Torques in a Bicycle With Gears
— Adapted from a text message at 6:02 PM CT on 21 Dec 2025:
This was my lesson for SWM today. RNM said that it needed to be brief, because they are packing for their trip to Houston early tomorrow. But after 15 minutes, SWM exclaimed, “Wait, we’re not done!” So I taught him the right-hand rule and mentioned how it is opposite to the 3D coordinate system of the video game Minecraft. Minecraft is teaching kids how to build left-handed worlds that are opposite to math and physics! Minecraft is left-handed due to some early decisions in computer coding that now cannot be reversed.
Understanding bicycle gears in terms of torques is pretty simple. RNM said that gear ratios had something to do with the cogs of all gears and the crank needing to be the same size — because the same chain must work with all of the cogs. So I think that gear ratios are basically Figure 2, ratios of cogs which make the torques work.
