What is that metallic & hydraulic sound?

Just returned to the US on an AB 330. During taxi at LHR, there was all this noise under the aircraft. I know I’ve
heard this before, but have always forgotten to ask about it. Is sounds like a clanking noise – also sometimes
combined with what might be hydraulics?

Thanks!

Gizmodo had a “general” type article about this sort of thing a week ago…

gizmodo.com/what-are-all-those-w … 1713676966

The comment section is fairly interesting, too, with many aviation types filling in more specific information.

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Thanks for the link! Answered all my questions…