28 March 2014

You raise me arch

Posted by Admin
There are many reasons why LEGO® parts get redesigned, for example to strengthen a part or to improve the moulding process. But sometimes a whole 'family' of parts will get redesigned, and this process can take years for TLG to roll out because moulds need to reach the end of their working lives before the expense of replacement is undertaken.

Over the last five years or so, the family of arched bricks have been altered and I was prompted to write this post because what I think/hope is the last of these, the 1X8X2 arch, has now begun to appear in its new form. The essential change to arched bricks is that they are being "raised" - the interior curve no longer sits flush to the bottom of the brick.


In 2009, the 1X6X1 arch had its curve raised and the new top point of the curve now sits one plate below the top of the brick. If employed as an arched top to a door or window the difference is negligible but for other uses, such as adding inverted slopes underneath, it introduced an unwelcome vertical facet.

There was a clear benefit to the change too; a 'telephone bow' (part 93273) now fits inside the arch, and of course all bows with the same shaped curve do as well. This serves to highlight the important fact that the height to which the arch has been raised is less than the height of plate; it's the same as the height of the 'lip' on bows and slopes. So you can't put a full-width plate inside the curve of an arch.


In 2011 it was the turn of the 1X6X2; the original version being amongst the most beautiful of LEGO bricks in my humble opinion thanks to the semicircular curve and its proportion compared to the brick itself.

After I came out of my Dark Age and learnt of SNOT, one of the first things I tried to make was a perfectly round window from two of these arches. I quickly realised that this was not possible - the semicircle is in fact not quite complete. It's worth mentioning The Hobbit 79003 An Unexpected Gathering contains a near-round window created with two of these old-style arches, using clip light plates to set them at 180° and separate them slightly to fit a square 4X4 window pane (made of turntable bases) inside. It's really beautiful and a very advanced technique for a kids' set - actually, 79003 is one of my favourite sets of recent years.

For the new 1X6X2, the near-semicircle has been raised (again, by the height of a lip) which has resulted in the 'round window' technique looking much better, as seen above - but it's still not a perfect circle. The important thing is that you can now insert a 4X4 rounded part in the hole, with some small gaps, without needing to separate the two arches. Sweet.

Notably, the top of the 1X6X2's curve is fractionally higher than on the 1X6X1. I am guessing this exception is because TLG wanted to be consistent about raising all arches by the height of a lip and did not wish to change the shape of this particular curve - i.e. it was necessary for it to remain perfectly round. This additional height, plus the removal of the reinforcing bar inside the arch, permits a technique with the new 1X6X2 that none of the other new arches do: a centred plate can be placed in a stack of five underneath, as you see below. I doubt that this is the answer as to why this arch is different to the others, as this technique isn't terribly useful. I'd guess it's just an accident of the geometry and might even be considered illegal by TLG, if those parts are in fact pushing against one another at a microscopic level. But it seems fine to me.


Next came the new 1X12X3 arch, which BrickLink lists as first appearing in 2014 sets, but I got some in my Friends 41015 Dolphin Cruiser last summer. Which is another fabulous set actually! Doth arches maketh the set?

As with the others, it has been raised by the height of a lip. Again, no existing bows fit the new curve perfectly but I noted you can place a 45° slope underneath quite snugly - however there's no room to add anything onto the studs on top of the slope. Unlike other raised arches, the topmost point of the curve has remained in the same place as the previous version, which in this case is two plates from the top of the brick.


So as I began by saying, what we are now beginning to see in sets is the raised 1X8X2 arch; again with the bottom of the curve raised by a lip and the top one plate below the brick's top. Like the 1X6X2, the reinforcing bar underneath has gone.

There's no guarantee you'll get the new version in the following sets whilst TLG use up the old stock, but for the record it might appear in: 70133 Spinlyn's Cavern, 10674 Pony Farm and 41057 Heartlake Horse Show. BrickLink are yet to add this variant to their catalogue but if you're simply dying to get hold of one, BrickOwl have listed it.

Another aspect to the new 1X8X2 as well as the 1X12X3 is bound to irritate many AFOLs. The interior walls have been thinned, meaning you can no longer attach parts along the curve (as shown here with the old-style arches).

I've heard many, many AFOLs claim the thinning of walls (and other general changes like the tiny hole in the tiny pins on the undersides of bricks) is a cost-saving measure by TLG... i.e. using fractionally less plastic in each brick. Maybe it's a factor but I've never believed it is the primary driver; in this particular case I feel it's far more likely they're deliberately removing the ability to make connections that are weak and/or not in System. Ironically enough, the technique was actually used in an official set in 2007 - the seminal 10182 Café Corner. Perhaps it was later felt that the single point of connection was pushing the limit of TLG's internal guidelines of model stability. Or more fundamentally, the parts were deemed to be being used in a way that was out of System.

It's worth noting that on the smaller new arches, the walls haven't been thinned (or not that I can tell; parts still kinda stick to them). Maybe this is because smaller parts need more strength. Or maybe the Parts Designers are really really mean and know that AFOLs don't tend to use this technique with the smaller arches!


There is another arch I've not mentioned whose history is a little more complex, as it received more than one redesign - the 1X5X4 half-arch. First it got thinner walls, but then a rather odd change was introduced.

The curve was not only raised but also the top point was brought one stud inwards. This enabled a connection point underneath the topmost section of the arch - not a massively useful change. A couple of major benefits were lost too. The curve of the old 1X5X4 described a quadrant and so could be used to make a perfect 8X8 round hole. Also, the 1X6X3 1/3 half-arch (part 6060, seen in White above) used to fit perfectly underneath, whereas the new design leaves gaps.

[EDIT: Andrew Barnick and other readers have pointed out important news; the 1X5X4 arch has now reverted back to the same original curve as 2339! Rumour has it that TLG considered the curve of 76768 to be a mistake - so I guess this news confirms the rumour. The new part number is 14395. The walls are, of course, thin.)


As with all design alterations, there are pros and cons. TLG obviously weigh these up, and involve different departments in the decision-making process. Of course, the pros and cons as far as AFOLs are concerned are somewhat different, since TLG are driven by what's best for kids and keeping everything within System. In the case of these arch changes, I'm still a little puzzled. Changing the top of these curves to be one plate (or two) below the brick's top feels nicely in System, but as mentioned the 1X6X2 breaks the rule. As to the benefit of raising the curves by the height of a lip - perhaps one of you can enlighten me. Only the 1X6X1 shows any clear advantage to me... in fact, taking the lead from the telephone bow combination, I'd love it if the reason is that TLG intend to release new bows in the future designed to fit perfectly inside other arches. A semi-circular smooth brick to fit the 1X6X2 would be a really nice decorative part!

So, is this the end of the arch-raisings? The top of the curves on the 1X3X1 and 1X4X1 are already one plate from the top of the brick, so we're all good there. The 1X3X1 already has generous verticals at the bottom, larger than a lip. The 1X4X1, being based on a perfect circle like the 1X6X2, should not have the shape of the curve altered otherwise 2X2 round parts will not fit inside. I doubt it could be raised by a lip in any event, otherwise surely the top of the brick would become too narrow?

Love or hate the changes to our beloved arches, the fact of the matter is we're lucky enough to be able to pick and choose which style we want by buying from parts reseller sites... within the constraints of budget and colour availability of course!


  1. One thing that you might not have noticed but should add to this article is to compare the 1x6x1 arch to the back of the 62361 fender, which started appearing in sets about a year before the 92950 version of that arch. I think it's far more likely that this was the origin of the geometry, and the shape of the 93273 curved slope/bow borrowed that when it came along two years later.

    1. Good point, the fender is an interesting arch. I'm not convinced they would have changed the 1x6x1 and then all other arches simply because of this part though. I feel it's more likely the 'raise by a lip' rule was decided (for whatever reason) around 2007/8 and the fender was simply the first to appear in sets as others were waiting for moulds to be decommissioned.

    2. The odd thing about that fender element is that from the back it matches the underside of the new 92950 arch, but from the front it looks like it should match the old 3455 arch.

      Anyways, the only other part I can think of that might have forced that change to the 1x6x1 arch is the 61068/88930 2x4x2/3 curved slope, which, to be fair, did come out one year before the arch was changed. Anything else I would think fits imperfectly enough under the arch that they wouldn't have bothered.

  2. This makes me sad. Most of TLG's part changes highlight their genius and careful dedication. With these pieces, I always enjoyed making seamless transitions from 90* to curves.

    As someone preparing for a large castle build, this means I'll not be looking at new sets as parts packs but instead look exclusively in the secondary market.

    As always, however, I thank you for detailing so well the changes.

  3. Weighing the pros and cons, do you think there's more benefits or loses coming from this? As a rudimentary system MOCer, who doesn't understand all the applications here, it comes off as more of a loss. The only advantage I see here is tighter circles on the 1X6X2 arches and the telephone bow on the 1X6X1's while you guys lose the connection technique under the arches, the seamless fit of the curved brick, and like you said the vertical lip being present in all of them. The techniques lost seem more valuable than the ones gained. Is that a fair assessment?

    You bring up the point that now we can chose between the two in aftermarket resale. That's true but at some point won't it become really hard to find the old arches, won't the become coveted, rare and therefore more expensive? I don't know about you guys, but any lego I buy I don't intend to give back ever. Once I buy 50 through ball joint pieces from a store, that's 50 the whole world that could have bought them won't ever see again unless I die suddenly and my family has the wherewithal to open a Bricklink store and sell off my parts or sells it in bulk to someone else who does. Now that number is nothing but what about you guys who buy quite a lot of a part, such as Nate buying arches for his Castle? With that in mind I can't shake the feeling of "You don't get this anymore there will eventually be no more of this for anyone." And that makes me sad and frustrated.

    1. My assessment is the same as yours. It seems to me this a case of TLC making changes in support of their primary target audience (though we may not understand the particulars) at the expense of us AFOLs. It's pretty disappointing but I guess there isn't a whole lot we can do about it.

    2. Personally, I see other advantages to the new arch designs in many cases. For one, raising the point where the curve begins means that an arch is not quite so obligated to be in line with the studs directly under it. If you had a half-stud offset between the old 1x6 arch and the studs directly under it, then it would collide, while that's not the case with the new one.

      The 1x6x1 and 1x6x2 are definitely the arches that have benefited most from the change, since they are the two that have parts that fit almost seamlessly within the curve. Less is gained from the change in the 1x8x2 (though you still gain the ability to fit slopes underneath as with the 1x12x3), and naturally there's nothing at all to be gained by changing the 1x3x1, which already has a sizable offset.

  4. As far as the thinner inside walls on the 1x2x8 arch, could that be done in order to "legalize" previously illegal builds?

    I am remembering a document I saw about the stress on bricks (I believe it was prepared by Jamie Berard) which showed an illegal build of a 1x2 plate with 1x4 bracket and a 1x4 tile attached to the bracket part, with this assembly placed up inside the arch of a 1x1x6 arch.

    It seems like if the TLG design team decided to thin those walls slightly (thereby widening the interior dimension), it might be to create a space that could fit a bracket and tile (one-and-one-half plates). Although why they would favor that over a space the width of a stud is lost on me.

  5. Great article, precisely why I love this blog..... brilliant!

  6. As I commented on FB, I believe 76768 has in fact been replaced again by the more traditional-looking 14395. None of my recent sets with the 1x5x4 half-arch contain 76768.

    1. I get it now - great news! Thanks Andrew. I did notice 14395 when researching the post, but assumed it must be some minor change that happened before 76768 came along. I think I'll update the post with your news.

    2. I can see how you might get confused. Larger design IDs tended to belong to more recent parts, but evidently when the LEGO Group rewinded to five-digit numbers starting with one after running out of five-digit numbers starting with nine. So most of the newest parts have numbers in the form of "1xxxx".

  7. I would like to point out that part 62361 (1x6 mudguard) follows the same trend with the arch raised by a lip. It follows the shape of the 1x6 arch precisely.
    On of my first thoughts about why they would have raised the arches was that when you put e.g. the 1x6 on a studded plate, the studs won't penetrate in the arch. But since they don't go anywhere near the walls, that can't be the reason.

  8. Thank you for writing another interesting article!

    I noticed that the images for the 1x6x2 and 1x8x2 arches show the same DesignID numbers by mistake.

  9. I have discovered that both 2339 and 76768 has 2 variations of the thickness on the curved wall on each side. On the arch with the thick wall, You are able to place 1x1 round plates, but with the thin wall they can't. Problem is how BL sellers knows about this.

    1. I'm surprised there are 76768 with thinner walls. Thanks Søren