Light Sport Aircraft - Two Seater Cruiser

[Lipko]

Hi all!

This will be my entry for the aircraft contest. It will be a normal airplane, more specifically a "light sport aircraft".

The model will focus on the looks but will have the main features that make an aircraft.

Planned features:

• variable pitch propeller
• rectacting gears
• nose gear with drag steering: gear self aligns. Some real small planes have this, and in the real plane the steering is achieved by skid-breaking the two main wheels.
• doors hiding the rectracter wheels (expendable)
• flight control surfaces:
  • ailerons
  • elevator
  • rudder
  • flaps (expendable)
• control system:
  • HOG for the main flight controls, triaxial joystick (expendable for two separate sticks)
  • ailerons and elevators are also controllable from the cockpit (dual setup)
  • propeller pitch from cockpit with the throttle lever
  • flaps from either cockpit or hog
• 4-cylider flat engine. At the moment it's a proper flat engine with counter-acting pistons, but I could only implement it with a very big offset between the two cylinder lines, so maybe I will go back for a V4 engine instead to save a little space
• the engine and the propeller will be driven somehow from the middle of the body, probably with some one-way button pushing ratcheting mechanism thing...
• opening canopy
• opening engine door (it doesn't have to be hinged, but has to be easy to remove)
• awesome luxury looks

After about 20 hours of work, the only thing I'm satisfied with is the variable pitch propeller... I have a basic shape defined, controls in the cockipt but I can't route the drive to the engine. I also have the nose gear steering, which looks kind of ugly but works. The mayor challenge in the gear was to add a very small return to center mechanism (otherwise the gear couldn't be retracted) and obviously the rectracting itself.
I will have a big rebuild this weekend, so the internals will change greatly. However, I'm satisfied with the overall proportions and size of the model. Inadvertently the scale will be around 1:10, so in the "supercar scale".

Propeller: I decided to go for a built propeller blades that fit the scale better (and looks better than the propeller blade part, which fit old-school planes better in my opinion) and can be connected to the pitch control more efficiently.

Sorry for my English and typos, my computer died, and also I haven't slept too much lately.

PICS (the propeller pitch hub needs some parts to replace, I guess you'll find which):

Edited February 15, 2019 by Lipko

[Jurss]

Very interesting functionality. 

[nerdsforprez]

I'm so glad that you decided to enter!  I recall quite a few posts on how Lego has been dull for you as of late, so happy that the bug has bit you again.....

[Rudivdk]

Good to see you active again! 

That's an impressive list on functionalities you have planned, and it looks like you made good progress implementing them. Good luck with your build, looking forward to next update

[Thirdwigg]

I like your utilization of the wheel hub for the pitch function. This works perfectly for a three blade propeller. A great idea I would not have come up with. Great job.

[Rudivdk]

I am working on a similar variable pitch setup with the wheelhub as well. I took my inspiration from @steph77's helicopter moc. Wouldn't have thought of it myself either.

Edited December 7, 2018 by Rudivdk

[mocbuild101]

Nice, I like all the manual controls, it's actually the same kind of thing I originally thought of building...

[Jeroen Ottens]

That pitch controller is a step-up from mine using the small turntable. Do you mind if I copy that idea?

[1gor]

First if all I really like that you use 'classic' engine type (somehow I could not find it appropriate to have cylinders falling out - like solution on Mack or Corvette), but I hope that you make it with less rainbow colors, if you want it would be very nice in Hungarian flag colors (I apologize if there is mentioned that final version will be more 'monocolor' like white or light bluish gray...)

So far I find very good solutions in your work 

[AFOLegofan66]

Very clever design!

[BrickbyBrickTechnic]

7 hours ago, Jeroen Ottens said:

That pitch controller is a step-up from mine using the small turntable. Do you mind if I copy that idea?

Same here?

[Lipko]

Of course anyone can "copy" the pitch controller idea, though it is really a straightforward thing you can do with the hubs. I tried several times to use the hubs for similar situation but this is the only place so far where it truly fits.

[Rudivdk]

After I found out about the hub part, it indeed feels like the only logical solution for this.

Nice to see everyone discussing ideas and feeling good about sharing them with others

[steph77]

Great choice of model.

I really like the proportion you already capture on your draft!

On ‎12‎/‎7‎/‎2018 at 6:30 PM, Rudivdk said:

I am working on a similar variable pitch setup with the wheelhub as well. I took my inspiration from @steph77's helicopter moc. Wouldn't have thought of it myself either.

If anyone care I would be glad if some of you all rebuild some of my own concept and stuff. I published with the help of @Ivan_M the instructions of Aw169.

Fell free, all, to take inspiration of it.

[Lipko]

I give up on the project. I worked hard on this almost every night and I still have hardly anything (it's not even worth it to take new pictures). The next time when I could probably continue is at the beginning of January, so I will have no chance to finish it with this development speed. This kind of complicated model is way over my head, I can only design simple cars with simple looks. Also my enthusiasm is not as big as it used to be, so I'm officially giving up on this whole Technic hobby once and for all. When I have kids (one is on the way  ) I will probably build simple town stuff for and later with them, but this "professionalism" obsession thing isn't working.

[Didumos69]

That's sad to read. But hey, this hobby is supposed to be fun. When it's no fun, you're right to give up on it. And with a kid on its way, you'll have plenty of challenges coming up.

Btw my kids have taken me out of my dark age, so who knows what the future has in mind for you. I started with building small cars that could steer and had suspension and could not come apart, at least that's what I thought. Seeing your kid play with something you've build is worth more than a 10.000 likes on rebrickable.

Edited December 13, 2018 by Didumos69

[Erik Leppen]

Sad to see you go, @Lipko. But, as @Didumos69 says, you shouldn't do a hobby if you don't enjoy it. Congratulations on becoming a father (if all goes well) and I hope you will remember your time at EB fondly.

PS The "simplicity" of your car MOCs, as you call it yoruself, is one of the things I particularly liked. At least for the one I recognize from your avatar :)

Edited December 13, 2018 by Erik Leppen

[Rudivdk]

Sad to hear it's not working out for you... but good that you're not pushing on against your own desire.

Having 2 kids of 5 and 3 myself I can totally confirm what @Didumos69 said, maybe at some point the 'demand' will get you back in the technic world.

All the best with becoming a father (and your wife in becoming a mother as well of course), as I found out myself it's the greatest joy in the world, no hobby can compete to being a parent.

We will remember you for the excellent MOCs you've created. Calling them simple doesn't do them justice in my opinion.

Edited December 13, 2018 by Rudivdk

[Appie]

31 minutes ago, Rudivdk said:

Calling them simple doesn't do them justice in my opinion.

Exactly, Lipko is being too modest.

Much has already been said by the posters above me that I also agree with, so I wish you all the best Lipko and your (soon to be expanded) family.

[Lipko]

I decided to make this model even if I can't finish it in time for the contest. I didn't want to end my career with an unfinished failed project. The two-weeks extra time gives hope to finish though.

Anyhoo:

There are a lot of compromises but the chassis came together pretty good after yesterday's build.
So the feature list:

• variable pitch propeller - OK
• retracting gears - OK, but front wheel needs to be connected to the main weels
• nose gear with drag steering: gear self aligns. Some real small planes have this, and in the real plane the steering is achieved by skid-breaking the two main wheels.
• ? doors hiding the rectracting wheels
• flight control surfaces:
  • ailerons - OK
  • elevator - OK
  • rudder - OK
  • flaps (expendable)
• control system:
  • HOG for the main flight controls, triaxial joystick (expendable for two separate sticks) - aileron and elevator OK
  • ailerons and elevators are also controllable from the cockpit (dual setup) - OK
  • propeller pitch from cockpit with the throttle lever - OK
  • flaps from either cockpit or hog
• 4-cylider flat engine. At the moment it's a proper flat engine with counter-acting pistons, but I could only implement it with a very big offset between the two cylinder lines, so maybe I will go back for a V4 engine instead to save a little space
• the engine and the propeller will be driven somehow from the middle of the body, probably with some one-way button pushing ratcheting mechanism thing...
• opening canopy - OK, but some linkage should be added
• opening engine door (it doesn't have to be hinged, but has to be easy to remove)
• ? awesome luxury looks. I'm pretty sure I can't get the looks as sleek as I wanted, but maybe I can go for a more classic "Lego Technic" look.

 

I'd like to highlight the tail. It turned out to be very simple and effective, still both rudder and elevators are implemented in a T-tail design. I didn't think I could implement this but I am very happy I could because this T-tail configuration is more common in such luxury aircraft than the standard fuselage mounted design. Notice the link to the elevator acts also as the pivot of the rudder.
The only thing I don't like is that the horizontal stabilizer is not flat, but maybe I can accept that (I don't want to increase weight).
Also the tail section is quite flimsy, but I don't want it to be more chunky and too heavy since the wheel configuration can't be changed (such planes never have landing gears on the tail).

[MegaRoi]

Glad to see you're back in the competition, and I'm waiting for the look of the completed model.

Congrats to you and your wife and all the best wishes.

All sad things are said ...

[BrickbyBrickTechnic]

I'm really happy to see that you're back, this was definitely one of the cooler entries. Can't wait for more progress!

[Jeroen Ottens]

This is shaping up to something good I feel. Loads of functions in an elegant styled package.

[Lipko]

Sorry for not keeping the project updated but lots of work went into the project and I still don’t have an own computer.

Anyhoo, wall of text:

The project finally is in the finish-line, all functions work okay and the look is also coming along nicely.

Changes:
Connecting the front gear with the main gears required redesign of the whole middle part of the chassis which was hard enough to design for the first iteration, but in the end, the final solution fits very nicely into the chassis. Just like the whole model was designed around the landing gear mechanism. After so mush struggling with the whole thing in the first iteration of the chassis, I was lucky in the second iteration because despite of the slightly different linkages for the main and front gears, the range of operating was the same and also the mechanism could be perfectly synchronized. So front and main gears snap into deployed position in the same time resulting in a very stable stance.

Another change is flaps, which was a last minute addition (I gave up on it early during development) after I realized that pretty much all airplanes have it. I struggled with it for hours and I could only come up with a very flimsy solution first (mounting on only one side of a flap), so I almost gave up on it again. Then I realized that actually flaps are longer than ailerons in real airplanes meaning that the proportions of the wings was very off, but also meaning that I could mount both sides of a flap, resulting in a very stable solution. I managed to make a linkage so it can be operated from the cockpit.
The kinematics is not perfectly realistic but it’s a decent compromise between simplicity and authenticity.

General challenges during the whole development:
The fuselage towards the tail was one of the toughest part of the design. It has to be relatively thin, stiff but also has to contain two linkages to the rudder and elevators. I decided to solve it with an “off-system” truss because no Pythagorean triangles fit the shape without being in way of the linkages. Also a 4-stud high straight chassis seemed to be too thick, especially because some linkages have to go below the lower beam, plus it has to be reinforced which would increase the weight, etc. But this off-system choice introduced other issues. I don’t know how many iteration went into the design because apart from the aforementioned requirements, there are two very important ones which I failed to realize in earlier iterations: the tail plane has to be parallel with the pulling vector/centreline (I don’t know the proper term) and also the centreline of the fuselage should lie on the centreline of the whole plane which is the same as the axis of the propeller. In the recent (ant probably final) version I had to sacrifice a bit of the cleanness of the linkages I already had. This also introduced slight rubbing between the two linkages, so I still have to add some kind of return-to-center at least to the rudder. I selected the rudder because it’s more obvious than the elevator if it’s off-center, and  also the elevator is more likely to be played with than the rudder.

Another thing that made the whole development very hard was that the wings point slightly upwards. This is a necessary design choice because this kind of aircraft have this feature. I hope that this model choice sets my entry apart from the others with the more “straight angle” models. Don’t get me wrong, all entries are awesome, I just fell in love with the shape of modern light aircrafts.

The bodywork:
This, again, was very challenging but I think I’m on the right track, and the biggest ”innovation” in it is the color stripe slightly above the centreline. As it divides the general appearance into “up” and “down” half, it effectively hides panel flow errors and gaps. Black color also hides panel flow errors which is especially important at the back of the canopy door with the hand-of-God joystick.

The model started as a four seater but there’s only enough space for two seats. I could squeeze four seats inside but that would be rather unproportioned so I dropped it. Or redesign the whole thing, but placing the HOG area towards the back with that much (about 4 studs minimum) would make the model very unbalanced and I won’t add a faux wheel, that’s a given.

Play features and operation:
There are two main groups of commands: cockpit and hand-of-God. The cockpit (apart from the working dual joysticks) has the controls that are less frequently used: propeller pitch and flaps control. The HOG area has the main operational features: ailerons, rudder and elevators. Near the area at the back of the left wing is the axle to rotate the propeller. It’s achieved through a ratcheting mechanism so it’s quite pleasant to use. The only thing I don’t like in this solution is that you are not able to swoosh around with the model while rotating the propeller and control the flight surfaces at the same time. My initial plan was to make a button-like device with ratcheting so the propeller could be operated with the hand that holds the plane but I couldn’t find a suitable spot for it (there’s not enough space in the middle of the chassis) and also pushing a button continuously would cause finger fatigue, so I dropped the whole idea.

TODO:

• seats. I haven’t decided yet if design it studless or studded
• rebuild with proper colors
• filling up some gaps in the bodywork
• fixing the panelling of the tail fuselage
• adding some weight to the front, the model tips too easily at the main gears
• adding return to center wherever I can
• fixing a small issue with the nose gear
• optional: add drag steering to front wheel (as there is not that much weight on it)

Bad English and here are some pictures.

EDIT: These pictures were taken very quickly and from the wrong direction: all showing the older itertion of the wing. The right wing will be the final version (now with orange flaps)

Edited February 6, 2019 by Lipko

[BrickbyBrickTechnic]

@Lipko I can't see the images.