Gravity Vehicle C

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windu34
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Re: Gravity Vehicle C

Postby windu34 » September 15th, 2019, 5:09 pm

So yes, if you look at the Vehicle as a closed system, at the end of the run, kinetic energy has to be 0. If you haven't stored any of that kinetic energy in something (like elastic or gravitational potential), then it all must have been dissipated as heat by your brakes.
Actually, magnets might (emphasis on the might) be a feasible idea, that solves latch issue we mentioned earlier. If you take kinetic energy from the vehicle as a whole, store it as potential energy in magnets, you could decelerate the vehicle, while also moving the mass to the front, making the braking more accurate.
You could also use springs and store the additional energy in that.
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Re: Gravity Vehicle C

Postby mnoga » September 16th, 2019, 11:08 am

Does anyone have any ideas on how to keep the vehicle going straight when going down the ramp?
Use a rail or guide system. I will not get into specifics, but there are many possible implementations and you can get clues by observing train systems, monorail systems, ski jumping and bobsled competitions, just to name a few.

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Re: Gravity Vehicle C

Postby Lorant » September 17th, 2019, 7:31 pm

So yes, if you look at the Vehicle as a closed system, at the end of the run, kinetic energy has to be 0. If you haven't stored any of that kinetic energy in something (like elastic or gravitational potential), then it all must have been dissipated as heat by your brakes.
Actually, magnets might (emphasis on the might) be a feasible idea, that solves latch issue we mentioned earlier. If you take kinetic energy from the vehicle as a whole, store it as potential energy in magnets, you could decelerate the vehicle, while also moving the mass to the front, making the braking more accurate.
You could also use springs and store the additional energy in that.
Is there a way to use a spring to slow down the progress of the wingnut across the threaded rod without locking it up? I'm just thinking, if you don't use two springs, or even if you do, one is bound to be marginally stronger than the other, putting the wingnut at an angle relative to the threaded rod should lock it up quite quickly shouldn't it? Is there a way to get around this?
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Re: Gravity Vehicle C

Postby lindsmaurer » September 18th, 2019, 5:12 am


Actually, magnets might (emphasis on the might) be a feasible idea, that solves latch issue we mentioned earlier. If you take kinetic energy from the vehicle as a whole, store it as potential energy in magnets, you could decelerate the vehicle, while also moving the mass to the front, making the braking more accurate.
You could also use springs and store the additional energy in that.
Is there a way to use a spring to slow down the progress of the wingnut across the threaded rod without locking it up? I'm just thinking, if you don't use two springs, or even if you do, one is bound to be marginally stronger than the other, putting the wingnut at an angle relative to the threaded rod should lock it up quite quickly shouldn't it? Is there a way to get around this?
First of all, wingnuts don't lock up quite that easily, as long as you have the right wingnut. Second, why not put a spring around the threaded rod so that the wingnut is centered on the spring? It may still be at a slight angle, but again, wingnuts need quite a bit of force to lock up.
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Re: Gravity Vehicle C

Postby windu34 » September 18th, 2019, 9:00 am


You could also use springs and store the additional energy in that.
Is there a way to use a spring to slow down the progress of the wingnut across the threaded rod without locking it up? I'm just thinking, if you don't use two springs, or even if you do, one is bound to be marginally stronger than the other, putting the wingnut at an angle relative to the threaded rod should lock it up quite quickly shouldn't it? Is there a way to get around this?
First of all, wingnuts don't lock up quite that easily, as long as you have the right wingnut. Second, why not put a spring around the threaded rod so that the wingnut is centered on the spring? It may still be at a slight angle, but again, wingnuts need quite a bit of force to lock up.
Agreed, the difference in force shouldnt be enough to lock it up, and this approach could be a good option. The idea with moving the center of gravity was to accomplish two things: optimize potential energy at the beginning and prepare the vehicle for braking. While it may be too complicated for most competitors, the benefits may be larger than many of us suspect, and I think it could very well be worth looking into for those with experience building high-tier devices already. Having springs in parallel with the wingnut could certainly be a good option to slow the device down, and Im curious to hear how it works out
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Re: Gravity Vehicle C

Postby T&J101 » September 19th, 2019, 3:36 pm

One thing that I've never figured out in my time in vehicle events such as mousetrap vehicle and scrambler was (a) How do high skill competitors get threaded rods into ball bearings such that there is no play between the rod and the bearings, (b) it seems that an adjustable start height for the vehicle would be best but how did teams do that in the past? I may be wrong, but with heavy vehicles this year it seems that bearings are a must. Also, the only way to accurately cut the ramp that I've thought of is to laser cut. What is the recommended wheel durometer, I've heard banebot wheels are good but what durometer is best? Last year in MV I got the hubs to the axle by tightening with two wingnuts, so I was wondering how other teams did it. In a bit of a noob, so I'm sorry for a barrage of questions. : |

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Re: Gravity Vehicle C

Postby MTV<=>Operator » September 19th, 2019, 8:14 pm

One thing that I've never figured out in my time in vehicle events such as mousetrap vehicle and scrambler was (a) How do high skill competitors get threaded rods into ball bearings such that there is no play between the rod and the bearings, (b) it seems that an adjustable start height for the vehicle would be best but how did teams do that in the past? I may be wrong, but with heavy vehicles this year it seems that bearings are a must. Also, the only way to accurately cut the ramp that I've thought of is to laser cut. What is the recommended wheel durometer, I've heard banebot wheels are good but what durometer is best? Last year in MV I got the hubs to the axle by tightening with two wingnuts, so I was wondering how other teams did it. In a bit of a noob, so I'm sorry for a barrage of questions. : |
I'm definitely not the most qualified to answer your questions, but here is my take on things:
(a) I was thinking of getting bearings with an extended inner ring and fixing them in place on the axle with one nut on either side of the bearing. The extended inner ring would make sure the nuts don't interfere with the motion of the bearing
(b) For an adjustable launch height, you can design your launch mechanism to be bolted to the ramp surface or ramp sides. Then, make multiple holes along the surface or sides of the ramp so that the whole launch mechanism can be moved to the locations of the different holes.
As for ramp making, laser cutting would probably be by far the most accurate option, but most people don't have one available to them. To cut the sides, I believe you could use plywood, maybe 3/16 to 1/4 in thick and cut out the profile with some sort of saw. There are also options to support the ramp without the need for accurate cutting, such as vertical supports that are on either side and at multiple heights.
Yes, banebots wheels are good, and the best shore hardness will likely depend on the mass distribution of your vehicle. You want the wheels to have a soft enough hardness to provide sufficient traction, but not so soft that they cause extra friction and slow the vehicle down.
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Re: Gravity Vehicle C

Postby windu34 » September 20th, 2019, 10:18 am

One thing that I've never figured out in my time in vehicle events such as mousetrap vehicle and scrambler was (a) How do high skill competitors get threaded rods into ball bearings such that there is no play between the rod and the bearings, (b) it seems that an adjustable start height for the vehicle would be best but how did teams do that in the past? I may be wrong, but with heavy vehicles this year it seems that bearings are a must. Also, the only way to accurately cut the ramp that I've thought of is to laser cut. What is the recommended wheel durometer, I've heard banebot wheels are good but what durometer is best? Last year in MV I got the hubs to the axle by tightening with two wingnuts, so I was wondering how other teams did it. In a bit of a noob, so I'm sorry for a barrage of questions. : |
I'm definitely not the most qualified to answer your questions, but here is my take on things:
(a) I was thinking of getting bearings with an extended inner ring and fixing them in place on the axle with one nut on either side of the bearing. The extended inner ring would make sure the nuts don't interfere with the motion of the bearing
(b) For an adjustable launch height, you can design your launch mechanism to be bolted to the ramp surface or ramp sides. Then, make multiple holes along the surface or sides of the ramp so that the whole launch mechanism can be moved to the locations of the different holes.
As for ramp making, laser cutting would probably be by far the most accurate option, but most people don't have one available to them. To cut the sides, I believe you could use plywood, maybe 3/16 to 1/4 in thick and cut out the profile with some sort of saw. There are also options to support the ramp without the need for accurate cutting, such as vertical supports that are on either side and at multiple heights.
Yes, banebots wheels are good, and the best shore hardness will likely depend on the mass distribution of your vehicle. You want the wheels to have a soft enough hardness to provide sufficient traction, but not so soft that they cause extra friction and slow the vehicle down.
This is a good answer. Only thing I would add is the following:
a.) Many teams will make an insert to fit between the rod and bearing to get a "interference fit". I always 3D printed a thin insert, but you could certainly do it other ways.
b.) I would argue against an adjustable height. Work on your braking mechanism to adapt for different distances.
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Re: Gravity Vehicle C

Postby cool hand luke » September 20th, 2019, 1:36 pm

what would be the advantage of adjustable height?

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Re: Gravity Vehicle C

Postby windu34 » September 20th, 2019, 2:14 pm

what would be the advantage of adjustable height?
In my opinion, there is none.
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