How do bicycle gear shifters work?
In: Engineering
All the derailleur does is move the chain left and right, it guides the chain along the gears.
When you press the shifter, it takes away or gives more slack to a metal wire that’s attached to the derailleur in the specific intervals of your gears.
I used to assemble bikes for a living.
Typically, there’s a rotating crank on your handlebars to change gears. As you rotate, it pulls tension on a cable that leads to the gear assembly by your pedals.
This cable is attached to your chain guide, which pushes the chain to one side based on that tension. Once you change gears, the guide moves to push the chain so that it catches on a different gear. This inly works while you’re pedaling because it’s the combination of motions that puts the chain where it needs to be.
Side note: adjusting the gear shift and chain guide was often the most precise and pain-in-the-ass part of the bike (at least for me).
I can’t tell you how certain three-speed hubs work, but most multi-gear kinds are really pretty simple. The chain runs through a derailleur which is a pair of guide wheels. These wheels have a spring action which takes up slack in the chain when it’s on the smaller gears. Also, the derailleur is made so it can move inward and outward. This is controlled by a cable connected to the shift lever. Moving the lever moves the derailleur in or out, which moves the chain from one gear to another. A similar device moves the chain from one chain ring (front gear) to the other on the crank set.
Answer:
As you turn the gear shift thingy it pulls on a metal cord. That metal cord pulls on a “guide” that surrounds the chain. Depending on the way you turn the gear shift thing, the guide moves closer or farther away from the tire/frame of the bike. This pulls the chain in a horizontal manner which cause it to skip off of the current gear and get caught on the next one. Those black plastic tubes that usually run down the frame of the bike house the metal cord.
Sorry for the lack of terminology, I know how it works but I’m not a bike mechanic.
Your bike has two tracks that the chain passes through. Shifting gears moves these track up and down the gears to drop the chain onto the intended gear
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