[Lego] Work in Progress: Hailfire Droid (October 25, 2020)

The Hailfire Droid rolls around just fine, until it suddenly goes to an abrupt halt...

Wait, that doesn't seem right... It seems I've hit a new kind of roadblock with the project. Well, shit.

I had some other plans for this month's blogpost, but ironically all of them have probably been pushed back to later this year, including the Xenoblade's Definitive Edition article, which I'm close to halfway done with the initial draft. It's currently about 25.000 words long. Might need another month (or two?) before I can publish it. That said, this Hailfire Droid roadblock surfaced today, which gave me an opportunity to talk about it, as it's quite fascinating.

Last time I've mentioned an issue where the thread links disconnect when driving backwards. This was caused by having too much clearance between the wheels and the drivetrain. I came to the conclusion that the disconnect happened because there's an unequal distribution of power: pulling the threads when driving forward is no problem, but it becomes one when you're pushing the threads if driving backwards. So, in order to supply an equal distribution of power for both pushing and pulling, I've doubled up the motors. That was a (partial) mistake.

So, if you look carefully at the GIF above, the Hailfire Droid seems to abruptly stop after a while. Even its eye goes out for a brief moment. This isn't a mechanical issue. It's one particular thing I completely forgot about, and it also has been a particular issue with my progress on the Constructor: a safety measure in every modern LEGO^® motor kicks in that prevents it from frying. Basically, the motors draws more current than what the battery can handle, and every time it hits this safety threshold, it shuts the electrical circuit off - a circuit overload. Woops.

Taking a look at the project on paper, it doesn't take long to figure out the problem. The motors I'm currently using are the popular Power Functions "L Motors", which are great for many applications, but they are notoriously known for drawing a lot of current. I didn't expect that I would hit this safety threshold with these motors, given that the wheels of the Hailfire Droid spin at full speed without any issues when holding the model in the air, but it seems that it kills the circuit when you drive it on a surface.

So, what now? The answer's simple: I need to use motors that draws less current. Fortunately, there are plenty of motors that draws half the amount of current, and ironically enough, this also makes the Hailfire Droid drive faster as these motors come with a higher RPM. 

Sometimes in order to prevent a circuit overload in LEGO^® is not to go slower, but to go faster. Funny how that works.

That's it for today - I'll see you guys again next post!