Last Christmas holidays at my mom’s place, I dived in my box of old Technic Lego and my eye fell on the 4,5V motor that was just lying there. Would it still run? Well, yes, hesitantly, with some hiccups and high-pitched whining. But the longer it ran, the better: fewer hiccups and less whining. Brilliant!
‘What shall we make?’, I asked my nephew N. who was also visiting. Let’s make tracks, he suggested. Okay, how do we start? Well, let’s do like this, he said, and came up with a very good start.
As a side note: this is Technic Lego from the 1970s and 80s. Notice the axle-pins that go into the 24-tooth gears? They are tight like the jaws of my dog, Kika (which is not the one in the video), on a stick. Difficult to get them together (which is where the metaphor ends because Kika easily and happily puts her jaws around a stick), and absurdly hard to get them apart again.
After N. had put the tracks together, I challenged him to improve the design and see if we could add the little engine. I asked him the questions ‘How could we do this?’, ‘What should we do next?’, ‘How can we improve that?’ and he provided the answers. Unfortunately, I didn’t document the steps, but it was wildly interesting.
At some point, we had the tracks connected to the engine, and it would run while being held in the air. However, on the rug, the engine lacked torque. Typically, one needs to introduce gears to gear down. I tried to explain that gearing down means that the machine will run slower, but with more force, so that it could also run on the rug. With a little help of pre-Technic Lego.
N. had to go home, so in the evening, I optimized the end result a bit, which is the design you see below. You can also download the design in Ldraw here. I made it on a Mac with Bricksmith, but the file should work with other Ldraw software for Lego designs.
Then I wondered, can we make it so that the entire mechanism fits in the loop of the tracks, so that it can drive upside down as well?