Trajectory B/C

[hollyberries230]

Look on the SO website, there is probably a link to a WIKI. Look on youtube (search, science olympiad trajectory), there are some videos there. There are also the more adult sites (not as in X rated, just for adults interested in catapults and trebuchets) with lots of info on assorted "siege engines" (weapons that throw heavy things). But to put it as simply as possible, just picture some sort of rubber band (maybe lates tubing or bungy cord) powered catapult. A simple lever with a large rubber band pulling it with a cup to hold your ball attached to it will do the job. There are many many other possibilities, and many fine touches that will contribute greatly to the accuracy (really repeatability) of the device, but the basic idea is a catapult powered generally by rubber bands or tubes.

You can try a torsion powered device as well, which would just be an arm (with the cup to hold the ball at one end), that rotates due to the force of winding a large rubber band or rubber tube or rope. You can also look up tons of info on trebuchets (was called strom the castle in Science olympiad jargon), and just change the power source from a falling mass to a rubber band. A basic trajectory device could be built in an afternoon, although the National winning ones probably takes dozens if not hundreds of hours to build and calibrate. Plan your time so that you have lots of time left after building to find the right settings to get your device to reach a certain distance and height target. For the more competitive teams the adjustments (calibrating) generally takes more time than building does.

Thanks; that really does help my visualizing the general aspects of the event. But after looking at the coach's power point, I had a few more questions. Could anybody explain how the targets are oriented? The powerpoint expresses that they're placed at different elevations, but I'm not really sure if that means the targets are still flat, or if they're held up like dart board targets. And are there specific graphs that we should make? Or is it open to anything that shows some sort of relationship between any variables in the event? Thanks again.

You probably should go here http://www.scioly.org/phpBB3/viewtopic.php?f=16&t=163
The targets are flat.
Also I believe that as long as your graphs show whatever variable your using tested at distances should be sufficent. I'll see about uploading some of our graphs to the wiki if I get the chance.

Thanks a lot for all your help

[binary010101]

<SNIP> Also I believe that as long as your graphs show whatever variable your using tested at distances should be sufficent.

Keep in mind the fact that, as they are used, the performance of any elastic material will slowly degrade. Therefore, it would be advisable to calibrate using new tubing/rubber bands, practice with them, and replace them just before the competition.

[croman74]

<SNIP> Also I believe that as long as your graphs show whatever variable your using tested at distances should be sufficent.

Keep in mind the fact that, as they are used, the performance of any elastic material will slowly degrade. Therefore, it would be advisable to calibrate using new tubing/rubber bands, practice with them, and replace them just before the competition.

Definitely make sure you use new rubber bands every time you test. I didn't think of that last year and my calibrations were all off. It might be better to use rubber tubing than rubber bands as tubing stretches less than rubber bands. I'm not doing this event this year, but I did it last year, so that's just what I experienced.

[captbilly]

Anybody figure out what release angle it will take to clear the worst case scenario of 2 meter high target and 2 meters between the ground level and elevated targets?

[andrewwski]

Going to depend on the speed your projectile is released at.

[Valpo Towers and Trebs]

I think our team calculated it to be about 55-60 degrees if you want it to be pretty safe.

[starpug]

I think our team calculated it to be about 55-60 degrees if you want it to be pretty safe.

we used 45 degrees at a high setting to get over a pair of targets at 6 and 8 meters at 1 high last year. So I think more power and a higher angle should logically get you clear, maybe 50-60 degrees depending on how much power your device has.

[captbilly]

I think our team calculated it to be about 55-60 degrees if you want it to be pretty safe.

we used 45 degrees at a high setting to get over a pair of targets at 6 and 8 meters at 1 high last year. So I think more power and a higher angle should logically get you clear, maybe 50-60 degrees depending on how much power your device has.

The angle you need is not related to how much power your device has. On the other hand the minimum power your device needs is related to the angle you use. The higher the angle you use (above 45 degrees, or below 45 degrees for that matter) the more power you will need to reach the target. The minimum angle that will clear the elevated target is only related to the height of the elevated target and the distance to the ground level target. If your device is powerful enough you can use an angle larger than the minimum required but the minimum possible angle has no relationship to power.

[Flavorflav]

I have a hard time imagining the regional event supervisor who decides it is worth his time to build a two meter platform and spend the whole day going up and down a ladder. My money is on garbage cans or targets on the floor.

[starpug]

<SNIP> Also I believe that as long as your graphs show whatever variable your using tested at distances should be sufficent.

Keep in mind the fact that, as they are used, the performance of any elastic material will slowly degrade. Therefore, it would be advisable to calibrate using new tubing/rubber bands, practice with them, and replace them just before the competition.

Just make sure you read the beginning of this topic and take that into account when using rubber tubing.