Shooting from opposite side of the field
 

After hearing the balls were foam, I was worried about how they would handle being launched with air resistance (as a foamy ball would barley go anywhere, like throwing a un-crumpled piece of paper). After I got my hands on one though, it seems a lot better then I thought it would be.

Anyway, my question would be do you think a shooter powerful enough to score from the other side of the field (or up against the bump on the other side, at least) be possible? and is scoring from the other side allowed? (I saw nothing in the rules)

Re: Shooting from opposite side of the field
 

Yes, I believe it is possible. However, to actually score, I believe it is a one in a thousand chance.

Re: Shooting from opposite side of the field
 

I think you'll see very competitive teams do it, yes.

Re: Shooting from opposite side of the field
 

I ran some quick calculations, and in order to score from an opposite corner, the ball would need to have an exit velocity of about 42 feet/second at a 45* angle.

Re: Shooting from opposite side of the field
 

corner, as in where human players put balls into play? what about somewhere closer but still on the other side?

What formulas did you use?

And thanks!

Re: Shooting from opposite side of the field
 

I used this trajectory calculator. It's pretty neat. This one may be useful, too.

Yeah, I meant the corner where the ball return is, but I can't see the velocity from the center of the opposite side being much different, maybe 40 ft/sec.

don't know how accurate your estimation will be. at 42 feet per second (12m/s) initial you will run into about 1.2 Newton of drag force.. which translates to approximately 3.5m/s^2 of initial deceleration.

Re: Shooting from opposite side of the field
 

By "do it" do you mean just shooting from the far side of the field or actually scoring...

Re: Shooting from opposite side of the field
 

I've been doing some math, and 6inches from the edge and 6 inches from the very far back wall of the lane, it's a 55.0568foot shot to the goal, not including the distance for an angle to the top of the goal. The extra distance it has to go, assuming the cannon/turret is at the very top of the 60" limit, is negligible (About an inch or so). At any rate, a 55 foot shot is going to be quite difficult.From the research I've just been doing, it's 42' to half court, then you'd add another 13' to that.

Re: Shooting from opposite side of the field
 

Look at the Peguineers robots from 2006.

Re: Shooting from opposite side of the field
 

On a less scientific note, I do remember nearly being pegged in the face in 2006 by an over propelled poof ball (I kept wondering why it was getting bigger and bigger...) while standing past the driver wall. While not quite the same as the basketballs this year, they can carry for some distance.

I don't think that's possible this year.. in order for this thing to go far, it needs to be at 45 degrees and have a really fast speed.. with this weight... any speed above 15m/s will slow down very quickly..

will mock up a simulation in the morning in python with an iterative estimator

Re: Shooting from opposite side of the field
 

Ran through Wikipedia and Google quickly and came up with this:
Drag force = (1/2) * p * v^2 * CoD * A

• p = air density
  v = velocity
  CoD = Coefficient of Drag
  A = relative area

Fill in with measurements:
Drag force = (1/2) * 1.204 kg/m^3 * (12.8016 m/s)^2 * 0.4 * 0.0162146393 m^2 = 2.010 Newtons (approx. 0.452 pounds).

Fairly negligible if my math is right. Mathematically, you could figure out how much force is needed to have the ball travel at a speed without regarding drag, then just tack the drag force onto that. Making something to force a ball to go at that speed will be hard, though.

EDIT1: Fixed a stupid math error (00:49)
EDIT2: Check out this post on drag etc. (01:13)

Re: Shooting from opposite side of the field
 

I haven't really done any math, but putting a wheel directly on a CIM spins terrifyingly fast, and has a sound to match.

Re: Shooting from opposite side of the field
 

You can even gear it down and have it go faster.

Re: Shooting from opposite side of the field
 

CIMs have a torque of 45 ounce-inches (0.234375 foot-pounds) at peak efficiency according to the manufacturer. The simplest solution is to just put a wheel on the end of a CIM to increase torque and increase linear momentum conveyed to the ball.

Re: Shooting from opposite side of the field
 

The fun thing about gearing though - it does come with a built-in cost. You can most certainly get a ball to go virtually any speed with a properly-geared CIM and wheel (within reason), but the higher the speed, the longer it will take the for motor to get the shooting wheel back up to launch speeds - don't expect to fire of a quick volley from that range with only one motor/wheel combo - expect a slower firing rate due to the energy required to fire the ball at that speed and the power available via the motor.

Re: Shooting from opposite side of the field
 

I think you will see some teams consistently (or nearly consistently) score from just past half-court.

Re: Shooting from opposite side of the field
 

If you can hit 1 of 5 or 1 of 6 from the far side of the court you are accomplishing 3 things.

1. you are scoring
2. You are feeding your team balls and elliminating the need for them to make a trip
3. You are defending by moving balls out of the opponents side

You still need to be accurate and we believe that you will also need to be 1 out 3 or 1 out of two in your zone to be truly an effective team mate.

Here is some info on targeting we have whipped up http://www.atomicrobotics.com/2012/0...ot-larry-bird/

Re: Shooting from opposite side of the field
 

but we are limited to 4 CIMs this year, and about 99% of teams are going to use them for drive.

http://www.andymark.com/product-p/am-0932.htm

http://banebots.com/p/S24K-C1-7

So the question becomes, FP or banebots.

And also, if banebots, one gearbox or two hooked up to a single wheel shooter? (Limit 2 FP, 4 Banebots [R65], and correct me if I am wrong but each box takes two motors)

Re: Shooting from opposite side of the field
 

Yet it worked in 2006 and 2009!

Re: Shooting from opposite side of the field
 

Everyone seems to be focused on whether or not a team can achieve the distance on a given shot. I believe that will be fairly easy to do. The real problem with distance is accuracy. remember that no design can be 100% consistent, and higher velocity could increase the error. The error in the landing point is given by:

err=tan(angle error) X distance

(assume two dimensional, looking down on the bot, the problem is compounded in three dimensions)

If the angle error is small, the tangent of that angle is small also, but if the distance is large, even that small error can make a big difference in landing point.

Example:assume you launch and have a 1° error in your launch direction. If you are 10 feet from the goal, you will have an error of ~2.1 inches. Assuming your aim was perfect, the ball will land ~2.1" from the center of the hoop and score.

Now move to 50 feet away (for round numbers) and keep the error the same. Your positional error is now 10.5 inches. if your aim was perfect. you will hit the rim and very likely not score. The center of the ball will be 1" outside the rim.

If you now add vertical angle error into the equation, it becomes much worse because your distance has the same relationship. Hitting a long field shot will probably happen, As I have seen full court shots hit in basketball, but I doubt many games will be won due to super long shots.

Re: Shooting from opposite side of the field
 

I agree with the above comment...
From my experience... when you lose contact with an object... all sorts of things happen to it that you can no longer correct for. The longer it is in the air the more things can happen...

Remember... at these big velocities you can no longer use the simple physics formulas that most of us learned in high school physics... air resistance is NO longer negligible .. and you may approach terminal velocity...

but even if you don't, you will have a constantly changing velocity due to air resistance...

Has anyone determined the terminal velocity of these basketballs?

I am very encouraged to see so many teams putting their effort into scoring from long range... I applaud their efforts... it is great physics/math and great engineering...

Now is it the best thing to win the field game with> ??? not so sure...
I do know that if I am watching an NBA game and a guard is getting ready to shoot from beyond the 3 point line ..that if he spies a team mate wide open with no defensive player on them closer to the basket ... that he will make the pass... and if he doesn't... the coach will pull him out...

That being said... who really is the winner in FIRST?
Doing the math/science to put in a shot from half court... that is also winning.... and maybe in a more important way....

Good luck to all of you

We will see you on the field!!

Re: Shooting from opposite side of the field
 

Do remember that after the first week the balls are going to be deformed from use which will affect the accuracy of long shots. Just to get them to the other side of the field will not take as much energy.

Re: Shooting from opposite side of the field
 

We did some imperical testing using our Aim High robot. It appears to be feasible to shoot this year's game piece from about 30 feet with some consistency.

Re: Shooting from opposite side of the field
 

FRC Regional competitions typically do not reuse game pieces from previous weeks.

Re: Shooting from opposite side of the field
 

Based upon our experiences with FP-driven pinch rollers, yeah, I'd say 30-35 feet with consistency is reasonable.

Here's team 95's 2006 Aim High robot, Lilly (whose accuracy is better than it looks, since it had three parallel firing channels):

Re: Shooting from opposite side of the field
 

How accurate was it at 30' though? Aim High had a 30" goal and Rebound rumble has an 18" hoop, so you'd need to be accurate within a much smaller area.

EDIT: Check out this post. It doesn't say how accurate the shooter was, but a 60' shot is pretty good. (19:14 EST)

Re: Shooting from opposite side of the field
 

Have you guys considered the fact that only 4 CIMs are allowed this year? Are you willing to sacrifice 2 CIMs to use for a shooter instead of on the drive? Just from past experience, only using one per gear box (6 wheel here, not mech or omni) will trip the amp breaker. We had to gear it lower to actually move and the max FPS we got was about 8-9 FPS. Is that worth it this year? What motors are a good alternate for the shooter? Fisher Price ones?

Re: Shooting from opposite side of the field
 

That's frightening. :ahh:

Re: Shooting from opposite side of the field
 

Here are some comparisons of torque and rpm at maximum power.

CIMs: 45.00 oz-in; 4614 rpm.

BaneBots: 11.69 oz-in, 7300 rpm.

Fisher Price: 35.7 oz-in; 10500 rpm. (Model 0080-0673)

Re: Shooting from opposite side of the field
 

Darn you GDC for limiting the usage to only 4 CIMs... But the FP is the next best thing.

Re: Shooting from opposite side of the field
 

Maximum 2 FP, 4 BB. If you compare 2 BB to 1 FP per pitching wheel, this is what you get.

(Models used: BaneBot M7-RS775-12, Fisher Price 00801-0673)

BB: 2 * 11.69 oz-in = 23.38 oz-in @ 7300 rpm (Max power)
FP: 1 * 35.7 oz-in = 35.7 oz-in @ 10500 rpm (Estimated max power)

Fisher Price > BaneBot

Also, I should have put the values in that list at max efficiency. Fixing....

Re: Shooting from opposite side of the field
 

Just a reminder that some people don't always let the mere quantity of motors control the number of devices for which to use them. ;)

(Of course, if you're planning on shooting while driving, this could be more complicated.)

Re: Shooting from opposite side of the field
 

There is a maximum of 22 motors... 4 CIMs for drive, 2 FPs for shooting, and 2 BaneBots or something for aiming a turret is only 8 motors.

Re: Shooting from opposite side of the field
 

How practical does this look, what do you think of it?

For the most part the ball enter the back of the robot is picked up by a belt which uses force against plastic/rollers to move it upward and to the launcher. it gets to the launching part (motor sets B & C). Then Set B gets it moving to a good speed so that when it hits Set C, it is propelled even faster.

I tried to mark the ball path with a consistant line and marking it with arrows to get an idea of speed.
What you think? (sorry for the crude drawing, and not being to scale...)
Davis

Re: Shooting from opposite side of the field
 

Do the math on a feeder bot actually being a shooter bot that coincidentally only feeds even most of the balls shot.

Assuming half of the missed shots from beyond the barrier are picked up by your alliance and the other half are picked up by the opposing alliance, what do you get?

25% shot accuracy yields a 1.5-1 advantage over your opponents.
33% shot accuracy yields a 2-1 advantage over your opponents.
50% shot accuracy yields a 3-1 advantage over your opponents...

And that doesn't take into account that every ball you score as feeder is a ball your alliance partners don't have to go get and score, which gives them time to do other things (like either play defense or go scoop up balls to make that ratio better than 50-50.)

Now mind you, the distance error in a shot is approximately x*tan(theta), where x is the distance from the hoop and theta is the number of degrees between the perfect shot and where you actually shot. This translates into a maximum tolerance of about one degree at half court (ignoring distance discrepancies). Crazy, unlikely, almost unbelievable -- but we're going for it. At the very least, it should improve our shooting from the key!

Re: Shooting from opposite side of the field
 

Who thinks that is it possible for a human player to make the shot from the corner? (doesn't matter which basket)

Re: Shooting from opposite side of the field
 

Possible, but not likely enough to make it much of a consideration in the game, methinks.

Re: Shooting from opposite side of the field
 

I know it's possible. Our best shooter made it from half court on our basketball court twice without much practice and that was in a hoop at regulation height.

I think you are going to see this a lot more than you think.

Re: Shooting from opposite side of the field
 

In '06 we could score from half court. In fact our autonomous mode was simply to have the driver line up the turret when they placed the robot, then spool up the motor (an FP, direct drive to a 6" wheel if I recall) and fire away.

We could have hit from further out, but the game had a built in speed-limit for the balls, so we were pretty much at maximum range.

Frequently, however, the balls would go in, but the massive backspin would actually toss them out of the aim high goal.

Backspin will be useful for stabilizing the flight of of the balls, but will also create lift, altering their trajectory and... in this game, unlike Aim High, will likely aid in scoring if you use it to bounce shots off the backboard.

My experience, however, after spending six weeks building a pan-tilt shooter that could (once you lined it up right) hit from anywhere was that in the time it took us to get our aim right, teams with far simpler shooters would drive in and hit ten shots from close range.

This year's target is smaller... there is nothing wrong with going for the slam dunk or lay-up approach... particularly if you have a hopper on the back of your robot that allows your "shoot from the other end of the court" colleagues to fire balls into your hopper (much larger than a goal) so you can finish the play.

Jason

Re: Shooting from opposite side of the field
 

I think they should include in one of the updates that baskets made by the human player in the last 30 seconds of the match are worth more; maybe like the normal score +2, so as not to get ahead of autonomous, but to still allow teams to score while balancing on the bridge.

Re: Shooting from opposite side of the field
 

They can't. This year the scoring is entirely automatic, hence the photogates at the baskets. There's no way to distinguish between a ball thrown by a human and a ball scored by a bot that will also allow for immediate scoring.

Re: Shooting from opposite side of the field
 

But did he have an 8' barrier in front of him?

Re: Shooting from opposite side of the field
 

If you plan to camp in the corner and launch balls, you could probably get away with 2 CIMs in your drive. You're not going to speed past anybody, nor are you going to push them, but who cares when you're going to drive into the corner, wait until the end, and then drive up the ramp. If you do autonomous right, you'll never even touch an opponent.

Re: Shooting from opposite side of the field
 

I wanted to add a spreadsheet I made to this thread. It helps with calculations for the ideal projectile in a variety of circumstances. Most importantly, it helps with the case of a fixed-velocity varying-angle shooter, as well as other cases. Please see my blog post about it: link

It doesn't take the drag into account, but will give an order of magnitude for different situations. It also tells you how much variation in your velocity or angle there would be between each of the hoops, so there is an indication of how much tolerance there is on the velocity or angle.

Re: Shooting from opposite side of the field
 

i would say its very difficult but possible and if a team perfects it then they would score alot of points

Re: Shooting from opposite side of the field
 

It was reasonably precise, and very accurate in altitude, but was difficult with that robot's drive train (which started holonomic and got a tank-drive conversion at the last minute) to get the azimuthal accuracy needed.

This year is definitely more challenging than 2006 for aiming.

Re: Shooting from opposite side of the field
 

I'm not sure if it was just the balls in our kit...

but they don't fly straight. Their CG is up to 1" off center... so you get some "wobble" mid-flight.

Re: Shooting from opposite side of the field
 

This is a product of the manufacturing process, when the ball is molded the side of the ball that is facing down ends up being more dense than the top part. Lower quality balls see this to a greater extent than higher quality (i.e. NERF). Depending on the manufacturer there may also be a had spot there the tube used for injecting the foam was inserted, this can also throw off the balance. All that said I haven't looked at these balls in person so I can't tell you what is actually causing it, I just know that these are concerns addressed when deciding on a manufacturing process for foam balls.

Who knew co-opping at a toy company would teach me something.

Re: Shooting from opposite side of the field
 

I really don't think it is worth pursuing. The chances of something like that happening are so remote...

With that attitude....