Gravity Vehicle C

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builderguy135
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Re: Gravity Vehicle C

Postby builderguy135 » September 3rd, 2019, 9:56 pm

Is it just me or is striving to make a brachistochrone curve or optimize time to reach the bottom of the ramp a useless consideration now that the timings start after the vehicle has left the ramp? Even if timing started when the vehicle was released, I doubt having a brachistochrone ramp curve would make a difference. IIRC, you would have to have the center of mass of the vehicle travel in the brachistochrone trajectory which is a pain. I predict 1-6 at nationals to be sub 10 :|
Might not be relevant, but brachistochrone curves were one of the first things we tried when designing our roller coaster. The difference between that and a regular arc of a circle was extremely minimal.

A brachistochrone curve gravity vehicle ramp might be worth it but I'd be surprised if it did.
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2020 Events: Detector/PPP/Sounds/Wright

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Re: Gravity Vehicle C

Postby MTV<=>Operator » September 4th, 2019, 6:44 am

Actually, correct me if I'm wrong, but I believe a brachistochrone curve would be useless for GV regardless because time is taken from the 0.5 meter mark to the 8.5 meter mark. This curve would allow the vehicle to travel down the ramp faster, but regardless of the curve, the exiting velocity of the vehicle should still be the same.
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2018-2019
Regionals/ Yale/ States/ best score
MTV - 9/ 30 (tiered)/ 22 ( failure)/ 18
Boomi - 3/ 20/ -- /1400
WS - 23/ 17/ 21/ 3:10

2020 Events:
Gravity Vehicle
Detector Building
Wright Stuff
TBD

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builderguy135
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Re: Gravity Vehicle C

Postby builderguy135 » September 4th, 2019, 10:01 am

Actually, correct me if I'm wrong, but I believe a brachistochrone curve would be useless for GV regardless because time is taken from the 0.5 meter mark to the 8.5 meter mark. This curve would allow the vehicle to travel down the ramp faster, but regardless of the curve, the exiting velocity of the vehicle should still be the same.
Read the rules wrong. I should know better because the timing for vehicle events has been consistent for years now lol. Thanks for the correction!
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2020 Events: Detector/PPP/Sounds/Wright

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Things2do
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Re: Gravity Vehicle C

Postby Things2do » September 4th, 2019, 7:09 pm

I'd say that the accuracy should be close to that of Scrambler last time it ran in C. Especially for those of us that're using our Scrambler car...
As for my questions,

* Do y'all think it would be worth building a adjustable ramp, as opposed to a fixed one?

* How about ramp surface materials? I was thinking of a stiff-ish vinyl or something similar, which would make for a smooth, supportive ramp without bending wood or anything like that.

Thanks for your input.
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Re: Gravity Vehicle C

Postby AngelMB » September 4th, 2019, 9:45 pm

I'd say that the accuracy should be close to that of Scrambler last time it ran in C. Especially for those of us that're using our Scrambler car...
As for my questions,

* Do y'all think it would be worth building a adjustable ramp, as opposed to a fixed one?

* How about ramp surface materials? I was thinking of a stiff-ish vinyl or something similar, which would make for a smooth, supportive ramp without bending wood or anything like that.

Thanks for your input.
Could you specify what you mean by adjustable ramp? Adjusting the position of the vehicle on the ramp? Or making the ramp easier to slide around horizontally on the starting line?

As for ramp surface materials, I think a stiff-ish vinyl material could be good depending on how you implement it and attach it to the base of the ramp. I know previously my school used a wooden base and acrylic for the surface material which seemed to work well.
Boca High '20

2020 Events
Boomi, Circuits, Detector, Gravity

Nats Placements 2019
Mission - 1st
Circuits - 7th
Mousetrap - 23rd

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Re: Gravity Vehicle C

Postby Dreamz » September 5th, 2019, 11:33 am

As for ramp surface materials, I think a stiff-ish vinyl material could be good depending on how you implement it and attach it to the base of the ramp. I know previously my school used a wooden base and acrylic for the surface material which seemed to work well.
How did you manage to bend the acrylic?

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Re: Gravity Vehicle C

Postby knightmoves » September 5th, 2019, 2:45 pm

How did you manage to bend the acrylic?
Acrylic softens when heated, so there are possibilities there - either bending it over a suitable form, or vacuum forming. Or, if you have thin enough acrylic so it bends, just force it to conform to your wooden base and screw it down.

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Re: Gravity Vehicle C

Postby MTV<=>Operator » September 5th, 2019, 3:02 pm

So far, I was thinking of using sheet metal as the ramp surface so that I could laser engrave lines into it for rails of some sort. As for an adjustable ramp (assuming you meant adjustable height), that probably wouldn't be necessary this year, though it might be next year. You would likely want the vehicle to be as high up as possible to give it the most gravitational potential
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2017-2018
2018-2019
Regionals/ Yale/ States/ best score
MTV - 9/ 30 (tiered)/ 22 ( failure)/ 18
Boomi - 3/ 20/ -- /1400
WS - 23/ 17/ 21/ 3:10

2020 Events:
Gravity Vehicle
Detector Building
Wright Stuff
TBD

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Re: Gravity Vehicle C

Postby Things2do » September 5th, 2019, 6:57 pm

As for an adjustable ramp (assuming you meant adjustable height), that probably wouldn't be necessary this year, though it might be next year. You would likely want the vehicle to be as high up as possible to give it the most gravitational potential
That's what I figured, but I wanted a second opinion. And since a partner is outta the question...
Could you specify what you mean by adjustable ramp? Adjusting the position of the vehicle on the ramp? Or making the ramp easier to slide around horizontally on the starting line?

As for ramp surface materials, I think a stiff-ish vinyl material could be good depending on how you implement it and attach it to the base of the ramp. I know previously my school used a wooden base and acrylic for the surface material which seemed to work well.
Thanks, I hadn't thought of acrylic. As for the ramp, I was thinking of a adjustable height, sorta like one of those cheap poolside chairs, or a clamp on both sides of the supports or something...
John 5:46-47
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Is this where I put the Builder Cult?
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AngelMB
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Re: Gravity Vehicle C

Postby AngelMB » September 5th, 2019, 9:54 pm

How did you manage to bend the acrylic?
Acrylic softens when heated, so there are possibilities there - either bending it over a suitable form, or vacuum forming. Or, if you have thin enough acrylic so it bends, just force it to conform to your wooden base and screw it down.
I believe the previous gravity vehicle competitors used a thin, flexible layer of acrylic and forced it to conform to the wooden base they were using.

So far, I was thinking of using sheet metal as the ramp surface so that I could laser engrave lines into it for rails of some sort. As for an adjustable ramp (assuming you meant adjustable height), that probably wouldn't be necessary this year, though it might be next year. You would likely want the vehicle to be as high up as possible to give it the most gravitational potential
I think sheet metal could work great for the surface material of your ramp given its properly implemented on your base ramp. I agree that an adjustable height may not be necessary this year, although could be useful. You can accomplish the same thing by just releasing your car from higher or lower heights on your ramp via using shorter or longer lengths of string for your your release mechanism so that your car hangs lower/higher on your ramp.

However, I don't necessarily agree that you want your vehicle to be as high up as possible. If you find that your car is simply going too fast/has too much momentum as it's exiting your ramp, you may wish to lower the height at which you release it to lower the gravitational potential energy it's starting off with. Alternatively, although mass ideally shouldn't affect the kinetic energy your vehicle has as it leaves the ramp (due to it cancelling out with mass in the formula for gravitational potential energy: mass * height * 9.8 = 0.5* mass * velocity^2), you may wish to decrease the mass of your vehicle as it will still affect your momentum (p = mass * velocity). Too much momentum and you may not be able to brake properly leading to worse accuracy scores. I believe I'll start off with more mass than I think I'll need and lower my mass from there until I find a good balance of momentum for accuracy to speed for timing.
Boca High '20

2020 Events
Boomi, Circuits, Detector, Gravity

Nats Placements 2019
Mission - 1st
Circuits - 7th
Mousetrap - 23rd


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