What is your opinion on using a rotating turret for this year’s game? How far should it turn? How would you use it?
This is for my own curiosity, and will not effect 256’s decision making process
We felt that the ability to score with any robot orientation is important especially since the number of balls is fewer than we’d like. It is easier to pick up a ball and go for another one and still be able to shoot. We think the benefits outweighs the complexity.
[strike]Wow, 100% no (at this time), that’s pretty convincing…:rolleyes: [/strike]
We considered this, and actually did it for Aim High, but it adds weight, complexity, and doesn’t add any features we can’t do with drivetrain. Yeah, I guess we can’t drive sideways and shoot, but if we’re touching the key, defense will be a challenge. So we stop, turn and aim.
Well, we decided that it is too risky to shoot form afar, so we are already lining up with the fender, and it should not be a problem.
Lining up with the fender is pretty much the only place on the field when defense can be played on you.
Back on topic, the turret adds a huge amount of complexity and complication in design where it would not have been before. 90% of that functionality can be done by moving the drive train.
Here’s something one of our members put together showing the relationship between distance and accuracy.
I will leave it to others to determine if a turret is necessary, but the precision required to sink shots from long distances is substantial.
It may be possible that hitting the backboard and bouncing balls in will be more forgiving. We don’t yet have good data on that.
The key doesnt start at 12 feet it starts at 101 inches, which is less than 9ft.
We still thought that defense wouldn’t be played that much, and that there would not be a downside. Of course, that why we went with 2 speed for the first time this year, just in case.
We got our turret made tonight, although the robot to put it on, and the shooter to put on it, are not really even started. We are looking for about 45 degrees maximum travel, but that can be changed pretty easily, it’s capable of close to 180, I think. We want to just have enough travel in the turret to do what’s needed, which is to get the shooter aimed at the basket when we park on the key.
The complexity of our turret is not very high, but then we don’t have it working yet, so we are not sure if it has sufficient complexity 
The turret we made in 2009 worked well and was also relatively simple.
I would say go for the turret.
that way, if you get pushed, so what. esp. if you have camera code ala Aim high that can track the target… you get pushed, the turret auto-aims and you can still (hopefully) make the shot.
not to mention all the legal motors… the AM gearmotor looks to be an excellent turret motor; it reminds me of the globe motors, which my team’s bot in 2009 used for a turret control… it worked well, dare I say perfect.
True enough; though the rest of the information is correct. Teams will need to aim with high precision for long shots. I think folks are grossly underestimating the difficulty involved here.
We are adding a turret for two reasons:
- We’ve done it before, easily.
- It involves software to aim well, but you can also manually set our turret and shooter assembly for autonomous mode this year.
If either of those things weren’t true, I would support a non-turreted shooter for my team. We just did well last time with a COTS lazy susan type bearing setup that we’re refining for 2012.
There’s rarely a question of “best” in FRC. There is only “best for your team”. That said, a turret for many ball shooters is a decision with a much lower opportunity cost than, say, a swerve drive. Thus you will likely see turrets at the top of play no matter what.
There are many factors that go into whether or not building a turret is the “best” strategy for this game.
- Prior experience with turrets (off-season or previous years).
- Whether you can get the desired precision with the drivetrain.
- Motor allocation.
- Time taken for iteration and development.
We ultimately decided against the turret due to several of these factors (one of which has yet to be determined). It comes down to realistically looking at what you can achieve, and what resources you are willing to allocate to achieve it. For us a turret may have been achievable, but it would require allocating more of our resources than we were willing to use in it’s development. Whether or not this puts us at a competitive disadvantage is yet to be seen, but it is less likely to put us at a huge disadvantage compared to attempting to do more than we realistically can.
I think you’re mixing up the width with the position. The key is 144 in., or 12ft, from the Alliance Station wall, and 48 in, or 4 ft deep. So 12 to 16ft.
We talked about a turret for many of the reasons already mentioned, and we have done it before and it would be fairly trivial to implement. However, we find it critical to keep the CG as low as possible, and adding a turreting mechanism adds weight up high and potentially moves shooter weight higher. Given how easily one can turn the robot to aim when protected in the key, and the relative scarcity of balls, we don’t think it’s worth it.
This is a great table. That said, achieving sub-1 degree azimuth accuracy does not in itself necessitate a turret.
Right-o. I think that the difference between passable teams, great teams, and awesome teams will be accuracy at range…
…and accuracy at close range is better than innaccuracy at long range (except for certain feederbot applications).
In my experience… nothing is trivial…
If you don’t have your design down at this point and you read one sentence on Chief Delphi, read this one.
Our turret so far. The plywood disc sits on a 6" lazy susan bearing. The ball is fed from the side. The shooter sits on top of this. The turret only moves a little bit, like 45 degrees. The belt is screwed to the wood disc. The pulley on the gearmotor had it’s hole opened up to 10mm to fit the gearmotor shaft. Design calls for about one second to move 45 degrees, so we have about an 8:1 ratio, with the roughly 1 rev/second gearmotor.
