[TC21] Plymouth SuperBIRD

[2GodBDGlory]

So, as some of you may have gathered from posts in other topics, I've already been working on my entry for a while. It wasn't that I wanted to start three or four weeks early, but I took a gamble on guessing that the official contest rules would be published soon, and was wrong. Therefore, the first half of my WIP thread is essentially just me talking, without input from others. Also, I expect to finish well before the due date, so please don't feel like I started early in order to gain an advantage that way! Anyways, to date I've taken pictures and written out WIP posts four times. I guess I could stagger posting them to simulate a more normal contest entry, but that seems overly confusing, so I'm just going to rapid-fire my updates here:

 

Update 1:

For this contest, the first idea I had that I liked for an entry was a car transforming into an airplane. Not a car transforming into a flying car, but hopefully something more dramatic. The basic idea was that the car would shrink in width to attain the profile of something like a fighter jet, that some sort of rudder/elevator assembly would rise from the trunk, and that the hood and grille would split in half and fold out to create wings, revealing some sort of airplane-style nose underneath. Finally, I hoped to have a propeller fold out of the trunk as well to go on the back. If I could get that all sorted, I would move on to adding as many car/airplane functions as I could fit, such as a piston engine, gearbox, working ailerons, elevators, and rudders, and maybe even flaps and a variable-pitch propellor. I knew that the changing width would cause a lot of problems, so I started by working on the rear suspension and drive. After trying a silly idea with sliding transverse axles, I settled on the design seen here, with two parallel trailing arms for each wheel, with a planetary hub driven with an old female CV joint, as Zerobricks has demonstrated, followed by bevel gears and longitudinal shafts with CV/universal joints at each end, allowing for the axles to slide towards each other freely. I then started working on the actual mechanism to change the width, using two medium linear actuators per end of the car, geared together, and attached to an 11x15 frame that I could build the un-sliding parts of the car off of. Each LA only used four studs of its travel, for a total change in width of eight studs. I then extended the sliding “walls” of the car forwards and started working on the front suspension. Again, I couldn’t do a basic double-wishbone independent suspension design, because of the changing width, so I did a simple sliding-pillar design using the springs from hard shocks mounted on an axle at the steering pivot. I then mocked up a strange steering setup like the one you see here. The Z-shape of the links keeps the hubs parallel to each other regardless of the current width of the car, though the central control axle has to rotate when changing width or the car will automatically steer.

Spoiler

Compressed inwards

 

Expanded outwards

 

Steered one way

 

Steered the other way

 

Front suspension

 

Rear suspension

 

Wing/hood mockup

              At this point, I began thinking more thoroughly about how I was going to transform the front into a plane-esque nose, and realized that I would probably have to design my car to have a pointy nose as well. My plan for the aesthetic had been to simply build something that would work and then try to make it look decent, but I wasn’t happy with the idea of building a nose like this, since it would make the car look very strange. Then inspiration struck, and I decided to forget about designing my own car (which would very likely be very ugly), and instead model a classic Dodge Daytona or Plymouth Superbird, the only real cars I can think of with the nose shape I was after. Another plus was that I could commandeer the massive rear wing on the real cars and use it as a set of dual rudders and elevators, hopefully, which would be easier than having it pop out of the trunk. Also, the fact that the car is very long should help the proportions work out better as an airplane. A final advantage was that I would get to model a good-looking car that is also very boxy—a boon, since my mock-up chassis was already very boxy on the sides. The choice was then between the Daytona and the Superbird, but I chose the latter for three reasons. First, I’ve built two second-gen Dodge Chargers before but no Plymouths at all, and I wanted to do something different, Second, the taillight design on the Plymouth will likely work better with having the propeller fold out, and Third, the name SuperBird is perfect for a car/airplane. With this idea in mind, I printed some blueprints, extended the wheelbase to match, and installed a pair of linear actuators for the front half, connecting them to the rear.

 

Update 2:

 

              The next thing I tackled with this MOC was trying to get the basic wing mechanism to work. I wanted the hood of the car to split in half and fold out to the sides, so I found a good pivot point for the wings and messed around with different gearings to get the wings to open the correct amount for the fixed number of rotations required to contract the car’s width. The best gearing for this turned out to be 1:24 worm gearing followed by 8:28 gearing with a small turntable. I also figured out a way to attach the wings from the sides to prevent their motion from interfering with the base of the windshield. I then moved forward, working to finalize the steering at the front. To do so, I added a second Z-shaped linkage to the steering to make the weird linkage sturdier. The linkage is run by a PF M-motor running a worm gear against an 8T gear (The worm is currently removed to make transforming the car during tests easier), which then drives a 12T gear against a 40T gear at the center of the main lever. As mentioned earlier, the change in width will steer the wheels to their maximum and beyond if not counteracted. I considered trying mechanical solutions to isolate these motions, but in the end, I think it will be far simpler and more reliable to mount the motor as I have here and just manually counter-steer as the transformation occurs. The only other change of note is the addition of a micro V8 piston engine under the hood, which will look dwarfed while in car mode, but which is all I can fit while in plane mode. I am now trying to figure out a linkage that will allow me to hook up the rudder(s) that I plan to add at the rear with the steering.

Spoiler

Airplane mode

Car mode

 

Improved steering one way

Improved steering the other way

Wing deployment drive

Update 3:

              I’ve now spent a lot of time working out some of the aesthetics on the front. This has meant building the side of the pointy front, which will hinge in and out depending on mode. In car mode, it will be out parallel with the rest of the car, fitting under the hood/wing panels, while in plane mode, it will hinge inwards to create more of an aerodynamic cone shape on the front. I built some of the central aesthetics for plane mode (which will be covered up by the hood/wing when in car mode), evicted the PF M-motor from the front, and got the hinged panel to line up fairly well in both modes. This panel is extremely complicated in shape, though, made up of lots of small pieces. I suspect that it could be made much more elegantly and easily using Technic panels, but the #1/2 and #3/4 panels that would likely be used here don’t exist in LBG, and I am unwilling to buy a lot of parts in some other color to recolor this car. I do have some of these panels custom-painted into LBG, but I’m pretty sure painted parts are not allowed in the contest. I think my shape works well enough, it is just rough to the eye because of the random texture on it. The next step will probably be to mirror these bodywork things and hook up a linkage to work the pulling-in of these panels.

Spoiler

Airplane mode

Car mode

Nose close-up

Update 4:

              This update represents a lot of work. I still haven’t worked out the linkage for the pulling-in panels, but I’ve made a lot of progress, nonetheless. The thing I mainly started with was fleshing out the wing/hood panels, but then the advanced weight caused major problems with the wing-deploying system. I should have known that three 8T gears in a row driving the 28T turntable would never take that kind of force without prohibitive backlash, but I was set on using the turntable and this was the only way I could think of. Anyways, I tossed that whole system and rebuilt a much better one using a worm gear to directly drive two 40T gears, to which the wings are attached. It was very hard building this module, since not only the worm shaft, but also the steering shaft and the engine shaft had to traverse this space, one on top of the other. I just managed to get it all to fit, though! Before I trashed the 28T turntable setup, I had realized that I could revive my dreams for working control surfaces on the wings that I had previously given up on by running universal joints right over the center of the turntables. I essentially carried this system over, but decided that since I can only get one shaft out onto the wings, I would have to combine the ailerons and flaps into flaperons. This meant that the bevel gear housing in the middle could not be fixed to anything, since it will have to rotate on its axis to activate the flap function. Unfortunately, I was at my width limit, with no room for support between the bevel gear housing and the U-joint (SaperPL’s 3D-printed U-joint with integrated axles would have been a lifesaver). The best solution I could think of was to mount the bracket on the thin circular holes from minifigure back brackets. I’m not happy with the strength of this setup, so I’ll plan on improving it soon. Other than that, I’ll need to get around to making the linkage for those front panels, reinstall the A-pillar bases, attach the steering motor, and hook up the wing folding mechanism with the linear actuators for compressing the car. (A 32T gear would fit perfectly with just the right ratio. Grrr!) I’m starting to feel like the car has hit the tipping point where it is now too complex to ever work correctly, which happens to me a lot. Hopefully I’ll have the patience to work through the increasingly difficult challenges of packing the rest of the stuff in!

Spoiler

Airplane mode

Car mode

Flaperons and wing worm drive

 

 

 

[GerritvdG]

Cool, speechless... 

The lateral forces on the wheels will be strong I'm afraid.

[2GodBDGlory]

8 minutes ago, GerritvdG said:

Cool, speechless... 

The lateral forces on the wheels will be strong I'm afraid.

Thanks! You're right, it is a lot of force. They definitely do bend in when the car is expanding, but it seems that driving it forward just a little gets them to straighten out.

[2GodBDGlory]

Update 5:

Since my last update, my main focus has been on getting the side panels at the front to fold in correctly. First I got the complex gearing system set up, which was challenging given the very limited space:

That 8T gear driven by the worm gear in the above picture runs the axle that drives the white 40T gear down here, which connects to the linkages that actually pull the panels in:

Because I'm pulling the linkages from the center of the chassis at the same time as the center is drawing closer to the outsides (due to the linear actuators elsewhere) the total travel of the linkage has to be increased to compensate for this relative motion.

 

I was having troubles with my older brick-built hood/wing and side panels catching on each other, so I took the opportunity to design much cleaner looking, stronger, and more Technic ones using pneumatic hoses, and redesigned the central "peak" to make it fit my new panels better. You can see the car and plane modes here:

This model has proven to be very challenging, requiring a lot of rebuilds on certain parts. It's certainly a refreshing break from building more conventional cars where I design a system I expect will work, install it, and don't touch it again. This one takes thought!

I'm not quite sure what the next step in this project will be. I'll probably make some tweaks to the side-panel-pull mechanism to enhance its reliability, but from there I suppose I could start working on the roof, which will have to have a retracting center section, or move into the back more.

[2GodBDGlory]

Update 6:

For this update, I started working to fill in the rear aesthetics and added the deploying "jet engine."

The wing is also fairly complicated, because it has to have the top section sliding on the pillars as the width changes, the top had to work as an elevator for the airplane mode, and both pillars had to work as rudders for the airplane. This section was actually designed in Stud.io since I had some time to kill away from my bricks... I still need to hook up these control elements to their inputs, though. I plan on hooking up the rudders to the steering and the elevator to some kind of joystick. Anyways, the jet engine was likely the biggest challenge in this largely aesthetic update. I had originally planned on doing a rear pusher propeller and hooking it up to the drivetrain (variable pitch propellers even existed in my mind!), but I quickly realized that any propeller that could fit simply would be comically small, and more complexity is the last thing I need, so I switched to a simulated jet engine. It was a bit tricky to figure out the right proportions and axis on which to rotate it to allow it to flip between normal rear aesthetics and the engine, but the bigger issue was driving it. It has to rotate very quickly when going from car to airplane mode because any delay will cause the rear deck to contract over it before it can escape. However, when going back to car mode, it has to do its motion at the very end, after the deck has expanded around it. I used two long parallel rubber bands and a bevel gear setup to hook it to the transformation drivetrain, allowing it to slip when its motion is blocked. However, I decided that I didn't want to wear out the rubber bands prematurely, I added a medium-strength linear clutch beforehand, which seems to have an ideal stiffness. However, I will need to add some kind of automatically opening lid over the engine, which may take more torque than it allows.

Spoiler

Jet deployed

Jet undeployed

Jet engine mechanism

Anyways, I've still got a lot of work to do, but I'm starting to feel like the end may be in sight, if only I can make the transformation reliable. My biggest issue there is that the sliding parts in the rear wing constantly bind up when the contraction is in progress, but we'll see what happens!

[Jeroen Ottens]

Wow! This one is really true to the spirit of the competition. Especially the width change of the chassis is a great bonus. I know you prefer building in dark grey, but adding some colour could make this entry even better.

I hope you get all the transformations to work properly.

[Jurss]

Coming together really good.

[2GodBDGlory]

10 hours ago, Jurss said:

Coming together really good.

Thanks!

10 hours ago, Jeroen Ottens said:

Wow! This one is really true to the spirit of the competition. Especially the width change of the chassis is a great bonus. I know you prefer building in dark grey, but adding some colour could make this entry even better.

I hope you get all the transformations to work properly.

I'm glad you like it! You're absolutely right that a different color would make it look way better (Azure, orange, red, or now lime green are all good candidates with the wheel arch available), but of these red is the only color I have any significant number of parts, and even then I'm far from where I'd need to be. I could always order parts, but it'd be a lot, and I'm cheap.

[whitepen]

This moc makes my brain hurt!

[2GodBDGlory]

41 minutes ago, whitepen said:

This moc makes my brain hurt!

It makes my brain hurt too! 

[MangaNOID]

Looks great so far! Any videos of the operation yet? Would love to see how smooth it all etc.

giing the extra but with this one and not just having the wing pop out. Although I have no idea where the passengers end up 

[2GodBDGlory]

3 hours ago, MangaNOID said:

Looks great so far! Any videos of the operation yet? Would love to see how smooth it all etc.

giing the extra but with this one and not just having the wing pop out. Although I have no idea where the passengers end up 

Thanks! I haven't taken any video yet, but I'll think about making one. Yeah, there certainly won't be any interior on this one! Today's build session revealed that I had less space than I was expecting, so stuff will be probably be crammed in desperately. I may have to drop some auxiliary functions, too.

[iLego]

Functionally, this is already quite amazing. I still get my head around the front underside mechanism photo.

[Thirdwigg]

I finally spent some time going through this thread and reading all the updates. I'm impressed with the creativity of this MOC, and the execution of the functions. The details of the steering, the moving jet engine, and the way the wings both fold and cover the hood are all great. I look forward to seeing the continued development.

Now maybe a little little color in one of your MOCs @2GodBDGlory? 

[2GodBDGlory]

10 hours ago, Thirdwigg said:

I finally spent some time going through this thread and reading all the updates. I'm impressed with the creativity of this MOC, and the execution of the functions. The details of the steering, the moving jet engine, and the way the wings both fold and cover the hood are all great. I look forward to seeing the continued development.

Now maybe a little little color in one of your MOCs @2GodBDGlory? 

Thanks for the thoughtful comment! I'd like to build more colorful stuff, but currently my desire for color is less than my desire to save money...

[EDIT] My inspiration won't work after all 

On another note, I just had a stroke of inspiration for two of the transformation functions: the jet deployment and the roof lowering (not built yet). Both of these need to work immediately when contracting and at the very end when expanding. My idea is to put put these functions going the wrong direction but much faster, so that when expanding, one taps the contraction direction for just a second at the very end of the transformation and when contracting, one taps the expansion direction for a moment right at the start. This ought to prevent binding, if it works as expected. I can't wait to get out of class and work it out practically!

Edited December 4, 2021 by 2GodBDGlory

[2GodBDGlory]

I'm pretty happy with the progress I've made since the last update!

 

I have:

1. Installed a battery. Space is tighter than I was expecting, so I was forced to use an old 9V train battery (and go buy a 9V battery!) under the floor. In order to hook it up to PF receivers, I'll use an old trick and run one from an output, and then run the second one from on top of that, avoiding the normal incompatibility at the cost of one port.

2. Installed a drive motor. Again, space was tight, so I could only fit a PF M-motor. It runs two long shafts on universal/CV joints with extending segments to reach both rear wheels. I had always planned on using a differential, but in the end I didn't have space. I also forgot about hooking it up to the micro piston engine, so I'll have to take a look at it later.

Spoiler

3. Installed the transformation motor. I had planned on using a PF L-motor, but it didn't have enough torque, and I lacked space for gearing, so I used an Xl instead. It seems to be struggling now, so perhaps some kind of modification is in order.

4. Tweaked the jet-engine deployment. Although the Defender rim looked good, it was too large to work reliably, and got jammed regularly, so I changed it to a Racing Small rim. I changed the mounting point of the cover, and added a small rubber band to make it easier for the engine to push the cover up. I also changed the linear clutch in this mechanism to a ball-joint design I shared yesterday in the General Technic Discussion thread.

Spoiler

5. Added the central section of the roof and its lowering ability. A 3L pin with the axlehole is used to make a linear clutch here, allowing two 2L beams to use linkages to pull the roof down a single stud to get it out of the way when contracting, and to get it back to normal height when expanding. One issue here is that when the Xl is turned off after reaching the end of its travel and stalling, it unwinds itself a little once power is shut off, which often lowers the roof back down. Using the speed control remote, however, seems to mitigate this.

Spoiler

 

6. Built the sides of the body. This section was very easy to do, and lacks really any detail. I had held off on installing it to keep access to the inside easy, but I decided to put it in now, making it look much more complete.

7. Redesigned the sides of the wing. Originally, I had the sides of the wing fixed upright and the top part sliding freely when contracting. This kept binding up, however, because the linear actuators were too far below the wing and thus didn't pull it straight. To avoid this, I have now fixed the top of sides to the wing with a hinge, and hinged them at the bottom, causing to to go from an | | shape to a \ /. This did mean that I had to sacrifice the elevator that was going to be built in to the wing, but I was doubtful that I'd be able to hook it up to anything at this point, so it was somewhat inevitable. I think I'll be able to keep the rudders, though.

 

I'm reaching the home stretch on this model, I think, with only a few things left to do! These are:

1. Install the steering motor

2. Install the receivers

3. Design some control mechanism for the flaperons.

4. Hook the rudders up to the steering.

5. Hook the piston engine up to the drivetrain

6. Increase the ground clearance at the rear spring mount

7. Decrease the length of the flaperons so they don't collide with the body

8. Make adjustments to many parts of the transformation mechanism for greater smoothness and reliability

Edited December 5, 2021 by 2GodBDGlory

[sm1995]

This is freaking incredible. I cannot wait to see it in action!!

[Lukes_Brick_Studio]

WOW, this is a engineered masterpiece, so cool functions. This project really hits the theme of this contest and I will definitely follow this thread with a lot of interest. 

[StudWorks]

Unbelievable, I have never seen a Lego car ever that is capable of narrowing itself.

The exterior looks just like the real Superbird as well, I just wish the transformation looked more like an actual jet instead of a cartoon flying muscle car. (Folding wheels, etc)

[2GodBDGlory]

Thanks guys!

57 minutes ago, StudWorks said:

The exterior looks just like the real Superbird as well, I just wish the transformation looked more like an actual jet instead of a cartoon flying muscle car. (Folding wheels, etc)

You're right that the "plane" mode could stand to look more like a plane. My model is in a bit of a middle ground between a "flying car" and an actual airplane, but I'm thinking that going beyond this would necessarily be even more prohibitively complicated than this already is! It would be a good ideal to aim for, though.

[Carsten Svendsen]

Looks good, but techniques like these are definitely not allowed if you ask me

[astyanax]

14 minutes ago, Carsten Svendsen said:

Looks good, but techniques like these are definitely not allowed if you ask me

[pic]

Can you explain what's wrong? I do care about legality, but I see no problem here: there are no pin endings stuck halfway a pinhole. Or are you merely taking issue with the strength of the construction?

[imvanya]

6 minutes ago, astyanax said:

Can you explain what's wrong? I do care about legality, but I see no problem here: there are no pin endings stuck halfway a pinhole. Or are you merely taking issue with the strength of the construction?

If you look closely, there is a small ridge that goes across the middle of the 2-stud wide section of the 3L pin with friction:

Very likely, having that connector or any 1-stud wide part with a pin hole on that ridge would stress both the pin and the part. Even on the frictionless 3l pin there is a similar, though less pronounced ridge:

By contrast, the new 3L frictionless pin with stop appears to have no ridges at all:

[2GodBDGlory]

You're correct that that connection would be illegal by Lego's standards, but the contest rules aren't concerned with this kind of thing (I'm pretty sure!), and I'm not concerned about any wear it could cause. Incidentally, though, that connection has been changed for my next update, but for unrelated reasons.

[imvanya]

Since I posted a comment in this topic anyway, I should say that I really like this project. I think what really impressed me was that the idea sounds crazy on paper, but you started the topic with some actual WIP photos that had all of the functions at least partially implemented. I am really looking forward to seeing the end result!