Trajectory B/C

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Re: Trajectory B/C

Postby old » April 26th, 2010, 3:57 pm

It's good to have an equation on your graphs to get a good estimate for obscure amounts like that...
an equation?! wtf how do u do that??
We use the equation for a ballistic trajectory, including aerodynamic drag, then we use our empirical data as a correction factor. We have a doppler wind speed indicator that, unfortunately, only gives us the average wind speed and direction between the trajectory device and the target. We are able to plug all this into a laptop to get the aiming offset and correct range setting. Of course at Nationals we shouldn't really need the windspeed (unless it is set up like last year's, with the A/C vents cycling up at the extremely low ceiling). All in all we still only get about 1-2cm accuracy at the fartest distances when it is windy. You could do all this without the math but it would require a huge number of data points to account for all the possible ranges, heights, wind speeds and wind directions. On the other hand I spoke to people at last year's nationals who said that with the A/C cycling unpredicatably in the gym where trajectory was run their accuracy went from centimeters (what they were able to get with no wind) to tens of centimeters in the gym at Augusta. You just have to decide how competitive you want to be.

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Re: Trajectory B/C

Postby thepro » April 26th, 2010, 7:41 pm

I read the discussion about triggers that you guys have had before..but it didn't answer my question. My catapult's [picture attached] trigger is the white bar with holes every centimeter. When we pull a string attached to the bar, it releases the arm which shoots the golf ball.
The rules say that the device must fit within a 60X60 cube prior to all launches, but when we load the catapult to some of the lower holes the white "trigger arm" extends out of the box. Is this considered part of the device? or is it part of the trigger..and thus allowed to extend out of the 60X60 cube?
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(Sorry, reposting this..to clarify..b/c the image didn't work last time)

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Re: Trajectory B/C

Postby wlsguy » April 27th, 2010, 4:33 am

I read the discussion about triggers that you guys have had before..but it didn't answer my question. My catapult's [picture attached] trigger is the white bar with holes every centimeter. When we pull a string attached to the bar, it releases the arm which shoots the golf ball.
The rules say that the device must fit within a 60X60 cube prior to all launches, but when we load the catapult to some of the lower holes the white "trigger arm" extends out of the box. Is this considered part of the device? or is it part of the trigger..and thus allowed to extend out of the 60X60 cube?

(Sorry, reposting this..to clarify..b/c the image didn't work last time)
My opinion;

The white bar will most likely be considered part of the device and will need to fit inthe 60x60 cube.
Some things that may change this (I mean may...)

1) if the bar is not permanently attached and is added seperately, it would be easier to argue that it is not part of the device.
2) making it a different color helps because you could say "everything white is part of our trigger".

If you can change it, I probably would.

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Re: Trajectory B/C

Postby haven chuck » April 27th, 2010, 5:10 pm

wlsguy, do you happen to know what the State tournament distance were for Ohio B this year, and perhaps the winning score?
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Re: Trajectory B/C

Postby wlsguy » April 27th, 2010, 7:32 pm

wlsguy, do you happen to know what the State tournament distance were for Ohio B this year, and perhaps the winning score?
I think the B distances were 7.5m and 4m @50cm high.
I don't know the winning score but I do know that a 240 placed 7th.
(Our team had trouble with one of the distances. 4cm at the close target but 2ocm at the far one)

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Re: Trajectory B/C

Postby RndmPplPrsn » May 22nd, 2010, 9:34 pm

could you elaborate on how we could use kinematics because so far we have been testing extensively however it seems impractical to calibrate for all the points that are possible.
I had graphed 90 or so graphs using the averaged data for each peg and angle (Some were estimated by using kinematics because we had all of the variables needed that we chose. I also payed attention to the small stuff). We printed copies, and used that in our testing and competing.

My machine is built where most of the human factors have been removed or greatly minimized. In other words it is really consistent and predictable, all except for the bungees and their mounts.

There is a slight difference in force and speed when shooting a steeper shot than when shooting a shallower shot. This is because of gravity. However it didn't make much of a difference at State Competition :P.

Also I have found that there is no reason not to use an electromagnet for the trigger device. It is the best idea ever. I also made a change to my last design before state, but forgot to post pictures, they should be up soon.
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State: 1st: Trajectory, 6th: History of Science, 11th: Picture This

North Lake Regionals: 3rd: Trajectory, 4th: Picture This, 4th: History of Science

Hutto Invitationals: 2nd: Picture This, 4th: Forensics, 4th: Trajectory

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Re: Trajectory B/C

Postby AlphaTauri » May 23rd, 2010, 8:19 am

Does anyone know the winning score for Traj. at Nationals (B and C)?
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Re: Trajectory B/C

Postby Lily Essence » May 23rd, 2010, 3:05 pm

I'm sure both are in the negatives. I'm guessing somewhere around the -170s for first and -60s for medaling, but I didn't watch alot of devices compete, so that might not be accurate.
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Re: Trajectory B/C

Postby Phenylethylamine » May 23rd, 2010, 4:57 pm

Does anyone know the winning score for Traj. at Nationals (B and C)?
Tech event raw scores don't seem to have been posted yet (and may never be, but there's some chance that we will get them eventually), but I know that Fayetteville-Manlius High School got first in Division C, and Fairfield Junior High got first in Division B. If nobody on this board knows, I might be able to contact someone from F-M and ask what their score was.
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Re: Trajectory B/C

Postby AlphaTauri » May 23rd, 2010, 6:09 pm

I'm sure both are in the negatives. I'm guessing somewhere around the -170s for first and -60s for medaling, but I didn't watch alot of devices compete, so that might not be accurate.
Really? I was thinking more along the lines of -400 for first (about 7 cm off each target, two bucket shots- one hit the bucket and bounced, the other went in, full graphs, and no penalties) and -200 to medal. Seems reasonable, but I have no idea.
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