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Unread 07-06-2010, 16:05
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JamesCH95 JamesCH95 is offline
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AKA: JCH
FRC #0095 (The Grasshoppers)
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Re: pic: Sheetmetal 6WD

Quote:
Originally Posted by Chris is me View Post
Spring loaded chain tensioners are fairly notorious for not working in more than one direction. There aren't exactly many successful spring loaded tensioners designs in FRC. Unless you happen to have experience in the area I wouldn't recommend something as "better" that you haven't successfully run yourself (and if you have, I'd love to hear about it).
I haven't done anything like this myself. I was basing my recommendation on this: http://www.popsci.com/invention which is an incredibly fast tracked vehicle, and it uses a spring/piston to tension the drive tracks, and hasn't thrown a drive track in 3 years, even with a broken suspension mount. Though perhaps not a great parallel to a FIRST robot.

I would be interested to see these designs that didn't work well, I bet there were issues where the drive wheel's tractive forces was also compressing the spring that was tensioning the chain. A workable design might be as simple as an adequately stiffer spring/piston/gas spring. Like I mentioned before, a piston or gas spring with constant force vs deflection (unlike a typical coil spring) would not slacken as long as it's force rating was not exceeded.

I think it would be a very cool idea to design and implement, but it certainly won't be as trivial as throwing some springs into your robot. Having thought about it for 10 minutes I think that one could design a cam with a 1-way clutch bearing that could eliminate the need for a spring entirely.
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