Springs?? (10 lbs. at 22 ft/s)

[pfreivald]

Exactly. The rules regarding safety are vague enough to give the judges/refs sufficiently leeway to keep us all safe -- and that means you need to be really careful about putting that kind of load on springs.

Patrick

[65_Xero_Huskie]

Originally Posted by pfreivald

Exactly. The rules regarding safety are vague enough to give the judges/refs sufficiently leeway to keep us all safe -- and that means you need to be really careful about putting that kind of load on springs.

Patrick

I think that Most judges will allow robots to have "Springs" or other devices ont heir robot no matter what it is they do as long as it is confined and not able to dismantle another robot. Like if a robot had some device that shot 1+ feet in any direction thats outside of their starting box, they would probably deem it unsafe, especially if you need 7+m/s force to get a ball up.

[JesseK]

I think the concept of launching has many people in first worried. The calculations we did about launching a ball came out to be
65-75 degrees is the ideal angle, but you need something about 7.8m/s just to get the ball over the rack when ur 3 meters away from it. Something that fast in Very dangerous in the wrong hands

These numbers are similar to what we've come up with. I'm not sure where 22m/s came from...

From the rules:

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.
...

HURDLE: When a TRACKBALL CROSSES a FINISH LINE while passing above the OVERPASS
and then contacts either the floor or another ROBOT before re-contacting the originating ROBOT.

Inherently, to hurdle one must also have a vertical projection on the ball. They have left the door open for teams to shoot the ball over the overpass. I think <R01> is there to ensure a compressed spring isn't being held back by shoestrings or other objects that could easily release energy outside of the arena and really hurt someone. I do not believe it's there to inhibit how you get the ball over the overpass.

You can't be afraid to fail if you want to launch the ball. It's a gambit, and the rules have technically left the option open for you. However, if you keep shooting balls out of the arena at refs, then perhaps they will deem your bot unsafe, but that's your driver's fault

[MrForbes]

22 ft/s is about 6 or 7 m/s

(English units vs. metric units)

[JesseK]

Whoops

[3DWolf]

Well I guess it's safe to say that the majority of us agree that any type of spring would be dangerous to use for this. The massive amount of force required requires a LARGE spring which are dangerous.

What I find interesting though is that so many people are getting different energy requirements for launching it though. I've seen numbers ranging from 5 J to 80 J. I know it depends on the angle but my teams estimated 7.5 J at 65 (I think degrees) is vastly different then then post above that gives that 80 J estimate.

[MrForbes]

If you figure that the mass of the ball is ~3.5 kg and you want to shoot it to a height of 2.5 meters (a little over 8 feet) then:

(3.5 kg)*(9.8 m/s^2)*(2.5 M) ~ 86 Joules

This is assuming that the horizontal componant of the balls velocity comes from your moving robot.

(posted by s_forbes on dad's computer)

[Alan Anderson]

Originally Posted by JesseK

From the rules:

Inherently, to hurdle one must also have a vertical projection on the ball.

I believe you've misread the definition of CROSSING. For "it", read "line". The definition refers to projecting the line to indicate a theoretical flat surface through which a ball or 'bot will move. Imagine light shining straight upwards from the line. It's not talking about throwing the ball.

[Brandon Holley]

squirrel I am with you 100% on this one. I do not see this being a safety hazard if design correctly.

And as for some of you people who are thinking of a large spring being pulled back to hit the ball with brute force, i think you should try thinking outside the box for a few .

[ALIBI]

What if you were the inspector, what would you be looking for?

How secure is the spring attached to the robot?
How secure is the launching pad between the trackball and spring?
What has been done to protect against pinch points between the launcher and robot?

These are just a few of the questions I would have (not and inspector). What other ones could you ask.

Aside: Putting your robot on display (grade schools, sponsors etc) will be a riot if you can hurdle the trackball 7-8 feet in the air! The only problem will be getting that blasted 41" trackball through a standard door.

[mneary]

If you're imparting 100-200 joules into the ball, be sure that the centerline extends back inside the wheelbase, or do the math carefully so your bot doesn't do a back flip.

If I were an inspector, I would also try to be sure that nobody's head is likely to be launched instead of the ball.

[akash155]

How would we go about testing the amount of force needed to propel the ball 8 feet in the air and once we go about testing that, and based on that calculation how would we quantify that in order to find how much energy would have to go into the ball? For example, we did a lever arm experiment where a mentor jumped on a lever and the ball was on the other side. We have the numbers and have calculated the energy lost from the jumping onto the lever to the ball leaving the lever. But we don't understand where to go from that point and I also don't believe that we calculated correctly. Any help would be greatly appreciated. Also based on that number, how do we determine what strength of spring we need.

[David Brinza]

Originally Posted by ALIBI

What if you were the inspector, what would you be looking for?

How secure is the spring attached to the robot?
How secure is the launching pad between the trackball and spring?
What has been done to protect against pinch points between the launcher and robot?

These are just a few of the questions I would have (not and inspector). What other ones could you ask.

Aside: Putting your robot on display (grade schools, sponsors etc) will be a riot if you can hurdle the trackball 7-8 feet in the air! The only problem will be getting that blasted 41" trackball through a standard door.

As an inspector, in addition to the intended function of the launcher, I would look for possible unintentional means of sudden release of this stored energy. Having a strong spring release accidentally while the robot is being carried on the field or in the pits can have very dire consequences. FIRST inspectors must decide whether your launcher is safe and that is a subjective judgment call. Expect to show the inspector how the spring can be inhibited from releasing accidentally (including failure of the firing restraint), how you can slowly/gradually release the energy in case you don't want it to fire and how the launcher responds when it fires without a ball.

You're probably not going to find a written, official checklist from FIRST, so you have to keep asking yourself what can go wrong and how can I avoid accidents as you design your launcher.

[pfreivald]

This is my point. I'm not trying to rain on anyone's parade, but better to hear it now than to get to competition and be disqualified for safety reasons (so that you have to dismantle your launcher and just be a race-bot for the rest of the tournament).

I did the math at 45 degrees and 2.5 meters and found the initial kinetic energy requirement to be 221 Joules (accounting for reasonable assumptions on energy loss, etc.).

I think that teams who try this method will (a) be disappointed in just how -hard- it is to throw that ball with a robot and (b) will be disqualified from play until they disengage their springs.

That said -- more power to you if you want to try.

Patrick

[MrForbes]

I think that you'll be amazed at the designs the different teams come up with to solve this challenge....putting twenty or thirty thousand creative minds to work to solve a problem can result in wonderful things.