20 October 2021

LEGO® Element Development: the Escalator Link – Interview with Stephan Breum Steen

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Thomas Jenkins (@thomas_jenkins_bricks) continues our series of Element Developer Q&As, once again with Stephan Breum Steen, Senior Mechanical Engineer in the Novelty Element Development department at the LEGO Group. This time Stephan answers our questions about the LEGO® Escalator Link Chain with Panel and Centre Divider (69900). Then, Thomas provides additional analysis and MOCs. Transcripts were edited for clarity, readability and narrative flow.

The Escalator Link was developed for 41450 Heartlake City Shopping Mall, where it is used to make a working escalator. It has only appeared in one other set to date: 71741 Ninjago City Gardens, where set designer Markus Rollbühler subverted expectations and used it to make a duo of serpentine statues, which got me really excited to take a closer look at this element.

You can read Ben Davies' comprehensive review of 71741 Ninjago City Gardens here.

Stephan has been involved in the development of over 100 elements and is one of the marvellous minds who takes a new element design and makes it a reality. As explained in the first article, element developers are one of the many, many different roles in the LEGO Group who work together to create each new element. They receive the brief from the product designer or element designer, and when complete the mould developer continues the work. It's a carefully considered process, but what interests us at New Elementary the most is how we can integrate it with parts from our collection of existing LEGO elements.


What was your background before joining the LEGO Group?

Stephan: I have a formal education as a mechanical engineer, and before the LEGO Group, I worked designing elements for wind turbines (blades and other glass fiber elements), thermostats (plastic elements) and various other projects as an engineering consultant.

When did you start and which teams have you worked in?

Stephan: I started with the LEGO Group in 1997, in the LEGO® Primo team. Since then, I have worked with most product lines.

What was your brief for the escalator link?

Stephan: My brief was to take the general shape of the element and work out how we could design it technically so it worked for its intended use (in this case an escalator for a shopping mall) and passed our product safety and quality tests. I received a 3D file containing the general shape of the element. Also, the model builder introduced me to the intended use of the element in the model. We needed to combine the features of elements 42479 and 18971 [Panel 1 x 2 x 1 with Rounded Corners and Center Divider, a.k.a. the 'foot plate'].

The escalator link features a thin protrusion which will fit in the gap between a minifgure's legs to keep them in place, much like how the 18971 Panel is often used.

Roughly how many prototypes were in the concept stage, and what sort of ideas were discarded?

Stephan: We didn't have many different prototypes during this process. For a short period, we tried with studs on top for the figure to stand on, but that didn't really work in the model, so we went back to the foot plate.

Is it ABS or did you need a different plastic? Did the material influence the way the part was designed?

Stephan: The element is made from High Impact Polyamide (HI-PA). This material can be hard to work with in production, due to a very low viscosity. Any complex geometry between mould parts will increase the risk of 'flashes' on the moulded part, so we tried to tweak the element design to get as simple surfaces as possible on the mould parts.

What testing, if any, was undertaken?

Stephan: This element underwent the thorough product quality and safety tests that all LEGO elements need to pass. Along with normal dimensional verification, we did a lifetime test on the parts to see if there would be problems in the shaft/fork connection over time, for instance if using a motor.

Did any issues arise during the Design for Manufacturing stage?

Stephan: Yes, initially we saw burn marks so we chose to add a loose core in the mould for improved ventilation.

If you could make one more change to this element now, what would it be?

Stephan: It's hard to say, but perhaps I would like to add some more LEGO identity by putting on a couple of studs.


Analyzing the escalator link

The Escalator Link is a unique element within a rather small family of 'Track Elements'. 

There are few members, but the Escalator Link most closely resembles Technic Link Tread Wide with Two Pin Holes, Reinforced (88323) - pictured second from the right - and the new Technic Link Tread 7L Wide with Two Pin Holes (69910), which I don't have yet but you can see in Alexandre Campos' review of 42131 Cat D11T Bulldozer.

Intended to be used as a flight of stairs, the element is basically a right angled triangle with attachment points at two corners to connect consecutive steps.

As Stephan alluded to in our interview, the element is devoid of studs. It relies instead on clip and bar attachments to interact with other elements. The bar end is a standard 3.18mm bar, much like Plate Special 1 x 2 [Side Handle Closed Ends] (48336). At the opposite end are a pair of clips which offer a much looser connection to other compatible elements than the standard clip elements that I can think of. Less grip here allows for a nice flexible chain of links.

As mentioned above, that flange that projects out of the top of the element is useful for keeping minifigures (and minidolls) firmly planted on an escalator step. It reminds me of the way Panel 1 x 2 x 1 with Rounded Corners and Central Divider (93095) is used in vehicle sets to keep minifig bums on seats.

I noticed that the width of the foot plate complemented that little recess found in Technic pins. Interesting, but I'm not sure if this is a particularly useful discovery.

On the underside of the element is a channel which allows compatibility with gear elements. 41450 Heartlake City Mall uses Technic Sprocket Wheel (57520) to provide its working escalator with some motion. I tried a few other gears that I had lying around but it was only the other Technic Sprockets that had teeth of the correct length and interval to bite the chain.

The recess on the underside is 2 plates wide. Interestingly, there are two pairs of small angled protrusions at either end of that recess, between which those plates can nestle as the pairs are spaced 1 module apart.

There's also a nice right-angled triangular recess on either side of the element. They give the element a potentially useful greebley quality for sure, but I wonder what we can jam into there…

A 3.18mm bar is a slightly tight fit but not enough to cause any worry. A rubber lipstick piece fits a little more comfortably here.

Thomas Jenkins' MOCs with the Escalator Link (part 66990)

General Grievous' Wheelbike

The Escalator Links might make for some pretty menacing looking treads on say, a tank, or maybe the chain of a chainsaw? Unfortunately, the number of links in my collection prevented me from building a vehicle as large as a tank, so I settled for just one wheel instead.

Coupled with a 6x6 dish, the Links make for a pretty well scaled wheel in this version of the cyborg's preferred mode of transport.

Exo Suit

It wasn't difficult to construct a pair of hands using my seed element, and the clip and bar connections made them quite easy to integrate into this mech that might be the little brother of LEGO Ideas 21109 Exo Suit. 

As well as being structural and functional in many places (they were quite useful to make joints in the legs and shoulders), the design of the element provides the model with some interesting mechanical details.


Unless I'm using this element as it was intended, I don't think it is one of those pieces that I'll be using out of necessity but as more of a novelty or perhaps a challenge.

Tom Loftus concluded last week that his Porsche Bows were undoubtedly specialized elements and I think I can safely say the same about the Escalator Link this week. This element only appears in two sets so far which isn't much of an opportunity to showcase this part's potential, so maybe I should reserve my judgments until it's a little more commonly used. Plus, seeing how Markus Rollbühler used it in the design for 71741 Ninjago City Gardens, I think there's a hint of some interesting uses for this part.

From our talks with the element developers over this series of articles, there is no doubt that a lot of thought goes into the design of these parts, and from what I can tell, this element works really well when used as intended. And working LEGO escalators are super cool. I'm looking forward to seeing a Modular department store building, to give this element its due.

READ MORE: We also asked Stephan Breum Steen about the 'Porsche bows'

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  1. Thanks Thomas for the excellent series of articles.

    The comment that this element is made from HI-PA triggered a thought in my head; is there a record anywhere (outside of TLG) of what type of plastics elements are made from? Does some of the colour matching issues that have been observed recently relate to different plastic types accepting dyes different? Whilst many in the community have been very critical of the colour issues having a bit of a product development background myself I can empathise with the challenges that the element designers and manufacturers face and my suspicions are that it's a lot harder to get right than most people think.

    1. That is absolutely one of the challenges, and there are many! e.g. the lime Technic thing was a supplier issue... lovely as it would be to have a continuous supply from one supplier, it just isn't practical.

  2. Ah its a shame putting studs on it didnt work out, that wouldve made for a really neat part

  3. Agreed, studs would have been nice. Or if not, even a pair of 3.18 holes in the step surface would add utility. However it looks plenty complex to mold as-is, especially if the plastic type is finicky.

    I wonder if the requirement to work with Friends minidoll feet influenced this part design in a way that made studs on the steps not work?

    I could imagine that studs might provide too much clutch, where it would jam an escalator if a fig got stuck, where this arrangement will eject a fig rather than jam?

    1. It could just be a matter of the material they chose not being conducive to studs, either because of the aforementioned risk of plastic "flash" when working with complex shapes or because it simply didn't provide reliable clutch.

  4. And as always, thank you all for this interview and analysis, I really appreciate the insights!

  5. These are begging to be used on a Metal Slug

  6. It has to be said that the little mech is just fantastic, and the escalator parts are perfect for shoulder and hand duties.

    1. This comment has been removed by the author.

    2. Kinda, but the clips part has no friction, he cheated by pinching them, normally those hands wouldn't hold.
      (sry for the deletions, wanted to fix a typo)

    3. @anothergol are you sure about that?

      The mech's left hand could hang that way with just gravity. And the extended right hand appears the be held in place by the Technic driving ring on the forearm. Only need enough security to hold a photo pose.

    4. Lol I also made a typo -swap mech's left and right in my comment above.

    5. Yeah perhaps (but the pinching alone would also hold it in place), I was just saying that the lack of friction makes it not ideal in general.

  7. This comment has been removed by the author.