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.
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.
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.
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.
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.
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?
i agree but how are they going to check that? are they going to take some radar guns and test the speeds before each match i think its going to take to much work to stop that
Just out of curiosity, couldn’t FIRST ask an organization like the USTA or MLB to donate some ball-speed measuring devices? Think about it, in almost every tennis or baseball event you see on tv (and probably a few other sports as well, I just can’t think of them offhand) they give the speed that the ball was served or pitched at. If those guns can record speeds up to 150+ mph, they certainly must be able to handle 26.8 mph, right?
And it is a bit of an off-season for both sports, so…
Umm, what about a beam-break sensor? Super simple to build, just as easy to calibrate, portable, battery-powerable, and will work with any shooter.
In case the idea isn’t clear: Think of a tube a few inches (maybe a foot) long. Have someone shoot their ball through the tube. In the tube is an emitter (of light) and a sensor (on the sother side of the tube). Simply measure the time that a 7" ball breaks the beam (a few milliseconds) and you have a speed. Of course, the exact size of the ball needs to be measured, and an accurate timer needs to be used.
On the other hand, ask any experienced police officer, they will tell you they can judge the speed of a car to within 2 or 3 miles per hour, just from experience. I’d bet the referees develop a similar feel for speed, and will send teams back to the inspectors often.
You’ve been reading people’s minds/posts, haven’t you? :eek:
Vince Wilczynski in this post proposed the very same thing. Vince’s setup uses 2 IR sensors (Emitter/Sensor combo, I recognized it as having been shipped in FRC kits sometime in the past 2 years), one at the start of a “tube” and the other at the end, and uses LabVIEW and a USB-DAQ device to measure the speed of the ball traveling through the tube (measures the time between the normally-low digital response from the sensors go “high”). It’s not battery powered to my knowledge, but could be. And it’s very effective, Vince said his tests worked out fairly well at a “mini-meet” he tried it out at.
Danny,
The official word is it will be a setup like the one you describe, or something similar. I recall seeing it on CD, in fact, it’s referenced higher up in this thread.
Aha! So it is, I don’t know how I missed that gem. It would be nice if NI Pilot Program teams (with the means to do so) would build one of these for people to use for spot-testing at their regional. If anyone wants “general” plans for one of these or the LabVIEW program I’d be happy to help out…
First question…is everybodies shooter shoot the same speed with every different ball in various states or destruction…i know we sure dont
Second question…unless a robot lines up to the edge of the field and delibertly shoots a few balls off into the crowd would the impact of a ball that most likely was lobbed into the crowd be that much of a safety hazard to the normal person (i say this because there may be some special cases where it could be dangerous such as an infant etc.) but how many of these cases do you see in the typical crowd.
