is not good enough yet to make it work. That is not to say that you should not try but it may help if you stop and think about more of the factors.

If you're keen on this I'd suggest you play with some designs and actually make some models of the craft but that are designe to only do one thing. Make a model that flyies normally and get that trimmed and flying well. Once you nail that design down then try to make a second model that is based on the first but is made only for hovering. As you find things that don't work on the one model and have to change them make the same changes on the other and test it to make sure the change is compatible if it's an aerodynamic change. Once you have the two testbeds flying well THEN try to make one that joins both into one with the ability to transition from hover to forward flight.

Lots of work I know but if you really want to do something that's out there then you need to do it in an organized manner. You're trying to make a flying machine and not a sketch for a techy anime movie.