Poll: Turrets for Rebound Rumble

[Jared Russell]

Originally Posted by Madison

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.

This is a great table. That said, achieving sub-1 degree azimuth accuracy does not in itself necessitate a turret.

[pfreivald]

Originally Posted by Madison

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.

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).

[Bob Steele]

Originally Posted by compwiztobe

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.

In my experience... nothing is trivial....

[Chris is me]

Originally Posted by pfreivald

...and accuracy at close range is better than innaccuracy at long range (except for certain feederbot applications).

If you don't have your design down at this point and you read one sentence on Chief Delphi, read this one.

[MrForbes]

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.

[pfreivald]

Originally Posted by squirrel

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.

Looks nice! Are you just using friction for the drive belt, or are you going to put teeth on the plywood disc as well?

[Austin2046]

Personally, i don't think a turret is needed for this game, it adds a variable that drivers have to more actively control. that is not to say it can't be a useful asset, but if you don't have the driver practice time to dial them in, than i believe it can be more of a hinderance to team performance, than a help.

a driver that simply drives to a certain spot on the field and points the chasis in the right direction will have a lot more success than a driver going to random locations, dialing in the shooter speed and pointing a turret in the right direction. i think many turret teams will find that they do the same thing as the non-turret teams, because their drivers can't get all the variables down consistently.

that being said, one area where turrets could be useful is on defense... a turret team driving in the backfield with turret pointed toward your end. the chasis is driving, turning and picking up balls while the turret just keeps shooting them to your end.

[JesseK]

Jim -- you could use Ethernet cable for your sensor wire there. Might tidy things up a bit and be easier to manage. Big spools are much cheaper (per foot) than what you'd get at a electronics store. The school's IT department may also have some spare you can use (10' should be enough). No need for connectors, just splice the twisted pairs like any normal wire. We did that for our 2 limit switches + 1 encoder last year on our wrist joint and it worked great.

[MrForbes]

On our turret, the belt was cut to the right length, and the ends screwed into the plywood disc. There's no need for much rotation, so we didn't make it so it could rotate much.

We are planning to use the turret for computer controlled aiming with the camera, so the drive just parks the robot so it's facing the goal, and the robot does the turret turning to "fine tune" the aim right at the basket. The idea is to make it easier on the driver, not more difficult.

I'm not in charge of wiring, but I'll suggest that to the electronics team. For now they just grabbed some old limit switches and wire to get it working.

[pfreivald]

Originally Posted by squirrel

On our turret, the belt was cut to the right length, and the ends screwed into the plywood disc. There's no need for much rotation, so we didn't make it so it could rotate much.

Gotcha! I was wondering because the addition of teeth would have added accuracy over just tension on the belt -- looks like you've got that taken care of with the drive sprocket.

[SteveGPage]

Originally Posted by compwiztobe

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.

I'm sure that's where they got the number, but if you put your back wheels on the front of the key, and aim for the center of the basket, you're looking at about a 9 foot shot anyway.

[MrForbes]

Video of a turret in action, but not connected to a shooter yet.

http://www.youtube.com/watch?v=Hu2llOOlR18

Originally Posted by squirrel

Video of a turret in action, but not connected to a shooter yet.

http://www.youtube.com/watch?v=Hu2llOOlR18

Looks great! The AndyMark gearmotor will probably be our choice of motor for our turret, too.

[Austin2046]

Originally Posted by squirrel

We are planning to use the turret for computer controlled aiming with the camera, so the drive just parks the robot so it's facing the goal, and the robot does the turret turning to "fine tune" the aim right at the basket. The idea is to make it easier on the driver, not more difficult.

if you're going to have a camera system auto-aim your turret, you can have a camera system auto-aim your robot.

[MrForbes]

Originally Posted by Austin2046

if you're going to have a camera system auto-aim your turret, you can have a camera system auto-aim your robot.

Yeah....maybe if you have a drivetrain that works a bit better than ours will.