2 bots v. 3 bots Trailer question

[Kevin Sevcik]

Originally Posted by Jaybee1405

I see that as very unlikely. If the trailer would indeed be place out alone, how would it be stood up? It only has two wheels so I assume the hitch would be used as a "leg," and I assume that could scratch the floor (which naturally wouldn't be desirable). Furthermore, it would be pushed and knocked over the playing field, likely falling over at some point due to its two wheels, and causing problems for everyone.

This is going to be a pretty stable thing. The wheels only stick 2" under the bottom of the trailer. With all the geometry, it will end up resting on the end of the trailer tongue, but only with a 4 degree tilt. It may scratch up the floor slightly, but it's a nice rounded corner, so I doubt it. I think the only real concern that might keep the trailer off the field without a robot is worry over the trailer tongue being damaged.

[artdutra04]

Originally Posted by Jaybee1405

I see that as very unlikely. If the trailer would indeed be place out alone, how would it be stood up? It only has two wheels so I assume the hitch would be used as a "leg," and I assume that could scratch the floor (which naturally wouldn't be desirable). Furthermore, it would be pushed and knocked over the playing field, likely falling over at some point due to its two wheels, and causing problems for everyone.

The trailers didn't seem to have any real problems staying upright at the Manchester Kickoff event.

They just kind of sit there chilling, like "Hey I'm a trailer, where's my robot?"

I stand corrected. Thanks.

[jgannon]

I'm certain that they'll still set the trailers on the field even if a robot doesn't show up. Otherwise, if your alliance didn't field any robots, the other alliance couldn't score any points. Elimination matches are going to be pretty boring if no one wants to put their robot on the field.

I do expect, though, that as in past years, human players will still be allowed to participate, even if they do not bring a robot.

[Siri]

Originally Posted by Daniel_LaFleur

My guess is that if a robot does not show up then the team would not be allowed to play during that match. That would mean that one of their payload specialist stations would be unmanned and 20 moonrocks would go unused.

I don't think so. This hasn't been true in the past, and according to 9.6.3, it doesn't look like it'll be true this year.
9.3.6 A TEAM is declared a no-show if no member of the team is in the ALLIANCE BASE, FUELING STATION, or OUTPOST at the start of the MATCH; a no-show team will be disqualified from that MATCH. (emphasis mine.) Thus, a team is only DQed as a no-show if a human player, not the robot, does not show up. And that seems pretty standard.

Originally Posted by pyrome

There are even a few more factors than that in optimizing traction.
However, to put it simply:
Friction is a function of normal force (weight).
Traction is a function of normal force AND surface area.

Notice: high school student in the room. I'm going to try my hand at this--please correct me if I'm wrong. Here goes nothing:
This distinction seems ill-placed. While both definitions are correct in certain circumstances, the circumstances, not the terms are different.

(I believe) there is no actual difference between friction and traction. Traction is simply a term frequently used to describe static friction, particularly in drive systems.

According to Columb (and basically everyone else), friction, in theory, is solely the product of the robots mass (essentially) and the coefficient of friction (static for rolling or non-moving surfaces, kinetic for sliding). Thus, the only ways to control friction are through robot weight (i.e. max it out at 120lbs) and wheel movement--keep them rolling, not sliding. The latter can only be accomplished by keeping acceleration below the maximum force allowed by the mu_s. (F=ma=Ff=mu*Fn=mu*mg, so a=mu*g, and so without modifying gravity, we're pretty stuck.)

Now, according to life in general, surface area plays a part. But it's not in the equation! Ah, but it is. Surface area can effect mu (actually, probably more often vice-versa). Softer surfaces (better traction) require more surface area (think side wall weight support) to be structurally sound and to withstand greater wear and tear. There are some other dynamic contact issues that arise when the "ground" surface is non-uniform, but that's less of an issue on regolith--not to mention even a little more out of my depth to explain.

So, MEs and physicists alike, help me out here. I think that's right.

[Thermal]

traction is calculated by Force of Friction combined the surface area of contact between two objects.

Force of friction is just the weight (in newtons) times the coeffecient of friction for the objects.

Or so I believe...

[jgannon]

Originally Posted by Thermal

If surface area didn't mean anything why do dragsters use wide racing slicks instead of lighter skinnier wheels?

The surface area vs. traction issue has been beaten to death on these forums, so here's the Cliffs Notes. Ideally, surface area doesn't change frictional force. In past FIRST applications, surface area typically has impacted frictional force, because of how common tread materials tend to interlock with the carpet. This is also what happens with soft rubber on asphalt, as in your example. However, since there's little to no interlocking going on with this year's materials, the results should conform much closer to the results expected in Ideal Land.

[Thermal]

Originally Posted by jgannon

The surface area vs. traction issue has been beaten to death on these forums, so here's the Cliffs Notes. Ideally, surface area doesn't change frictional force. In past FIRST applications, surface area typically has impacted frictional force, because of how common tread materials tend to interlock with the carpet. This is also what happens with soft rubber on asphalt, as in your example. However, since there's little to no interlocking going on with this year's materials, the results should conform much closer to the results expected in Ideal Land.

Ideal land rocks

Sounds good to me

[Jim Meyer]

This is an interesting question. An unhitched trailer arm could be pretty damaging to other robots. In the past it has never helped your own alliance in any way if one of your robots can not play.

I'd hate to advise a partner who isn't certain if their robot will run or not to sit it out. A dead robot with a trailer is much more of a detriment to the team that no robot and trailer at all. Heck even a robot that hasn't achieved proficiency at scoring is more of a detriment than an asset if there's an option for them to not be on the field (along with their trailer).

I think FIRST is going to have to have some sort of bot to hook to the trailer. It could be as simple as a chunk of plywood with wheels and bumpers mounted to it, or even the next robot who's going to play in that spot but disabled for the entire match. I definitely do not like the idea of them not putting all three trailers out there.

[ChuckDickerson]

I am inclined to think that all 6 trailers will always be on the field no matter how many robots show up to play. Otherwise, everyone would quickly learn the best way to win is to not bring any robots to the field only the human players and the game will become very boring very quickly. The question then becomes if only 2 robots show up which starting location is strategically the best to place start the odd trailer?

[AlexD744]

If a robot is missing can they still have a human player as a payload specialist? And if they're not allowed can the other teams put a person in there place? Also does that team lose some of it's moon rocks?

[vhcook]

Historically (particularly on practice day), teams could send their payload specialist (then known as the "human player") to play even if the robot was not present. This avoided a disqualification for no-show. From my initial reading, 9.3.6 would appear to permit that.

A TEAM is declared a no-show if no member of the team is in the ALLIANCE BASE, FUELING STATION, or OUTPOST at the start of the MATCH; a no-show team will be disqualified from that MATCH.

Note that no-show is based on team member presence not robot presence.

[dodar]

Well also, if a team cant make a match, wouldnt that mean that the other alliance has one less goal to score in on the field?

[The Pre]

Originally Posted by dodar

Well also, if a team cant make a match, wouldnt that mean that the other alliance has one less goal to score in on the field?

yea there would be one less goal but one of the robots would be double teamed

[Katie_UPS]

Originally Posted by dodar

Well also, if a team cant make a match, wouldnt that mean that the other alliance has one less goal to score in on the field?

Originally Posted by The Pre

yea there would be one less goal but one of the robots would be double teamed

Although, if you haven't noticed, the trailers can't hold an unlimited amount of balls, so assumingg they still have their human players (who are doing well), and their robots are scoring just as much, it could be evenly matched, if not tipped in favor of the smaller alliance.