Placement of the SHIELD GENERATOR Structure on field

We have built a full size SHIELD GENERATOR structure for our practice field and we are trying to determine the correct placement of the structure on the field.

In reviewing the 2020 Field Layout and Marking Diagram, I was unable to find any dimensions for where to place the SHIELD GENERATOR structure on the field. It looks like you just sort of rotate the structure as far as you can keeping the structure inside the lines marking out the trench and line up the side legs near the CONTROL PANEL so that the structure is basically centered in the length of the field.

Has anyone found any specific dimensions to use for placing this structure on the field? Or is it really just a matter of wiggling it around until it is equal distance from the two end walls and rotated until it just touches the trench run boundary tape?

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Don’t know of the measurements off the top of my head, but I’d suggest pulling up the CAD file and taking measurements from there. That way you can make any measurement you want from any two points anywhere on the field.

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I think that what’s in “Sheet 4 of 5” of the Field Layout and Marking will be all you’ll get. You use that to line up the Control Panel / Trench structures, and then the corners of the Shield Generator abut those.

The inset in “Sheet 5 of 5” shows where the initial ball placements are relative to the initiation line and the loading port center, which is probably about as good a way to check your work as you’re going to get.

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I think it is just that. The corners are 55.5" away from the side walls (94.66"-39.16").

The distance from the alliance walls to the corners of it looks to be the same distance as from the alliance wall to the side of the trench, so I think it would be 206.57" away from the alliance wall.
Shield Generator 2

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I will ask one of the students to pull up the field CAD and take some measurements.

I was expecting that they would have this somewhat defined so that the people that are building the competition field at events would be able to place the structure on the field as they assemble it. I imagine that this structure is quite heavy on the real field (heck, our practice structure is very heavy) and you wouldn’t want to have a bunch of field crew personnel forced to lift all 4 corners at the same time and wiggle it into place and then check the distances from the end walls to see if it is centered.

Maybe they will update the drawing at some point for those folks (I am going to be one of them).

Although some of the measurements are hard to find this year, if you look hard enough, they are in the either the manual, the field markings document, or a combination of both. The best approach in my opinion when constructing your own practice field is to tape out anything you’re unsure of and double check those measurements before setting down field elements, especially heavy ones.

Also good job on making the full SHIELD GENERATOR! It looks about as challenging to make as the robots this year!

Since we have one of the few full size fields in the area, we make every effort each year to try to create an accurate representation of all the field elements so that when other teams come to practice, they have a fully functional field to practice on. We had planned on making the generator switch structure, but really didn’t have a solid plan until we saw the one that 118 built. We modeled ours loosely off of their design. Other than the fact that 2x12s are heavy, it was not exceedingly hard (but we are also not done with the assembly yet).

I was able to do most of the wood cutting in a couple of hours in my driveway and then I spent most of the meeting last night getting the pieces screwed together and getting the main structure upright. Then we tried to figure out how to position it correctly on the field and came up empty on measurements. Once we get it into position, it will probably take the better part of another full meeting for me to finish it off.

I think everyone was a bit surprised at how large it is in real life. I think a lot of teams are going to be shocked when they see it for the first time.

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@wgorgen Using pages 4 of GE-2000 and page 4 of FE-2020 you can layout the placement of the Shield Generator using a couple chalk lines.

I think you are suggesting using the dimensions for the placement of the power cells to create a set of points on the floor and then draw a line through those points and then extend those lines until they intersect at the corners. That is actually not a bad idea. There will be an offset from that corner mark since the power cells are located on the centerline of the BOUNDARY pieces and the edges of BOUNDARY pieces meet at the corner of the GENERATOR. But that offset is easy to calculate. We will give that a try if we can’t get to the CAD easily.

I mixed up page numbers for FE-2020. I have it corrected now. Page 4 will let you lay out the Shield Generator with three lines.


I haven’t seen this year’s field manual yet, but in the past, the field manual provided to FTA/FTAAs and Field Supervisors has sometimes included layout instructions for chalk lines that are used for aligning field elements. These lines sometimes reference “internal” or structural parts of the field elements, so that may be why they aren’t given with the drawings released to teams. Could be some other reason for not providing that information publicly; I’m not FIRST so I don’t know. Rest assured, you shouldn’t have to derive any field element alignment measurements during field setup (though reading the tape line diagrams is a pain sometimes).

It was not obvious that those dimensions applied to the generator structure (although I admit they are obviously close, so that would probably be good enough for a practice field).

IMO, Pouring over the 3D CAD representation those dimensions in fact don’t apply to the generator. But they are within a few inches of being correct.

Worse I can’t find any easily measurable spot except the center of the structure is in the center of the field and the generator is oriented 22.5º to the rest of the field.

Thanks for checking. It didn’t look like those dimensions applied to the generator, but if they are close, we will put a couple of tape marks on the floor to get us started and then adjust from there. The angle is helpful. We can measure that to at least get the rotation correct.

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As you can see we are kind of going through the same problem at the moment. Anyone with a better answer would be a great help.

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It’ll probably be given to the field builders how to do it, but remember it’s a rectangle, not a square in plan. Find the center of the field, midpoint between alliance walls and side walls; size is given of the four verticals; turn 22.5-degrees; some {x,y} math off the center point to get to the four verticals; check diagonals to be equal; check them again; have someone else check the math and the dimensions; lay the floor plates; check everything again; build.

Probably have to check clearances to side walls to the nearer verticals so the Control panel will fit. That I learned from Stronghold, the defenses did not give an inch to spare across the field.

After building and moving an airship, cargo ship, and pyramid, I get super careful with the layouts.

@KelleyCook nice construction, by the way. Invoke rule S7 to everyone.

@wgorgen and others: What did you use as material for the boundary on the carpet? I am planning to use pine (2x4 ripped and planed to 1x3) but worried our swerve will chew it up.

The boundary for the Rendezvous zone? We used 1x4s off the shelf at Home Depot. They are not quite thick enough, but we used joining plates to connect them together and then added velcro to the bottom. It is close enough for our purposes.

They are holding up OK. There are a few wood splitners on the field that were chewed off of these boards, but I am not sure whether they were the result of our robot driving over it or some of the other robots that have been at our space to practice. I don’t think our swerve drive is any more or less damaging than other types of drive.

We tried OSB last year for the cargo holding area bounadry. It did not hold up at all. So the 1x4s seem to be better. But I think any wood is going to take a beating. If this is critical for you, you probably want to use metal.

Thanks - yes, for the rendezvous zone. We’'l go ahead with the pine and see how it goes!