LEGO Education kit 9686, or equivalent subset of parts
Printable building instructions and parts inventory: phone_racer.pdf

Ok, I admit it – I’m not a huge video-gamer. I’d rather play strategic board games. And when it comes to racing, I’d rather be moving at high speed with at least two wheels spinning under me. But I am a huge fan of LEGO and I love my iPhone. So, when I see people combine the two, it gets my attention. Such was the case a few years ago, when this video was shared on The Brothers Brick LEGO blog, showing a tiny racing simulator. “What a cool idea,” I thought, “and I bet I could improve on that design.” I tried a few methods using gears, chains, and rubber bands, but in the end, settled on a simple linkage of levers held together with friction pegs. The resulting “driving” experience is smooth and satisfying. It’s just removed enough from directly holding the unit to create a novel experience.

This model can be divided into subassemblies:


Taking it further:
This project demonstrates just one way to solve a problem. I’d encourage you to experiment and see how else it can be done. For example, I built a totally different solution using only the parts from a current LEGO kit 42007. Or, try expanding or improving upon this design. My husband built an alternative base that allows the user to adjust the angle of the display and steering by turning a knob. Other ideas: Stabilization could probably be accomplished in a more elegant-looking way. And I’d love to see a nice solution for the need to tap the screen while driving. (Because the iPhone uses a capacitive touchscreen, you should be able to integrate some wire and conductive foam to trigger the effects of gas and brake pedals.)

Finally, if you’d like to read more about using LEGO TECHNIC and the basic principles behind building your own machines, I recommend taking a look at The Unofficial LEGO TECHNIC Builder’s Guide by the Polish builder known as Sariel. A good portion of the book is available for free viewing via Google Books or

Have fun!

Project Steps

Construct the base.

A sturdy base will be the foundation of your model. This one uses two connected triangles to keep things in place.

Construct the core.

This section will be at the center of your model when it’s finished. Notice the long black axle. This will later receive your steering wheel.

Construct the phone holder.

This is a simple frame which serves to keep your phone secure. It also includes elements that drive the steering. Note the use of two dark gray TECHNIC “half-pegs” in the round pulley. All other pegs are standard black “friction” pegs.

Attach the phone holder to the core.

The phone holder attaches to the core via two elements. One is the long axle mentioned in step two. The other is a tan peg. Thread the axle through the center of the round gray pulley element while the tan peg pokes into a hole midway across the bottom white beam in the phone holder.

Attach the base.

Use four red pegs to attach the core/holder assembly to the base. Mount it as high up in the frame as possible to allow for connection of the stabilizers in the next step, if you plan to use them.

Select a steering wheel.

Your choice of steering wheel is a personal preference. Look through your LEGO collection and try different ones to see what feels (and looks) right. A toothy gear may leave you with sore fingers if you use it a lot. A large wheel may look and feel more like a traditional steering wheel, but perhaps motorcycle handlebars are what you need! Attach your choice to the black axle.

Build and attach optional stabilizers.

Two rubber tires can prevent your model from slipping around while you use it on a hard surface. They are optional, but you may find them useful. Each one pokes into the side, through both the frame and core.

Try inserting your phone and make any adjustments.

This model was built for an iPhone 4 without a case. To swap in my iPhone 5, I removed the upper elements and rubber bands, as they got in the way. Instead, I placed a simple friction peg on either side, to hold it steady. See what works best for your phone and re-build if necessary. Note also that the steering column can be slid in or out of the core, to adjust the distance between wheel and screen. And, if you’d like to change the angle that your phone and wheel are sitting at, you do that too – by altering the length or position of the beams at the ba

Launch an app and drive!

There are a number of apps which make use of smartphone gyro/accelerometer technology for steering. Some free games that I’ve enjoyed from Apple’s App Store are: Shrek Kart, Real Racing GTI, Waterslide Extreme and Rollercoaster Extreme.