[TC15] Lockheed Martin P38 - White Lightnin'

[steph77]

have you evaluate of how many studs back wheels have to go?

For 2 or 3 studs it could be ok for design, if it is more you'll need to make the rear way lighter.

The heaviest parts are the panels. Maybe remove them one by one until the balance is done and redesign the tail with the authorized amount of left panels?

[Rudivdk]

Thanks for all advise guys! I have planned a building session tonight and will try some out, lets see how far I'll get...

[1gor]

Good luck 

[Rudivdk]

Succes!!!

In the end a very small and simple redesign to the landing gear leg solved the issue. I kept the entire landing gear mechanism in place, but added a small 2x4 l-beam that secures the wheel two studs back. I might 'beautify' this later, but for now it works. I was also able to remove all added weight in the front, cleaning up that part as well.

Ain't she a beauty...:

Edit: one more pic, just because I can...

Edited December 29, 2018 by Rudivdk

[steph77]

Yeah!

This is one cool news. You only have to keep your balance problem in mind while finishing it. Btw I notice you miss one propeller which represent quite a lot of weight.  Good progress! 

[1gor]

6 minutes ago, Rudivdk said:

Ain't she a beauty...:

Yes, she definitely is 

I'm glad that you solve an issue with landing gear leg. It is very familiar feeling to me when you spent hours of work and then you could not believe how simple solution should be...

[Rudivdk]

4 minutes ago, steph77 said:

Yeah!

This is one cool news. You only have to keep your balance problem in mind while finishing it. Btw I notice you miss one propeller which represent quite a lot of weight.  Good progress! 

 

4 minutes ago, I_Igor said:

Yes, she definitely is 

I'm glad that you solve an issue with landing gear leg. It is very familiar feeling to me when you spent hours of work and then you could not believe how simple solution should be...

Thanx guys! Actually it took me only 5mins to find this solution, but I spent a good hour and half trying other similar solutions. Didn't improve so I'll stick with this.

From now on most of the weight will be added in front of COG, so I think I'm good now. Might have to change the rear wheels though, in current setup they have moved one stud outwards and they will touch the fuselage I think... I'll go through my collection to see what other options I have.

[BrickbyBrickTechnic]

Awesome! I'm glad the fix was so simple and that no major redesigns were needed! Cheers!

[pleegwat]

That prop's probably significant but, in the real model, the engine right behind it even more so.

[Rudivdk]

Just now, pleegwat said:

That prop's probably significant but, in the real model, the engine right behind it even more so.

That was exactly my problem, the PF M-motors I put in position of real engine represent less weight scalewise. Otherwise it would have worked in original setup I think.

Just now, BrickbyBrickTechnic said:

Awesome! I'm glad the fix was so simple and that no major redesigns were needed! Cheers!

Thanx!

[grum64]

31 minutes ago, Rudivdk said:

Ain't she a beauty...:

She is indeed   

[Rudivdk]

Hi all,

After a long period of silence I have a new update on this build. I managed to put most of the functions in and connect everything to their final controls. The 3-axis yoke is working like a charm!

I still have to tidy up large parts of the plane, and reroute some functions to allow other parts to properly fit in, most notably the rear left landing gear (that's why the plane is now on a stand). But it is coming along very well:

In chronological order:

• opening canopy
• 3-axis yoke controlling ailerons, elevator and rudder
• left and right PF M-motor (activated by PF switch in center wing parts) spinning the props (in opposite direction to each other, like in the real P38)
• right motor also driving a forward/reverse function gearbox for the landing gear (gear up in the video)
• left motor also driving a forward/reverse function gearbox for the flaps (flaps down in the video)

Also there but not shown in vid:

• opening hatch in center fuselage for easy battery box control (on/off switch + charging outlet)
• prop blade pitch control (manual, from sides of engine fuselages)
• turning nose wheel for taxiing (manual)

I hope that on next update she will stand on her own wheels again !

[1gor]

 I was afraid that you went to winter sleeping since no sign from you for some time. I have even watched several videos on tube for p-38 but nothing new. Now I see on what you were doing all that time. To be honest tail looks a bit hollow and I do not know what to use instead of those white rocket ends... All in all moc looked very good considering the fact that Lego parts are no help at all when designing elegant vehicles like lightning, not to mention some sled or custom...

Regards

[BrickbyBrickTechnic]

Great build, one of my favorite overall for sure. However, there are some ugly gaps around where the wings hit the jets and the wings hit the fuselage. 

[Rudivdk]

@BrickbyBrickTechnic: I know, I need to fill those gaps. But before I do so, I first have to take apart almost everything to fix some inner structure weak points. So I will only fix the gaps in the end, because after that it will be a big pain taking it all apart again...

@I_Igor I had lost my interest in this build for a good week, then picked up on it in LDCad, and finally over the last few days I have been back at building bricks again. Seems the two added weeks might be my rescue after all...

As for the tail looking hollow: it might be the angle of the video, here are some pics from different angle:

 

And while I'm at it, here some more details:

Cockpit:

PF battery box hidden in the nose:

Prop pitch control:

"Steering" front wheel:

Rear landing gear:

[1gor]

Now it looks better 

[LEGO Train 12 Volts]

Beautiful technical details, the joystick is impressive!
Epic model 

[Thirdwigg]

I’m happy you stuck with it. It’s looking good.

[Nikolay]

how well the project is progressing

[brickhappy]

I have always been interested in WWII warplanes and I love what you are building. Great stuff!

Edited January 29, 2019 by brickhappy

[Rudivdk]

Thanx all for the kind words! Keeps me motivated to finish this

[steph77]

looks good. some point so far:

-is it possible to speed up a little the main landing gear movement?

-Don't you have some structural issue? the global frame and particulary the external wings seems a little flimsy ?

Keep it up!

[Rudivdk]

54 minutes ago, steph77 said:

is it possible to speed up a little the main landing gear movement?

It currently runs through 2x wormgear to get the desired torque for locking them in extended position. From the motor it is going through a 24t clutchgear, to prevent the propellers from stalling. There is not much room left to change this drivetrain.

 

56 minutes ago, steph77 said:

Don't you have some structural issue? the global frame and particulary the external wings seems a little flimsy ?

True. Although it will not easily come apart, the whole build has flex indeed. Mainly the parts where the twin booms are connected to the wings has a lot of flex, because I have only 2studs high space to make the transverse connections (due to panel covers). It is less noticable when the plane is on its own wheels though.

Guess this build would classify as a functional display-model, not a swooshable play-model.

[Lipko]

For the landing gears you could try a self locking linkage too. I managed to make a mechanism that fully folds/unfolds the gears with only an approximately 360° gear turn, but the gears are very stable when fully out. Maybe it would take too much space though...

Anyway, this is coming along nicely, you managed to fit the same amount of functions in a much smaller space than I did.
For reference and maybe you can see the landing gear mechanism:

 

Edited January 29, 2019 by Lipko

[Rudivdk]

@Lipko: rear landing gear legs have a lock built into the folding hinge already, front leg locks itself because it unfolds beyond 90 degrees. But all the (worm)gears, u-joints and linkages in the drivetrain require a lot of torque, without stalling the white 24t clutch gear.