Re: Car Nack Predicts 3/06
 

Car Nack is wise and I agree.
Certainly there will be many complaints about teams that exceed the 12 m/s rule.
Resolving the complaints will be interesting to watch and I am not even sure how or why they would consider doing it.
You know that resolving the complaint WILL NOT slow the throughput by testing the accused on the field of play.
Post inspection of the accused is possible if a method and location is readily available to resolve the accusation - but I can't believe that 10 -20 minutes after a match AND the accusation is resolved - the scores would be revised.
The NASCAR example is fine except it takes them TIME to resolve the complaint and they do it back in the garage - AFTER the race.
This is an issue that needed a clear methodology defined and included in the inspection process. It would be nice to be informed what that method will be in advance so we can validate using the same methodology before hand.
We used the guideline that was included at kickoff to validate, as we don't have access to a radar gun or other sophisticated equipment. We compensated the distance to include for being a certain distance from the horizontal (the ground).
Our design drives the motors through a speed controller so if we do exceed the velocity rule we will dial down until we meet it - but that does kill all our pre-work establishing the correct autonomous settings for the controls.
What does 12 m/s look like anyways?

Re: Car Nack Predicts 3/06
 

well, just drive a car at about 43 km/h (roughly 27mph) and you'll find out ;)

Re: Car Nack Predicts 3/06
 

This seems to me to be unfortunate. It does two bad things.

#1 It continues the uncertainty. What FIRST teams need more than anything is a quick ruling that they know they can trust to not change. Uncertainty causes delay or forces teams to go with a safer but less optimal solution. In both cases teams are justified in being upset with FIRST.

#2 It takes away an easily repeated test method from team. 30 Degrees is easily measured. The height of the shooter from the ground is easily measured. The distance a ball flies is easily measured. Seems as good of a method as anyone could have hoped for.

Does anyone have any insight into why there has not been a clear ruling on this? The only thing I can think if is that the folks in CO may have less air resistance than they have at Altanta, but I think teams can deal with that.

I don't think that the robots will be significantly more dangerous if balls exit the robot at 12+delta m/s in Altanta and 12-delta m/s in Denver especially if they fly the same distance.

As for me, I hope FIRST rules in favor of the Angle, Height, Distance method.

Joe J.

Re: Car Nack Predicts 3/06
 

From what I have been told wouldn't spin on the ball effect the distance the ball where to travel?

We used a photogate like sensor system to measure our shooter velocity on our prototype and got different measurements then when we used a radar gun.

Re: Car Nack Predicts 3/06
 

I think you missed my point, but thanks for converting it to mph for me.
I wanted to get a feel for what it looks like as an observer - if I drove, the perspective would be different than if I were stationary, watching something fly out at 12 m/s. I think that an object moving at a constant velocity may not "look the same" as an object moving at an instantaneous velocity.
If accusations are based on what something "looks" like - we could be surprised to find out that we were wrong.

Re: Car Nack Predicts 3/06
 

Jon got it right. The problem with the simple "height, angle, distance" method is that it is a very basic analysis of the actual flight dynamics of the ball that does not account for several (legal) variables that can significantly affect the distance traveled. For example, the distance guideline given in the manual is based on the initital constraint of no spin on the ball when it exits the robot. During some experimentation, we found that putting a serious backspin on the ball - while keeping all other performance parameters the same, including the 12m/s exit speed - could increase the distance traveled by up to 30%. If FIRST were to rely on just the "height, angle, distance" analysis, they would incorrectly classify a shooter that put a lot of backspin on a ball, and thereby got increased range, as an illegal solution.

-dave

Re: Car Nack Predicts 3/06
 

has anyone here played paintball? If you have then there is your answer. Paintballs are only allowed to travel about 300-350 ft per second. Before you enter the feild you have to get your gun clabrated and you shoot your paintball gun though a small barrle that tells you how fast you are shooting. I will see if i can find a pic.


shaun

Re: Car Nack Predicts 3/06
 

but I believe that the paintball chronographs only work with faster velocity's (300 mph! *edit 200 mph*). I am pretty sure that 12 m/s would not measure on a paintball chronograph.

Re: Car Nack Predicts 3/06
 

nope its 300 feet a sec



http://www.ehow.com/how_8414_calibra...tball-gun.html

shaun

Re: Car Nack Predicts 3/06
 

yeah, i know its 300 ft/sec. I accidentally typed a 3 instead of a 2

300 ft/ 1 sec * 3600 sec/1hr * 1mi/5280 = 204.5 mi/hr

I play tournament paintball, and usually shoot around 280 fps, but mph is so much easer to understand to the average person

whoops :o, but its still far faster than the 12 fps of a poof ball

Re: Car Nack Predicts 3/06
 

its 12 meters per sec
that about 38.4 fps
or 27 mph

shaun

Re: Car Nack Predicts 3/06
 

whoops! wow, i am just full of mistakes today, sorry

Re: Car Nack Predicts 3/06
 

I agree that there are going to be difference due to spin. And I appreciate that FIRST is trying to do the right thing.

My thoughts are basically this. Safety is the main concern. There are 2 aspects to safety: If the balls are exiting too fast, someone could get hurt from a short range direct hit. If the balls go too far, unsuspecting folks will take a hit.

If we classify the exit speed by range, we only take care of the second but not the first.

Or have we?

I don't think there is anything magical about getting hit with a 12m/s Poof ball vs a 15m/s Poof ball (which is 25% higher than the "true" limit). I realize that it would have 56% more energy, but I don't think there is a bright line between what will hurt a human and what won't. Robots are dangerous things as are the machines we use to make them. I don't think even a 15m/s Poof ball is among the more significant risks associated with building and competing FIRST robots.

There is also something to be said for a limit that all teams can easily test for themselves.

I would urge FIRST to go with the angle, height, distance method, knowing that it is going to be wrong in some cases but that an obviously flawed standard that is easily implemented & understood is better than an improved standard that is less easy to implement & yet to be defined in Week 6 of the design/build cycle.

Joe J.

Re: Car Nack Predicts 3/06
 

I point to the answer given on the Q & A when the official answer asked the team if they would provide a complete cover for the entire field ( wording was like that).

How about if all teams brought a piece of Poly carb and we covered the entire field after attaching them all together?

I make light (humor) because the real issue is not being addressed even as we approach the end of build.


What is the EXACT way the rule will be applied - MEASURED -TESTED or whatever. The Game committee better have an answer or there will be many unhappy teams.

Re: Car Nack Predicts 3/06
 

I wasn't particularly worried about hanging in 2004 (1293 had bigger concerns, like moving...), but how were the hangers with their 10-feet-per-second limit enforced? I don't have a 2004 manual in front of me, but I seem to recall the basic requirement being that teams had to prove through math or testing or black magic voodoo that their hanger was within the requirements.

If I'm right, what's stopping us from implementing a similar thing this year?