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Hi i am a freshman and this is my first time doing gravity vehicle. So I finished my car but I was wondering if anyone could give me tips on how to make the ramp. I am planning to use wood and curve it, but I was wondering if it is easy to cut the wood into this shape, which will probably be a brachiostochrone curve, and also how should i make the best release mechanism. I only have 9 days till comp so I am looking for a more simple and efficient solution.

GravityVehicleHelp wrote: ↑February 19th, 2020, 5:16 pm Hi i am a freshman and this is my first time doing gravity vehicle. So I finished my car but I was wondering if anyone could give me tips on how to make the ramp. I am planning to use wood and curve it, but I was wondering if it is easy to cut the wood into this shape, which will probably be a brachiostochrone curve, and also how should i make the best release mechanism. I only have 9 days till comp so I am looking for a more simple and efficient solution.

First, you do not need a brachistochrone curve because this simply reduces the time it takes for the car to go down the ramp. However, time is not taken until after the vehicle exits the ramp, so a brachistochrone curve is not necessary. As for the release mechanism, the easiest way to do this is to simply drill a hole in the ramp surface where the vehicle will be released from. You can stick the release pencil through this hole and through a loop of sorts at the back of the vehicle, and then pull out the pencil to release the vehicle.

I couldn't really tell you the easiest way to build the ramp because the way I did mine was quite difficult and time consuming, but I don't think cutting a curve into a sheet of wood is the easiest method. I would think the easiest way is the method pictured here https://istem.illinois.edu/images/ISO.G ... SC0662.jpg. This doesn't give you the smoothest path from the ramp to the floor, but it should be relatively easy to build.

MTV<=>Operator wrote: ↑February 20th, 2020, 7:04 am I couldn't really tell you the easiest way to build the ramp because the way I did mine was quite difficult and time consuming, but I don't think cutting a curve into a sheet of wood is the easiest method. I would think the easiest way is the method pictured here https://istem.illinois.edu/images/ISO.G ... SC0662.jpg. This doesn't give you the smoothest path from the ramp to the floor, but it should be relatively easy to build.

What is easy here very much depends on what tools you have access to.

Cutting a curve in a sheet of whatever-you-make-your-sides-out-of is reasonably easy with a big bandsaw, or with a jigsaw, and a spindle sander to finish it. I know at least one team that cut their curve with a sawzall. It's very much slower with hand tools, and if all you have access to are tools (hand or power) that like to cut straight lines, it's a complete nightmare.

knightmoves wrote: ↑February 20th, 2020, 11:52 am

MTV<=>Operator wrote: ↑February 20th, 2020, 7:04 am I couldn't really tell you the easiest way to build the ramp because the way I did mine was quite difficult and time consuming, but I don't think cutting a curve into a sheet of wood is the easiest method. I would think the easiest way is the method pictured here https://istem.illinois.edu/images/ISO.G ... SC0662.jpg. This doesn't give you the smoothest path from the ramp to the floor, but it should be relatively easy to build.

What is easy here very much depends on what tools you have access to.

Cutting a curve in a sheet of whatever-you-make-your-sides-out-of is reasonably easy with a big bandsaw, or with a jigsaw, and a spindle sander to finish it. I know at least one team that cut their curve with a sawzall. It's very much slower with hand tools, and if all you have access to are tools (hand or power) that like to cut straight lines, it's a complete nightmare.

I agree with knight here. It's relatively simple to cut the curve of the ramp if you have the tools for it (ie a jigsaw). I built mine in 2 hours using this method.

You can make one with little hand involved cutting with a CNC Machine. If you don't have one at school go to a local public fabrication lab. After the CNC finishes, there's very little time that goes into actually assembling the ramp. Would go with what's suggested from individuals from before if you don't know what you're doing.

CPScienceDude wrote: ↑February 20th, 2020, 12:00 pm

knightmoves wrote: ↑February 20th, 2020, 11:52 am

MTV<=>Operator wrote: ↑February 20th, 2020, 7:04 am I couldn't really tell you the easiest way to build the ramp because the way I did mine was quite difficult and time consuming, but I don't think cutting a curve into a sheet of wood is the easiest method. I would think the easiest way is the method pictured here https://istem.illinois.edu/images/ISO.G ... SC0662.jpg. This doesn't give you the smoothest path from the ramp to the floor, but it should be relatively easy to build.

What is easy here very much depends on what tools you have access to.

Cutting a curve in a sheet of whatever-you-make-your-sides-out-of is reasonably easy with a big bandsaw, or with a jigsaw, and a spindle sander to finish it. I know at least one team that cut their curve with a sawzall. It's very much slower with hand tools, and if all you have access to are tools (hand or power) that like to cut straight lines, it's a complete nightmare.

I agree with knight here. It's relatively simple to cut the curve of the ramp if you have the tools for it (ie a jigsaw). I built mine in 2 hours using this method.

GravityVehicleHelp wrote: ↑February 19th, 2020, 5:16 pm Hi i am a freshman and this is my first time doing gravity vehicle. So I finished my car but I was wondering if anyone could give me tips on how to make the ramp. I am planning to use wood and curve it, but I was wondering if it is easy to cut the wood into this shape, which will probably be a brachiostochrone curve, and also how should i make the best release mechanism. I only have 9 days till comp so I am looking for a more simple and efficient solution.

As for the shape of the ramp, just try to make the transition from ramp to floor as smooth as possible. To do this, I would use a curve, but you shouldn't worry about a perfect brachistochrone.

To build the ramp, you could frame it with 2x2s or similar wood. The entire ramp surface (the part the car rolls down) doesn't have to be supported, so a simple L shape made from 2x2 should be fine. Then cut/sand the wood down at the top and bottom to force the ramp surface to curve.

If you do use the pencil and loop starting mechanism, are you penalized if the loop drags on the ground? According to Rule 3g, "The only parts of the Vehicle allowed to contact the floor during the run are wheels/treads. Pieces falling off during the run constitutes a construction violation."

thehuntfornedoctober wrote: ↑February 24th, 2020, 3:43 pm If you do use the pencil and loop starting mechanism, are you penalized if the loop drags on the ground? According to Rule 3g, "The only parts of the Vehicle allowed to contact the floor during the run are wheels/treads. Pieces falling off during the run constitutes a construction violation."

If the loop is attached to the car, yes. I would build the car so that the loop is attached to the ramp and goes around a part on the car, holding it in place, so the loop is not attached to the car, if that makes any sense.

Tendan wrote: ↑February 24th, 2020, 6:34 pm

thehuntfornedoctober wrote: ↑February 24th, 2020, 3:43 pm If you do use the pencil and loop starting mechanism, are you penalized if the loop drags on the ground? According to Rule 3g, "The only parts of the Vehicle allowed to contact the floor during the run are wheels/treads. Pieces falling off during the run constitutes a construction violation."

If the loop is attached to the car, yes. I would build the car so that the loop is attached to the ramp and goes around a part on the car, holding it in place, so the loop is not attached to the car, if that makes any sense.

I had a small eye hook on the back of my car. It doesn't sag, it doesn't scrape the ground, it's simple to install and operate, and it provides a firm loop that will never stretch or wear out.

Things2do wrote: ↑February 24th, 2020, 7:20 pm

Tendan wrote: ↑February 24th, 2020, 6:34 pm

thehuntfornedoctober wrote: ↑February 24th, 2020, 3:43 pm If you do use the pencil and loop starting mechanism, are you penalized if the loop drags on the ground? According to Rule 3g, "The only parts of the Vehicle allowed to contact the floor during the run are wheels/treads. Pieces falling off during the run constitutes a construction violation."

If the loop is attached to the car, yes. I would build the car so that the loop is attached to the ramp and goes around a part on the car, holding it in place, so the loop is not attached to the car, if that makes any sense.

I had a small eye hook on the back of my car. It doesn't sag, it doesn't scrape the ground, it's simple to install and operate, and it provides a firm loop that will never stretch or wear out.

And if you can't get an eye hook or some other sort of metal loop before competition, some good strong zip ties will never fail you