[TC15] Skycrane helicopter

[Erik Leppen]

OK, so let me join the fun of TC15. I never build aircraft, so for one it's a nice experience to try building one. My choice of model is inspired by a old competition on Techlug.fr where the assignment was to build a Skycrane helicopter. I wanted to join but didn't have the required blades, but the idea remained in my mind so a picture of the original was added to my build-inspiration folder.

So when TC15 came along, I was immediately reminded by that and it sounded like a fun project to try building a Skycrane.

First, a reference picture:

By Bidgee, CC BY-SA 3.0 au, https://commons.wikimedia.org/w/index.php?curid=62840938

One of the cool things is the 6-blade rotor that I wanted to replicate.

Then, my first draft:

There seems to be a lot of progress, but remember everything is a draft :)

As the theme of the contest is Aircraft, I want to prioritize the flying mechanisms above the crane. So I figured I wanted some control over the rotor. I fondly remember the great 8856 helicopter set,

which move the whole rotor, and I also remember some discussions about how that is neat, but not actually realistic, because in actual helicopters the individual blades rotate.

So that inspired me to try do it like in real, and with all the new parts something should be possible.

This is the mechanism I have so far and I'm already quite proud of it, even though it doesn't fully work yet. The turntable works as a swashplate and only houses the hxagonal ring with 6 ball-joints. The rotor axle goes through the center of the turntable and is fixed (the mount is behind the 2x6 suspension arm so cannot be seen), while the turntable can move in 2 independent axes, using the same mechanism as 8856 did with the whole rotor.

The black 13L beam on the tan axle pins controls the left and right suspension arms. The front and rear suspension arms are not linked yet. The idea is that I want to have a joystick somewhere that controls these 2 motions. Ideally, in the cabin, but as I also strive for playability maybe somewhere that's more reachable. Suggestions are welcome!

Main problem is that the turntable is not driven, so right now it's "pulled along" by the 6 dark-gray 6L links, but this only works somewhat-well in one direction. Also, it has friction. I'd rather have the turntable's rotation linked to the rotor in some way. I haven't found a way yet and it may not be possible without loosing other things, like the support for the central shaft that's needed for rigidity.

What's cool is that the whole mechanism fits in 9 studs width. Next up was a long, thin, strong frame. Because I wanted it to be rigid, I wanted to use studded bricks for that. Which limits my color options.

My main gripe with it so far is that I think it's too wide, and together with the required paneling it also takes a lot of room. But I needed the 9 stud space in between for the rotor mechanism. Also, it is quite rigid indeed! But I'm nto sure I awnt to keep the studded frame. Also, not sure how I'll fit in any crane machanism, there's not much space left in the center. Also, I don't like the white transverse 15L beam at the bottom, but it's needed for the strength of the side wheel mounts.

Third up is the cabin. My first take on replicating its round shape:

Not sure yet. Epecially since it lacks the side doors from the original. I noticed in pictures there are doors at the rear of the cabin, which I did add.

Here are all the loose bits of paneling that together with the functional modules, were used in the first draft.

I'm not sure about the color yet. I feel that the paneling dictates white as the primary color, (thanks, again, to 42025) but I rather use a somewhat more interesting color. Especially together with black, white seems a bit boring to me. So I added a splash of yellow as a secondary color, but again, with all those interesting new colors of recent years, maybe I'll opt for something else later on. That said, yellow has good part availability (including axles). Maybe I should do a similar "blue stripe" effect of 42025B, but using another color.

That's it for now. Any tips are welcome! Especially on how to link the turntable rotation to the rotor. But also on model size, position of the joystick, and anything else you notice.

[Rudivdk]

Haven't read through your entire post yet, but from the pics it seems like you're off to a good start. Smart thinking in using old style beams for rigidity, these will help a lot. 

[pleegwat]

Maybe you could drive the turntable instead of the central axis?

Driving both in sync would be tricky from a gearing ratio perspective, because the 56 teeth on the turntable is a multiple of 7 you'd need a different source for a factor 7 on the inner axle. Maybe the small 28-tooth turntable?

[Lipko]

Maybe I'm wrong, but couldn't you just replace the 6L links with beams? That would drag the turntable more efficiently.

[KikoTube]

Very damn good already!

I see potential in this build...

[steph77]

very good start!

Curious about where you will place the joystic and handle of collective pitch.

 

[nerdsforprez]

I am loving this competition already.  This build looks very promising..... glad that you have entered.  I will be following this build....

[arijitdas]

wow - this one will look awesome once completed.

[JonathanM]

Might the older turntable with the gear ring on the interior help with the drive? Pity it doesn't fit a bevel gear inside.

Looking really great though!

[steph77]

The only solution for Driving the turntable is to create a 'drive compas' taht can absorb the swashplate movement and angle modification.

The Bell huey has a good exemple of that technic piece:

 

ex1:

or this one

and the best one i ever build:

 

 

I hope it may help :)

 

Edited December 10, 2018 by steph77

[mocbuild101]

Wow, that's already looking great!

On 12/9/2018 at 10:07 PM, Erik Leppen said:

Then, my first draft:

- image -

Is it just me, or is one of the blades not connected properly?

 

[Erik Leppen]

On ‎12‎/‎9‎/‎2018 at 3:17 PM, Lipko said:

Maybe I'm wrong, but couldn't you just replace the 6L links with beams? That would drag the turntable more efficiently.

Replacing with beams probably won't work, since the turntable is also moving up and down, but maybe replacing one of the balljoints with pins may work. It's a thing I will experiment with, thanks! (Haven't had time yet)

On ‎12‎/‎9‎/‎2018 at 12:41 PM, pleegwat said:

Maybe you could drive the turntable instead of the central axis?

Driving both in sync would be tricky from a gearing ratio perspective, because the 56 teeth on the turntable is a multiple of 7 you'd need a different source for a factor 7 on the inner axle. Maybe the small 28-tooth turntable?

I'm not even sure how to drive the turntable at all, since it's on a "floating" platform supported only by the 4 suspension arms. Driving the turntable from the main rotor using some kind of beam system seems like the best bet so far.

Also, I want to support the main rotor's axle, as I find a single axle much too weak and wobbly. So I don't want to give up the 3 stud diameter smooth hole in the large turntable. Edit - sorry I thought you suggested to replace the large turntable, but you were talking about driving it. The new turntable is actually 60 teeth, which is 2 x 2 x 3 x 5, which may be doable (no weird factors). Provided I find a way to drive it at all :)

On ‎12‎/‎10‎/‎2018 at 9:54 AM, steph77 said:

The only solution for Driving the turntable is to create a 'drive compas' taht can absorb the swashplate movement and angle modification.

The Bell huey has a good exemple of that technic piece:

There are some neat ideas there, thanks! I don't fully understand them yet, but it's food for thought certainly. Thanks! Also, @jwarner has shown a really nice solution using an extra linkage in his rotor unit. I'm afraid it's too large though for my version.

20 hours ago, mocbuild101 said:

Wow, that's already looking great!

Is it just me, or is one of the blades not connected properly?

Correct, one of the linkages has "flipped" the wrong way. A mistake I only noticed after taking the pictures.

Thanks so far for all the replies (also the ones I didn't quote, of course). I probably have some time to build coming Saturday :)

Edited December 12, 2018 by Erik Leppen

[Erik Leppen]

Update time! I have spent some time building again and have mainly worked on the tail rotor, the cabin, and the rotor head, and some paneling for the rear wheel "legs".

For the rotor head, I followed the suggestion by @Lipko of replacing one end of the 6L links ball joints by a pinned connection, that only allows rotation in 1 direction. This improves the behavior of the turntable. It still rotates better in one direction than in the other, becasue the links are at an angle. The reason for the black #3 angle connectors is that I needed the links to be somewhat shorter than 6 studs, and to prevent the gray 1x5 suspension arms from intersecting other things. When U use vertical bars, the suspension arms just don't fit and introduce a lot of friction.

If I get no other ideas, I think I keep the current solution, even though it's a bit too large for my taste.

Also, I found another way to secure the tail section, which is basically a trapezium shape, so if not reinforced, the tail can wobble left and right. In the previous take, I used a beam to center it, but I found another solution that makes the beam superfluous and makes the room free for something else. (either a joystick mechanism, or a crane mechanism).

It's the little black X-shape between the angled beams of the frame, that does the trick.

I also added a tail section that holds the tail rotor.

The day after, I also improved the shape of the cabin, and added 3 seats. I read that there are 2 driver's seats and one crane operator's seat. I positioned the latter sideways.

Also, the cabin is moved slightly forward and up, and the bottom is now yellow.

To do list:

• add joystick mechanism for rotor controls. Probably it's not doable to connect this to any driver's controls…
• add a wheel to rotate the rotors
• add crane mechanism somewhere (just a winch may be enough, but 2 parallel winches would be cooler)
• add landing gear (one steerable wheel below the cabin, two fixed wheels under each "leg")
• add a container that can be lifted
• add detailing, such as the engines at the front of the rotor head
• whatever I am forgetting now

[nerdsforprez]

I am following this because I really enjoy this build.  Great updates - couple of things

- I don't mind the large rotor head.  Looks very complex and for Technic models it may need to be unnecessarily large.

- The pic from the top lakes the tail end appear as though it is veering of to the right (from pilot's point of view).  Any way this will be corrected when additional stuff is put in?

 

 

[AFOLegofan66]

This a fantastic Moc...looking forward to the final product!!

[mortil]

ooh.  nice.  this will be nice :) 

[Bartybum]

Looks nice, but I'd try make the tail boom thinner at the rear.

[Erik Leppen]

On ‎12‎/‎22‎/‎2018 at 11:30 PM, nerdsforprez said:

- The pic from the top lakes the tail end appear as though it is veering of to the right (from pilot's point of view).  Any way this will be corrected when additional stuff is put in?

It's actually straight, but I think the paneling and the angle of the photo makes it look like it's not. Maybe I could change the panels on the tail, but it doesn't have high priority.

On ‎12‎/‎30‎/‎2018 at 12:24 AM, Bartybum said:

Looks nice, but I'd try make the tail boom thinner at the rear.

If you mean the upward-angled part, yeah I might change that. I'm not supe happy with it. The horizontal section is also wider than in reality, but I think I need the space for mechanisms. The gray bricks + white panels are taking a lot of space, unfortunately, but the bricks are needed for strength and the panels are needed for looks. The only way I can think of to make it better is to use white bricks, which would make the panels superfluous. But I think that would break the style.

Anyhow, I have an update again! I added a joystick mechanism in the tail area. I found it the most obvious place to add this.

I also added some gray axle stuff at the sides.

If I'm right, the joystick is actually about 45 degrees off, because when moving it sideways, the blades that change the most are those in the right-front and the back-left. I'm not sure I can do much about that, except changing the links that control the blades. Swapping the vertical and horizontal controls of the joystick would make the mechanism a lot more complex and I don't think it will fit in the space. It's already a pretty tight fit.

 

The other update is that I added wheels. The front wheel can turn, directly from the axle on the roof. Probably won't be connected to any driver's control. I don't think there's room for that.

This is what the bottom looks like now. It's hard to see, but in the back there's a 36t gear that can be rolled by hand to rotate the rotors. I think that's as advanced as it gets for the rotors. I'm very glad the 36t gear just fits (less than a millimeter of space between the gear, the gray bricks and the cross-joint at the rear).

The gray thing with the 2x4 connectors supporting the main rotor axle is now only to provide support, but maybe the holes in the 2x2x2 connectors can be used to hold the string for the winch. There's not much space left for that by the way, only the part behind the cabin.

I have noticed that the bricks + paneling being at a 0.5 stud offset makes it hard to add knobs to the sides to control stuff. This is a bit annoying because knobs at the top isn't handy because the rotor is in the way.

Anyhow, I think it's nearing completion, which is cool because holiday is almost over :)

[Erik Leppen]

Sorry guys, for not posting any updates for such a long time. So I guess I have to make a huge bump of the topic to show the finished model. The first months of the year were occupied by other hobbies, which are time-of-year-bound, so I had less time for Lego lately. Also I had the Bugatti project. Fortunately, the Dutch LUG forum had a meeting last week, which I wanted to attend, which was an extra reason to build a bit on my helicopter and have it done in time.

The model is not 100% to my satisfaction, but I think it's still rather cool and with the container added I think it's now complete. It has surely been a fun model to make, and something different than I usually build. Also I think the color scheme works well.

Basically, the most important addition is the container and winch. I added a small mechanism to connect the container to the winch. I'm not 100% happy with it, but I was running out of time and I preferred having a mechanism than none at all. I think it's still decent.

The white transverse 15L beam at the bottom holding the wheel arms in place was sitting in the way, but I didn't want to remove it, so the container's sides do not run all the way to the top. Also, the containre's top is open, mostly because the locking mechanism is rather large (I didn't manage to include the locking mechanism in the hook, which I wanted at first).

Of course, there's also a winch, controlled by the 12t gears at the sides.

I made a few small tweaks to the bodywork too.

• The front 2 pairs of white 3x11 side panels are now better fixed in place by a gray pin-with-pin-hole just above the rear of the cabin (on the sides)
• some light-gray greebles have been added, including wheels to simulate engines.
• The wheels have been mounted 0.5 stud lower, because they were touching some parts when rolling. (their diameter is 3 studs, but with the weight they need just slightly more room)

 

Of course, there's the video too. I still dislike doing video, but as it's required for the contest, here it is.

For demonstrating the container functionality, I quickly threw together a few stands with transparent parts, to display the model higher off the ground. As they were rushed (because not part of the model), they weren't very strong at first, which resulted in a nice blooper. I thought it was fun to put it at the end of the video :P Have fun watching :)

[Rudivdk]

Nice to see this one finished as well, I was afraid you had abandoned it after the long silence... 

Really cool rotor head with the blade pitch in six-blade layout. That probably creates an extra challenge over two or four blades (never built it myself, but it looks more difficult with the 60º angle between the blades). Colors work well together, and overall build is impressive. Your approach with the studded beams payed off, the body looks really solid and there's no sagging at all. I also like that container lock mechanism, works well!

I was watching the video (from your contest entry post) and thinking: how can it stand so stable on those thin transparent supports". Then the blooper .