Trajectory B/C

[starpug]

Can we keep this to talk directly related to Trajectory, not your personal chat session making fun of other schools?

[zyzzyva980]

Agreed. I didn't like the way this was going, anyway.

I think I posed a question earlier in this thread, and I'm still wondering: has anyone attempted a bucket shot yet? Or, going one step further, has anyone else created a bucket shot graph? Where have the buckets been in any competitions thus far? And how successful have people been when shooting for the bucket. To merge with a former topic, lasers. We're planning on using them on bucket shots after our last attempt failed. Has anyone converted a bucket shot without a laser?

I know that's a lot of questions, but I'm curious about how teams have reacted to the new option.

[andrewwski]

I supervised the event at an invitational and one team hit the bucket on a bucket shot. They hit the ball right on the rim of the bucket - a few more tenths of an inch and they would have been in. They didn't use any sighting devices.

I had the bucket placed 1 meter to the right of the center line at a distance of 6 meters.

These results are far from indicative of general trends, but it seems absolutely feasible that some teams will land in the bucket twice. At state competitions, I'd expect to see it happen frequently.

[sj]

Me and my partner have managed to get the ball in the bucket multiple times at practice and hit the bucket at regionals. we received a total of 290 for second place. also we used a laser for alignment.

[Draylon Fogg]

now with the bucket and target shot which is better for each, catapult or trebuchet or is there another design that is better???

[andrewwski]

Well, I'm not sure your question makes much sense if you're asking which design is better for each specific shot, as you can only have one device.

But no, one design wouldn't be better for a specific target than another - you just need the best accuracy and precision possible.

I don't know how you'd use a trebuchet under the rules - since trebuchets use gravity as the energy source. You can only use a non-metallic elastic solid. I suppose you could modify a traditional trebuchet design to use an elastic, but that seems extremely complicated.

I'm not convinced there's one design that's better than others. I've seen catapults and cannon-type devices that do very well. Cannon-type devices seem to be very precise, as you can alter both the distance that you pull the elastic back as well as the launch angle. Although you can certainly make similar adjustments for catapults, as well as other designs.

[Balsa Man]

Our folk just got a nice ballista up and running yesterday. Lot of work ahead to get it calibrated, of course, but at around 3 and 5m, its grouping shots in what seems to be about a 10cm circle.....

First attempts with just a quick stick w/ bow & string, using, I'll call it a slingshot approach, were, uh, erratic. But, they discovered, if you set the ball up on one place along the stick, and vary the pull-back on the bow string, launch distance varies. Its pretty cool. Tool a few weeks to turn that initial proof of concept in to a finished machine.

Carbon fiber bow, practice golf ball. Trigger mechanism runs back and forth along the.....main stick via a threaded rod; easy to make precise, repeatable trigger position settings.

As Andrewski was saying, there are pros and cons to all the various types. It'll be interesting to see if the precision in distance adjustment this approach seems to offer works out in testing/calibration. One of the very nice things is how quick and easy it is to set up for re-firing.

[starpug]

Our folk just got a nice ballista up and running yesterday. Lot of work ahead to get it calibrated, of course, but at around 3 and 5m, its grouping shots in what seems to be about a 10cm circle.....

First attempts with just a quick stick w/ bow & string, using, I'll call it a slingshot approach, were, uh, erratic. But, they discovered, if you set the ball up on one place along the stick, and vary the pull-back on the bow string, launch distance varies. Its pretty cool. Tool a few weeks to turn that initial proof of concept in to a finished machine.

Carbon fiber bow, practice golf ball. Trigger mechanism runs back and forth along the.....main stick via a threaded rod; easy to make precise, repeatable trigger position settings.

As Andrewski was saying, there are pros and cons to all the various types. It'll be interesting to see if the precision in distance adjustment this approach seems to offer works out in testing/calibration. One of the very nice things is how quick and easy it is to set up for re-firing.

Sounds pretty cool. The question is, is the ball guided as it is launched?

Well, I'm not sure your question makes much sense if you're asking which design is better for each specific shot, as you can only have one device.

But no, one design wouldn't be better for a specific target than another - you just need the best accuracy and precision possible.

I don't know how you'd use a trebuchet under the rules - since trebuchets use gravity as the energy source. You can only use a non-metallic elastic solid. I suppose you could modify a traditional trebuchet design to use an elastic, but that seems extremely complicated.

I'm not convinced there's one design that's better than others. I've seen catapults and cannon-type devices that do very well. Cannon-type devices seem to be very precise, as you can alter both the distance that you pull the elastic back as well as the launch angle. Although you can certainly make similar adjustments for catapults, as well as other designs.

I've had experiance with Canon type devices for 2 years, the first year of the event in B and last year in C, I have discovered one major flaw in the design. The flaw is that canon type devices rely on pulling the projectile straight back, and as the rules require the devices to be smaller and smaller, the amount of power you can get from one of these devices drops. Because of this elastic with high and higher resistance is required in order to get the projectile to travel the required distance (I couldn't even achieve that with the strongest elastic I could find last year, but I had limited time so it's possible I could have gotten it to work eventually.) The greater forces generated by the stronger elastic can lead to other problems, for example last year I had the force of the launching device hitting the stopper rip the end cap of the launching device right off. In a catapult you are pulling the arm in an arc, meaning as the devices have to get smaller, the power is less greatly effected.

These are just my experiances, the design of your device maybe slightly different. My devices looked like this:
164|2/a2j_IMG_0021.jpg

976|2/a2j_img0154oqu.jpg

[Balsa Man]

Sounds pretty cool. The question is, is the ball guided as it is launched?

Yup, sure is - rails along the main stick. Big part of where that 10cm circle of landing points is coming from.

[scifipi]

My trajectory device is a ballista, we finished it and it works. The only problem is that it isn't the most accurate or repeatable in its shots, and we need an answer to this madness. Does anyone out there have a solution? We're asking our coach, but we wouldn't like to bother her too much... Someone MUST know!!!