# What Does It Take For A LEGO Car To Roll Downhill Forever?

Cars (including LEGO ones) will roll downhill. In theory if the hill were a treadmill, the car could roll forever. In practice, there are a lot of things waiting to go wrong to keep this from happening. If you’ve ever wondered what those problems would be and what a solution would look like, [Brick Technology] has a nine-minute video showing the whole journey.

The video showcases an iterative process of testing, surfacing a problem, redesigning to address that problem, and then back to testing. It starts off pretty innocently with increasing wheel friction and adding weight, but we’ll tell you right now it goes in some unexpected directions that show off [Brick Technology]’s skill and confidence when it comes to LEGO assemblies.

You can watch the whole thing unfold in the video, embedded below. It’s fun to see how the different builds perform, and we can’t help but think that the icing on the cake would be LEGO bricks with OLED screens and working instrumentation built into them.

## 11 thoughts on “What Does It Take For A LEGO Car To Roll Downhill Forever?”

1. I’ve seen many “quizzes” on facebook and fora that ask about vehicles on downhill threadmills, but they all seem to rely on the idea of apeed relative to the road, which is a fallacy. A car with frictionless axle bearings will roll downhill with the same speed regardless of the threadmill speed*.

At least this video implies that it’s the friction that holds the car from running downhill.

And kudos for trying to implement the
Brabham BT46B “fan car” idea!

*well except if you factor in wheel inertia, undercarriage air flow drag and many other factors, which I believe will not contribute majorly until at higher speeds.

1. Andrew says:

1. spaceminions says:

In real cars, it’s easy to observe air resistance, rolling resistance, and the effects of accelerating a mass or moving it up or down a slope. Real tires flex and have enough resistance that a frictionless bearing will not be enough to necessarily isolate the inertia and drag factors.

2. C says:

Needs a wind tunnel to be realistic.

1. Nobody says:

1. Andrew says:

The plural of Lego is, uh, Lego.

1. Michael Church says:

It’s actually LEGO System A/S if you want to be specific, and since you seem to be trying to it’s important to go all the way.

1. Andrew says:

No. That’s the name of the company, not the name of the product. But, thanks for trying.

2. m1ke says:

I’ve rolled down many hills in my day. None of them were in a wind tunnel. To be more realistic I’d say it needs a surface of dirt and dry grass. Also some large rocks that you want to avoid bashing your head against.

3. Garth Bock says:

Excellent progression video! Watched it until the end. I did get a chuckle when the little cat exploded or came apart and the green car bouncing back and forth between the sensors. However, I did have a flashback when I saw the opening with the just the gray treadmill. It was of George Jetson on it yelling ” Jane stop this crazy thing !”

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