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I'm working on a game project where I have to design sounds for the interior of a robotic suit. It's very similar to the inside of an airplane cockpit, with a lot of dials/switches/levers, etc. The developers want a very grinding and responsive feel. When the suit breaks down, it'll need large mechanical breakdown and alert-type sounds.
+1 on Wall-E. Might also be worth having a look at this post on Designing Sound. It's a great sound library from Michael Raphael that may inspire you to get recording. Or you can buy the whole library from Rabbit Ears Audio...
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District 9 has some shots inside the exosuit towards the end, and sounds really good!
Also steel battalion for xbox happens entirely inside a mechwarrior.
The audio quality on the video is quite bad, but i hope it gives an idea
Sounds like you'll need to search for items in a junkyard. Lots of scraping metal, hits. I saw a foley video for Spiderman 2 (it was the one with Dr. Oct) and I think he scraped a wheel hubcap against an old car door for Dr Oct ripping out the vault door. Really nice.
Works wonders -- go to my profile tab at www.c3sound.com and watch the starcraft 2 trailer.
The majority of a lot of those robotic arms were processed combinations of forklifts and dentist drills to catch either the low or highs, then throw it some sort of detail sound to make it more electronic... a zap, digital blip, etc to give it character.