what is grease they use in gears and stuff? Why does it need to be replaced occasionally?
In: Engineering
Take a simple example, a bicycle with a chain, sprocket, and derailleur set up. Basically the standard cog change shifter that we understand for most bicycles. The metal touchpoints is the chain and the sprocket. A standard maintenance is to scrub the sprockets and then clean each link on the chain. Then, you do a dab of grease/lubricant on each chain link to assist smooth transition from different sprockets and to keep it from squeaking and sounding cruddy.
In the case of the bike, you have to replace it because, being that it is exposed to the elements, dirt and grime build up and that reduces the effectiveness of the lubrication. In, say, a wet dual clutch transmission, like many transmissions in small VW/Audi/Skoda cars; the lubricant loses effectiveness due to heat. Same reason you change the oil in your car’s engine.
Whenever you have two pieces of metal that have to rub against each other you usually need lubricant and often lubricant plus a bearing. Without that the metal would become so hot and scrape together so hard that they can literally change shape. You don’t want that.
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