Gravity Vehicle C

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Re: Gravity Vehicle C

Post by chalker7 »

blazer wrote:
illusionist wrote:
blazer wrote:An event supervisor at a recent invitational tried to dq me because my point is towards the center of my car, and although it is accessible, it is not on "either side" of the car. Was he right?
Can you say how far from the middle? As of now, my point is 6 cm from the outside of the vehicle, still 7 cm from the exact middle.
Pretty close to exactly in the middle, about 15cm from the outside of the vehicle.
If I was an event supervisor, I can see having difficulty reaching a measuring point 15 cm from the outside of the vehicle.
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Re: Gravity Vehicle C

Post by illusionist »

Yeah, that might be stretching it a little.
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Re: Gravity Vehicle C

Post by Jdogg »

For our car, since the wheels are close to the sides of the chassis and their is no point at which it would be easily accessible to mount the paperclip on the sides, it would actual be more convenient to have the measuring point at the center of the car. I completely understand why the point has to be between the axles, and i understand why those that made the rules want the point to be easily accessible. Though, it seems to be a very unclear on what is acceptable and what isn't. Does anybody have any suggestions on a easy solution, I know shifting the ramp the same distance of the difference of the location of the paperclip to the center would work, but i'd rather keep the ramp centered as it is easier and more convenient at competition.
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Re: Gravity Vehicle C

Post by sj »

Jdogg wrote: Does anybody have any suggestions on a easy solution, I know shifting the ramp the same distance of the difference of the location of the paperclip to the center would work, but i'd rather keep the ramp centered as it is easier and more convenient at competition.
Keeping the ramp centered, or even in one place for that matter is only possible if your car runs straight enough to not deviate from the centerline at the longer distances. for us our car follows a slight curve so we have an equation that allows us the shift the ramp along the start line to compensate at any distance... so while keeping the ramp centered may be more convenient will your car be running straight on the center line? I suppose another approach would be to run the first run from the centerline and then adjust for the shift on the second run based on where the car stopped on the first run... any thoughts on that? In my opinion going in with an equation is better as we already have a general idea and then we can make minor changes.
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Re: Gravity Vehicle C

Post by illusionist »

...an equation?

Maybe a little overkill in my eyes, but whatever floats your boat. My method has always been to correct for the curved path. My current vehicle is separated into two parts, connected together with an adjustable joint. The path of the vehicle is essentially straight. I think it's much easier than moving your vehicle/ramp to compensate for the curve.
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Re: Gravity Vehicle C

Post by illusionist »

First, sorry for the double post.

So I just ran my vehicle to a distance of 4.7 meters.
Without a 5 pound weight: 2.07 seconds average
With a 5 pound weight: 2.09 seconds average.

Should they be that similar? sj, since you already ran your vehicle, can you give me some data on how much difference there was in your vehicle's time with and without the weight at this distance?
Also, it was faster without the weight (the mass of the vehicle is probably <0.7lb, I'm horrible at estimating)... Any thoughts?
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Re: Gravity Vehicle C

Post by sj »

We did indeed have similar results even as far out as 6 meters.

The reason for this, in my case, is that the time it takes for the car with extra mass to slowly skid to a stop makes up for the other cars slightly slower runtime causing both to be approximately the same.

Now in your case was that with brakes or just letting the car run past the point?
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Re: Gravity Vehicle C

Post by illusionist »

That was just letting the car run past it. Brakes were not involved.
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Re: Gravity Vehicle C

Post by Jdogg »

Thanx for the suggestions SJ, our car goes pretty straight, like within 10cm of the target, if we let it off the ramp straight. I might have to compensate for the curve by angles or something, a equation seems to be a great idea. We will definitely have to do that.
On a side note, adding extra weight to our car throws our consistency way off. That's why we are only using a little bit of weight, due to the increase of momentum.
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Re: Gravity Vehicle C

Post by Littleboy »

illusionist wrote:First, sorry for the double post.

So I just ran my vehicle to a distance of 4.7 meters.
Without a 5 pound weight: 2.07 seconds average
With a 5 pound weight: 2.09 seconds average.

Should they be that similar? sj, since you already ran your vehicle, can you give me some data on how much difference there was in your vehicle's time with and without the weight at this distance?
Also, it was faster without the weight (the mass of the vehicle is probably <0.7lb, I'm horrible at estimating)... Any thoughts?
With previous experience from other things, I can say that too light is bad and too heavy is just as bad. Without the weight, it does not go down the hill as fast but while traveling on the ground it has less weight to carry so it doesn't slow down as much. Too heavy it can go down faster but loses speed faster. There is a tradeoff. It probably is a coincidence that the 2 times were so similar. I would recommend that you add a 2.5ish pound weight and see how that effects it.
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