Wishful Coding

I designed this robot to experiment with so-called “single track vehicle dynamics”, or in other words, balancing on a bike.

The challenge with designing a motorcycle like this is keeping he wheelbase short, and positioning the steering motor in a sturdy way.

The program for this robot is based on the principle of “steer into fall”, which means that if the bike leans over to the right, it needs to steer right to correct that.

A problem that I have with this robot is detecting the angle of the robot. The ultrasonic sensor is not precise enough and my floor not uniform enough to use the light sensor, like the NXTway does.

If you have a very uniform floor, you could use my code, but it is probably best to get a HiTechnic gyro with the software from this guy:

If you want to build this model, you need some extra wheels, check the parts list.

Download building instructions

A while back I was making some large LEGO vehicle of sorts, and I was faced with the choice of gearing down my motor or dedicating a whole extra motor to controlling a gearbox.

I chose to do neither, and build an automatic one. The ones I found where to big and relied on friction and differentials. After a few email exchanges and iterations, I arrived at this compact 2-gear automatic gearbox.

The gear has 2 sides, one with a 1:1 ratio, the other with a 12:20 slowdown.

When no torque is applied, the front lever is pressed onto the 1:1 chain by a rubber band, causing it to turn faster than the 12:20 side, and thus pushing the rear lever up.

When torque is applied, the front lever is pushed up by the force, and starts to slip, making the 12:20 chain turn faster, causing the rear lever to fall back into position.

Automatic Gearbox Building Instructions

I found some lost and forgotten Lego building lessons. I think you’ll love them.

Over at Lugnet, in an old thread, someone asked for tips and tricks about studless building(using smooth beams rather than the classic Lego bricks). Someone linked him to the “LEGO TECHNIC Design School”, which sounded really good, but unfortunately, the links where dead.

I searched, and searched, but LEGO just seems to have removed them. Are they to good for this world? Finally, I found them using the Wayback Machine. Enjoy!

• Gearing 101
• TECHNIC 101
• Stability with LEGO TECHNIC

Unfortunately, a few images are missing, but it’s still interesting to read.

Diagonal Connections

One thing they teach that I have not seen “in the wild” much are all sorts of diagonal connections, like this 1:2 gear ratio and right-angle connection.

It is possible to build all integer Pythagorean triangles, although few of them are practical.

It might at first be confusing to build a triangle with sides of 3, 4 and 5 in length using beams of 4, 5 and 6 of length, but think of it like this:

What would be the length of a dot? Zero, right? So when talking about LEGO units, a beam with one hole also has a length of zero. Start counting at zero, and it’ll all make sense.