[TC21] Plymouth SuperBIRD

[2GodBDGlory]

4 hours ago, imvanya said:

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!

Thanks! I probably would have started the WIP with a lot less if I hadn't started so early (kind of by accident.)

As for the end result, here's my mini-update:

I got everything tuned up and installed since my last update, and was going to film it last night. I had never tested it with my alkaline 9V battery because I knew that I'd never had much success with them in the past, and assumed that I'd need full charge if it was going to work. It didn't. It worked alright with my transformer and lithium batteries, but not this one. I was distressed for a bit, and eventually decided to order a lithium 9V battery from Amazon, which would likely give me the torque I need in the right form factor. However, I don't like spending money, I don't want to wait for it to arrive, and using a long-retired battery is kind of bad form anyways, so I didn't really want to do it. This morning I was thinking some more, and I think I might be able to squeeze in my PF rechargeable battery at the cost of some ground clearance, but I'll have to see. After that, I should be ready to do my final documentation and share the results!

[Pattspatt]

Can’t wait to see the video - difficult to figure out how it all works! It really looks awesome so far.
 

I noticed what looks like two extendable driveshafts using 24t gears. If you’re still in a “modifications and tweaks” phase of the build, this design could come in handy: https://imgur.com/gallery/RPJsN3c

[2GodBDGlory]

26 minutes ago, Pattspatt said:

Can’t wait to see the video - difficult to figure out how it all works! It really looks awesome so far.
 

I noticed what looks like two extendable driveshafts using 24t gears. If you’re still in a “modifications and tweaks” phase of the build, this design could come in handy: https://imgur.com/gallery/RPJsN3c

Hmm, thanks for the tip! I actually did redesign that part because the teeth kept catching on stuff. Now I'm using a setup based on the grey halves of small shocks, and it's working pretty well so far. I may look into that suggestion, though!

Really what I need is the extending CV joint from the Zetros...

[2GodBDGlory]

5 hours ago, 2GodBDGlory said:

Thanks! I probably would have started the WIP with a lot less if I hadn't started so early (kind of by accident.)

As for the end result, here's my mini-update:

I got everything tuned up and installed since my last update, and was going to film it last night. I had never tested it with my alkaline 9V battery because I knew that I'd never had much success with them in the past, and assumed that I'd need full charge if it was going to work. It didn't. It worked alright with my transformer and lithium batteries, but not this one. I was distressed for a bit, and eventually decided to order a lithium 9V battery from Amazon, which would likely give me the torque I need in the right form factor. However, I don't like spending money, I don't want to wait for it to arrive, and using a long-retired battery is kind of bad form anyways, so I didn't really want to do it. This morning I was thinking some more, and I think I might be able to squeeze in my PF rechargeable battery at the cost of some ground clearance, but I'll have to see. After that, I should be ready to do my final documentation and share the results!

Ok, it turns out that my hopes of fitting the rechargeable battery box were in vain. It can't fit without drastic changes, so I'm going back to plan B of buying lithium 9V batteries. I'll plan on ordering them tonight with projected arrival on Monday, after which I can make my final presentation. In the meantime, I'll probably add a final progress post with a video--tonight or tomorrow, I expect.

Edited December 10, 2021 by 2GodBDGlory

[2GodBDGlory]

Yeah, it'll be tonight...

Here is my (hopefully) final update on this MOC, with a video of an informal test. As mentioned earlier, I'm going to need to get a Lithium rechargeable 9V battery to actually run this thing without an external power supply, so I'll wait for that to arrive before I do my final presentation, but otherwise this model could/should be done.

Since the last update, I've checked off a bunch of little things. These are:

1. Added steering M-motor. This took a few iterations because of the tight space, but I got it working eventually.

Spoiler

Steering motor. Also note flaperon joystick

2. Added PF receivers. This is always annoying!

Spoiler

Receivers. Also note PF L-motor

3. Hooked up the rudders. You can't really see the mechanism well in the pictures, but I essentially hooked up two preexisting axles attached to the top of the steering pivots (so that they slide fore and aft when the model steers) to 2L beams connected to the rudders through some tortuous connections. In the end it works, but the axles tend to disconnect at the front, and are hindered by slack. I also hadn't thought about the direction they would go, assuming they'd go the same direction as the wheels for a crab-esque steering. In the end it turned out to be the other way, and it would have been challenging to change, so I kept a more 4WS-esque setup with "counter-steering." I imagine the crab-style would work better on a real vehicle because it is better for stability at high speeds, and aerodynamics is much more important at high speeds, but I think this is alright.

4. Added a basic lever for the flaperons.

5. Hooked up the piston engine to the drivetrain. This required significant reworking of the drivetrain, but it ended up being stronger in the end, so it was a double win. It used a bizarre geartrain of 20:12:16:8 to fit in the given space, with all but the 16T gear being at a half-stud offset from the main chassis. I rather doubt this setup has ever been used in a MOC before!

Spoiler

Redesigned drivetrain. Also note extendable driveshafts.

6. Redesigned the rear extendable driveshafts. My original extending driveshafts based on 24T gears kept catching on stuff, so I looked for something smaller. Zetros CV joints would work great, but I don't got 'em. My solution was to work the light bluish grey half of 6.5L shock absorbers into the shaft, and I am quite pleased with the solution.

7. Tweaked stuff! To get the transformation to work better, I tweaked a bunch of stuff. I increased torque on the transformation by swapping the 1:1 XL motor for a 1:3 L motor, made the roof skinnier to ease its transformation, and did some other little things to improve reliability.

8. Added stickers. I put together some custom stickers using the "LBG" sample color from some online Lego color guide with real Superbird decals superimposed over them. The color is a bit off, but I think it adds some nice authenticity. I got five stickers, one on the nose, two on the rudders/wing, and two above the rear wheels.

Anyways, here's my first video of the model. It's nothing fancy, just me giving the model a try powered from an external Lego rechargeable battery.

 

[imvanya]

My guess would be that the wheels, specifically the friction of the tires is what's resisting the body narrowing part of the transformation. If that is the case, some kind of deployable stand or outriggers could probably help, but it doesn't look like it would be easy to do at this point.

[GerritvdG]

@2GodBDGlory cool, a real technic masterpiece. Nice video, hopefully everything will come together when the new battery is delivered! 

 

[2GodBDGlory]

6 hours ago, imvanya said:

My guess would be that the wheels, specifically the friction of the tires is what's resisting the body narrowing part of the transformation. If that is the case, some kind of deployable stand or outriggers could probably help, but it doesn't look like it would be easy to do at this point.

Yeah, I agree that the friction of the wheels is a major factor. In my experience (and demonstrated a bit at the end of the video) is that simply driving forwards and backwards a little causes the tension to be released and the wheels to be moved in. I think the rationale for this is at least related to the fact that steering a car is always easier when moving.

5 hours ago, GerritvdG said:

@2GodBDGlory cool, a real technic masterpiece. Nice video, hopefully everything will come together when the new battery is delivered! 

 

Thanks! I didn't manage to get the battery ordered last night, so it may arrive on Tuesday instead. Oh well, it's not too long.

[EDIT] Rats, it'll be Wednesday!

Edited December 10, 2021 by 2GodBDGlory

[2GodBDGlory]

Ok, mini-update:

I got my Lithium 9Vs today, and tried the MOC out with it. Sadly, it doesn't work. The batteries themselves are great, and I'm sure I'll find uses for them, but after trying a lot of tests, I think the root problem is the way I'm running the receivers off of their output from the 9V battery box. I could fix this using the old aluminum-foil trick, but contests require purity... (Metallic Lego stickers are not conductive, by the way!)

Anyways, I've got a rough idea to put my Lego rechargeable box where the transformation L-motor is now, and then hook up the L-motor where the battery once was. I think it should all be possible--the issue is just time. I've only got 39 hours before I leave my Lego behind and go home for Christmas, and I've got other things to do, like eat, sleep, go to class, do homework, go to the library, and pack. Here's hoping I can pull it all off in time! I guess I should stop wasting time on here now...

[2GodBDGlory]

I am pleased to make my final update and presentation of this model!

Update:

After my last post, I stayed up late finding out ways of fitting the 8878 battery that didn't work, and went to bed with merely an idea. The next afternoon was spent executing it, and the evening in filming. So, the plan to fit the transformation motor on the bottom and fit the battery in its place didn't work. I simply couldn't come up with a strong way to attach the motor with enough gear reduction in the available space, so I left it where it was. However, by rearranging some of the linkages in the roof-lifting function, I just managed to free up the 4x5 space needed to slot in the battery. It actually worked quite well there, but it required me to relocate the receivers, which was quite challenging in this tight model. One sat in the rear window, in a logical if somewhat ugly place, while the other was jammed in the underbody in some of the space the battery used to use. Anyways, I got it all together and working! I got all the functions working on camera except one: The jet retracting as it transforms into car mode. This had generally worked in my testing, though not as reliably as I would have liked. However, while I was filming, one of the two rubber bands driving it snapped, and I didn't have any spares of the necessary tightness to replace it with. I'll present it in another post in ~30 minutes, because I'd like to keep the update and the final presentation separate. 

 

[2GodBDGlory]

Rats! I don't know why I keep accidentally submitting stuff before I'm ready! Please ignore this for now...

Here is my finished entry to TC21, a Plymouth Superbird that can transform into an airplane of sorts! The idea here was to build something at least moderately plausible to exist and work in real life, with as many moving parts in the transformation as possible, and as much auxiliary functionality as I could fit. As expected, the model ended up being fearsomely complex, which had the natural result of making it fairly unreliable. However, this is a tradeoff I'm usually willing to make for the more interesting design challenges it offers.

Features:

Aesthetics

Transformation

Drive with piston engine

Steering with rudders

Full suspension

Flaperons

 

Aesthetics:

I think the car mode looked ok. I'm never much at making bodyworks, and the transformation gave me a whole different set of constraints to follow. Nonetheless, the car is both boxy and easily recognizable, so it didn't turn out too badly. I also printed some custom stickers to emulate the decals on the real car. The airplane part of it didn't have to match anything in real life, which was nice, but it certainly didn't look like any real airplane. I'm fine with that, though, since the hope was really just to replicate a hypothetical way that a car could have a flying mode, and I think I succeeded there. A real car/plane would have to balance the complexity of the transformation mechanism with the aerodynamics of the resulting airplane, and I think my model looks like a reasonable compromise between the two.

Spoiler

 

Transformation:

The transformation was powered by a single PF L-motor in the rear of the car, and moved five main segments. These were:

1. The wings

2. The width change

3. The "nose pinching"

4. The roof lowering

5. The jet deployment.

It took a bit of time to complete the transformation, and had to be punctuated by steering to counteract the relative motion between the motor and the wheels and driving to help the wheels to slide side-to-side. The hardest function to keep working was the jet deployment, but with the right tuning it all worked tolerably reliably.

The wings were attached to two 40T gears, which were driven by a worm gear between them. It was tricky to work the A-pillars around them, but it ended up being quite reliable.

Spoiler

The width change was done using four medium linear actuators placed in two pairs between the axles (in retrospect, I think it would have been better to try to fit the second pair behind the rear axle.) This too was reliable, but the wheels would drag opposing the motion, requiring the operator to drive the car forwards and backwards to allow them to work there way to where they need to be.

Spoiler

The "nose pinching" used a convoluted drivetrain to run a 40T gear on the bottom of the front of the car, pulling links inwards to pull the pointed sides of the car inwards to a pointy nose in the airplane mode. Because the sides were moving in relative to the links in the transformation, I had to increase the link travel to compensate. 

Spoiler

The roof lowering used a basic slip clutch and linkage setup to pull the center of the roof down immediately before transforming into the airplane mode, allowing the two sides of the roof to cover it. In returning to the car mode, it would press up against the roof until there was room for it to actually move up.

Spoiler

The jet deployment was especially challenging. It was driven by a carefully tuned slip-clutch using a Bionicle ball-and-socket setup, followed by a bevel gear and two long rubber bands in parallel. These rotated the assembly with the jet on one side and the center of the rear bodywork on the other. It had to push up a central section of the rear deck, which was rubber-band assisted to help it deal with the weight.

Spoiler

Drive:

Although the car looks fairly large, I was really limited to its size in the airplane mode, so space was at a premium. The only motor I ended up being able to fit for drive was a PF M-motor, but the drivetrain was fairly efficient (No gearbox!), and the car didn't need speed, so it worked fine. It drove a 8:24 reduction, followed by two shafts geared to each other with 16T gears. These drove two independent shafts to each rear wheel, using extendable driveshaft sections using halves of shock absorbers. These were necessary to allow the track width to change while still driving the wheels. They were followed by bevel gears and planetary hubs driven using Zerobrick's method of sticking an old female CV joint half into it. Additionally, I stuffed a micro V8 piston engine into the front of the car. It was driven by a ridiculous 20:12:16:8 geartrain, with all gears but the 16T at a half-stud offset from the rest of the car. It worked, though!

Spoiler

 

Steering:

Steering was also done with a PF M-motor, also in tight quarters. It drove a complicated drivetrain of 12:24:8 followed by universal joints, followed by 8:8, followed by a 1:8 worm reduction, followed by 12:40 reduction. The 40T gear had a strange Z-shaped linkage attached to it. The central bar of the Z was attached directly to the gear, causing the two flat lines to pull in and out on the two steering arms. Actually, to increase stability, there was an independent backwards Z linkage just below this one. The weirdness was necessary to allow the motor to steer the wheels regardless of the width between them. As mentioned earlier, it had the unfortunate side effect of automatically steering as the model changed width, but this could easily be counteracted with the controller. Beyond this, I hooked up levers on the top of the steering pivot, which pushed/pulled long longitudinal axles, which moved other levers at the rear connected to twin rudders built into the sides of the wing at the rear. This was intended to allow the pilot directional control in flight, but unfortunately had to be a counter-steering setup, rather than the in-phase setup that is preferable at the high speeds where aerodynamics actually starts making a difference. 

Spoiler

Steering motor

Double-Z linkage out

Double-Z linkage in

Lever for the rudder mechanism above wheel

Part of the longitudinal rudder axles

The bottom of the rudder mechanism

 

Suspension:

The suspension was also complicated by the changing track width. Most ordinary suspension setups only work with a fixed width, so I had to got to be creative! The rear has what I would describe as a longitudinal double wishbone setup, with two roughly parallel links connecting the hub with the frame. A hard shock was crammed against the edge of the bodywork, but proved too soft, so I added a loose soft shock to the sliding vertical axle responsible for preventing transverse motion of the hub. The front suspension was slightly more conventional, being a sliding-pillar design used on vintage cars (And Caterhams and/or Morgans today, I believe), with the hub being sprung on a physical support coinciding with the steering pivot. My setup used a loose hard spring per wheel, and worked quite reliably.

Spoiler

Flaperons:

I had always wanted to include all the control surfaces an airplane could have, but it became increasingly clear that I could only get one driveshaft into the wings. Rather than choose ailerons or flaps, I decided to try the combination of them known as flaperons. To do so, I hooked up the flaps to a central joystick using universal joints. Moving the stick forwards and backwards would move both sides together as flaps, while moving it side to side would rotate the bevel gears in the mechanism to make them rotate opposite directions as ailerons. Because of width constraints, I had to mount the bevel gear housing on minifigure neck brackets! This function ended up being simple but satisfying. (By the way, I regrettably had to give up on adding a working elevator.)

Spoiler

Flaps

Ailerons

Joystick

Overall, I was satisfied with the result. I managed to pack a lot of functions into the model, and a lot of them were new, exciting challenges for me!

Transformation starts at 4:55 in the video

 

More images can be seen here: https://bricksafe.com/pages/2GodBDGlory/transforming-plymouth-superbird

Edited January 29, 2022 by 2GodBDGlory

[pleegwat]

This looks very impressive

[MinusAndy]

Ironically I think this fiendishly complex set of mechanisms is also some of your best looking bodywork! I think it looks and works great and it’s really ambitious.

Edited December 19, 2021 by MinusAndy

[imvanya]

4 minutes ago, MinusAndy said:

Ironically I think this fiendishly complex set of mechanisms is also some of your best looking bodywork! I think it looks and works great and it’s really ambitious.

Totally agree! Any troubles you had with the bodywork definitely paid off. The shape of the front is great, it's curved in multiple directions, yet it still incorporates some details like the headlights and looks just as well when in the narrowed plane configuration. Great job!

[Josephiah]

Loving the concept, the complexity, and the execution of this! Some lovely mechanisms in the, combined with some nice sculpting.

If I may make one tiny suggestion: I think your entry video would be much improved by showing the transformation up front - at present the viewer has to search through 12 mins of gear/mechanism close-ups to find the real highlight!

[2GodBDGlory]

1 hour ago, Josephiah said:

Loving the concept, the complexity, and the execution of this! Some lovely mechanisms in the, combined with some nice sculpting.

If I may make one tiny suggestion: I think your entry video would be much improved by showing the transformation up front - at present the viewer has to search through 12 mins of gear/mechanism close-ups to find the real highlight!

Thanks! That is a good point about the video, but I'm kind of lazy at that kind of thing, so maybe I'll just put a note in the description of where to jump to to see it.

[imvanya]

Congrats on a well-deserved win!

[Maaboo the Witch]

Great job! You should be so proud. 

[2GodBDGlory]

Thanks guys! I was really shocked by how many people voted for my entry once the votes started coming in!

[vascolp]

6 hours ago, 2GodBDGlory said:

Thanks guys! I was really shocked by how many people voted for my entry once the votes started coming in!

Now imagine if you had used colors! 

:Congratualtions!