Mousetrap Vehicle C

[Vizard007]

I know for one thing that last year (at regionals, which is strangely harder than states where I live) a team brought a vehicle with three wheel and the wheels were HUGE. And it was just crazy fast. So, I always thought that the smaller the ratio between the wheel to the axle the better? (correct me if im wrong) So, just a thought... get custom made giant wheels! But, yea, tiny lego wheels would just "destroy" your vehicle.

[bwy]

I just have a couple questions. (Our vehicle's mostly built.)
1. Are CDs the best wheels, or would it be okay if we used tiny Lego wheels? (These things are really small. I don't have any with me right now, but they're about an inch in diameter.) Would that hurt our performance?
2. Is the best braking method the wingnut-threaded rod method? We're trying to pick one, and that seems to be the braking method of champions.

Actually, I always thought smaller wheels were something to consider, as long as you're not using the tiny wheels for the DRIVE wheels, since small=light. (which everyone already mentioned is ridiculous). If you're using design 3 from the wiki, i think the wheels that are not attached to the mousetrap can be smaller. (though 1 inch is tiny).

As for my time/car weight, I'm definitely not using balsa wood. (and my time has since dropped to 8.5 sec)
The problem is my distance score. Out of desperation to fix it, I'm wondering, what kinds of sighting devices are there? are they even helpful/worth it?

I also want to make sure: let's say the ----- is the +3m line, and the ( ) is the cup. If the cup ends up like this, -----( )-------, it's a score of 0 right? As opposed to, the cup must be like this (__) so that only the rim touches the tape perfectly? What I'm trying to ask is, is there a margin of error that allows for a distance score of 0? (the length of the cup, basically)

[penclspinner]

I also want to make sure: let's say the ----- is the +3m line, and the ( ) is the cup. If the cup ends up like this, -----( )-------, it's a score of 0 right? As opposed to, the cup must be like this (__) so that only the rim touches the tape perfectly? What I'm trying to ask is, is there a margin of error that allows for a distance score of 0? (the length of the cup, basically)

After reading the rules again, as long as the cup is touching the 3m line you get the 0 distance score. In both examples that you presented the cup is touching the line so I'd be inclined to think that both examples are valid.

[illusionist]

What kinds of times/scores are you guys getting?
I have a 9.2 second car that weighs 140 grams and pushes the cup to within 5 cm of the 3 m line (I haven't really looked at the -4m distance score yet since that's more of a problem)

How did you get it to only 140 grams? I'm looking at 370ish grams on my vehicle, although I'm around a 10 second run. I'm thinking about dropping my weight so that I can make my acceleration more rapidly. I have a design that should get around 200 grams, but 140 is pretty impressive, haha.

I'm getting a horrible 28 seconds for the combined run.

Have you tried dropping the weight, using a thinner drive axle, or better traction? That should be the best way to increase your speed. As stated in the wiki, and earlier in this thread, if you make the mousetrap arm bar (the one that pulls the string) shorter, you will have greater power, just less string to pull with.

He probably got that score because he's probably using Balsa wood. As for the "horrible" 28 seconds, is that with the cup reaching the 3M line? Also, can someone explain to me why a thinner drive axle increases speed? Thanks.

That is the whole run, from the start line, forward three meters, and backward seven so i end up at the -4 meter line. I'll have to try the axle to wheel ratio

[winneratlife]

I know for one thing that last year (at regionals, which is strangely harder than states where I live) a team brought a vehicle with three wheel and the wheels were HUGE. And it was just crazy fast. So, I always thought that the smaller the ratio between the wheel to the axle the better? (correct me if im wrong) So, just a thought... get custom made giant wheels! But, yea, tiny lego wheels would just "destroy" your vehicle.

Meh, actually, bigger wheel to smaller axle ratio = less string needed, so more power directly from mousetrap, but that same power is lost through the axle to wheel ratio.

In essence, ideal wheel to axle ratio really depends on the specific car, particularly the distance from your mousetrap to your driving axle.

Remember, work = force x distance, and work is constant.

[bwy]

That is the whole run, from the start line, forward three meters, and backward seven so i end up at the -4 meter line. I'll have to try the axle to wheel ratio

I don't know about other peoples' cars, but mine (using CD wheels) needs an axle more than 1/4 inch wide to get a good speed with a bar about 30 cm long

[illusionist]

That is the whole run, from the start line, forward three meters, and backward seven so i end up at the -4 meter line. I'll have to try the axle to wheel ratio

I don't know about other peoples' cars, but mine (using CD wheels) needs an axle more than 1/4 inch wide to get a good speed with a bar about 30 cm long

Right, my bar is also around 30 cm long. Okay, so what options do I have to increase the diameter other than to replace it with a thicker axle? Could you explain how you did it? Thanks

[winneratlife]

That is the whole run, from the start line, forward three meters, and backward seven so i end up at the -4 meter line. I'll have to try the axle to wheel ratio

I don't know about other peoples' cars, but mine (using CD wheels) needs an axle more than 1/4 inch wide to get a good speed with a bar about 30 cm long

Right, my bar is also around 30 cm long. Okay, so what options do I have to increase the diameter other than to replace it with a thicker axle? Could you explain how you did it? Thanks

Uh, you could wrap the axle in tape

[bwy]

Uh, you could wrap the axle in tape

I hate to admit it, but that's exactly what I did.
It's pretty good though-- consistent, removable, and adjustable so that you use exactly the right amount of string.

Anyone have a brake idea that doesn't involve a wing nut? Lego axles don't work too well with them.

[masterhat]

Have you checked out http://scioly.org/wiki/Mousetrap_Vehicl ... 010_Design ?

It's pretty helpful and can be easily modified for this year's rules.