I have seen multiple matches/practices on different intake systems. The top, free floating axis is common in most robots http://www.youtube.com/watch?v=wbu1D8OZe2Y; undoubtedly the side mounted intake proved to be quite popular in New Zealand http://www.youtube.com/watch?v=Gkst0HZg2g8. I am still puzzled so as to the advantages and disadvantages of each system. Which one performs better overall?
Both see interest in New Zealand, we used exclusively top suckers for World Cup - but both teams in the final used side suckers (Perhaps this is why we lost :D). Both seem to work fine, and have advantages and disadvantages. Which is better really depends on the structure of your robot and your driving style.
I see the main advantage on side mounted intake system because you can pick up stacks, and also pieces better (In my opinion). For stacks of 2, you can pick them up better because you do not have to lower the arm onto the pieces. You would have to do this with the top mounted intake system because you have the intake in the way. I hope that made sense! And you can also just pick single pieces up better because you can just drive right into them. You can also do this with top mounted but I feel that it works better with the side mounted.
if the top intake is made and tweaked well enough, they can just gobble up a stack as if it were one
(the rollers expand over the stack, intaking the top ball in first, then the bottom barrel immediately after)
We had a pre-set for picking up stacks, involving running the intake over the stack and grabbing both. But overall our robots were designed for high school competition, not for skills or college gameplay.
(Disclaimer: The list below is based only on what I have seen. It is subject to being wrong.)
It’s easier to get side rollers to pick up stacks, which is nice in skills.
Top rollers generally have a wider pickup angle, meaning that if your driver misses to the side it’s easy to correct and still get the object without moving the drive forwards or backwards.
Side intakes descore better.
Top intakes work better when pushed up against walls and in corners.
Each intake has one barrel orientation that makes it jam or have intake trouble.
Neither really inherently performs better than the other; it’s a matter of execution and usage. If you’re going for skills, side roller intake will be easier to execute well, but I feel that the top roller intake is easier to drive. When in doubt, build both and see for yourself.
I do agree with most of the points you make, except for the comment about descoring. The top intake is able to descore any object in the goal above the highest support ring by putting the rollers inside the goal and outtaking. This forces the object upwards and out of the goal. For the side intakes however, my team had to make a separate mechanism to enable it to descore.
Also, in my opinion the side intakes are just all around better. They seem to intake and outtake more efficiently overall than the top intakes, which is why my team has switched from top intakes to side intakes. Then again, this is just my opinion.
The first point there is entirely dependant upon the second point. There is no need to have an undesirable intake orientation if the intake is executed effectively.
The key part is working out how to remove this issue, but it can easily be done, as various teams have discovered.
For descoring, I haven’t seen any teams use that method, although it is certainly interesting. What we do with our side roller intake is to push the rollers through the goal posts and intake the object while halfway inside. Then, when we raise the arm, we have full possession of the object. Of course, that probably doesn’t work with most side rollers as seen on the forums; our entire chute and intake structure is made up of lexan bars and straps so there are a lot of spaces for the goalposts to go through.
When it comes to efficiency, there are some differences between the two, but I think they feel almost negligible in game. Top rollers have a larger intake radius, side rollers can pick up stacks slightly better most of the time, etc. The better option is to pick whichever one of these you feel like making and tweaking it until it is as efficient as you can make it (What configuration of zip ties/tread paddles intakes best?).