Gravity Vehicle C

[Balsa Man]

There are a number of interesting factors and trade-offs going on, and THE optimal combination, if there is one, is not obvious...
I believe Chalker7s note on the importance of precision is right-on, and very important.
I agree with Illusionist - building the chassis light so you can get a big/concentrated chunk of mass where you want it clearly makes sense- and there is not really any downside, as long as its strong enough to not break, or flex significantly (in directions you don't want it to).
Longer wheelbase will tend to/will be easier to make run straighter than shorter wheelbase - at any given level of precision in aligning the axles parallel
Longer axles (i.e., wider track) can be aligned parallel more precisely than shorter ones.

There is some limitation to the degree of precision you can build to -depends on how much time you take, the tools you have to work with, the materials you have to work with; the more precise you can be, the straighter and more consistent the run line of the vehicle is going to be. If you can build to a few thousandths of an inch precision, your vehicle is going to much straighter and more consistently than one built to 1mm precision.....

Let me throw a new variable out there that hasn't been discussed yet. Wheelbase and track, and aligning the axles parallel is going on in one (2-dimensional) plane. The third dimension is part of the alignment problem, too, though. Three points define a plane. If you have four points - as in four wheels, the "what level of precision can you build to" issue comes into play again. Unless you're incredibly good, or lucky, when you get it put together, and put it on a smooth, flat surface, one wheel will be out of the plane of the other three. It will "teeter-totter", with two diagonally opposite wheels in contact, and the other two above the flat surface. If you push one down into contact, the other will lift up- if you push the other down, the first one will lift off. If you're good, the amount one wheel is out-of-plane will be small. But the fact that the wheel loading can shift around will induce variability in the run-line. It may be minimal during the run- it will be more dramatic under braking. There are solutions. 3 wheels is an obvious one; there are 4-wheel solutions, too. Something to think about, something to play with.

[illusionist]

I don't think this has been asked before, but can the pencil be used as the release mechanism? For example, insert the pencil into a hole in the vehicle and a hole in the ramp, then pull out the pencil. It does not say in the rules that it cannot be done like this, but I just wanted some more opinions. I get this isn't place for clarifications and such.

[ChrisYim]

Can someone post some scores that one would consider "good" for this event? It doesn't have to be your real one, but I'm just wondering what to at least aim for...

[hmcginny]

I could be totally wrong, but I would guess a "good" score would fall around sub 4.00 seconds, within 5 cm for a 10 m run. The time would obviously vary for shorter distances, and sub 4.00 seconds is just a general guess based on some math and 10 m tests without full weight. The within 5 cm is just a general measurement guideline for most car events. So number wise that would be a score around 250, just as a ballpark estimate for a good score. That seems ridiculously high after mousetrap scores in the past couple years, but then again there is no longer a lane bonus and time and distance are now worth even more points.

[haverstall]

I don't think this has been asked before, but can the pencil be used as the release mechanism? For example, insert the pencil into a hole in the vehicle and a hole in the ramp, then pull out the pencil. It does not say in the rules that it cannot be done like this, but I just wanted some more opinions. I get this isn't place for clarifications and such.

That's kinda what I assumed, that as long as the pencil is responsible for starting the vehicle, it doesn't actually have to press down on a trigger. Still, would be nice to submit a clarification.

[fleet130]

can the pencil be used as the release mechanism?

Almost the exact same issue came up at one of the national tournaments (Sorry, I don't remember which tournament, but the vehicle was dark green, the distance was adjusted by adding/removing gauge blocks and a metal rod was removed to start the vehicle. at that time the rules Said: "a pencil, pen, dowel or similar instrument.') I initially told the team I wasn't sure it complied with the rules and gave them some options.

1. Impound the vehicle as is and file an appeal if it was disqualified.
2. Modify the vehicle to comply with my interpretation.

I told them they could wait until I had some time to think about it, but any modifications had to be completed and the vehicle impounded before the impound time expired. After a couple of minutes I came to the conclusion that, while it wasn't what was intended, the vehicle complied with the rules.

The language in the current rules leaves some question. First, they state: "...using an unsharpened #2 pencil ... to actuate the release mechanism". They go on to say: "Competitors must not touch the vehicle or the release mechanism...". If the pencil is the release mechanism, it would be impossible to start the vehicle without touching the "release mechanism".

Personally, I would allow it, barring further discussion/guidance from the national organization. It's possible individual event supervisors will come to different conclusions. Even if a clarification is posted on soinc.org, there is no guarantee the event supervisor at another tournament will know about it or honor it. If you think it may be an issue, you should ask your tournament organizers at the earliest possible date for their opinion. Be sure to include any info from soinc.org that supports your argument.

[chalker7]

Personally, I would allow it, barring further discussion/guidance from the national organization. It's possible individual event supervisors will come to different conclusions. Even if a clarification is posted on soinc.org, there is no guarantee the event supervisor at another tournament will know about it or honor it. If you think it may be an issue, you should ask your tournament organizers at the earliest possible date for their opinion. Be sure to include any info from soinc.org that supports your argument.

I'd do two things in this instance.
First, I would submit an official clarification since there seems to be enough confusion on the matter.
Second, I would design a launching mechanism that leaves no question as to its legality. Even if the national clarification says it's ok, a regional supervisor might disagree and there is almost no way to make them change their minds. It's always better to be safe in these instances.

[Balsa Man]

From the description of the pencil acting as a pin, it would seem that an easy way to avoid any question/potential issues at Regionals/State would be to make/use a pin - (heck, you could even make it out of a piece of pencil), with a hook or loop on one end.

Then you use "the official launching pencil" to slip into/through the hook/loop, and you pull the pin out with the pencil.... That, without any clarification/interpretation seems clearly within the rules....

[illusionist]

Alright, so I'm going to be starting the ramp construction tomorrow. Any construction tips?

[chalker]

Alright, so I'm going to be starting the ramp construction tomorrow. Any construction tips?

Measure twice, cut once.