It’s not a question you ask yourself every day, but it’s one that the [Brick Experiment Channel] set out to answer: how fast can you spin a LEGO wheel by hand? In their typical way, they set about building an increasingly complex contraption to optimize for the very specific case of maximum RPM.
The build starts with a LEGO wheel fitted to an axle, supported in two LEGO Technic beams. A white flash mark is also attached onto a part of the axle for measuring the rotational speed with a photo-tachometer. A first attempt gets as fast as 1,700 RPM. Upgrades come thick and fast , and with a three-stage compound geartrain, the handcranked wheel reaches 6,300 RPM. Adding a further stage introduces the problem that the plastic Technic axle begins to twist under the torque input by the hand.
Taking a new approach of pulling on a string to turn the wheel, the first attempt nets 8,300 RPM. Gearing pushes this further to 12,900 revs, but adding more gears again leads to the problem of axles bending under the strain. A bidirectional rope pull design helps, though, and the system reaches 13,100 RPM.
Some of the parts have been damaged thus far, but a rebuild with fresh parts that are nicely lubricated provides a huge boost. The now-slippery shafts run smoother and the wheel hits a blistering 19,300 RPM as the mechanism disassembles itself.
It’s a less complex pursuit than some earlier works from [Brick Experiment Channel], like the impressive pole climbing designs we’ve seen previously. However, it’s a video that shows the power of iterative design and the gains possible from that process.
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The video points out that, at best, even a decent RC car will have pretty crappy aerodynamic parts from the factory, with a lift-to-drag (L/D)ratio of 2-3:1 at best. This means that, while they may create some small amount of downforce, they’re also creating plenty of drag at the same time.
