Re: Underestimating the Trailer
 

Just remember that the hitch has to be on the bumper perimeter. Even if you put an indentation, the outer vertices would still define a polygon which would put your hitch not on the bumper perimeter.

Also, to EricH, you only need bumpers on 2/3 of the bumper perimetier. The entire bumper perimeter exists whether on not there are bumpers on the robot.

Re: Underestimating the Trailer
 

Whats the advantage?

If you're dragging the trailer wheels sideways while you turn your gonna make steering much harder.

We've found that jacknifing the robot/trailer back and forth quickly is a great way to steer. Seems to work better than just plain tank steering.

Re: Underestimating the Trailer
 

Exactly. Instead of fighting it, why not work with it?

Re: Underestimating the Trailer
 

What kind of drive train did you use when you were jacknifing to steer? Tank? 4WD?

Thanks,

Patrick

Re: Underestimating the Trailer
 

My team made a basic tank drive chasis from VeX kits, hooked up a trailer (also made of VeX) and drove it on a smooth table (the wheels being gears) and while it did seem to jacknife(?) quite a bit it didn't seem to matter too much since the wheels also slid fairly easily.

of course, it's just VeX on a smooth table, and it may be entirely different in competition

Re: Underestimating the Trailer
 

I dont think it will be as hard as people are saying, because with less friction it will be close to impossible to get jack-knifed. This is because when you slide, the force from hitting a wall or another bot will send the trailer flying past or hit the wall (or bot) too.

Re: Underestimating the Trailer
 

FYI, unless there's something that I missed you cannot move the hitch location once the match has started. The rule regarding the trailer hitch says a rigid, fixed location which has been interpreted by most to mean that the hitch cannot be actuated.

As for detecting the trailer location, you could have ultrasonic sensors pointed out the back of the bot to where the tongue meets the trailer. If the trailer swings to one side, the range finder on that side will get shorter and the range finder on the other side will report a longer range or just noise. Of course, this assumes you already have a crab drive system and there's an actual benefit to keeping your robot wheels oriented with the trailer wheels.

Re: Underestimating the Trailer
 

That's what I said. You only need 2/3 of it (the perimeter). Though maybe I should have added "covered" to the end.

Also note, though this is not official by any means: the trailer hitch will (most likely) take up 7" of the 1/3 uncovered. I don't think the GDC will rule that it's a bumper...

Re: Underestimating the Trailer
 

4WD "long" configuration.

Tank steering.

Re: Underestimating the Trailer
 

That's nice to know. We only have a single 4x8 sheet of the FRP so far, and we were looking at 4WD tank steering, probably wide configuration... As a team that experiences a lot of ice and snow on a regular basis, we've been thinking about 'using the slipperiness' instead of somehow trying to fight it since day one.

Patrick

Re: Underestimating the Trailer
 

Wouldn't today be one of those ice & snow days?

Re: Underestimating the Trailer
 

What if you designed the robot to be mainly driven backwards?

Have the trailer be like the "skis". When you want to turn, just jackknife the trailer and drive straight. The wheels would that way aid in turning.

Or else maybe drive forward, turn backwards.

I honestly didn't think turning would be an issue... until we tried to turn today on linoleum. If you start off spinning you're fine, if you try to turn while driving straight, you better be prepared to wait. And that's without a trailer BTW.

I think the trailer could be used advantageously, if used properly. Just some testing is needed to figure out how that would work. Hopefully we'll have a trailer by Monday. I am thinking of taking some video of it and recommend other teams to do the same, that way we can all examine it and try and figure out how to drive with this thing.

Re: Underestimating the Trailer
 

If i planned on building to utilize the trailer for steering i would get practicing now.

Re: Underestimating the Trailer
 

We were looking into that too, but our team came to the general consensus that FIRST was trying to articulate that the trailer hook-up was to be attached to the "outer-edge" created by the bumper polygon. For those curious about the bumper polygon it is shape created by the outermost points/corners of the robot. (Note, by definition polygons cannot have indentations, or in other words internal angles greater than 180 degrees.) But I would love for someone to prove us wrong.

Re: Underestimating the Trailer
 

I think that if you have enough speed when you are backing up the jack-knife problem won't be a problem since the wheels on the trailer have no more traction than the robot wheels so they will slip and slide even going sideways when jack-knifed. As long as you keep some speed when going either backwards or forwards you cann still keep going into a possible orientation spot.