Kids and kids at heart love Legos, especially motorised Legos. It's fun to dream up challenges and engineer solutions to eliminate obstacles. Or watch from the sidelines while someone builds something clever. That's why Lego videos on YouTube are fun to watch. 

This video is titled "Driving Lego Cars in the Sand" and was put together by Brick Technology, who also did one on parallel parking and another where they built a hot rod with a working clutch and four-speed gearbox. They have a number of videos on their YouTube channel, which is like a cross between Engineering Explained and Lego Movie 2.

They try to solve an issue that frustrates four-wheelers everywhere, getting stuck in the sand. Starting with rear-wheel drive, they learn wider wheels make a difference, as do the steering and a locking differential. Weight distribution also plays into the equation, as people with rear-wheel drive cars will tell you. Adding weight over the drive wheels is one of the keys to not getting stuck.   

When you add obstacles, it gets more challenging. Lego barriers, potholes, slopes, and hills eliminate the direct route to the finish line, which means the rear-wheel drive car can no longer power its way through. That's where the all-wheel drive comes in handy, along with another locking differential. 

One of the biggest things that makes a difference is tyres. Not only does the tread design affect the vehicle's performance, but its shape also affects it. Tyres with a flatter-shaped tread are much more effective at manoeuvring through the sand than ones where the tread is more rounded. Additionally, the number of tyres makes a difference. The most successful design used a six-wheel drive configuration to further aid weight displacement. That's why you see heavy trucks with extra wheels fitted. 

The six-wheel drive truck with independent suspension is the most successful vehicle. It navigates all the obstacles except for the occasional cat, which scouts out of the sandbox in an attempt to make a few obstacles of its own. Since the final iteration six-wheeler has a flatbed, the Brick Technology crew should also consider adding a scoop to keep the litter clean.