whale2

I was unable to find it at LEGO - can't see it in Pick a Brick even if I set region to UK, Denmark, USA, Germany. Please tell me where should I look :) And chances are I can work around shipping problem :)

And I made coupling for potentiometers for rudder and elevator, placed linear actuators controlling pneumatic switches in different way and now there is no stress on them. All RC stuff still on it's way, I hope. Also seems like I need some 60 pcs of 15068 to make symmetric tailplane and I'm checking it daily at BL, there was no single place having such quantity. Surprisingly, I checked right now once again and there are some, though 2.5 times more expensive. I still got plenty to do except of tailplane, so I'll just hope that price will go down a bit eventually.

I think Ripsaw should be fast as hell, that's why 4 RC motors :) Looks great.

Lovely :)

Impressive! Did the remote survived? :)

This is exactly what I did.

I share BrianZ's point, there is no sexy way to connect RC servo to the rest of Lego construction. If size and weight of Lego servo is acceptable for given application, I'd go with it.

We need remote controlled technic figure to operate this :)

Leaf springs are great. How hard are them in this setup?

Thanks for all good words, guys :) I don't want to put myself into any kind of holy war, therefore I call it 'plane with Lego airframe' and this is to certain extent close to truth :) I mean scrapping wing v1 in favor of wing v2. Just to save some pieces :) Your advise is absolutely right. Landing gear of last version is not that weak, however, I understand that may be I will have to redesign it again and again. And that's that most funny thing of all of it :) Yep, this part also need a rebuild. I just tested that micro-motor is able to operate pneumo-switch. Next main step is to check layout with new powertrain and I expect those new thingies to arrive in two weeks. I'm going to do some experiments meanwhile and share results.

Can't argue with weight saving. But about weakness - I'm already cheating here, the left wing v1 is already glued and is very rigid, though I will have to scrap it.

I will consider that :)

Technic panels are very uneven and with lots of holes. I'm targeting to 5000 - 5200 grams and this seams feasible.

These are ailerons, they are used to bank. Airliners have interceptors for slowing down/losing lift. Other aircrafts just cut on throttle or lower propeller pitch for slowing down or reduce angle of attack to lower lift (usually both)

Hi. I've been working on it for a year or bit more. I think I'm on the finish line now as most problems I could think of are more or less solved. It started in that way - one of a rainy weekend we played with my son with some Lego and it turned to be a half-done airplane of mixed color. A few days after my son came up with 'Dad, will it fly?'. I answered "No, of course. It's too heavy and too weak for flying", but this idea literally stuck in my mind so I started to think about it from time to time. I started to evaluate things from different points of view. It was obvious that I should give up using Lego powertrain, there were no match for 0.8 - 1.2 KW required power. Other two main problems were weight and strength. Problem of weight could be moved away with enough power and enough speed. To cope with strength issue I decided to move on with glue. There was also no chance of controlling such a thing with IR stuff, so controls also should be implemented using standard RC 2.4 GHz equipment. This left me with only the airframe made of Lego, but nevertheless I'm pretty happy with it (Purists may stop reading here :))). However, the model could stand on a shelf (and this shelf have to be rather big :) without any glue, operate landing gear and may be even control surfaces using only Lego parts. This means there are no cheats like 'just glue this piece to that'. All connections are at first usual Lego connections, glue just added for stiffness. But to flying. First, I had to implement airfoil using Lego pieces. I did not choose Carsten Swendsen's way of making only wireframe with Technic axles and using some kind of monokote to cover it and instead decided to use System parts to make the wings and fuse. I managed to implement Kline-Fogelman airfoil using 93606 and some plates with stud inversion. May be this is not the best airfoil, but I think it weighs less than, for instance, flat bottom airfoil with some curved slopes on the trailing edge. Wings implemented that way have many space inside and could accomodate LiPos and motor controller. My first version of wing have following layout: Speed controller on the root part of wing, then nacelle with landing gear, doors and retraction mechanism, then batteries in configuration of 2 cells one above another and one another cell next to them. My chosen configuration was 2700 KV 590W motor and 3x2200 mAh batteries in each wing. (With covering removed) (Speed controller inside wing root) Landing gear was implemented using single 9.5L shock absorber with double springs and spacer made from modified 4624 wheel hub. Single 9.5L shock with extra hard spring compresses fully at 1.2kg and I had no chances making the plane lighter then 4 - 4.5 kg and any design with some kind of levers would weigh more and take more space. (And a bit boring video:) My evaluations showed that take-off speed with flaps deployed will be about 40 kph, so landing gear must be able to sustain this speed for at least 30 seconds. There were some doubts how much load could be handled by Technic axle rotating in shock socket at speed of 7000 RPM. I did some experiments with it. Now I know that axle will be damaged if used without grease handling load of 1 kg at ~ 5000 RPM, but could live with this load for 30-35 seconds if greased. This made me move away from that simple landing gear design, it was also rather weak and any non-ideal (or may be even ideal?) landing could break the strut or move it away from extended position - the locking was not good. (I'll post pictures of damaged axle and video of experiment a bit later) At the same time I was thinking of other ways to reduce weight and came up with idea to reduce weight by cutting flight time. I was targeting for 10 minutes before, but now I think that even 3-4 minutes will be enough to prove the idea of flying Lego airframe :) I found another motor/prop/battery configuration and combined it with new landing gear with 4 wheels per strut and more reliable locking. New layout is using 4x950 mAh batteries, 1200 KV 530 W motor and smaller speed controller and potentially could fit in root part of the wing at whole. However, root part have to be lengthened. This is going to enlarge wing area (which is good) but also probably will load root spars more (which is not so good). On the other hand, heavy batteries are moved from outer wing section into root section (and their weight is reduced; with lighter ESC saving is 90 g per wing) First version of wing also featured front spar for almost all wing length. In second version I decided to end front spar soon after engine nacelle. After gluing wing v1 it was obvious, that front spar of that length is not needed - wing is rigid enough. Also, when making wing v1 I had some mess with covering root section - it was 10st length and there is no 10x8 tile to cover it. Wing v2 have root part of 18st and could be covered easier. (Unfinished nacelle v2) To make control surfaces I used micro-motor directly connected to axle, holding the surface (except of flaps - flaps are connected by worm gear. On ailerons other side of surface is attached to potentiometer, connected to PCB of standard RC servo. Micro-motor is connected to PCB via H-bridge. RC servo operates at 5 V and this is very low voltage for Lego motor. With help of H-bridge, micro-motor is being fed by full battery voltage (11.1V or 14.4V) and moves with reasonable speed. For rudder, elevator and flaps I will have to add some gears to connect potentiometer. I hope the play in gears could be compared to play in servo-to-surface linkage of traditional RC setup. I started some mock-ups of fuselage about the same time as wing v1. Seems like I can fit all the required equipment (air compressor, front landing gear, flap mechanism, pneumo-switches) under the floor (slightly raised in nose section) and some other things (RC receiver, air tank) in aft section. This makes realistic look for cabin, it can be fitted with seats, crew and passengers :) Fuselage, however, is a quite ugly being made from System pieces. With one wing attached: Some amusing details :) Now I'm waiting for new powertrain and some missing pieces for nacelles. After that, if this layout proves doable and reasonable, I'm going to glue both wings, finish fuselage and rear control surfaces and attach wings so CG is in the right place. I think I'll be almost done at that point. However, there are some minor unsolved problems. Design of front landing gear and bay doors make it impossible to close doors when landing gear is down like in main struts. On the other hand, doors must open before extending gear and close after. And there is no place for third pneumo-switch. My idea is to make some kind of throttle to create delay in pneumo-cylinder operation. Also, there is no place for mechanical sequencer, so I'm going to make some simple microcontroller stuff for sequencing door-gear operations. I don't see anything hard here. And yes, there is still a bigger problem - will the whole thing work as expected? :) Well, at least it will be fun to watch how it crash. Sure I should have started with some simpler design - no retractable landing gears, some simple fuselage, something like WWI era airplanes, but my current design is so much fun to build, so I probably revert to simpler construction only after I done with current one. Hope you enjoyed this crazy thing.

I don't know why there are no such parts, but in case you need this 'lever' to work as lever, parts with cross holes can rotate around 'bars', like 61184 or 30374 and bushes like 3713 / 4265c sit firmly on that bars to fix 'levers'.

There are some real life examples of this. Many off-road cars have lockable differential. Early Audi Quattros have it. Fully lockable, not limited slip. Many modern cars have electronically controlled differential. It works by pulse-braking slipping wheel by applying pressure to it's brake mechanism.

Well, does this count? Larger: http://img.osudim.org/221/Original_860672_484874674905849_1286094917_o.jpg This is the early variant of the thing I'm working on during last year. Yes, this bricks are intended to fly (or at least crash nicely) but there is some cheating involved of course (third-party powertrain, controls and lot of glue). However, airframe is 100% LEGO. I'd like to make separate topic about it if this would be interesting for community. (I eagerly watched for Carsten Swendsen progress, pity that his work is stalled)

Well, yes :)

I managed to get it work. 2.4Ghz RC system, controller from some de-cased micro-servo, Bourns 3310C potentiometer and Lego micro-motor driven via L293D.

I did some kind of stuff you referring. I took mini-servo, dropped out it's motor and potentiometer and attached servo controller to Lego micro-motor and bourns 3310C potentiometer. Last one could be fitted into standard technic hole after some treatment by needle file and it's axle is very close to technic axle. Controller then was attached to 2.4GHz receiver and SBEC. Then I did very basic testing of this setup. Whole thing was kind of operational with following issues - first one it has trouble standing still, however I managed to set it still at some position of transmitter joystick. I did not tried any trimming or pot adjustment. And second one - reaction is not very fast. To solve this issues I'm going to test another pot (original pot in servo has 3.3Kohm resistance, my 3310C-s are 1Kohm and 5Kohm, I only tried 1K) and connect motor via some kind of electronic gate made of 4 transistors. SBEC has ~5V output and Lego motor would definitely work faster if powered by 11.1 V I expect required electronic components to arrive by the end of this week and if lucky will test it on the weekend. Will post some photo/video.

In theory 5 Ah battery can feed 50A for 6 minutes (5 A * h / 50 A = 1/10 h = 6 min)

You will hardly find 6-blade propeller in RC world. Also, you can't just scale down original propeller and have it do required job in desired way. When scaling aerodynamic kind of thing many factors do apply. For instance you could take a look to this page how scale factor applies to different physical values - http://www.mnbigbirds.com/Scale%20Factors%20Page.htm May be you could combine two three-bladed propeller and make it 6-bladed, but I would rather started with propeller that will do right job and then go forward to similarity with original aircraft. Also remember, that adding blades increases a load of propeller of same diameter, perhaps you will have to experiment with different props. Variable pitch propeller, however, do exists, but they should be combined either with specialized motor with hollow shaft or with gearbox. Examples: http://www.hobbyking.com/hobbyking/store/__6220__Variable_pitch_prop_motor_set_10_Type_A.html http://www.horizonhobby.com/products/EFLPVPP100 And variable pitch should probably take it's own control channel, unless you are able to generate PWM for ESC for constant speed. Variable pitch propeller is harder to implement, but it have the same advantage over constant pitch prop as having a car with single gear or complete gearbox (or even variator)

I don't get why you would ever need metal propeller. For rough estimation on propellers and motors combination you could use this nice tool: http://flbeagle.rchomepage.com/software/webocalc_1.7.6/webocalc.html How are you going to integrate Lego servomotor with RC servo or RC receiver? AFAIK, PWM frequency used by Lego servo motor is significantly higher than that used in RC servos.

Wing camber is important too.