air brakes

[rotccapt]

i think that i have developed a way to build airbrakes into the ailorons of an a-10 but i do not know of a good way to actuate then. i have thought of using a cable to pull a split bar with a hing that would force the two slats apart. the design of the brakes is two flat panels that make up the trailing edge of the ailoron that when actuated open up to form about a 140 degree angle.

here is a ruff sketch of my design

[globemaster3c17]

Looks like a pretty neat idea to me, kind of like the "rudder" control for the B-2. Looks like it would be a bit tricky to get it set up though to me.

[theKM]

kind of like split flaps.

You'll need to make some horns that have a track instead of just a hole. pushing both horns together will open them up.

Here's a nasty diagram...

[BMatthews]

I think you're going to find that you need either two servos per control surface or two servos in the middle of the wing with complex linkages. You need to move both together in concert to provide aileron control and then move them opposite to provide airbrakes. But they still need to be able to deflect as ailerons while in the airbrake mode so you have roll control still.

If it's a smaller size model all I can say is good luck. The linkages and slop will be your main enemy. If it is small then two micro servos per panel and external control horns would work but it'll require some careful mixing to ensure they two servos to not fight each other.

Or one micro servo per panel on a fore and aft moving tray with either internal or external rods and horns (depending on model size again) and a central brake servo. The aileron rods would move differentially, and via carefully angled horns and output arm geometry to avoid binding, with a rod off each side of the output wheel so they move as ailerons. Then when the servo is slid towards or away from the surfaces, depending on the action, they would act as brakes.

I still think the aileron action would be greatly compromised though.

[rotccapt]

actualy the airbrakes will be part of the ailorons they will make up the trailing edge and the atatchment piont for the airbrakes is the alioron.

[BMatthews]

Oh, so there will be a narrow portion that is hinged like a normal aileron and then the drag brakes are attached to that? If so then you're back to the issue of very short control horns that fit inside the thickness of the aileron and the importance of tight hinges and pushrod terminations since the travel needed to achieve your deflection of the brakes will be very small and any play or backlash in the system will be a significant percentage of the servo travel.

A single pushrod to activate both brakes isn't going to work since the arms will move apart. A slot that the pushrod end can travel in sounds like a good idea until you realize that it requires a bushing to keep it located. That bushing would need to rotate in the aileron portion to control the pushrod. I suspect it would be better to use two parallel pushrods off a common arm bolt with each going to a separate but close spaced control horn on the brakes. An advantage with the dual rods is that the internal horns could be as long as possible up to the point of not quite touching the surface above. This would potentially offer you longer horn lengths than the slotted horns where the rod end must be in the middle.

But all this also supposes that you're making a model of large enough scale that you have room for practical linkages. If you're trying to do all this in only 3/8 of an inch or less of thickness at the leading edges of the brakes then I think it's doomed before it starts. If you've got 1/2 an inch then it's possible with care and custom hardware. If you've got more then it's a piece of cake with relatively common hardware. But if you have more tha 1/2 an inch to work with that's going to be one big A-10!

[rotccapt]

my a-10 is ging to be on the big side about a 6' span i do have alittle over 1/2 inch of space. i was thinking of using a pull cable and a spring like what is in a cloths pin to colaps the brake

[Andy W]

.. why not simply activate each half of the aileron with a seperate servo. Adjust the curves so that with aileron, only one half moves, one when 'up' is needed, the other when 'down'.. that would be relatively simple to achieve with an Evo (I assume you're using a high end Tx..)
..a

[rotccapt]

did not think of that i will have to look into it first i need to finish the plans :D
thanks for the idea