Has anyone experimented with a jointed frame w/ the segment in the center? Have the results been favorable? - Steven 2474
Do you mean an articulated frame perimeter? If so, it’s illegal under <R11>. (insert your favorite reminder to read the manual here)
If, on the other hand, you simply mean to have the wheels articulate, then there are a number of threads out there with various ideas for how to do that. Search can be found in the orange bar at the top of this page. Results have been somewhat variable.
While not applicable this year, BERT 133 built one in 2008 to play Overdrive. It worked really well throughout practice actually, but to meet weight they needed to replace the steel gears that did the actuating with aluminum, and the aluminum had a nasty habit of shearing mid match. I’ll see if I can track down some pictures from BAE that year.
190 had a flex chassis with a horizontal pivot in 2005 to allow all 4 mechanum wheels to maintain contact with the floor at all times.
There are likely pictures of it somewhere in this archive, but it’s a lot of pictures to look through, so it’s left as an exercise to the reader. 
Here’s their first match at BAE in 2008. The camera moves quite a bit, but there’s a little bit of video of them turning (particularly at about 1:10).