Making Lego fly, new design suggested by agrof

[Marxpek]

Here is an idea i wanted to test for a while, maybe it is not the correct place to post this, but i think technic fans might like this the most.

The "air-tank" is not Lego obviously, it is a converted fire extinguisher, made to be pressurized by a bicycle pump.

Don't take it too seriously, it was just something fun I had to try ;)

Edited February 4, 2018 by Marxpek

[Davidz90]

The plane has far too much mass aft. The planes centre of gravity should lie about at the leading edge of the wing and the horizontal stabilizer should be inclined a bit. Like in the image below, the stability is all about balancing forces:

Balans1 by David_Z1, on Flickr

[Jurss]

Anything can fly, if You apply enough force. This is really the exact case.

[agrof]

It is indeed a great fun and creative projects to do, thanks for sharing!

Don't get me wrong, I would sure also enjoy the experiment in person, but as many times stated: throwing, shooting out, dropping a Lego built model is anything but flying. Or I need to revisit my dictionary.  

[Marxpek]

18 minutes ago, Jurss said:

Anything can fly, if You apply enough force. This is really the exact case.

Very true ;) and:

 

8 minutes ago, agrof said:

but as many times stated: throwing, shooting out, dropping a Lego built model is anything but flying. Or I need to revisit my dictionary. 

also very true, "Launching Lego" might be a better way to describe it.

@Davidz90 I knew in advance this would not do well in terms of "flying", the way this is powered/shot means it is more like a rocket rather than a plane, asking for yet another design, fins in the rear with the COG on 1/3 of the silloutte.

Perhaps i will try other designs, I had a "blast" doing this, maybe better designs can glide better and further. (a 42044 MOD springs to mind..)

If anyone is interested: feel free to suggest your own (digital) design, i'd be happy to testfire them in real life, just make sure it contains https://www.bricklink.com/catalogItemPic.asp?P=87944

[Davidz90]

Maybe something like this would do? Russian Yak-15. The tube would be at the front.

YAK-15 by Stewart Callan, on Flickr

It would be interesting to see what glide ratio can be achieved. My bet is 1-2, so that angle of descent would be something like 40 degrees.

[Marxpek]

2 minutes ago, Davidz90 said:

Russian Yak-15. The tube would be at the front

Worth a "shot"

[agrof]

I would like to see where this goes, and like this play, so I put a very simple glider skeleton together - You need to balance it though, it is just a raw quick idea. HERE you can download the LDD file. 

[Marxpek]

@agrof Lovely! i dont think i have that rear wing, any other option?

Edited February 3, 2018 by Marxpek

[agrof]

Bionicle theme had a lot of wing or wing-like weapons, they are not in LDD though.

https://www.bricklink.com/v2/catalog/catalogitem.page?P=60935#T=C

One thought: my sketch is probably too small in term of wing surface, but I am quite optimistic, that with some test, You can actually make something like this glide. If it happens, I think it can be called: flight! Smells like a challenge, right? 

Edited February 3, 2018 by agrof

[Marxpek]

@agrofAh yes i did not think of bionicle, i have a box of those somewhere, i most likely have something good for it.

But looking at your design, mounting the air tube might prove difficult; it has to be mounted on the 15l beams, if it is mounted directly to the panels it will tear the thing apart upon firing i think, any suggestions? (i gues that part is not in LDD..)

[Johnny1360]

3 hours ago, Jurss said:

Anything can fly, if You apply enough force. This is really the exact case.

Yep, it only takes two things, Money and Airspeed. 

[agrof]

@Marxpek Yes, You will definitely need a rigid console in the middle, which to you can attach the starter tube. Something like this:

[dr_spock]

^Replacing the red cyclinder with a model rocket engine could make it fly too. 

 

[Marxpek]

@agrof ok i've built it, it looks very good (except for the colors, i do not own that much panels) and im pretty pleased with how the air tube was built in, please take a good look at the 3rd picture, maybe you have a better suggestion, it could be sturdier, but with the half beam as cross-brace my guess is it will hold.

Maybe @Davidz90 can say something about the COG?, shown in the 4th picture, it should not be hard to shift it.

 

 

If the construction holds, i have high hopes!, suggestions and other designs still welcome ofc!

 

[Davidz90]

1 hour ago, Marxpek said:

Maybe @Davidz90 can say something about the COG?, shown in the 4th picture, it should not be hard to shift it.

COG is still far too aft - it should be slightly behind the leading edge. I'd suggest adding a beam at the front, and then adding weight at the end of it - this way You can shift cog without adding much weight. 

Moreover, the tail has to generate a force pushing it down - it might need some inclination. Maybe use a thin string to connect tip of vertical stabilizer and front of an airplane? That way You can bend the tail up a little and make it more rigid at the same time.

Lastly, since dihedral is not an option with this construction, moving COG downwards (like in a hang glider) is a good idea too.

 

Edited February 4, 2018 by Davidz90

[agrof]

Looks great, I was also wondering about rotating the rear stabilizer, to create opposite momentum for balance if the COG is in the front (upper pic). But if it is behind the elevation vector, than it should be like the original (lower picture here, but lazy to rotate the panels back - You get the idea).

I am not an aviation expert by any means, but I would like to see, how a Technic construction like this behave. For sure there is a lot testing needed, for sure the technic panels create a lot of turbulence and non predictable forces, but let's see what can be done with existing parts. I am very interested to see some videos. 

P.S.: prepare further panels with, to increase the wingspan.

Edited February 4, 2018 by agrof

[Davidz90]

@agrof, great pictures and explanation. You are right, both configurations are viable. I'm no aerodynamics expert either, but my worry is that the stabilizer, as pictured, would not act as a smooth wing. Instead, it would just shove the air in one direction, like this (sorry for butchering Your sketch :D):

img by David_Z1, on Flickr

 

Anyways, lifting tail is a more tricky configuration - when the tail stalls, nose goes up and tail stalls even more. With stabilizer pushing downwards, stall causes the nose to drop - aircraft dives, accelerates and restores proper airflow over the tail.

[Marxpek]

ok so i tried to apply what @Davidz90 sayd, i hope i understood correctly, in the next picture you will see 2 out of place pins, the COG is now along that line, if you put the pins in from underneath you can balance the plane nicely on 2 fingers.

But to make the COG shift to that point there had to be added quitte alot of bulk to the front as you can see, wich I do not really like, maybe @agrof has a nice design idea for this? I do want to mess with your design to much, but i do think the cog has to be where it is now if we want a decent shot here.

i also feel it is a good idea to put the wing more to the back, further behind the bulk of the air tube, but that might mean loosing the front middle curved panel.

Edited February 4, 2018 by Marxpek

[Davidz90]

Great design! Yes, the COG is in proper place.

3 minutes ago, Marxpek said:

that might mean loosing the front middle curved panel

That panel is pretty much blanketed by front anyways and contributes very little to lift. Moving wing back is a good idea - You could unload the front a bit. Moreover, the current front design has pretty significant area and might generate lift on its own.

[Marxpek]

So today i have launched this:

Launched with 5,5 bar of pressure from the fire extinguisher (just like the previous plane)

I will try to upload the video later today. 

what do you think happened?

- actual gliding?

- "thrown" lego? (like the previous plane)

- an explosion of parts?

- 

 

[dr_spock]

Explosion of parts would be the more fun to see results. 

 

[captainmib]

Crash into the ground?

[kolbjha]

I would love #1 (gliding) and #3 (explosion), but I have to admit that I think what happened was #2 (thrown), possibly with a few loose parts.

[mocbuild101]

15 hours ago, Marxpek said:

what do you think happened?

Well, seeing the size of the wings, and the power of the launcher, I would say that the wings come off...