Antonov AN-140

[Carsten Svendsen]

As long as you add a fairing in front and rear of the micro motor, it shouldn't affect flying caracteristics. Otherwise, it would be like a spoiler. Better explain this with a drawing.

[iMAGE]

On wing A you can see how a normal wing works.

Wing B has a deformation that causes airflow to be disrupted and produce vortexes. A disrupted airflow creates very little differential pressure, diminishing lift by a great amount, and the energy to power the vortexs comes from the motion of the airplane, therefore increasing drag. In fact, the efect is so strong, that some airplanes are equipped with "spoilers" that deform the wing to slow down and descend faster (For example gliders)

[iMAGE]

And on Wing C the fairings avoid most of the "spoiler" effect, but still there is a deformation of wing shape, which causes lift to be roughly equal to drag.

Cheers :D

I'm glad it can be solved that easily. It's only half a stud higher than the wing it self - still 25% though, but on a very small area on all of the wing surface

Nice drawing :D

My two cents - micro-motors are very slow. Being geared down to 1:8 it will be very-very slow. Typical servo used in RC models are 2-3 times faster (80-90 RPM vs 35 RPM) and have ten times more torque. I believe torque, developed by micro-motor could be considered enough for mild and slow flight, but response time when using geared down micro-motor will be very big so it will be very hard to control aircraft.

Also RC servos have feedback circuit with potentiometer on output shaft (and microprocessor, one task of which is to keep requested angle on control surface), which, in turn, leads to question - how are you going to control the aircraft if it is supposed to lift off the ground?

There is no question about whether or not i should use micro motors for the ailerons since it'll reduce play by a great amount. The torque has been increased 8 times though, remember that.

I haven't thought of adding servos in the tail. I would need a total of 3 servos which would add a lot of weight, especially when it's that far back on the plane. I have measured and it seems I can be able to fit all 3, but I only have 1 atm and am using that for the steering wheel, so I'll have to order some on BL to test with. They're expensive but not as much as the micro motors.

It will take more than 3 seconds to move aileron from 45 degrees up to 45 degrees down. So if plane is banking right and you move a stick to left, the plane will respond in 3 seconds or more. This makes the plane very hard, if ever possible, to control.

Well, that's just for turning. The important aspect of the whole flying thing is the up/down movements, and that's where I think you're right about the servo motors. Turning and banking isn't as important as I can't crash in mid-air :)

This is what I have spent the last few days on. Getting a micro motor in there. Although, it does turn very slowly and there's some play in it. I haven't tried with the newer 8t gears since I don't have any. I could order some on BL along with the servos

Here's an example of the above

Edited June 6, 2015 by Carsten Svendsen

[whale2]

Well, that's just for turning. The important aspect of the whole flying thing is the up/down movements, and that's where I think you're right about the servo motors. Turning and banking isn't as important as I can't crash in mid-air :)

No, this type of things should be given more attention. Roll bit too far and you will stall.

I was talking about servos used in RC model aircraft like this: http://www.hobbyking.com/hobbyking/store/__9549__Turnigy_TG9e_9g_1_5kg_0_10sec_Eco_Micro_Servo.html

I can think of two option for controlling an aircraft - use production non-Lego servos or re-implement such a servo using micro-motor, some potentiometer installed on control surface shaft and control board from production servo.

Nevertheless, how are you going to control the plane?

[Carsten Svendsen]

No, this type of things should be given more attention. Roll bit too far and you will stall.

I was talking about servos used in RC model aircraft like this: http://www.hobbyking...icro_Servo.html

I can think of two option for controlling an aircraft - use production non-Lego servos or re-implement such a servo using micro-motor, some potentiometer installed on control surface shaft and control board from production servo.

Nevertheless, how are you going to control the plane?

What do you mean by that I will stall? How can I get no where when I'm everywhere (in the air) ??

It was the meaning that I'd go all-in as much as possible with LEGO parts, but I guess you're right that it's pretty important to control the plane the way it is. How much torque do you think is needed to control the flaps while airborne?

I found this one and I don't know if it's got enough torque. Nevertheless, how am I going to fit an axle on such a thing? And does it work like intended just because it says "servo" in the name?

Size: 22x11.5x27mm

Speed: (4.8V @ no load): 0.12sec/60 degrees

Turningforce: (4.8V): 17.5oz/in (1.2 kg/cm)

Temperature : -30 to +60 grader

Voltage: 3.0-7.2 Volts

weight: 9 g

I was just going to fit in some LiPo batteries and a some non-LEGO transmitter/receivers to control it.

Added: This controller looks good and has a lot of functions: http://hobbyfly.com/kaempe-januar-udsalg-511/spektrum-dx6i-dsm2-m-ar6210-modtager-6201.html

If purchasing that controller + receiver, I can also purchase 4x of the servo's a bit cheaper it seems. But is it the right thing? To do?

[whale2]

What do you mean by that I will stall? How can I get no where when I'm everywhere (in the air) ??

Roughly speaking lift force is directed perpendicular to wing surface, while gravity force is directed always straight to the ground. When aircraft is banked, vertical projection of lift force is lower. It's very easy to imagine if plane is rolled by 90 degrees - no lift force at all. High roll angle accompanied by lack of airspeed could lead to stall.

Like here from 2:20 --

It was the meaning that I'd go all-in as much as possible with LEGO parts, but I guess you're right that it's pretty important to control the plane the way it is. How much torque do you think is needed to control the flaps while airborne?

It depends on current airspeed, control surface area and angle of attack. To get some approximations you can play with some numbers here: http://www.grc.nasa....lane/foil3.html

Flaps indeed should not deploy very fast, but ailerons, rudder and elevator should be controlled in real time.

I found this one and I don't know if it's got enough torque. Nevertheless, how am I going to fit an axle on such a thing? And does it work like intended just because it says "servo" in the name?

Size: 22x11.5x27mm

Speed: (4.8V @ no load): 0.12sec/60 degrees

Turningforce: (4.8V): 17.5oz/in (1.2 kg/cm)

Temperature : -30 to +60 grader

Voltage: 3.0-7.2 Volts

weight: 9 g

I think almost every production servo will do, as no exceptional characteristics are required, only make it flyable.

I was just going to fit in some LiPo batteries and a some non-LEGO transmitter/receivers to control it.

Added: This controller looks good and has a lot of functions: http://hobbyfly.com/...tager-6201.html

If purchasing that controller + receiver, I can also purchase 4x of the servo's a bit cheaper it seems. But is it the right thing? To do?

You will also need good brushless motors and speed controllers. Comparably weighed models have 1-2 KW of power.

6 channel receiver/transmitter is a minimum - you have to control

ailerons

rudder

elevator

flaps

landing gear

engine RPM

Also, if controlling each aileron with own motor, some synchronization should be implemented, so when stick is in the middle, both ailerons are aligned with wing surfaces.

Youtube link not displaying properly. Try this: http://goo.gl/6Cl97

(From 2:20)

[ap0r]

I haven't thought of adding servos in the tail. I would need a total of 3 servos which would add a lot of weight, especially when it's that far back on the plane.

Servos are ideal solution for control, you can place them anywhere you want and use lightweight pushrods to move the surfaces.

[Carsten Svendsen]

I saw the video. I don't think my plane can handle such a crash...

I have no flaps on this airplane at all. Replace every reference I made about flaps with ailerons, I must've mixed those two up. As far as I understand, flaps only increase drag, which increases lift when taking off. Finding a long run-way is no problem and integrating that on all of the wing would certainly not be possible (Or else the wing should be 3 studs instead of 2, thereby breaking the scale)

I need a total of 7 functions:

- Aileron, left

- Aileron, right

- Elevator, left

- Elevator, right

- Rudder

- Landing gear

- Engines

All those are outputs, do I need any inputs to the controller, or is that configured in the hardware used in real rc planes?

I've ordered three servo motors on bricklink to play around with. I forgot all about the pushrod method - still, one servo is needed all the way at the back.

[whale2]

I saw the video. I don't think my plane can handle such a crash...

I have no flaps on this airplane at all. Replace every reference I made about flaps with ailerons, I must've mixed those two up. As far as I understand, flaps only increase drag, which increases lift when taking off. Finding a long run-way is no problem and integrating that on all of the wing would certainly not be possible (Or else the wing should be 3 studs instead of 2, thereby breaking the scale)

Flaps increase lift for cost of increasing drag, most important thing that they are lowering stall speed making possible to take off at slower speeds and do landing approach at slower speed.

I need a total of 7 functions:

- Aileron, left

- Aileron, right

- Elevator, left

- Elevator, right

- Rudder

- Landing gear

- Engines

Elevator works as a single surface, there is no need to separate it into left and right.

Ailerons movement is mirrored, either mechanically or electronically, so it uses only one receiver channel. Otherwise you will have to have very unusual handling on controller - two sticks for two ailerons.

All those are outputs, do I need any inputs to the controller, or is that configured in the hardware used in real rc planes?

Are you talking about telemetry? If not, generic RC receiver only provides outputs and not require any input.

[Carsten Svendsen]

I need a total of 7 functions:

- Aileron, left

- Aileron, right

- Elevator, left

- Elevator, right

- Rudder

- Landing gear

- Engines

Elevator works as a single surface, there is no need to separate it into left and right.

Ailerons movement is mirrored, either mechanically or electronically, so it uses only one receiver channel. Otherwise you will have to have very unusual handling on controller - two sticks for two ailerons.

Oh, I thought that I could use the ailerons + elevator when taking off and landing, and both again when turning/rolling for maximum control. I see this is not how it works irl.

Then I only need a 5 channel setup which makes it far cheaper :D

[whale2]

Oh, I thought that I could use the ailerons + elevator when taking off and landing, and both again when turning/rolling for maximum control. I see this is not how it works irl.

Then I only need a 5 channel setup which makes it far cheaper :D

Combined flaps and ailerons do exists (flaperons) but AN-140 does not utilize them :)

And on take-off elevator usually produces negative lift force to raise nose wheel and increase wing angle of attack. Using of separated elevator for banking is not effective as force arm is much less then arm of ailerons.

[Carsten Svendsen]

- Just purchased a DX6i (AR6210 reciever incl.)(on sale too) for control and 2 small servo motors for testing.

Now I just await my orders from BL before I can get any further with the tail. Building the rudder first and then the elevator wings second is far the easiest.

In the meantime, I think I'll optimize the landing system. It's just not right yet.

[whale2]

Regarding necessary torque for control surfaces - here are some approximations:

http://www.mnbigbirds.com/Servo%20Torque%20Caculator.htm

[Burf2000]

Looks very cool!

[Carsten Svendsen]

I'm glad I purchased a 6 channel controller setup because I just remembered that I should need a channel for the nose wheel steering too

I made a few changes today regarding the landing gear and back of the plane.

I added a few springs to main wheels for a better management of the landing gear. When the pressure in the system becomes low, the springs will help keep the landing gear retracted.

I also experimented with how long the connection between the nose wheel and valve should be since the previous solution of a 7L liftarm could make the connector fall off the valve easily.

Furthermore, I have fastened the tail triangle connection better to the main chassis (not in picture) and removed all the stuff that would make it more hassle than worth, when I'm about to install the servo motors. I thought of making a 1:1,667 gear reduction thereby making the total degree of movement 60°.

Edited June 6, 2015 by Carsten Svendsen

[locoworks]

are you expecting the model to actually fly? you don't need a seperate output for the nose wheel, it can use the same output as the rudder. rc planes use the same channel.

[Carsten Svendsen]

Are you expecting the model to actually fly? You don't need a seperate output for the nose wheel, it can use the same output as the rudder. rc planes use the same channel.

Yes to your first question.

Well, the 6 channel hardware was so much more awesome than the 5 channel hardware and it was on sale too, so that's why I bought it over the 5-channel hardware. Besides it's nice to have an extra channel if something unexpected comes up :)

[Blakbird]

If you post the final weight, the wingspan, and the average chord length, I can very quickly tell you how fast it will need to go to actually fly.

[whale2]

Wing camber is important too.

[Blakbird]

Wing camber is important too.

Only in finding the lift coefficient. Since this plane will have an undefined airfoil, well have to assume an arbitrary shape of fairly low efficiency.

[Carsten Svendsen]

If you post the final weight, the wingspan, and the average chord length, I can very quickly tell you how fast it will need to go to actually fly.

The weight was 4,15 kg last time I weighed it. That is not counting any batteries and (servo)motors. I assume maximum 5 kg

Wingspan is 155 cm

chord lenght at fuselage: 19cm

chord lenght at tip: 11 cm

The very first shape somewhat matches the wings I made: http://en.wikipedia....of_Airfoils.svg

Edited January 13, 2013 by Carsten Svendsen

[vmln8r]

Add me to the list of doubters.

I can't help feeling sorry for your efforts to get this thing to work. The ad-hoc approach is also puzzling, since this is clearly a massive investment. Have you tried making a much smaller plane, that might stand a greater chance of at least uncontrolled flight (however briefly), rather than getting bogged down with landing gears and such?

(and of course, there's that train of thought that if if you're using non-Lego parts to improve the performance, why not go the whole hog and carve the thing out of wood?)

Edited January 13, 2013 by VMLN8R

[Carsten Svendsen]

(and of course, there's that train of thought that if if you're using non-Lego parts to improve the performance, why not go the whole hog and carve the thing out of wood?)

The whole plane is built in LEGO. The only non-LEGO parts are, as you know, engines, propellers and control system. No one else can say that they've built a model airplane in LEGO that is aerodynamic, stable and looks like the real deal and actually flies if adding powerful enough engines and propellers.

[locoworks]

lego started out making wooden toys so maybe they already made a plane that can fly???

[Blakbird]

The weight was 4,15 kg last time I weighed it. That is not counting any batteries and (servo)motors. I assume maximum 5 kg

Wingspan is 155 cm

chord lenght at fuselage: 19cm

chord lenght at tip: 11 cm

OK, so your approximate wing area based on average chord is S = [(11+19)/2]*155 = 2325 cm^2. We need this in square meters so that's S = 0.2325 m^2.

For calculation purposes, I'm going to assume that you have an airfoil equivalent to NACA 2415. In order to by able to fly with a reasonable amount of drag, we'll assume that you need to be able to take off with an angle of attack of alpha = 10 degrees (which is very generous). Based on the lift coefficient charts, your lift coefficient is CL = 1.0. This is really good and your actual airfoil will probably be less efficient than this.

For the density of air, we'll assume standard sea level conditions. rho = 0.0023769 slug/ft^3 or 1.2012 kg/m^3.

Lift is equal to weight which is 5 kg (this is actually a mass).

Now we can get the velocity V for takeoff (no climb) using V = SQRT [2L/(CL*rho*S)] = 5.98 m/s or 21.5 km/hr

This is not a scale speed, this is actual speed. To actually be able to climb and maneuver you'll need a lot more speed than this and you really don't want to be flying at an alpha of 10 degrees, so you'll want your top speed to be about 3 times this or 60 kph. The drag forces on your plane at 60 kph are going to be very high, so you will need very high power to achieve this speed. I would plan for at least 2.5 kg of thrust.

Structurally, you'll need to make sure that your plane can be lifted by the wings with a factor for gusts. I would lift it up by the wings at about 1/2 span and shake it up and down and make sure they stay on. If they don't they will break off in the air.

Plan your center of gravity to be at about the 1/4 chord point of the wing.

[camaudio]

will need videos of the wing tests :)

[Rishab N]

Now this is truley a masterpiece

155 cm? Thats just 22 cm smaller than me!

about how many pieces is it?