Gravity Vehicle C

[retired1]

The velocity at the bottom will be the same no matter what type of ramp is used, so I fail to see how it's worth the trouble to build a specially shaped ramp when one can be approximated by something similar to an L. Am I missing something simple here?

Not so. Look up the reference that I posted or google it.

The last response is very close to dead on.

[iwonder]

When I mentioned a specially shaped ramp in the previous post, I was referring to the b-curve, not just any curve. Read as, "I fail to see why one would go to the effort of building a ramp with a b-curve when a more ideal choice would be a smoothed out L shape, or one more like the picture in the wiki(which is not technically a b-curve)".

I wrote all this up, then reread your post and think I've found the miscommunication, but I'll leave this here for future reference

Regardless of ramp shape, the idea of conservation of energy will be held, so assuming all vehicles start from the same height, they will reach the transition point of the ramp at the same speed(also assuming the same friction, rotational inertia, etc). The point behind the discussion is that the vehicle can hit a 'bump' while transitioning from the ramp to the floor, this is where the ramp shape effects velocity. As Mrsteven said, as long as the ramp shape is as close to horizontal as it can be(which minimizes this 'bump') the velocity of the car leaving the ramp will be as high as possible, regardless of the shape above the transition. Now, that being said, the fact that you want as horizontal a transition as possible does mean that the ramp shape is a smooth curve. However, if you were to use a b-curve, the curve would need to extend from the start of the ramp all the way to the target point in order to be most effective, which obviously is impractical. The curve also does not provide the highest possible velocity at the end of the curve, due to the slight slope up at the end, so it isn't an ideal ramp choice in that regard either.

[JimY]

I'm not sure the discussion on this is going in the intended direction. As long as you have a smooth transition off the ramp that is relatively horizontal, yes, the horizontal velocity at the bottom of the ramp should be the same for the same vehicle on any ramp that has the same vertical drop (assuming there is nothing goofy going on). The point is how long it takes to get off of the ramp and onto the floor, since time is measured from the moment the vehicle is triggered rather than the moment it leaves the ramp. I'm just wondering how many teams that were at the top of the event at nats last season had ramps that followed a modified Brachistochrone curve (perhaps with a longer transition to horizontal at the bottom) to minimize time on the ramp. Is the b-curve that is mentioned above the same as the Brachsitochone curve?

So, we built two ramps last season due to having two teams competing at an invitational as well as at the regional level. We purposely made them different in shape (with neither following a modified Brachistochrone curve), but did not compare time on the ramp for the two, mainly because the same car did not sit at the same vertical height on both ramps (the trigger point on each was for a specific vehicle and not the other). We'll definitely explore that question this season. I'm guessing that the vehicle will take less time to leave the ramp that has shorter arc length. The question is whether the difference is significant or not.

[iwonder]

Yes, the b-curve is an abbreviation for Brachsitochone curve.

[penclspinner]

Chalker,

I recall in this thread last season that some posts were discussing optimum shaped ramps that allowed the maximum linear velocity to be reached in a minimum amount of time. I translated this to mean that these ramps were shorter in total length than, say, one that is circular in shape with a near vertical section at the top, as this shape would have a longer total length than one that is, say, more like a quadratic or cubic function. At nationals last season, did you happen to notice if the top teams had ramps that were relatively similar in shape? If so, can you share what they had in common? I downplayed the optimum ramp idea last season, mainly because once someone posted the actual shape, the change in direction at the bottom from more vertical to horizontal just seemed too extreme and might cause repeatability issues with steering. Then once I saw the results, it seemed like accuracy was far more important than speed, which is what I anticipated all along. Since I wasn't there, I'm just asking what you are willing to share on ramp shape.

Thanks.

I watched Gravity Vehicle a bit at Nationals and I do recall a few brach curve ramps. Not sure if they were top teams or not.

[bearasauras]

Chalker,

I recall in this thread last season that some posts were discussing optimum shaped ramps that allowed the maximum linear velocity to be reached in a minimum amount of time. I translated this to mean that these ramps were shorter in total length than, say, one that is circular in shape with a near vertical section at the top, as this shape would have a longer total length than one that is, say, more like a quadratic or cubic function. At nationals last season, did you happen to notice if the top teams had ramps that were relatively similar in shape? If so, can you share what they had in common? I downplayed the optimum ramp idea last season, mainly because once someone posted the actual shape, the change in direction at the bottom from more vertical to horizontal just seemed too extreme and might cause repeatability issues with steering. Then once I saw the results, it seemed like accuracy was far more important than speed, which is what I anticipated all along. Since I wasn't there, I'm just asking what you are willing to share on ramp shape.

Thanks.

I didn't run the event at Nationals, and only saw a handful of ramps when I was walking around (which all seemed to be a rather 'normal' slightly curved version). However I know the people that DID run the event lurk on scioly, so I'll defer to them if they want to chime in...

Woah! Really? The people that ran this event lurk on scioly.org too?! We have to find them! *gets this pitchfork*

[illusionist]

I thought bear ran the event? O.o

[chalker]

I thought bear ran the event? O.o

For certain definitions of 'ran the event', I guess so (if you could call standing around and letting everyone else actually do all the work;)

[retired1]

I thought that the rules of this site called for being nice or politically correct. I think that response could have been phrased a bit kinder. Granted, the truth is not always nice.

[bearasauras]

HEY CHALKER! THAT WASN'T NICE! I TOTALLY RAN THE EVENT! I SAT ON 6 VEHICLES, BROKE 3, AND I USED 8 OF THE RAMPS AS SLIDES. THAT TOTALLY COUNTS AS RUNNING THE EVENT.