You mean wood gears like in https://www.alamy.com/gears-of-a-windmill-image245974580.html https://www.alamy.com/gears-of-a-windmill-image245974580.htm... ? I g

You mean wood gears like in https://www.alamy.com/gears-of-a-windmill-image245974580.html https://www.alamy.com/gears-of-a-windmill-image245974580.htm... ? I guess they were replaced a few times during the non harvesting season. To replace the main gears of a rotating shell in space, you must "turn off" gravity for a week (or month).