06 March 2023

LEGO® Technic parts review and MOC: 42140 App-Controlled Transformation Vehicle

Posted by Alex Campos

The LEGO® Technic line of simple "ripsaw"-like remote-controlled vehicles began in 2017 with 42065 RC Tracked Racer, which was an excellent source of Power Functions elements. The latest entry in this line is 2022's 42140 App-Controlled Transformation Vehicle, which I am dissecting for its inventory of juicy parts, before trying to come up with a very different use for it.

Products in this article were provided by LEGO®; the author's opinions are their own.
LEGO® Technic™ 42140 App-Controlled Transformation Vehicle
US$149.99/ £129.99/ 149.99€/ AU$249.99
772 parts
1 March 2022
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Recoloured elements

A few moulds appeared in 2022, all of which we have already presented in New Elementary articles last year. Therefore,  the Transformation Vehicle doesn't introduce anything you likely haven't seen yet. However, the set still has some novelties, thanks to their colours.

Panels #3 and #4 have been around for many years, and the colour blue even harkens back to the very beginnings of LEGO bricks. So, it's quite surprising to discover that these two combinations of mould and colour had never appeared before. 

This is their distribution in the set; not many of each, but still welcome:

  • 1x Technic Panel Fairing # 3 Small Smooth Long, Side A in Bright Blue/ Blue (6381988 | 64683)
  • 1x Technic Panel Fairing # 4 Small Smooth Long, Side B in Bright Blue/ Blue (6381987 | 64391)

Technic Beam 2x5 L-Shape with Quarter Ellipse Thick (80286) is a much more recent mould, introduced in 2022. Here, it also appears for the first time in blue, with element ID 6407067. As with the panels mentioned before, only one of these is in the set.

I already talked about Vibrant Yellow/ Neon Yellow in the 42145 Airbus H175 Rescue Helicopter review. Interestingly, none of the neon yellow parts supplied in the Transformation Vehicle are in common with the Airbus. So, if you want to complete your neon yellow Technic collection, you'll have to grab both sets. 

This is 42140's assortment:

  • 2x Technic Beam 1x7 Thick in Vibrant Yellow/ Neon Yellow (6381983 | 32524)
  • 2x Technic Beam 1x13 Thick in Vibrant Yellow/ Neon Yellow (6381984 | 41239)
  • 2x Technic Panel Fairing 2x1x1 in Vibrant Yellow/ Neon Yellow (6385239 | 89679)

Other interesting parts

This set is a rich source not only of new colours, but also of uncommon elements.

Axle Hose, Soft 11L appeared in White (6384174 | 32199) in only 2 other sets (9748 Droid Developer Kit and 8461 Williams F1 Team Racer). Not only did those sets come out more than 20 years ago, they were also very expensive, which made this element hard to find nowadays for reasonable prices. Well, not any more: 42140 brings this white soft axle back, and comes with 2 of them.

These are other uncommon parts.

This set comes with 2x Technic Connector Beam 3x3 (39793), also known as a "biscuit", and each is in a different colour: Bright Bluish Green/ Dark Turquoise (6252655) and Bright Reddish Violet/ Magenta (6252656 | 39793). While I understand these may make the building process a bit easier, I'm a little annoyed to not only have them in one colour each, but also that the colours chosen aren't the most neutral and MOC-friendly.

Hub, Powered Up 4-Port (Technic Control+) - Screw Opening (6375901 | 85824) and 2x Motor, Large, Powered Up (6342598 | 22169) aren't that uncommon, but are nonetheless relevant because in this relatively inexpensive set, you get one of the former and two of the latter.

Rubber Technic Tread Attachment in Black (6139223 | 24375) is in the odd position of being at the same time both common and uncommon. It's appeared in a total of 7 sets since 2016, but at the same time it ought to have appeared in more. This tiny nub is great to add traction to treads, and the 96 included here make this set an even better parts pack.

LEGO Technic parts analysis

Many of 42140's interesting parts have already been discussed here on New Elementary, but I thought they deserved a deeper look.

Old and new Powered Up hubs

The Technic Powered Up hub originally required no tools to replace the batteries, as you can see on the left in the above photo. Those times are over as all new sets come with the new version on the right that requires a very small screwdriver to open; a size that many might not have on hand at home.

At least the screws are attached to the battery lid and don't fall off, so you won't lose them.

The old and new 12T and 20T gears

The new 12T and 20T gears, here in blue and azure, have the exact diameter and number of teeth as the versions that have been around since 1999, here in tan and grey. However, the older ones are double bevel, while the newer ones are spurs.

If you want to have a linear geartrain, the two versions can be used interchangeably. However, as you can see above, the old versions have a much greater area of contact with the beams they are mounted on. This can lead to greater friction, and, if there are imperfections in the moulding, the gears can get jammed. With their narrower profile, the new versions should avoid this problem.

On the other hand, the old versions' beveled teeth mean they can mesh with each other at 90º angles, something that can't be done with the new versions.

Finally, the wide teeth on the old versions can't engage with the small chains. The new versions behave like other LEGO spur gears, and so have no problems with this.

Motors without absolute positioning markers

The motors included in this set have internal angle encoders with absolute positioning. This means that a motor knows what angle its output is at, independently of where it was when powered on. This is a great feature on paper, but sadly it's undermined by the lack of external markings that denote 0 degrees. 

As you can see above, the Powered Up angular motors and even the old Power Functions servo, all of which also have absolute positioning, have clear markings. Without these markings, the builder has no way of knowing which of the 4 possible positions is zero, and any program that reads angles on these motors needs to have additional initialisation code to compensate for that uncertainty.

Technic Panel Curved 2x1x1

Affectionately known as "the comma" or "toilet paper panel", part 89679 can be used in functional roles, not just aesthetic. I suggested such a usage in the 42141 McLaren Formula 1 review, as a single-direction cam. 

Continuing the single-direction theme, it can also work as a ratchet: in the photo above, the azure gear can only turn counter clockwise.

MOC inspired by the pieces of set 42140

From what I could find, many people have made MOCs using the parts from this set, but they all tend to be some variation of the main model: cars or tracked vehicles. I wanted to see if I could take full advantage of the "smart" possibilities offered by the PU elements and the excellent Pybricks programming environment, and build something drastically different. 


Have you heard of the Hardiman project? In a nutshell, it was an early attempt at a powered exoskeleton (think Power Loader from Aliens), from the sixties and seventies. I read about it in my first robotics book many decades ago and never forgot its cool looks and name. So, I decided to try my hand at building something fun in that vein. The final result is frankly lacklustre due to many factors, but given a wider array of elements to choose from, could prove an interesting proof-of-concept for a fun model. 

Speaking of fun, when the time came to name the MOC, I opted for a silly shout-out to the original. Enter: the Fartiman.


No, this isn't a butt-ugly speeder bike from Star Wars. Fartiman represents a tiny part of the original Hardiman prototype: just the end of one arm.


The motors included in the set are used here for two distinct functions: opening/closing the claw, and tilting the wrist up/down. Their internal angle encoders are essential, since here they're physically blocked from continuously spinning.

The claw mechanism couldn't be this compact without the holes in different directions provided by the Technic Beam 1x11 Thick with Alternating Holes (73507), also known as "flip-flop beam". It opens and closes the claw by sliding longitudinally.

A serious flaw of Fartiman is that the claw motor needs to be constantly powered to keep the claw closed and maintain a grip on whatever is being grabbed. Unfortunately, this subjects the motor to a lot of stress and leads to overheating. If the set contained a worm gear (either 4716, 15457 or 27938), that could be excellent for keeping the claw at the desired position without effort from the motor. 

The Technic hub has a single button, normally used for powering it on and off. Fartiman has two more functions that need control from the user and I didn't want to use any external phone or LEGO remote controller, so I had to squeeze more functionality from this button: short-click it to open and close the claw, double-click it to change the wrist mode between fixed and tilting, and long-click to stop the program.

The hub has another built-in feature: an accelerometer. In the official model, it's used to detect when it's upside-down and reverse its controls accordingly. In Fartiman it's used to sense the arm's tilt angle and rotate the wrist to always keep the claw horizontal, a bit like the camera stabilisation gimbal on a drone. Double-clicking the hub's button will toggle the wrist between "stabilised" and "fixed".

Fartiman offered another opportunity to use a part in a different than usual way: the tread link. These are perfect to form armbands to keep the model strapped to the user's arm, and the fit can be easily adjusted by adding or removing links. The links connect to the main frame by their pinholes; this connection isn't very strong against traction forces, but here they're subjected only to compression forces. 

I tried many ways to interface the LEGO model to a human arm; the biggest challenge was providing a comfortable grip for the hand and balancing the weights involved. The solution was, among other stuff, to move the hub's weight as far back as possible to balance what's being grabbed by the claw. This was the best solution I came up with considering the limitations of the set's inventory.


Like its predecessors, 42140 is a great parts pack for those who want to begin motorising their creations. Tracked vehicle builders will also find this set useful with the plentiful track links and the uncommon rubber attachments. The set's neon yellow parts are also exclusive in this colour.

There are two major negatives with this set, regarding the potential for single-set MOCs: due to its "split personality", it contains lots of primary colours (blue, orange, black, and neon yellow), which makes building a cohesive alternate model hard. Also, although I understand the usage of spur gears for performance and reliability, their inclusion instead of their double-bevel versions also hinders what mechanisms can be built.

Now that I have the claw and the cat: I'll get you next time, Gadget! NEXT TIME!!!

READ MORE: LEGO® element design interview: 10316 The Lord of the Rings: Rivendell

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  1. This review was great, and made me laugh! The MOC sections of these reviews are already inspiring and a Technic alt-build with functional engineering is amazing. Thanks for this write-up and for making me look for the Inspector Gadget opening to get the earworm out of my head!

    1. So glad to hear that thank you!
      Doo-pee doo-pee doo...

    2. Thanks! Even though the model itself isn't practical due to the motors' strain, it was fun to try to come up with an unusual usage for the parts.

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  3. Nice review!

    The ratchet mechanism you show off using the small panel reminds me of the much bulkier ratchet mechanism in 6949 Robo Guardian. Being able to do something like that at such a compact size could be very useful indeed!

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    1. Great, now we have spambots copying other users' posts and attaching spam links to them...

    2. Yes a noticeable increase in spam recently. On the upside, it means our content must be more popular on Google :D

  7. This comment has been removed by a blog administrator.

  8. Purple and Dark Turquoise.... Reference to the old Technic Competition theme? The vehicle is in a similar aesthetic style to those used in the theme.

    1. Hmm, well spotted! I was thinking of SPIKE Prime, but you may be on to something there.

    2. Bricklink Purple / Bright Violet - Rest In Peace!

  9. Interesting review, and a good exploration of some of the parts.

    But one stylistic thing that I found very jarring: on several occasions, the review refers to things that happened after this set was released as happening before it was released. For example, when talking about rare parts, some of them are described as "previously available only in..." and then lists sets that were released 3-6 months after this one was. Which means they were first released in this set. And were *subsequently* available in those other sets.