Why aren't bicycles geared?

The advantages of chain drive are: 1. Good fault tolerance, low requirements for assembly accuracy, allowing front and rearSprocketThere is no small relative error; the transmission efficiency is high, and it can reach more than 0.95 without very high-precision processing, and the two-stage gear transmission is generally about 0.8.

The advantage of gear transmission is that it can adopt a closed structure to achieve maintenance-free, and can better withstand the harsh environment of sun and rain.

In the early stage of bicycle development, the engineering lion considered over-shaft transmission.Let's talk cost first.The most expensive part of a bicycle in those days wasChain.A chain consists of more than 400 parts.The chain is so expensive that all the parts on the car combined are not as expensive as the chain.Later, the standard of the chain was unified.This enables the chain to be mass-produced automatically on a large scale.Costs have thus dropped to the horrific levels they are today.This makes the shaft drive lose its cost advantage.In terms of riding experience, the biggest disadvantage of shaft transmission is that it is heavy.Anyone who has ridden Mobike knows that.on reliability.The more industrial products are used, the more perfect they are developed.Regarding the problem of dropped chains and maintenance, it is actually much better than before due to the widespread use of chain drives.Positive and negative tooth technology, chain guide, anti-drop chain plate, Teflon lubricant.To a large extent, it makes up for the lack of chain transmission.process angle.The chain drive can tolerate the errors of the bike frame.It works smoothly and reliably even if the chainring and cassette are not in a straight line.But this is a nightmare for shaft drives and belt drives.As for gearbox technology.Internal transmissions are essentially similar to car transmissions.This type of transmission has a longer history than the common external transmission.But this thing is expensive and heavy, and the transmission is inefficient.