The Unofficial LEGO Technic Builder’s Guide

I often get asked how I come up with the mechanisms that power my models. There’s no real secret to it. If you take a look back through the history of human invention, you will find a treasure trove of solutions to pretty much any problem of moving some object, or collection of objects, from one point to another. Since the Industrial Revolution, and the advent of mechanical automation, the number of such mechanisms has exploded, and you can fall very far down the rabbit hole of YouTube videos watching these beautiful, hypnotic and fascinating devices.

So, finding cool mechanisms isn’t really the hard part. It just takes time and research. The real challenge lies in translating these mechanisms into LEGO form, and a large part of succeeding at that is knowing what LEGO Technic pieces exist and how they can be used. In the past, I usually suggested the best way of becoming familiar with the LEGO Technic system was by building a bunch of Technic sets.

Upon further reflection though, this probably isn’t the most efficient way of doing it. Any given set only has a subset of the parts that are available in the system, and buying a lot of sets can get very expensive very quickly. Not to mention, buying current sets won’t expose you to the useful parts that may be out of production, but still available on the second hand market. Also, building instructions show you how all the pieces go together, but they don’t explain the underlying engineering principals behind why they are put together in that way. It can be very easy to just merrily follow the building instructions and by the end have a cool model with little understanding of what is actually going on.

Unofficial LEGO Technic Builder's Guide

Enter The Unofficial LEGO Technic Builder’s Guide (Second Edition), authored by well known builder Paweł Kmieć, better known as Sariel in the online world. He has a very popular YouTube channel where he showcases his incredible custom Technic models and does Technic set reviews. Full disclosure, I did receive a free copy of this book from the kind people at No Starch Press but, having now read through most of it, I have no idea why I never bought the first edition. Here we have a book that has managed to capture, in one concise volume, the knowledge that would otherwise take years of experience with the Technic system to accumulate.

This book starts off covering the fundamental concepts that are critical to pretty much any mechanical creation, including speed, torque, friction, efficiency, backlash, etc. It’s a great refresher of some key engineering concepts, even if you are well versed in Technic building. Next up is a summary of all the basic Technic parts and how they work together. The Technic system has evolved a lot over the last 30 years, and this section discusses these changes in detail. Even as an experienced builder, I still found this section very informative. As an example, I never really knew what the point of the 4L axle with stop was, until seeing it plainly illustrated here.

4L axle with center stop

I was quite excited by the next section of the book, which covers basic mechanical concepts. This includes gears and chains, pulley systems, levers and linkages, pneumatic devices and techniques for reinforcing Technic builds. There are all kinds of useful mechanisms illustrated in this section, including ratchets, couplings, differentials, clutches, valves, compressors, etc. These form the fundamental building blocks of Technic models, and not only are they explained in detail, but instructions are included to show you how you can build them yourself.

The chapter on levers and linkages was of particular interest to me, and it was pretty cool to see systems like Hoeken’s linkage included, which is what drives the legs of my Sisyphus model. If there was one chapter in this entire book that I would have liked to see expanded, it would be this one. There are a lot of cool linkage systems out there, like those I used in my mini AT-TE and Steampunk Walking Ship, or the legs of my galloping horse, that I think would have been very interesting additions.

Hoeken's Linkage

Another section of the book covers motors, including a detailed look at all the Power Functions and RC system components, and the final section includes general tips on building models, which covers many of the challenges faced when trying to build scale models of real world machines.

The shining glory of this book though, and the section that is perhaps the most interesting and useful, is the one on advanced mechanics. This section spans almost 1/3 of the entire book, and rightly so, as these are the components that form the heart of a model’s behaviour. This section covers, in great detail, steering and suspension systems, various types of transmissions, adders and subtractors, and planetary gearing systems. Again, in addition to explaining how these systems work, building instructions for many different systems are also included, which will give you a solid starting point to incorporating them into your own models.


Setting aside the fact that this book is targeted towards LEGO Technic builders, it is fair to say that this is also a great reference for mechanical systems in general. Ever since I built my first Technic set, I have always been amazed with how the LEGO Technic system can be used to accurately recreate many mechanical systems. Had I owned a book like this when I was a child there is no telling what elaborate models I would have built.

From a technical standpoint everything in this book is clear and concise. The text is clear and easy to read. The illustrations and instructions are clearly rendered and easy to follow. Sprinkled throughout the book are photos of Paweł’s beautiful models, to give you inspiration and show you what is possible.

So, is this book worth purchasing? If you don’t have the first edition, and you are looking for a resource to expand your Technic knowledge and take your building to the next level, then I think this is a must have. I personally think the building instructions alone are worth the price of admission. If you already own the first edition, then the answer is less clear. There are 4 new chapters in this edition, which include discussion of wheels, planetary gearing systems, the long out of production LEGO RC system and custom 3D printed parts. 13 of the other chapters have been updated with new information, but I can’t speak to those changes since I don’t have the first edition.

Ultimately the choice is yours. All I know is that I have only had this book for a couple of weeks and I think it is already the most read book in my LEGO library, and I know I will continue to refer to it again and again in the days, months and years to come.

You can find more information about The Unofficial LEGO Technic Builder’s Guide, or purchase it, from No Starch Press using this link.

Tales from the LEGO Crypt

In just under two months, the Pop Up Book project Grant and I posted to LEGO Ideas has obtained 5,000 supporters, which is half way to the 10,000 needed for it to enter the LEGO review! This is a huge accomplishment, and we would like to thank everyone who has supported us so far. To celebrate reaching this milestone, and since Halloween is only a few days away, I thought it would be cool to build a spooky interior for it.

For this interior I wanted to incorporate some interactive features, which you often find in traditional pop up books. The ghost coming out of the crypt can move up and down as you rotate a gear in the back (achieved via a small piston inside the crypt), and you can make the skeleton in the open grave rise up using a small lever beside it.

I also decided to try building the book in a different color and add some decorative pieces to the front of it. I’m really pleased with how it turned out, and think it adds a little more interest to the exterior of the book. I had a lot of fun adding the spooky details to it, which include some jack-o-lanterns with creepy vines, a skeleton digging his way out from a grave, a Dementor coming through the fence, and the detailed crypt.


Halloween Chocolate Thrower

For Halloween this year I thought it would be an interesting challenge to break out my LEGO Mindstorms EV3 set and build a robot for dispensing candy. These mini chocolate bars are pretty common where I live, so building a machine that would toss them at the kids seemed like a great idea!

It uses the EV3 Infrared sensor to detect when something is in front of the machine to trigger the delivery mechanism. The chocolates are stored in a gravity feed stack and are pushed out from the bottom using a simple piston arm. Once they are pushed out, they land on a platform that is rotated up to throw them.

I designed the feed system to be adjustable, so it can accommodate a range of these mini chocolate bars. Or pretty much anything that will fit and stack reasonably well.

The building instructions and program file for running it are here, and there are some construction notes below, along with the wiring info.


Building Guide

PDF File

Digital Model Files

LDraw File

Instructions for wiring the motors and sensor are as follows.

Infrared Sensor: Port 1
Motor under the throwing platform: Port A
Motor under the feeding tower: Port B

This robot performs best with items that are rectangular and stack well. Some mini chocolates which are rounded on the top might not stack so well, so you might get mixed results with them. All the chocolates I showed in the video work quite well.

I had an absolute blast building and playing with this model, and eating all the chocolate that’s been lying around! I hope you have fun with it too.

Chocolate Machine

Hoberman Sphere Stand Instructions

It’s not often that I revisit older models, and even more rare that I’m able to provide instructions for them. Many of those models just aren’t together anymore, so going back and reverse engineering them would take time and effort that I’d rather use to create new things.

On rare occasions, dedicated builders will spend the time to got through the video and photos I created for those models to build their own versions. This is a huge accomplishment in itself, but in this case Kevin Williams not only built his own copy of my Hoberman Sphere stand, but also saw fit to create instructions so that others could do the same.

A huge thanks to Kevin for doing this! I know how much time it takes to put together instructions, and I’m really excited that he’s done this for one of my models. Most of the time when people ask me for instructions, I have to say, ‘No, sorry, I never made instructions for that one.’ Now I can finally say yes for one more model! 🙂


Building Guide

PDF File

Digital Model Files

LDraw File

Additional Resources

Parts List


He’s also designed a hand crank for it, which is a pretty cool addition, and included the modifications you need to make to the Hoberman Sphere to be able to insert it into the stand.  Also included are instructions for powering it using the old LEGO 9V electric components, which is what I originally used. There are probably not many of those around these days, but it should be fairly straight forward to swap in some Power Functions components instead.

My original instructions for building the Hoberman Sphere itself, along with a video of it in action, can be found in my original blog post for it.

Stand Open


The Dragonfly

Kristal has been building again, and the result is this kinetic LEGO sculpture of a pair of hands releasing a dragonfly.

There are a couple of things I really like about this model. The first being the contrast of the monochromatic exterior (with the gray hands and subtle detailing of pond life on the black base) with the small little punch of colour on the interior.

The second being the relatively simple, but elegant, mechanics of the interior, which allow all of the motion to be controlled using a single crank on the side of the base. As the hands open, the dragonfly lifts off from the surface of the pond and its wings begin to move. As you reverse the direction of the crank, the dragonfly lowers back down and the hands come back together.

You can watch the video in its entirety to see exactly how it all works together.

Dragonfly Open


Jason Strikes Back!

This week marks three years since I built my Ultimate Useless LEGO Machine! In all that time, I still haven’t figured out a way to turn it off. At last I will have my revenge! Or will I?

There is actually some cool programming going on here. The black box and the hand robot coordinate their behaviors using the Mindstorms Bluetooth capabilities. I have to say, I was super impressed with the ease and performance of this feature. Kudos to the EV3 team for such a fantastic implementation!

Despite what it might look like, the black box robot is actually driving the entire sequence. It sends messages to the hand robot to tell it what to do, then it either does an evasive maneuver, or waits for the hand to turn the switch off.

It responds to the switch being turned off the same way it always has, using the light sensor inside. It doesn’t use the proximity sensor to detect when the hand is there though. Since it is telling the hand what to do, it always knows what is going on. The hand would always trigger it anyway, since it is always above the sensor.

Instructions for building the the black box can be found in my original blog post. I haven’t put together instructions for the hand robot. Had a lot of fun making this video, hope you enjoy it!

LuuMa Hand

Escape From Jakku Maze

It’s been on my todo list for a while to see what kind of maze I could design by combining the parts of another LEGO set with the 21305 Maze set. I finally decided to see what I could come up with using 75099 Rey’s Speeder.

I wanted to keep the theme of the maze related to the set, so this maze has you navigating the alleys of the Niima Outpost, avoiding the scrap piles, and eventually getting to the Millennium Falcon in order to escape from Jakku. Despite the limited selection of parts, I was able to design a couple of dynamic obstacles, including a rolling canister and swinging pendulum, which are pretty easy to get through, but will slow you down if you are trying to do a speed run.

It is a variable difficulty maze, in the same style as the other mazes I’ve designed, so that you can increase the difficulty by progressively removing the tan 1×2 log brick pieces. Instructions for building it can be found below the video.


Building Guide

PDF File

Digital Model Files

LDraw FileLDD File

Additional Resources

Parts List



Jakku Maze

Pop-Up Book Adventures

I couldn’t resist using the LEGO pop-up book to make a little video retelling the stories of Little Red Riding Hood, Rapunzel and Humpty Dumpty. With my own little twist of course! I hope it illustrates how much fun you can have with this model. Kristal and I certainly had a lot of fun making the video.

If you’d like to see this model potentially become a real LEGO set, head on over to the LEGO Ideas website and add your support:

Here are pictures of the two new interiors I created to make the video. Rapunzel’s tower.


And Humpty Dumpty’s wall.

Humpty Dumpty

Pop-Up Book Ideas Project

A few months ago I was approached by a fellow builder, the very talented Grant Davis, to help flesh out an idea he had for LEGO Ideas – a fully functional LEGO pop-up book. Of course, I was already familiar with Grant’s work, and was really impressed with his original pop-up book when he posted it on YouTube a couple of years ago, so I jumped at the opportunity to help him with this project.

We finally put the finishing touches on it a few days ago and it is now live on the LEGO Ideas website, so if you’d like to see it potentially become an official set, be sure to head on over there and add your support:

You can see the book in action in this showcase video we put together.

The book features a simple and reliable mechanism, built around a couple of constrained Technic axles, to raise and lower the main pop-out scene. We also added a clasp to the keep it closed, so everything remains securely inside when you are handling it.

The aspect of this project that I am most excited about is that you can completely customize the interior scene to tell any story you can imagine. I think it really expands on the core values that already exist within the LEGO system, especially exercising your creativity and imagination.

I designed a couple of interiors for the book, including a cottage and castle, which could serve as the backdrop for many popular fairy tale stories. I also have a few more in the works, which I’ll be posting over the coming weeks with some other updates to the project. Stay tuned!




Remote Control Monowheel

Towards the end of last year, with the release of The Force Awakens on the horizon, I started conceptualizing what a LEGO BB8 droid might look like. That project hasn’t gone very far yet, but in the process of prototyping I also started working on this (much simpler) monowheel model. You can see it in action and how it works in the video, but there are some more notes and photos below as well for those interested.

The core engine of the model is designed using a counterweight system, with one Power Functions M-motor used to propel the wheel and another one for steering. The steering motor slides the counterweight from side to side inside the wheel to tilt it, which causes it to turn. The propulsion motor just rotates the wheel around the engine core.

There are some issues with the steering system, most notably there is no means of self-centering using the M-motor, which means bringing the counterweight back to center is hard to do reliably. I tried to use a Server motor in some early prototypes, but there just wasn’t enough space inside to fit it. I do have some ideas for improvements though, so hopefully I can refine it in the future.

The wheel also has a tendency to fall over due to the erratic steering. I think that’s just a matter if increasing the size of the lip that runs around the edge of the wheel track, but I’ll experiment with some other solutions as well.

The track is built using flexible tubes (also called rigid hoses), wrapped around the sidewall discs. Each tread of the track is created using a couple of curved slopes, and slide onto the flexible tubes through some Technic bricks with Axle Holes.

Despite the performance issues, it is still pretty fun to play with, and if I iron out some of the problems I’ll put together instructions for a future version.