Throwning the ball over the over Pass

Is it possible to throw the ball over the overpass? And if so are there any velocity or safety restraints?

I have not seen anything in the game rules saying that you cant catapuls balls. I have also not seen anything about restraints either. It is also possible that I just completely missed them both. I dont think they are too worried about a velocity though. I dont think that ball will be able to go yery fast, I think if you launch it it will just kind of float like a beach ball, however I have not got to see one of the balls up close yet. None of these are definate facts, so take them for what their worth.

ok thanks i was just wondering if it was at all possible. because to have a 10 lb ball flying through the air there might be some restrictions

alright our team has been discussing this option a lot…but I realized that the catapult idea wouldnt work if they wanted to say…hurdle…the ball
first off, in the definition of hurdling, it states “be moving toward the OVERPASS and/or elevating the TRACKBALL so that the top of the
TRACKBALL is higher than the LANE DIVIDER.”
that means ure catapult will have to start at 6 feet (ht. of lane divider) in order for your robot to succesfully hurdle

correct me if Im wrong…

and then contacts either the floor or another ROBOT before re-contacting the originating ROBOT.

You are right about the hurdling part, but not about the hurdle part. Nowhere in the definition of a hurdle does it say that you need to be in the process of hurdling. I see it that they are two seperate things. All being in the process of hurdling is protection from contact with other teams robots.

well the trackball itself is 40 inchs high on the ground, giving the facthat it is the “TOP” of the trackball must be over 6ft.

the ball is already 3’ 8" without any support so really the catapult only needs to hold the ball up another 2’ 4" which realy isn’t a big deal!

You said it yourself, “and/or”. You are hurdling when you are in your home stretch, in possession of a Trackball and moving towards the overpass (you do not need to have the top of the Trackball above six feet). G42 gives you protection while in the act of hurdling. The rules do not say you have to be in the act of hurdling (by definition) to hurdle. A hurlde is when the Trackball passess above the overpass (nothing more, nothing less) and will be scored if over your alliances overpass. For that matter, I do not see anywhere where it says that the Trackball must pass over in a counterclockwise direction, wow, does that open up possibilites! Please, someone correct me if I am wrong.

The rules could care less about how a Trackball gets above an overpass. You should be able to use a catapult, even if you are setting still and the top of the Trackball is not six feet off the ground. You will not be getting the protection of G42 if you are not moving towards the overpass tough.

yea your right i dont see anywhere where it clearly states that you have to throw the ball in that motion which leaves alot of options open

So that means that if…

                /  Robot was    |                   \
               /      O <- here  |                    \
              |_____________ | ___________  |
              |      Alliance      |   Ball could     |
               \       Home       |   be thrown    /
                \     Stretch     |   here -> O   /

…and still count as a hurdle. As long as it passed over the alliance’s overpass,

Our team believes it would, and the only down fall was that the robot wouldn’t be considered “hurdling” and under the protection.

*If I’m wrong please let me know. I don’t see anything wrong with it though.

Today team paragon tried a mock game with students and a ball. We tried to toss the ball over the overpass but it didn’t work out to good we only got it once. Also when we threw it over after the field was built someone got knock down on to the floor. :]

No you cant throw the ball over backwards, look at the definition of crossing

CROSSING: The act of a TRCKBALL or ROBOT passing through the plane defined by a line (i.e.
LANE MARKER or FINISH LINE) when it is projected vertically upwards. A TRACKBALL or
ROBOT shall have CROSSED a line when all parts of the object, while traveling in a counterclockwise
direction, have completely passed through the plane.

and then contacts either the floor or another ROBOT before re-contacting the originating ROBOT.

You can throw the ball backwards over the overpass, but you wont get any points for it.

My last post had a text picture that did show up so below should be a corrected pic.

Apparently spaces don’t show up???:confused: :confused: ???

…/ Robot was…|…
…/ O <- here…|…
…|_____________ | ____________|…
…|…Alliance… |…Ball could…|…
…Home…|…be thrown…/…
…Stretch…|…here -> O /…

to ccsingle07

yes, I think. It is traveling counter-clockwise, so I see no problem with this.

anybody know of a fairly reliable formula for figuring out air resistance on the ball?

I’ve looked up the formulas online, but all I’m able to find is “high velocity” formulas and I’m not sure what exactly a “high velocity” would be.

Unless I have messed up my kinematics, an initial velocity of 6.25m/s should launch an object 2m into the air, which should be plenty for hurdling. Given that this is about 23km/hr, I suspect you could adequately account for air resistance by just aiming to put the ball 30cm or so over the crossbar.

Now how you accellerate the ball to 6.25m/s… that’s another issue.


Cd = 0.1 for Reynolds number ~666k (10m/s)

Turn CD into a Force at velocity x by using info from here:

Extra credit

Integrate air drag loss to peak of trajectory and you get an idea of how many joules extra kick to give it vs doing this in a vacuum.


At the velocities we will be moving the ball, air resistance would be insignificant. The problem with hurling (not hurdling) the ball is coming up with the energy to accelerate the ball to 20-25 ft/second without using quite a bit of stored energy. While rule <R01> is quite vague regarding stored energy; it says:

“Storage achieved by deformation of ROBOT parts. Teams must be very careful when
incorporating springs or other items to store energy on their ROBOT by means of part or
material deformation. A ROBOT may be rejected at inspection if, in the judgment of the
inspector, such items are unsafe.”

It is probably safe to assume that a robot which stores enough energy with steel springs, latex tubing, etc. to throw a track ball over the overpass might have trouble passing inspection because of the safety issue of, for example, the possibility of releasing this energy suddenly into someone’s head.