Trajectory B/C

[robotman]

We had to change Everything!!!! Our calibrations had to be redone, we screwed up on our proportions, and we have SO much work to do!!! PLEASE HELP US!!!!! MY PARTNER IS COMPLETELY USELESS!!!!

It is extremely hard to help someone with out a specific question.
If you want help Read through the Trajectory Wiki and the rest of this thread.

than if you have a specific question please ask it

[starpug]

We had to change Everything!!!! Our calibrations had to be redone, we screwed up on our proportions, and we have SO much work to do!!! PLEASE HELP US!!!!! MY PARTNER IS COMPLETELY USELESS!!!!

Seems to me like you know what you need to do, you shouldn't have much problems doing it yourself. I built my device last all by myslef in under 4 weeks and I don't think that NY has regionals until sometime in Febuaray.

[zyzzyva980]

Our machine has a problem- our triggering device is a rope, that when pulled, releases the arm that launches the tennis ball. The problem is that when we pull it, the machine "jumps" and the tennis ball makes a slight curve off target. To get a good score, my partner has to account for the jump when he aims, causing him to basically shoot blind. We've tried to fix the problem using weights, but it still jumps. We can't pull the rope any slower, because the catapult requires quite a bit of force to trigger. Any suggestions? We're nearly out of the size limits, so adding on to the front or back is out of the question.

[starpug]

Our machine has a problem- our triggering device is a rope, that when pulled, releases the arm that launches the tennis ball. The problem is that when we pull it, the machine "jumps" and the tennis ball makes a slight curve off target. To get a good score, my partner has to account for the jump when he aims, causing him to basically shoot blind. We've tried to fix the problem using weights, but it still jumps. We can't pull the rope any slower, because the catapult requires quite a bit of force to trigger. Any suggestions? We're nearly out of the size limits, so adding on to the front or back is out of the question.

So it the rope attached to a pin of some sort? If the problem is friction then some silicone lubricant on the pin and such should reduce the friction somewhat. But you can really never have too much weight. How much weight do you have on it right now?

[zyzzyva980]

I think we have 2000 g in weights, though I'm not sure exactly. The rope is attached to a part of the triggering device that hooks into a loop under the arm. When we pull the rope, it unhooks and releases the arm.

The weights are on the inside of the machine. We tried to glue some to the bottom, but it wouldn't stick well enough.

[andrewwski]

2000 g is only 2 kg - that's not a lot of weight. Try a few 20 pound weights or something.

[AlphaTauri]

From last year's Trajectory thread:

This is because the device will move if it is not weighed down correctly (we used 50lbs of bricks on our device, 45 on the base of the device and one 5lb brick on the arm, you do have a point it was hard to carry around 50 lbs of bricks but we managed because it was necessary to our reproducibility)

I'm not sure you'll need 50 pounds of bricks, but it's the general idea. You can carry the bricks separately from the catapult, as long as you can fit everything into a 70cm cube when they ask you to impound it. My suggestion would be to screw a sheet of plywood to the base of your catapult then stack all the bricks on top of that- just make sure they don't interfere with the arm or the surgical tubing/bungee cords/whatever you're using.

[starpug]

From last year's Trajectory thread:

This is because the device will move if it is not weighed down correctly (we used 50lbs of bricks on our device, 45 on the base of the device and one 5lb brick on the arm, you do have a point it was hard to carry around 50 lbs of bricks but we managed because it was necessary to our reproducibility)

I'm not sure you'll need 50 pounds of bricks, but it's the general idea. You can carry the bricks separately from the catapult, as long as you can fit everything into a 70cm cube when they ask you to impound it. My suggestion would be to screw a sheet of plywood to the base of your catapult then stack all the bricks on top of that- just make sure they don't interfere with the arm or the surgical tubing/bungee cords/whatever you're using.

Funny thing is that's exactly what we did we had a milk crate with the bricks in it that we impounded with the device.

I think we have 2000 g in weights, though I'm not sure exactly. The rope is attached to a part of the triggering device that hooks into a loop under the arm. When we pull the rope, it unhooks and releases the arm.

The weights are on the inside of the machine. We tried to glue some to the bottom, but it wouldn't stick well enough.

Ok, I advise you increase your weight atleast up to 10 kg, if you could go to 15-20 kg that might be more effective. Weight is rather critical to this event as you have a lot of friction on the triggers and often the force a device requires to launch the ball the required distance is enough to move the device if it is not weighed down enough.

[zyzzyva980]

All right, thanks everyone. I'll go buy some more weights.

[Lily Essence]

Since trajectory is basically the only event in which the weight of your device does not matter in the scoring, heavier is definitely preferred. My partner and I used 40 lbs of weights on our device to keep it on the ground. Now that I think of it, 40 lbs was probably a little overkill, but better safe then sorry. You get no penalty for using weights as long as they are inside the specs. If you're worried about the weights being difficult to carry around, use dumbells ('cause they have handles) or have a strong guy carry them to impound with you.

When the device itself doesn't weight enough to keep itself down, you get the same "jumping" problem that zyzzyva98 descibes. If a device jumps, it's basically a non-competing device in my eyes. At my local invitational, I watched about three hours worth of trajectory devices (about 8-13 devices give or take), and can honestly say that every device that I saw that "jumped" did not have wieghts and did poorly. The ones that did do well either weighted alot by itself or the partners stacked a good deal of weight on it.

In a nutshell: A heavy, almost immovable, device is one that gives more consistent data! Consistent data =