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SirBobo wrote:How does a dowel facilitate timing like stated in rule g?

If the event supervisor is using photo gates, the dowel will make it much easier to trigger the gates.

It will actually help a tiny bit for stopwatch timed events as it has each timer looking at the same point. Unfortunately, angles make a difference and this event is typically run in a hallway at regionals and state events which makes the angles a lot bigger. Not good, and it can make a difference in team positions. Measuring to a hundreth of a second in a narrow hallway does little for true accuracy. 1 or 2 tenths would be more probable.

I was wondering what kind of wood ya'll would recommend using for the vehicle. My partner and I have thought about it and just can't seem to find what kind of wood would be best. If you can, please help us.

Balsa is the lightest possible, but if you go light, cross brace in a couple of places. If you plan on using bushings for bearings or micro ball bearings, I would go with basswood to be able to keep the axles true. If you have access to a table saw, have an adult rip a piece if 1 x 4 light pine into 3/16 thick. After you have built one, try a bit thinner wood.
One of the most important parts is to have the axle true to the car. This normally means taping the two sides together and line drilling them. Reinforce the corners with blocks or gussets and have the whole car perfectly square while the glue sets. Homemade jigs are nice.
Remember, friction and weight are your enemies.

What are everyone's thoughts on the timing system? Like it, or not?

Lobo wrote:What are everyone's thoughts on the timing system? Like it, or not?

What do you think about it?

I did this event last year, and the biggest problem we ran into were with axles and wheels. What worked for you guys in the past?

My car goes up really fast at first but loses speed at the last couple meters. My car is really light, so it goes fast as first, but the momentum is not high, because p=mv. Is that right? Would making it a bit heavier do the trick?

Not knowing all your car dimensions it is a bit hard to say. There is a tradeoff of initial speed vs ending speed. You could lengthen your kill bar a tiny bit or you could decrease your drive axle a very tiny bit.both will decrease your initial speed and increase your ending speed. make tiny changes. Where does your string run out at?

You might try changing your mousetrap out. There is about a 50% difference in the strength of the spring from one trap to another in the same package. The spring weakens a bit the more you use it or play with it.

would 1/4" alumium dowel spinning in hole in balsa chassis frame have significant unwanted friction?

I am just doing this for physics project...6.0m forward, 4+m backwards(more=extra credit)

only 1 mousetrap though.. :[
Using 12" diameter styrofoam wheels. cut out 6 triangles on each wheel, weighs 15grams each, but will add rubber band or sand paper around outside. good/bad idea?

Any suggestions for axle?

If I used 12" diameter wheels, 1/4" diameter axle(15.25cm radius, .3175cm)
Then:
2 * (length of bar)
Total distance = ------------------------ X 2 (.1525m) pi = 96 * (length of bar)
2 * pi * (.003175m)
so...if I make .5meter long bar, my vehicle could go forward 6meters, and backwards 42meters....
With the energy from one mousetrap, is that practical? Speed/time doesnt matter for me.......just distance
Could I go with even longer bar for more distance? or is there already too little torque/force and too much friction with this setup.
truth is, there will be maximum extra credit I can receive..but my teacher wont say how much..

Also, I have fishing wire, but its very plastic-y and smooth, is that okay?