Lego Build Diary: 10303 Loop Coaster

29 August 2022

When Lego announced a replacement for the retired 10261 Roller Coaster I knew immediately I'd be buying one. I had wanted the old set for years but never had the space to display it, and when I finally did have space, the set was retired.

I finally got my hands on the new 10303 Loop Coaster at the beginning of July and I was so excited to build it that I live tweeted the process with lots of photos.

I've collected all those tweets here for better preservation of the build diary.

It all started with me tipping out all the bags onto the floor and tweeting a before and after.

A disorganised pile of bags of lego on the floor

The same lego bags but organised by number into 16 piles

From there, it turned into a spontaneous thread with over 100 tweets. I've replicated the thread mostly as-is below.


Another brick separator for the collection.

Twelve orange brick separators (plastic wedges with two lego studs at the thick end) lined up in two rows of six

The instruction book has 454 pages of goodness.

The instruction book for the lego looping roller coaster

We’re at a theme park so of course a wide array of colours to work with.

8 pots of lego sorted by colour. There are reds, blues, greens, browns, blacks, whites, tan, and a pot of minifigure parts

The gang’s all here.

Eight lego minifigures standing side by side. There’s a person in a chef’s jacket and red baseball cap, a person in a green hoodie, a lady in a pink blouse, a woman in a blue and white striped shirt, a man in a red leather jacket, a person with blue hair and a blue cardigan, a person in a white shirt with pictures of balloons, and a child with a denim jacket.

Where can I get this shirt?

A closeup of a lego minifigure wearing a white shirt with pictures of balloons and candy floss. They’re also wearing purple trousers and a pink baseball cap.

Pretty sure this guy is a chaser…

A closeup of a lego minifigure with slicked back hair and sideburns. He has orange tinted glasses, a red leather jacket, and jeans.

Congrats on your transition timeline, total glow up!

A closeup on two lego minifigures. On the left is a man with light brown hair wearing a green hoodie over a black tshirt with an EQ visualiser design. He looks sad. On the right is a woman with blue hair and a blue cardigan over a pink flowery top. She looks happier and she’s wearing eyeliner and lipstick.

As soon as I turned the page in the instructions, I spotted immediately that the typeface Lego uses has changed. There's a distinct difference in the shape of the number 2. The one on the left is the newer one.

Two lego instruction pages overlapping so that both have a number 2 side by side. The new version has a distinctly different shape

Adorable squirrel and a lovely map with references to older amusement park sets.

A lego bench next to a sign showing a map of an amusement park. In front of the sign is a squirrel.

A close up of the squirrel and the sign

I need to find more of these balloon dogs to make earrings.

A balloon cart attached to the back of a bicycle. There are four classic round balloons and two translucent blue balloon dogs

A closeup of one of the balloon dogs

I am also desperate for lego hot dog earrings.

A lego hot dog cart shaped like a giant hot dog with the sausage poking out at each end. On top are two sausages and two buns, and a ketchup and mustard bottle.

A closeup of a lego hot dog with a curved red sausage in a bun

Who’s paying 4 currencies just for mustard?

A closeup of the sign on a lego hot dog cart. A plain hot dog is listed as 5, and a hot dog with mustard is 9.

And if a whole hot dog costs 5 how can they justify 7 for a pretzel??

A lego pretzel cart. It’s red and white and there’s a pretzel sign on the roof.

A closeup on the cart showing the sign, where a pretzel costs 7

It has been correctly pointed out to me that these pretzels are HUGE and therefore totally worth 7 currencies (it’s bigger than her head!)

A lego minifigure holding a pretzel that’s almost as big as her torso

I already have lego pretzel earrings 😏.

A selfie of liv wearing earrings made from lego pretzels

This brings us to the end of the “accessories” arc.

Four small lego models. From left to right there’s a pretzel cart, a bench and amusement park map, a balloon cart, and a hot dog cart shaped like a giant hot dog

What does a roller coaster need? A train of course! With working lap bars even.

A lego roller coaster train with 3 cars. They are two shades of blue. There are minifigures in two of the cars, one with the lap bar up and one with it down

Considering this is going to be a looping coaster I think I’d use shoulder restraints instead of lap bars, but good luck making those out of Lego.

On to bag 2: seemingly just the floor judging by the colours and pieces.

Seven small tubs of lego sorted by colour. The pieces are mostly grey and green, but there are a few red, brown, and blue pieces

Lots of floor nubbins, presumably for attaching buildings and coaster supports to.

A rounded rectangle of green lego with many strips of tiles that have a single stud in the middle

Bag 2 is over already with all these little foundations.

A rounded rectangle of green lego with grey rails around the outside with tiny hooks at each end

Onto bag 3 and we’re already starting some of the track!

Six tubs of lego sorted by colour. There are grey, black, red, blue, and yellow pieces. The tub with the yellow pieces contains some roller coaster track.

I don’t know why I’m surprised but these are really convincing roller coaster supports.

A partially built lego set. There’s a green base with grey railings, and dark blue poles sticking up from where the railings meet

The first piece of track is in! I feel there’s quite a lot left before it’s a functioning roller coaster…

A partially build lego roller coaster. There are nine support poles and a tiny piece of track supported by four of them.

Escaping the confines of the base.

A partially built lego roller coaster that only has a few supports on a green base. One of the support poles has a horizontal strut attached that extends outwards off the base

I feel this is quickly going to outgrow the space I have for building Lego.

I believe this section of track is the ending segment coming back into the station.

A partially built lego roller coaster with a section of track that does a 270 degree turn while going down a slope

(This was the end of bag 3).

Bag four? More like bag floor.

Seven plastic tubs of lego sorted by colour. There’s a lot of green and grey, and a few red and blue pieces.

This is just one part of the floor from bag 4, so this set is going to be huge.

A rectangle of green lego that’s 50 studs wide by 17 studs deep

Holy guacamole this is big. There may still be more floor to build, and it has to connect up to the section from bags 2 and 3.

A big rectangle of green lego that’s 50 by 30 studs. There’s a cutout in the middle of the rectangle.

This looks like a path to me so this is most certainly the entrance to the queue.

A lego structure with a flat pale brown section on the floor. It’s four studs wide and zig zags a little bit.

It’s a tiny thing but I love how they designed the subtle zigzag of the path using the triangular pieces.

At the end of bag 4 and it now takes up the entire width of my building space.

A partially built lego roller coaster with a small curve on track on the right side, and unfinished floor on the left side. It’s so wide that the edges of the desk it’s being built on are visible

Bag 5: leaves, railings, and one lonely piece of support pillar.

Seven tubs filled with lego sorted by colour. Most of the pieces are light grey, but there’s a tub with a handful of green leaves. The tub of blue pieces only has four, one of which is a cylinder used as a support for a roller coaster.

Lego designers are on another level, example #32,837: this random hinge piece that was added in bag 3:

A closeup of a lego roller coaster support pillar. There’s a grey piece clipped to the pillar that doesn’t attach to anything.

Turns out that two bags later you rotate it down to clip onto this railing you didn’t even know would be there (remember this pillar is on a separate base to this new section).

Teeny tiny support pillars.

A closeup of two lego roller coaster supports. One is a single brick high, and the other is only as tall as a single tile.

What are these Mysterious Contraptions? … I literally don’t know yet.

A closeup of three lego structures that are grey rectangles with black pins sticking out the front

Bag 5 complete!

A partially built lego roller coaster. On the right hand side is a small curve of yellow track that’s not connected to anything. The rest of the build is mainly grey railings in a grid layout.

Bag 6: a little bit more track, and the entrance to the queue line (yes I can tell just from looking at the pieces, the light blue tiles give it away).

Six tubs of lego sorted by colour. Most of the pieces are grey or dark blue, but there are some yellow roller coaster track pieces and three light blue tile pieces.

It wasn’t a tiny support pillar, it was the foundation for the stairs!

A set of lego stairs leading up to a small grey platform

With a cute little ladybird at the top.

A closeup of the top of a lego staircase where a ladybird is sitting

This is the bottom of one of the loops.

A partially built lego roller coaster. There are two slopes of yellow track side by side which aren’t connected to anything

The entrance, which sadly bans the cute little squirrel from riding.

The entrance to a lego roller coaster. It’s a yellow arch with a sign saying “entrance”, a poster that bans hats, balloons, hot dogs, and squirrels, and another sign with a measuring scale showing how tall you have to be to ride.

Bag 6 complete!

A partially built lego roller coaster. The left side is mostly empty and on the right side is a few pieces of disconnected track as well as an entrance archway.

Look at all these track pieces in bag 7.

Seven tubs of lego sorted by colour. Most of the pieces are dark blue, and there are a lot of yellow roller coaster track pieces.

Someone has carelessly dropped their balloon and now it’s trapped under the tracks.

A lego roller coaster track with a red balloon under one of the track supports

Lots of technic shenanigans to get the vertical loop curves in place. I don’t even know how they designed this.

A half finished loop of a lego roller coaster

Loop number two straight in, a less complex design because it’s a smaller loop.

A lego roller coaster with one small loop and a half finished bigger loop

Not quite enough track to get round the loop yet.

And the second loop completes bag 7.

A half built lego roller coaster with a mostly empty left side and two loops on the right

The train can now make it through the smaller loop.

Bag 8 is a weird one: there are so many blue pieces I had to subdivide by type as well as colour.

Seven tubs of lego sorted by colour. One tub has yellow pieces, one has grey pieces, and the rest all have dark blue pieces.

From bag 8 onwards most of the rest is built in little isolated parts that are attached to the coaster when they’re done, rather than building on the set as a whole. So before it gets too unwieldy I’ve taken the opportunity to move what I have so far to its intended location.

I literally had to rearrange half the furniture in this room to get the coaster to fit anywhere.

A partially built lego roller coaster displayed on a white cabinet

This section is comically long.

A long straight structure made of dark blue and yellow lego. It stretches almost across the entire desk.

Bag 8 complete: it’s a… ladder?

A dark blue ladder shape made from lego seen from above laying flat on a desk

Bag 9 has this very dissatisfying mixed colour pot because there are two types of blue pieces that need their own pot.

Seven tubs of lego. Five contain blue pieces, one contains yellow pieces, and the last one has a mixture of red, black, and grey pieces.

The moment you realise you’re in for a repetitive time…

A section of lego instructions showing that a step requires 8 of one piece and 48 of another

To be honest, it was nowhere near the most tedious step of Lego instructions I’ve ever done.

Eight small blue pillars made of lego

When you have to build loads of the same thing so you make a little production line.

Four piles of lego pieces and four partial builds of a specific segment where all four are the same

Now it’s a ladder for climbing 4-dimensional objects.

A lego structure that looks like a ladder where each of the rungs has another smaller ladder attached perpendicular to it.

Bag 9 complete: there’s track on my ladder!

A lego structure that looks like a blue ladder with yellow roller coaster track down one side.

Bag 10: there’s definitely been a theme for the last few bags.

Seven tubs of lego. Four tubs contain dark blue pieces, one has grey pieces, one has yellow pieces including roller coaster track, and the last one has black and brown pieces.

It’s officially too big for my desk.

A lego structure that’s so long it doesn’t fit on the desk and is resting on a filing cabinet next to the desk.

Bag 10 complete: someone please buy me a bigger desk.

A lego structure that looks like a blue ladder with yellow roller coaster track down two sides

Bag 11 is looking a bit short on pieces if you ask me…

Six tubs of lego sorted by colour. The tubs aren’t very full and only contain a handful of pieces each.

Yet more incredible lego engineering with this 90 degree curve that’s made from two flat curves perpendicular to the rest of the track and still forms cohesive rails.

A closeup of a lego roller coaster showing two curved pieces on their side relative to the rest of the track, forming a 90 degree curve going from flat to vertical.

Loop (or LBP I suppose if you want to imagine a Sackboy-themed roller coaster).

A small lego structure that spells the word loop out of light blue tiles. The Os are joined together and look almost like a capital B.

Bag 11 complete: the tower is installed! I had to stand on my office chair to get the top parts attached.

A lego roller coaster with a vertical drop and two loops. The track isn’t quite complete and cuts off at the front.

Another angle of the roller coaster showing it in scale next to a bookcase, with the tip of the lift tower taller than the bookcase nearly reaching the ceiling.

Double loop action!

Bag 12: wow that’s a LOT of chain pieces.

Seven tubs of lego sorted by colour. There are two tubs of dark blue, a tub of light blue, three mixed tubs, and a tub full of black chain link pieces.

Time to start mechanising!

A small lego structure that’s rectangular with a cutout where a gear is mounted.

That’s a lot of tiling to do.

A very long lego structure that’s mostly grey on top but the very end has a pattern of tiles in different shades of blue forming diagonal stripes.

It was indeed a lot of tiling.

A long thin lego structure that has diagonal stripes in two shades of blue.

Send help…

A screenshot from lego instructions showing that the next step requires 33 of one type of piece and 222 of another type.

Bag 12 complete: we have the beginnings of a lift!

A lego roller coaster with dark blue supports and yellow track. It has two loops on the right and a tall tower on the left.

A closeup of the tower showing a chain that stretches from the bottom to the top.

Bag 13 has lots of wheels and a Mystery Box.

Seven tubs of lego sorted by colour. There are lots of grey wheels, and a small square cardboard box that only says “6219055”.

This is somehow going to be a lift carriage and I do not know how.

A small lego structure with two thin walls on the sides, a slightly thicker wall at the back, and four wheels on the inside of the walls.

It wouldn’t be a lift carriage without some more wheels.

A small square lego structure with four wheels on the bottom and two sets of thinner wheels on the top.

Okay more wheels I guess.

A small lego structure with four wheels on the bottom, two sets of two thinner wheels in the middle, and two red wheels on the top.

You can’t be serious, it doesn’t need more wheels.

A small lego structure with four wheels on the bottom, two sets of thinner wheels in the middle, and a pair of red and a pair of grey wheels at the top.

Phew, that’s all the wheels, time for some string.

The back of a lego structure that has a shooting star design. There’s a long piece of string attached to the top and coiled up on the desk.

TRICKED YOU, MORE WHEELS!

A lego structure with fourteen wheels in various colours placed in the corners and down the sides.

And finished off with some railings.

A lego structure with a shooting stars design above two bright yellow rails and a piece of string attached to the top that trails off screen.

Bag 13 complete: a carriage to be lifted up using the chain from bag 12.

A closeup of the bottom of a chain lift of a blue and yellow lego roller coaster.

I don’t believe it, bag 14 has EVEN MORE WHEELS.

Seven tubs of lego sorted by colour. There are light grey, dark grey, black, and beige coloured wheels of various sizes in the different tubs.

Ah yes of course it’s a… uh…

A lego structure with holes in the front and black legs sticking out the side. There’s a small yellow lip below the holes, and triangles in two shades of blue on the top.

It goes at the top of the tower to stop the lift coming off.

A closeup of the top of a tower on a lego roller coaster showing four black pegs at the top.

Minimalist tron bike?

A lego structure with a wheel at each end and two bars connecting them together.

The counterweight for the lift is technically made of another roller coaster train.

Two dark blue lego roller coaster cars attached together.

The roller coaster cars upside down embedded in a black box with sloped sides.

Cute little ratchet mechanism for the pulley.

A lego structure with string wrapped around a spool attached to two gears. There are grey pegs resting on the gears so they can only turn in one direction.

Counterweight installed on the back of the tower.

A closeup at the top of the tower on a lego roller coaster. There’s a pulley mechanism and a black block acting as a counterweight.

The mechanism is getting more complicated…

A closeup of the base of a lego roller coaster. There’s an axle connected to the bottom of a chain lift and extending out into the open.

Now there’s a tyre linked to the chain lift.

A closeup of a lego roller coaster showing a tyre on its side connected up to the chain lift using a series of axles.

Only one tiny segment stopping the track being a full circuit now.

The track of a lego roller coaster showing the final curve before reaching the chain lift again. There’s a tiny gap between the end of the track and the lift.

Feeling cranky.

A red hand crank attached to the base of a lego roller coaster.

Bag 14 complete: I'm very close to being able to run this thing now.

A lego roller coaster with blue supports and yellow track. It has a tall tower on the left leading into a vertical drop and two loops before curving back round to the beginning. There’s a chain lift going up the tower. A tiny segment of track is missing between the end of the track and the lift.

Bag 15 is the final bag! I see the teeny tiny track piece we’ve been missing, and some surprise new minifigures.

Seven tubs of lego sorted by colour. The yellow tub has a tiny piece of roller coaster track, and there’s a tub filled with pieces to make three minifigures.

I’ve never seen this on a lego person before, I think she has a hearing aid!

A lego minifigure in a yellow polo top and blue trousers. She has what looks like a hearing aid on the side of her head.

You’re telling me a queer coded this minifigure?

A lego minifigure with bright red short spiky hair, a denim jacket, and denim trousers. They have pale pink lipstick and freckles.

The control panel is quite realistic, especially the OH NO IT’S ALL GONE WRONG button

A closeup of the control panel for a lego roller coaster. It has various lights, switches, and dials, and a big red button.

These little queue gates are cute.

A partially built lego ride queue with three queue lanes that have tiny barriers at the front.

The roof of the station is made from track.

A roller coaster station platform with a roof made of curved yellow track pieces.

The naughty squirrel hasn’t been following the rules.

A lego roller coaster station with ride photos displayed on tv screens. One of the photos has someone dropping a hotdog while on the ride, and another has a picture of a squirrel with its nose pressed up against the lens.

The station is in!

A lego roller coaster station. It has a curved yellow roof with grey tiles, a blue striped design on the front, and blue and orange lights down the supports.

The track is complete! I was half expecting them to make me wait and put this piece in last.

A lego roller coaster focusing on the station and chain lift, showing the final piece has been placed to form a full circuit.

It feels a bit anticlimactic that the last piece you put in is the tree.

A lego palm tree in between the station platform and entrance archway of a roller coaster.

The moment we’ve all been waiting for: the completed roller coaster doing a full circuit!

The question on everyone’s mind: is it actually a good ride? Roller coaster tycoon tells us that… no, you may sustain grievous injuries if you ride it.

A screenshot from roller coaster tycoon showing a coaster with yellow track and blue supports. It has a vertical chain lift, a vertical drop, two loops, and a small circuit to get back to the station. The stats screen is open showing a low excitement rating of 1.6, an ultra extreme intensity rating of 16.08, and a very high nausea rating of 8.92. The maximum vertical g force is 6.58 and the maximum lateral g force is 3.25.


This was the first time I've made a build diary like this but I think I'll be doing more in the future!