Originally Posted by Scott358

Based upon the fact that it's very difficult to measure the speed for most teams (we had theoretical values, tested per the angle/distance method, and even purchased a radar gun.. but even then tested (at our own request) a bit too high), why would the muzzle velocity not be a part of the robot/safety inspection (obviously only for those with a shooter).

With the exception of those who would change the value after it's checked, this would ensure compliance for those that wish to play by the rules. As it is now, many teams who probably think they are in compliance may not be, and hopefully they won't have issues after the fact.

I would suggest this be an added inspection check at Nationals.

Originally Posted by ChrisH

At the LA regional last weekend every shooter went under the speed gun. If you couldn't pass or if you ripped up the inspection ball, you were not allowed to shoot. They will prpobably do the same at all the other regionals next week end and again in Atlanta.

Originally Posted by hillale (team 1625)

The 1 meter long speed tester at the St. Louis Regional was a joke. After breaking their tester by not lining it up correctly and hitting it with a ball, we got inconsistent readings all day. After finding a speed that the sensor said we could use, we tested our distance and we couldn't shoot 10 feet. If they are going to require speed testing at nationals, I should hope that they will come up with a more acurate way of testing.

Originally Posted by Richard

I don't have nearly enough data to reach a conclusion on this, but the following experiences might be helpful to those who perform ball speed tests, or to teams with robots that require ball speed testing, at the remaining events.

At STL, the head ref (Frank Kusiak, who was also head ref at MWR the following week) and the lead robot inspector (I) met Thursday to develop a procedure by which ball speed tests would be conducted. It went like this:

1. No ball speed testing was included in the required robot inspection checklist. This is established by FIRST headquarters and is not a regional option for lead robot inspectors.

2. Our interpretation of <S02> was that the head ref is the only official at the event who can order a ball speed test. The head ref may rely on his/her own observations and those of the other referees when deciding to order a test, or he/she may choose to respond to protests from competitors; i.e., drivers and/or HPs on the field.

3. When a ball speed test is ordered, the test equipment provided by FIRST is to be used in a manner directed by the FTA at the event. Robot inspectors will conduct the test with the assistance of the FTA if required, and with the cooperation of the team whose ball speed is being tested. This ensures that the team receives immediate feedback from the test.

4. Test conditions are as follows: the team is instructed to fire one ball per test through the FIRST ball speedometer into a curtain, and the speed of that ball is read using LabView. At STL we had the team repeat this test with several (at least five) balls, and looked for a consistent result. We ignored measurements that were inconsistent, assuming that high results were due to the shooter contacting the ball at the hard spot and that low results were due to incorrect speedometer alignment with the ball launch path.

5. When a consistent result exceeding 12 m/s was obtained, we advised the team that they needed to take corrective action. Teams were permitted to make software corrections at the test area and repeat testing immediately.

6. When a consistent result at 12 m/s or lower was obtained we advised the team and the head ref that the ball speed test had been passed.

Six teams had ball speed tests ordered by the head ref at STL. The only team for which multiple tests were ordered was 1625. My opinion is that 1625's shooter was legal in all matches that I observed; however, the backspin imparted by their shooter mechanism created a relatively flat trajectory and increased range, making their initial ball speed appear faster than it actually was. It was this appearance (IMO) that caused the head ref to order repeated ball speed testing. Again IMO, time spent on testing and overcorrection of the shooter wheel PWM level caused 1625 to perform worse than they could have in a few qualifying matches.

Two weeks later while volunteering as a robot inspector at Waterloo, I saw team 1596 suffer similar results for similar reasons: backspin caused flat trajectory and overcorrection caused low initial ball speed (with significant loss of range) in one or two qualifying matches. As with 1625, my opinion is that 1596's shooter was legal in all matches that I observed. In each case (1625 and 1596) the robot had one of the best (arguably the best) shooter at the event.

The point here is that it does not matter what the inspector or lead inspector thinks, only what he/she measures. What matters is the head referee's judgement, and in my opinion that factor has been remarkably consistent at events I attended and at those I watched via webcast.

My feeling is that there must be some method for ensuring compliance with <S02> and that the head referee's judgement is the best method. Test equipment and procedures can certainly be improved, and hopefully FIRST will provide some guidance.

Originally Posted by ChrisH

Assuming the measured length is 1 meter, there is a simple calibration that can be performed to check the speed tester. Simply hold it so the ball can drop through it vertically. Hold the ball close to the first sensor and drop it through. The ball speed should read 2.2 m/s.

Don't belive me? do the math! Hint d=(at^2)/2. If anybody needs more than that post here and I'll walk you through it. I figured this out for our own tester.

ChrisH

Originally Posted by TubaMorg

Uh without actually checking anyones math, how is it that the speed of a 1 m drop is 2.2 m/s and the speed of a .876 m drop is 2.37 m/s ?