Underestimating the Trailer

[lbl1731]

I agree that it will hurt your manuevering, but I really don't think jack knife will be a problem. Think about it. The wheels on it are the same as are on the robot. It'll slide easy. I say jack knife it. You'll just push it backwards and sideways. Don't worry about backing it up staight or anything.

[MrForbes]

The problem is that if the published wheel friction specs are accurate, then it's going to be very slow going backing up with the trailer jacknifed.

[Ali Ahmed]

I think that will be underestimated now but once teams have finished drive trains and once they build a trailer they'll get used to it. So i say in about 10 days we will see threads like, "Driving Is Impossible!". Hopefully not.

Maybe talking to truck drivers might be helpful.

[Enigma's puzzle]

Originally Posted by lbl1731

I agree that it will hurt your manuevering, but I really don't think jack knife will be a problem. Think about it. The wheels on it are the same as are on the robot. It'll slide easy. I say jack knife it. You'll just push it backwards and sideways. Don't worry about backing it up staight or anything.

But you are pushing the wheels the way they don't want to roll, I heard somewhere on CD that the transverse friction is twice that of the normal forward travel friction. There probably not enough friction to catch the ground to cause the trailer to flip but you will be fighting it the entire way.

You the kind of person i'm talking about, that is going to underestimate the potential problems.

I know that we are building a trailer tonight and the next coupe of days so we can test it to foresee possible problems.

[dani190]

really good point, tomorrow i am starting to build our trailer, and hopefully we can have it up and on last years robot or something that way we can see how driving is...

[Petey]

Something to think about:

Can you build a robot in such a way that the trailer's wheels are always oriented like the robot's?

[EricH]

Originally Posted by Petey

Something to think about:

Can you build a robot in such a way that the trailer's wheels are always oriented like the robot's?

I don't think so. The contact is to be bumper-bumper instead of bumper-tongue (<R18>E) and the hitch is to be on the outside edge of the robot (<R18>D) and the the trailer must be easily removed after the match by removing its pin (<G36> and <R18>C).

It's possible, but it'll be pretty hard. You also have <R08> to consider, which includes the bumper perimeter.

[Petey]

Originally Posted by EricH

I don't think so. The contact is to be bumper-bumper instead of bumper-tongue (<R18>E) and the hitch is to be on the outside edge of the robot (<R18>D) and the the trailer must be easily removed after the match by removing its pin (<G36> and <R18>C).

It's possible, but it'll be pretty hard. You also have <R08> to consider, which includes the bumper perimeter.

I bet it'd be hard, but I'm pretty sure it's possible. You don't need a square chassis, all you need is a way to construct your back end in such a way that the sides of the hexagon abut the back end of your bot while the trailer tongue is pulled pretty far in while also observing the other rules about attaching easily and not hitting the walls before bumpers.

e: what's the shear strength of the bolt?

[EricH]

Originally Posted by Petey

I bet it'd be hard, but I'm pretty sure it's possible. You don't need a square chassis, all you need is a way to construct your back end in such a way that the sides of the hexagon abut the back end of your bot while the trailer tongue is pulled pretty far in while also observing the other rules about attaching easily and not hitting the walls before bumpers.

Bumper perimeter is defined as the outermost polygon in the bumper zone. However, you only need 2/3 of it. I'm sure you could come up with something like that.

[kirtar]

Originally Posted by Petey

I bet it'd be hard, but I'm pretty sure it's possible. You don't need a square chassis, all you need is a way to construct your back end in such a way that the sides of the hexagon abut the back end of your bot while the trailer tongue is pulled pretty far in while also observing the other rules about attaching easily and not hitting the walls before bumpers.

e: what's the shear strength of the bolt?

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.

[EricH]

Originally Posted by kirtar

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.

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...

[GaryVoshol]

Originally Posted by EricH

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...

More than that - you've got to have a big enough gap in your rear bumper so that the trailer tongue doesn't hit the edge side of your bumper.

[Ziaholic]

Originally Posted by GaryVoshol

More than that - you've got to have a big enough gap in your rear bumper so that the trailer tongue doesn't hit the edge side of your bumper.

According to some "back of a napkin" math we performed, the 7" is an adequate bumper gap if you are in the "wide" formation and have the remainder of the 38" covered in bumpers.

The trailer/bot bumpers should contact before the trailer tongue touches.

[silicon_ghoti]

Originally Posted by Petey

I bet it'd be hard, but I'm pretty sure it's possible. You don't need a square chassis, all you need is a way to construct your back end in such a way that the sides of the hexagon abut the back end of your bot while the trailer tongue is pulled pretty far in while also observing the other rules about attaching easily and not hitting the walls before bumpers.

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.

[menace101]

It's definitely possible. I think if you have your normal chassis but at the back, you leave some sort of indent that pulls the tongue in so that the trailers bumpers will rest on your bots bumpers. It's not that hard, Petey, is it?