Re: How will FIRST measure muzzle velocity?
 

Maybe they'll test, like they test many rules; the honor system.
FIRST has said it must be less than 12 m/s, design accordingly.

Re: How will FIRST measure muzzle velocity?
 

exactly! it would be very easy to turn down your launcher speed while the bot is being inspected, then turn it back up on the field.

and it would be very contriversal if someone is able to put a lot of spin a the ball, so a 12M/s ball can float from one end of the field to the other like a frisbee.

Part of GP is that FIRST expects us (the teams) to be professionals, ie. that we know what we are doing.

Re: How will FIRST measure muzzle velocity?
 

Thanks for the clarifications:

In NASCAR as well as SoapBox Derbies, your vehicle may be inspected before and/or after the event...

So, best to simply abide by the rules of 12M/sec and not risk a total DQ....It's just a game...it's just a game....it's just a game.

ps; please explain the aerodynamics of a relatively-hard-surfaced round ball being able to be shaped to fly like a Frisbee or airfoil? ;)

Re: How will FIRST measure muzzle velocity?
 

Someone above mentioned that you have to be on the near side of the field to score legally. This is wrong. There is only a limit on muzzle velocity. You can go much farther if your robot is moving 14fps and applying 500rpm backspin to the ball..

Re: How will FIRST measure muzzle velocity?
 

I think John and Ken (in his follow-up post) are exactly right. This is one of several FIRST rules that are best enforced by the GP ethic that we all aspire to.

That said, as a lead robot inspector I will follow whatever procedure FIRST calls for. My personal opinion is that the head referee's authority under <S01> and <S02> is very broad and gives him/her several options, including a 10 pt. penalty, DQ, and mandatory re-inspection. So I don't think team compliance with the muzzle velocity rule will be an issue.

Re: How will FIRST measure muzzle velocity?
 

any ball that is spinning as it flys through the air will have a curved trajectory. This is what happens when you slice a golf ball, it curves off to one side in flight

this is how a curve ball, sink ball and floater in baseball works.

with enough spin you can actually make a ball curve upwards (instead of downwards) as it flys through the air.

The reason it happens is the spinning surface of the ball moves the air in contact with it in one direction. The front surface is hitting more air than the back surface so it pushes the air to one side. If the ball is spinning in the vertical axis the path will curve sideways.

Doesnt anyone play wiffle-ball anymore?!

Re: How will FIRST measure muzzle velocity?
 

I respectfully disagree - Rules enforced by the honor system have honor-system-y requirements: "Strategies aimed soley at the destruction of other robots won't be tolerated", for example. Rules with measured numbers in them seem like they should require something to be measured.

There ought to be an incentive for a team to take the extra time to specifically tune their shooting mechanism to be below the limit, instead of relying on their design, which may have assumed things (ball mass, coefficients of friction, motor constants, air density, moon phase) that might not be true.

Re: How will FIRST measure muzzle velocity?
 

Suppose a team designs and builds a mechanism driven by an electric motor that can launch a ball at 20 m/sec; to comply with <S01> and <S02> they limit motor voltage by setting an upper bound on PWM command in their software. They could then pass an inspection that includes a muzzle velocity test. The inspector might not realize that the team had some means of increasing that PWM limit later, so the team is on their honor not to do so.

In any case the head referee will be in much better position than the lead robot inspector to ensure that the intent (i.e., safety) of <S02> is not violated.

Re: How will FIRST measure muzzle velocity?
 

I dont know about that. Ive never seen a judge pull out a pair of calipers to make sure your primary battery wire actually was 6 AWG wire?

Ive never seen a judge pull a pressure gauge out of his pocket to make sure our pressure gauges were calibrated?

Re: How will FIRST measure muzzle velocity?
 

With any inspection checklist item, you are on your honor not to modify the robot to violate it after inspection, or to have it re-inspected if you do modify and it might violate a rule. ANY inspection item. I fail to see how this will be different. Like any other inspection item, it will be incumbent on refs, teammates, and other teams to bring it to the attention of officials if they believe some team might (accidentally) have modified their robot to violate this rule.

To Kris: The entire Fix-It Window set of rules is on the honor system. It still has numbers in it.

Re: How will FIRST measure muzzle velocity?
 

I think the intent of the original question was;

"Do you suppose they will have an inspection station with a radar gun"

not

"How will they make sure teams do not change their muzzle velocity after inspection"

It seems to me that a radar gun muzzle velocity check during robot inspection would be simple and probably will happen. I know that is how we intend to tune our robot.

Re: How will FIRST measure muzzle velocity?
 

I say that they will have a gun, or some sort of sensor, maybe even a pressure sensor that they'll have teams shoot at and then measure the velocity there. Then on the field, the Refs will throw a flag if they see a shot that is out of the possible range (isn't it around 34 feet?) or that looks to be firing faster than it should be. They then could use the the same sensor and test it right on the field after the match.

It'll be intresting, expect an update after 2/22 that'll announce it.

Re: How will FIRST measure muzzle velocity?
 

I hope that they have some station where you can test the velocity of the balls. Something similar to a chronograph at a paintball field. We can do all the calculations in the world but its impossible to know exactly how fast the ball is going with out some kind of radar machine. That would allow us to fine tune the speed of the ball launcher and get everyone on the same playing field. Just remember "cheaters never prosper"

Good Luck
~Kirk

Re: How will FIRST measure muzzle velocity?
 

Maybe something similar to what they use on paintball guns...just on a bigger scale. (The pic attached is one kind, another kind rests on a bigger tripod like chrono. They may put a big round chrono machine near the exit point of the ball.)

Re: How will FIRST measure muzzle velocity?
 

If the ball is spinning it can go further than the specified distance at 12m/s

and to confuse things even more, a radar gun would not work if the ball is spinning. I believe a radar gun registers the highest returned reading, which would be the part of the ball that is spinning towards you, including the angular speed along with the linear speed.