Thanks guys,
To answer some of the questions and proposed solutions:
Yes, the rake loads up like this regularly when I use it after first bush hogging (or flail cutting) in areas that have a lot of bull briar. The material is mostly roots/canes that are fairly close to the surface and are ripped up when I try to smooth out ground following stump digging or simply ripping out saplings.
I find it is more time efficient to simply let the rake load up than to stop every few minutes to kick out a few roots/canes. As I noted, I'd guess it takes about 5 minutes to clean after doing an area about 1/8 to 1/4 acre. I still have at least another 10 acres to go so would love a more efficient method of cleaning.
Believe me I've wondered about why no one has developed a mechanical or hydraulic comb!
Where's 3RRL when you need him? I have rear remotes so I just need drawings and instructions! I imagine that most people don't use their rakes primarily for this sort of clearing and that it is not a big enough issue for anyone to have gotten mechanically creative yet.
John Bud's suggestion to remove the wheels is something I could try. I don't know that it will prevent the rake from loading up though as I have the wheels and 3pt toplink set up so the rake does allow the tines at least an inch of penetration and the front is tipped down so the rake doesn't "scoop" too much. Should I try the opposite and put the rake in a more aggressive posture by lengthening the toplink? I did not take a before photo of the area I raked but you don't see this debris on the surface. It is 90% subsurface roots/canes. If the tines dug in further I'd be moving more dirt than I really want to and I believe that the roots/canes would simply migrate up the rake anyway. It looks like a basket weave when fully loaded and when the roots get all stacked up it really takes some force to get them out.
If I do remove the wheels then I can try the suggestion several of you made regarding backing into a brush pile and scraping it off. I'll give that a try. I am not doing fine finish grading so the wheels are not really critical for me. I got the rake used and it came with wheels.
Thanks again.