Legality of Downwards-Sloping Ramps

[PAR_WIG1350]

Originally Posted by Jeffy

The rulebook

<G19> MINIBOTS must remain completely autonomous and move up the POST solely through electric energy provided after the start of DEPLOYMENT by the permitted, unaltered battery and converted to mechanical energy by the permitted unaltered motors (and associated, appropriate circuitry). <G19> means that HOSTBOTS are not allowed to launch the MINIBOT up the pole at the TARGET, or otherwise contribute to the vertical movement of the MINIBOT. Energy for vertical movement may not be stored in the MINIBOT before DEPLOYMENT (except that which is contained within the battery and excluding incidental kinetic energy stored in the motors or wheels, but NOT, for example, in a flywheel).

I meant after the start of deployment, sorry for not clarifying that.

[Justin Montois]

Oh boy look what we started. It was on my Facebook that the video of our downwards sloping ramp was posted.

Our minibot never "rolls" down the ramp. Any movement on the ramp is purely from the battery and minibot motors.

Chris said it best, the minibot stays below the deploy line the entire time and our "exit" point off the ramp is higher then the starting point so any energy gained by the ramp is lost.

I mean if we're going to lawyer this then the refs should have used a bubble level to make sure all deployment mechanisms fired out level or downwards. Any increase in degrees would mean the deployment mechanism is "pushing" the minibot up when it contacts the pole and arguably providing vertical movement to the minibot.

[Tom Line]

Our team was also slightly confused by the wording, and noticed several teams on our field (Arch) at St. Louis with downward-sloping ramps. We asked the lead inspector of the field and he very specifically told us that they ARE legal as long as all the other language is met (below the deployment line while in the tower cylinder, etc).

[Kevin Sevcik]

I'll throw in against downward sloping ramps. Actually most ramps if you're strict about the rules. I'll admit up front that this is all going to be based off an extreme examples that have never and would never make it to the floor. The first example being a ramp that starts several feet above the top of the pole, and a deployment mechanism that's smart enough to trigger far enough in advance that the falling minibot crosses the cylinder just after the endgame starts.

That said, I think it's patently obvious that said minibot gains an advantage from dropping from such a height. That can be pretty readily demonstrated by the fact that you could use this ramp to create a (highly dangerous) ball bearing minibot that wouldn't be fundamentally different from a spring catapulted minibot. So I'm failing to appreciate how slapping two motors and a battery on to would appreciably change the situation. You're storing potential/kinetic energy in the minibot that it pretty directly transfers into vertical motion. It seems patently obvious to me that said minibot has gained a significant advantage over minibots that run a straight track out to the pole.

If you admit that the extreme example creates an advantage, then you're down to deciding how much of an advantage is too much. Which I'm fine with, but we should be honest that that's what we're discussing.

Similarly, I think the argument could be made that nearly ALL ramp systems are illegal by a (very) strict reading of the rules. G19 etc. state that the minibot must move up the pole with electric energy provided by the battery AFTER deployment. Deployment starts when the minibot crosses the cylinder. Ergo, any ramp system where the minibot starts a significant distance away from the cylinder is putting significant energy into the minibot system before deployment starts. It's kinetic energy stored in the inertia of the battery and frame, but it's stored energy all the same, and it would still provide an advantage.

You're again down to the question of what degree of advantage is acceptable. Which again is fine, but we should admit that.

Don't believe me? Grab your current interpretation of the deployment rules and reason along with me. Let's assume that the no-load speed of a legal minibot is 30 fps, versus a climbing speed of 15 fps. The following systems all have deployment timing such that the minibot crosses the cylinder after the endgame starts. Which, then, is illegal? Which is going to be the fastest?

1. A ramp system where the minibot starts just outside the cylinder at a dead stop.
2. The above sloped ramp system, where a minibot is dropped from a height sufficient to achieve 30 fps as it crosses the cylinder.
3. A novel flat ramp that is long enough that the minibot reaches 30 fps before crossing the cylinder.
4. An even more novel spring-loaded system that shoves the minibot up to a speed of 30 fps, releasing it just before it crosses the cylinder.

Timing and construction issues aside, I think system 1 loses to systems 2-4. But the interesting question is which of 2-4 seems illegal to you by your current reading of the rules. A really strict reading should deem all three illegal. If you think any of 2-4 are legal, ask yourself what real difference there is between them, as regards energy stored before deployment. On the plus side, it'd make rulings a lot easier, since you'd just be judge the speed of the minibot before deployment started.

Like I said, for me it all comes down to just how picky you want to be and want what degree of advantage you're willing to tolerate with the minibot rules. My level is set somewhere around all net energy coming from the battery, and the equivalent energy of a 3 foot long ramp. Mostly for practical reasons, since this would pass most ramp systems out there.

[Chris Hibner]

Originally Posted by Kevin Sevcik

... The first example being a ramp that starts several feet above the top of the pole, and a deployment mechanism that's smart enough to trigger far enough in advance that the falling minibot crosses the cylinder just after the endgame starts.

That said, I think it's patently obvious that said minibot gains an advantage from dropping from such a height.

This is clearly illegal since after deployment not all of the energy came from the batteries - some of the energy came from the potential energy of having the minibot well above the deployment line.

If the minibot starts below the exit point of the ramp, then ZERO potential energy is used in the speed of the minibot at the end of deployment - even if the minibot travels all the way down to the floor before starting upward. Thus ALL energy comes from the batteries, which is 100% legal.

Similarly, I think the argument could be made that nearly ALL ramp systems are illegal by a (very) strict reading of the rules. G19 etc. state that the minibot must move up the pole with electric energy provided by the battery AFTER deployment. Deployment starts when the minibot crosses the cylinder. Ergo, any ramp system where the minibot starts a significant distance away from the cylinder is putting significant energy into the minibot system before deployment starts. It's kinetic energy stored in the inertia of the battery and frame, but it's stored energy all the same, and it would still provide an advantage.

I agree with you here. Our ramp was constructed so our minibot starts on the edge of the cylinder (at least as close as can be repeatable). Starting the minibot a long distance from the the cylinder does provide an advantage as kinetic energy is stored before deployment begins.

[Ether]

Originally Posted by Kevin Sevcik

...

Excellent post Kevin. Reps to you.

[Colin P]

I guess as long as the minibot's starting position on the slope is lower than the end of the ramp on the deployment end, there isn't a net gain in energy, so it skirts around the rules.

It seems like the slope just gives the motors a break, they aren't exactly the best so it's a good idea to have them run as little resistance as possible before running up the ramp and pole.

I'd call it legal, but there's a lot of illegal things I'd try to call legal too

[The Zevling]

One thing that I haven't seen mentioned is that there are two fundamental parts to a ramp: the downward sloping part that gets the minibot to the pole, and the upward sloping part that transforms the horizontal movement into vertical movement. I think they have been regarded as the same, but they should be regarded separately.

The downward sloping part should be considered legal, I think. Energy-wise, it's no different from storing the energy in a spring, or however else you're getting the minibot to the pole. A downward sloping ramp with a horizontal end seems perfectly legal to me.

The upward sloping part is the part that transforms any horizontal momentum into vertical momentum, and this is the part that I think is illegal. This is the piece that separates "Energy for vertical movement" which is forbidden in G19 from energy for horizontal movement, which is necessary to get the minibot to the pole.


I hope there's no flaw in my logic.

[EricH]

Nope, not quite.

Minibots are to use only the power in the battery, delivered through the motors. Springs (for traveling along the pole) would be considered illegal, for example--though certain types of springy material could be used for latches. So the downward portion would be illegal--gravitational potential energy is not listed as a legal minibot upwards power source (though it's the primary method for getting down).

With respect to the second part of your argument (upward ramps), there are actually 2 holes. The first is that ramps were considered legal at multiple events. Translation: either multiple inspection and ref crews really screwed up, or there's a legal way to do it.

The second is this: Power for vertical motion only comes from that battery, through those motors. The fact that it starts out horizontal does nothing to the motors providing all of the vertical motion. Somehow, that horizontal motion gets converted to vertical--in this case, by a stationary part of the hostbot that the minibot runs on.

In other words, it's precisely because the minibot is supplying all of the energy that the upward ramps are legal, and because it is not supplying all of the energy that the downward ramps are illegal.

[Al Skierkiewicz]

Kevin,
We should keep in mind in your examples, practical implementations for weight and size which plays heavily on the actual advantage gained. Also it should be noted that the GDC did allow motors to be running throughout the match if a team wanted to use that approach. (Q&A 2/1/2011)

[Ether]

Originally Posted by Al Skierkiewicz

Kevin,
We should keep in mind in your examples, practical implementations for weight and size which plays heavily on the actual advantage gained.

He was using hyperbole in those examples to make a point. He clearly stated that:

Originally Posted by Kevin Sevcik

I'll admit up front that this is all going to be based off an extreme examples that have never and would never make it to the floor.

Originally Posted by Al Skierkiewicz

Also it should be noted that the GDC did allow motors to be running throughout the match if a team wanted to use that approach. (Q&A 2/1/2011)

Kevin addressed the above point in his post:

G19 etc. state that the minibot must move up the pole with electric energy provided by the battery AFTER deployment. Deployment starts when the minibot crosses the cylinder. Ergo, any ramp system where the minibot starts a significant distance away from the cylinder is putting significant energy into the minibot system before deployment starts. It's kinetic energy stored in the inertia of the battery and frame,

Rule <G19> allows the minibot to store up kinetic energy in its spinning motors and wheels prior to start of deployment. That is a separate question from using those running motors to store up kinetic energy in the body of the minibot prior to start of deployment; a point which GDC did not clarify when asked, and which is at the heart of much of this discussion.

[Rick TYler]

You all know that the season is over and that there are other more deserving expired horses to beat, right?

[Ether]

Originally Posted by Rick TYler

You all know that the season is over and that there are other more deserving expired horses to beat, right?

Like what, for example? :-)

[Basel A]

I think one point to be made is that even if there is a positive change in net gravitational potential energy, any decrease that is converted to vertical kinetic energy is still illegal.

[Chris Hibner]

Originally Posted by Basel A

I think one point to be made is that even if there is a positive change in net gravitational potential energy, any decrease that is converted to vertical kinetic energy is still illegal.

I'm not sure what you mean - could you please explain that.