Trajectory B/C

[Flavorflav]

Re: Ballistae.

I don't think there is any need for a clarification on this. The energy clearly comes from the torsion bundle, and I have seen at least one ballista compete in NY at the B level.

[captbilly]

I thought I posted about this a couple of days ago but I don't see my post anywhere. I was the one who posted about the trebuchet hitting the ceiling 2 years ago. That was a different event (Storm the Castle), which required a gravity powered device (trebuchet). This year the Trajectory event requires an elastic solid powered device, so a trebuchet would be a clear violation of the rules.

I never really got an answer about my previous question regarding the number of trajectory devices that are getting multiple bullseyes. We took some video of our trajectory projectile hitting the sand last year and it was quite clear that the crater did not form directly under the the "initial impact point" as per the scoring rules. In addition the crater center, even if it was a relaible indicator of the impact point (which it is not), is not clearly enough defined to measure to anything remotely like mm accuracy. I would be expremely surprised if the measurement error of the true initial impact point in sand was within better than 3-5cm. When we were calibrating out trajectory last year we tried using a system that would leave a mark at the exact impact point. The system worked fine and we could measure to within better than 1 cm where the ball landed, but we realized that the event coordinator was going to use sand (with it's inherent errors) so we ended up calibrating that way. I wouldn't be concerned about it except that if it is infact the case that many of the competitors are getting within a few cm of the target I can see no reliable way of determining who the actual winner is.

So the question is again, how many people are consistently hitting within a cm from the center of the target?

[starpug]

I thought I posted about this a couple of days ago but I don't see my post anywhere. I was the one who posted about the trebuchet hitting the ceiling 2 years ago. That was a different event (Storm the Castle), which required a gravity powered device (trebuchet). This year the Trajectory event requires an elastic solid powered device, so a trebuchet would be a clear violation of the rules.

I never really got an answer about my previous question regarding the number of trajectory devices that are getting multiple bullseyes. We took some video of our trajectory projectile hitting the sand last year and it was quite clear that the crater did not form directly under the the "initial impact point" as per the scoring rules. In addition the crater center, even if it was a relaible indicator of the impact point (which it is not), is not clearly enough defined to measure to anything remotely like mm accuracy. I would be expremely surprised if the measurement error of the true initial impact point in sand was within better than 3-5cm. When we were calibrating out trajectory last year we tried using a system that would leave a mark at the exact impact point. The system worked fine and we could measure to within better than 1 cm where the ball landed, but we realized that the event coordinator was going to use sand (with it's inherent errors) so we ended up calibrating that way. I wouldn't be concerned about it except that if it is infact the case that many of the competitors are getting within a few cm of the target I can see no reliable way of determining who the actual winner is.

So the question is again, how many people are consistently hitting within a cm from the center of the target?

Arden most definately got zero distance on both targets. We had gotten a perfect score when practiceing inside, both of the competitions I went to were outside so our black surgical heated up and we lost power and accuracy.

that was my reply to your question. Yes we could hit the center consistently, inside. At regionals the event coordinator used circles with sand and the center point was a ball, golfball I believe but I don't know for sure. We were the only ones to hit the center at regionals, the impound was in the shade and we were one of the first teams to go. When we hit the center, near target, the ball rolled backwards so it was kind of obvious that we had hit, from what I hear from someone who was looking from the side we hit the ball right on the top.

[haven chuck]

I think the reason they say in the rules mm is to make scoring easier. While most judges will go to the nearest cm, if they can just give 1 point per mm, it makes it simpler.

[captbilly]

So besides Starpug, is anyone else consistently hitting the exact center of the target?

I've been in SO for 4 years now and I know how iffy things can get when the judging gets real close. I watched the winning trajectory at nationals last year from the balcony. They hit the nail on the head on three out of four shots (literally, the event coordinator had a nail standing straight up in the center of the target, and they knocked the nail out). From the way he was acting it seemed as if the event coordinator hadn't seen anyone else do that, but then I heard later (rumor not confirmed) that a bunch of other competitors had perfect scores as well. I only watched a few people compete but none of them got even one direct hit, and the variation from shot to shot was huge. I am just wondering how the event coordinator (I am assuming it will be the same guy since he also did Storm the Castle back in 2007) could differentiate between a ball that just touched the nail, and one that hit it squarely on the head. It's not a problem if few if any people are even hitting it, but if 10 people are each getting direct hits on each target/nail I can't see how he could tell who was actually closest.

Starpug's experience with the event coordinator using a golf ball as the center of the target is a perfect example. How could one possibly tell if someone hit the golfball exactly in the middle or just glanced an edge? I am not suggesting that Starpug didn't hit it exactly in the center but I'm wondering how the event coordinator would have picked a winner if 5 other competitors had also hit the golf ball each time?

[starpug]

Well non-metallic elastic solid for now means to most people rubber tubing, bungee, or something of the sort. It has yet to really become extremely widespread about the inconsistencies of rubber when heated, or cooled in the states with early competitions. So for now hitting the center is not really a problem because until people start changing their devices to keep their bungee cool or find other ways of powering their devices, something new that will end up being probably like the FAT trebuchet was in Storm the Castle. If the non-metallic elastic solid rule is ever droped then we are also likely to see an increase in perfect scores. I think that we should start seeing these adaptations by some of the better teams in B this year and I think it will probably be pretty widespread by atleast next season. This means that Nats this year might be interesting in the B division and possibly the C division if a few enterprising teams come up with a way that either combats this or does not rely on a rubber to power it. So there might have to be rule changes after this season.

[fleet130]

When I ran this event several years ago, I drilled a small hole in the center of the target and inserted a red pipe cleaner (chenille stem) so it extended about 2 inches above and 1 inch below the target surface. The part sticking out of the bottom of the target was bent over and taped it to the bottom of the target. With a little adjustment It was fairly easy to get the top part to stick straight up so the teams had a fixed reference point to aim at. The pipe cleaner would bend out of the way when hit by a projectile hit, minimizing the projectile's deflection and the point of impact on the target's surface could be determined by the indicating substance (sand, talcum powder etc). I'm sure there are other ways, some possibly better, to accomplish the same end. The problem is getting these ideas out to the people who need them (event supervisors).

[SuperSherbertxxOtaku]

So, would a catapult work better in trajectory or do I need to consider something else? I'm a noob.

[trombonegirl23]

I am going to make a ballista I made a catapult last year though

[binary010101]

Are torsion springs legal?