Gravity Vehicle C

[Balsa Man]

True that a lower start height means slower time, but it's really important to look at/understand the math in the scoring. What it tells you is...dramatic.
Bottom line -180cm is WAY more than you want

Height score is 400 x h/300-h. Time score is 25 pts/sec.

So, for a 180cm h, height score is 600 points.

Go to a 1m (100cm) h, and points go to 200. That's a 400 point difference. 25 goes into 400 16 times. That means it could take 16 seconds longer and you'd still end up with the same height + time score. That's a LOT of time.......

Go to 50cm height, H score goes to 80 points. That's a 520 point difference; almost 21 seconds to get equal h + t score.

The rate at which time score increases w/ h reduction is much lower. Velocity off the ramp is a function of the square root of the difference in h. At 1/2 the height, v(initial) will be about 70% (1/1.414 (sqrt of 2)). Time difference will depend on the.....friction appetite of the vehicle; the rate at which friction losses eat into momentum.

The initial #s above really tell the story most clearly, though- how much slower you can go at a given h reduction and end up with the same h + t score. You obviously need enough h for the vehicle to be able to go 10m. You don't need or want very much more than that. So, optimizing h is pretty simple. Get to the h that gets you 10m. Check out a little more (h score + t score). The way the scoring works REALLY favors a low friction setup- big-time - the ability to go 10m with as little h as possible.

[Stingray355]

Here is an example of what Balsa Man is talking about. This is a run from our most recent invitational. The vehicle can make the 9.5 meter distance in well less than 4 seconds but it scores better if we run it from a lower height. In this case the time was 4.61 but the difference in the height produced a better score. This one was was 1st place and our other run was within a few hundreds of a second and 3 mm difference in the target distance. It is a very consistent device and has had lots of attention to details and calibration time. Next stop Regional's. Good luck everyone.

http://www.youtube.com/watch?v=XMkT5exT ... e=youtu.be

[lmatkovic3]

What kind of wheels are you using? I'm referring to the green ones.

[Stingray355]

Banebot

[joeyjoejoe]

Banebot? Then surely they were bushing mounted, right? Your car seems fast but I would've assumed that you wouldn't have gotten that kind of speed with bushings. Live and learn.
And what was your launch height? Looks to be in the .6m range.

[Stingray355]

Roller bearings and you are in the right ballpark on the height.

[joeyjoejoe]

Does anybody know if there is a rule about how many events in which you must take part in so that you can compete? I just got word that THREE students will be unable to attend due to a Math Team conflict. These three were the sole memebers of our Circuit lab and Robot Arm events. One of the other coaches thought there was a rule where you couldn't participate if you didn't field a team in a certain percentage of the events. The time is too short to build a team in the Robot Arm event and I dont want our other teams, who have been working tirelessly, to be punished because of it.

[lmatkovic3]

Hey Joey. There really isn't a minimum. My school's D team had ~10 people at our invitational, so I'd imagine any number is fine. You just get (participation+1 or 2) points if you don't participate.

[Stingray355]

OK in response to a team member request we put up a clip of a calibration run shot with a micro DVR camera. Not much scientific value but here is a link, http://www.youtube.com/watch?v=Tj9SK0oP ... e=youtu.be
Target is on the blue tape

[jacobxc]

So Stingray355 what is your average score