Contradicting dimensions?
 

In the specs sheet, the tunnel dimensions are said to be 32.5" by 16.5". However, under section 6.2.4, the dimensions are 36" by 18".

Does anyone know which of the dimensions are correct?

Re: Contradicting dimensions?
 

In Update #3, the GDC ruled that the drawings take precedence over the Manual for determining dimensions of field components.

Re: Contradicting dimensions?
 

I find it highly inexcusable to have different measurements in different documents. I would have hoped FIRST actually read and looked over that kind of stuff.

Re: Contradicting dimensions?
 

If you read the manual you will find no contradicting dimensions.

Re: Contradicting dimensions?
 

What we're talking about is the fact that the Manual says one thing and the drawings say another thing. The ruling from the GDC is that in this case, the drawings take precedence over the Manual.

Re: Contradicting dimensions?
 

It's too bad because the drawings are pretty poor

Re: Contradicting dimensions?
 

OK. I just read a bunch of drawings and here's what I think. First, you may have misread DWG FE-10043-01, the side panel is 16.5x32.5. The 32.5" is the dimension that goes in the direction of the length of the tunnel (but not the total length), not the width. 16.5" is indeed the height of the tunnel before it is installed onto the base of the tower. The base of the tower has a 1.5x3.0" Aluminum U-channel that the tunnel sits on top of. Therefore, 16.5+1.5=18" total height. The width is easier. The top panel of the tunnel is 37" wide and sits on top of the 2 side panels (which are 1/2" plywood). Therefore, total width is 37-1=36". Thus giving the final dimension of !8" high by 36" wide for the opening of the tunnel.

Hope this helps. Rookie Mentor for Potential Energy Team #3323.

Re: Contradicting dimensions?
 

+1 to this sentiment. I always have had difficulty determining measurements on the FRC Field Drawings.

When we do drawings of our drive units and such we always dimension each thing back to 1 edge of the item in the X direction and likewise for the Y. It makes it easy to determine things. The FRC field drawings often leave you doing math to figure out where stuff is supposed to be.

Re: Contradicting dimensions?
 

When you do Ordinal dimensions (back to a single edge in X and Y) you are implying a different set of tolerances than the typical dimensioning you will get from FIRST drawings. I do wish they would give us higher resolution PDFs, or even better DWG/DXF or solid files. I wonder how many people simultaneously recreated the fields in various cad packages this year.

Also note that PTC was planning on releasing Pro/E models of the field, so you can always take measurements from that.


If you want to know way too much about dimensions, pick up a copy of ANSI/ASME Y14.5-2009 (I have a copy of the 1978 version that I got for a buck).

Re: Contradicting dimensions?
 

To be honest, I would be happy if they just put more dimensions on. They put so few on that they leave us guessing and doing math on alot of things when they could have easily stuck a dimension in.

Re: Contradicting dimensions?
 

I have yet to see a single drawing from FIRST that does not suck. I've seen high school kids produce more complete and easier to read drawings. It's not as though the field has a lot of (or any) complex geometry to dimension...

Re: Contradicting dimensions?
 

It's the lack of dimensions (or dimensioning that is stupid like to the edge of a hole) that is the frustrating part. When you have to spend 2 hours going through all the drawings adding the length of all the pieces up just to get some very basic, critical dimensions of the field pieces, it's quite frustrating.

And then you do all that and you build a ball return chute that is to "spec" (even though the specs are not really available on the actual positioning of the chute on the field) to the best you can do to their "competition field" drawings and the returned balls continually bounce off the tower top bar...it's quite frustrating...

And then the field you had parents and students work a week building per the "low cost" field drawings and you find that parts of it are off not by fractions of an inch, but by inches (because the drawings are wrong), FIRST quickly becomes the low bar by telling students "Your drawings for parts at least must be better than FIRST drawings..."

It's quite sad actually... Oh well...at least they got the KOP right...oh...wait...

Re: Contradicting dimensions?
 

Same in the 'real world'... I deal almost daily with house plans & missing dimensions, or dimensions that don't add up.

Speaking of which, the TRIDENT, GE-10010. Page one - Item#5 (part GE-10011), is dimensioned as 1" x 48, but on page 2 it is 1" x 36"

Has anyone seen a revision or update to correct this?

Re: Contradicting dimensions?
 

It is, unfortunately, pretty much the norm in any industry.

Consider any document from FIRST to be uncontrolled, and always keep an eye out for clarifications. If the hard copy is more then a week old, it's probably out of date and needs to be replaced. You can always make corrections by hand, but I'd rather just redownload and reprint. Corrections and errata sheets should be placed before the body of the document.

Welcome to industry.

Re: Contradicting dimensions?
 

Yeah, I am in the Industry where we use documents to build and of course, we are humans and make errors. But, in this case I still feel it is highly inexcusable. FIRST pays some engineers to design the game and documents. They know, 1800+ teams need those documents to build what FIRST has designed. How is it possible that there can be different dimensions in different documents, AND have totally WRONG dimensions in the documents at first then update the later after a week in a team update? It is embarrassing.

Re: Contradicting dimensions?
 

And why can't they just give us the field model they made all the drawings from...

Re: Contradicting dimensions?
 

Possibly one of the most massively misinformed posts I have seen so far this year.

Either that, or someone has been stealing a bunch of checks from several GDC members....






,

Re: Contradicting dimensions?
 

Are you saying, there is not ONE paid engineer on the FIRST staff?

Re: Contradicting dimensions?
 

LOL. How many members on GDC? Less than 20 I guess? Generate hundreds of pages of documentation, which is then proof read & scrutinized by thousands of mentors and dozens of thousands of students, all looking for loopholes......

I'd like to say great Job GDC, IMHO more loopholes were closed this year prior to kickoff than in prior years.

Re: Contradicting dimensions?
 

Oh, I am quite sure that there are several paid engineers on the FIRST staff. But that is irrelevant to your original comment.
I am sure the entire GDC would thank you for the comments. There are actually only 8 formal members, not 20.



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Re: Contradicting dimensions?
 

Technically less than 20. :rolleyes:

I agree that the drawings DO make you have to stop and think, but I have never found them to not ultimately provide all the information necessary.

Re: Contradicting dimensions?
 

Like I said, this kind of thing is normal not only in any industry, but FIRST.

It's easy to end up with conflicting dimensions and tolerances on the same drawing, let alone across separate documents prepared by a staff. The manual likely isn't written at the same time or by the same people who prepare the field drawings. A minor miscommunication, last minute change or just a straight up typo is all it takes. Catching these errors requires careful proofing and, as has been pointed out, FIRST has neither the time nor the staff to catch all errors. All you have to do to deal with these situation is designate the preferred document and refer to that, in this case the field drawing. In general, drawings are going to be updated and proofed more often then a manual or other document.

For instance, most production drawings have an production manual or guide that goes along with it. This contains general information about the part or assembly like preferred processes for certain features, general tolerances, material selection etc. But when it comes time to build the part, the dimensions, tolerances, surface finishes etc. are always pulled from the drawing.

If in doubt, refer to the revision number and date. The manual may or may not have this, but the drawings will. Use the latest revision you can find. FIRST's website will always be up to date. Most drawings will also have a revision block, detailing changes.

We've been dealing with unclear or incorrect field documentation since the 90's. Part of the challenge is that field elements can and do change in detail as the build progresses, and sometimes even during regionals.

Re: Contradicting dimensions?
 

I really fail to see how its even possible to end up with conflicting dimensions on a single drawing, if it was made with any remotely recent CAD program. And really, for the field, I don't understand why there should be conflicting dimensions across different drawings. I'm sure that they draw it up in Inventor or AutoCAD or similar, and then make drawings off of the model. If you use the same model for the source of your drawings, then the dimensions have to add up.

Re: Contradicting dimensions?
 

I've modeled the center section of the field (basically the only part your robot should be interacting with anyways.)

http://www.3dcontentcentral.com/Down...=171&id=183867

You can download it in varying file formats from here.

Re: Contradicting dimensions?
 

I'm laughing again at the lack of thought as I try to print out the 38" diameter target on our pretty much industry standard 36" wide plotter...

Re: Contradicting dimensions?
 

Would a metric plotter be 39.37" wide? :rolleyes:

Re: Contradicting dimensions?
 

Hmmm. That is strange. Because I am noting that our industry-standard 44-inch wide plotter has absolutely no problem printing out the target. On many different sizes of industry-standard paper. Including the industry-standard ISO B-series Size 0 sheets and the industry-standard 44-inch wide rolls.

Before branding something with the "lack of thought" label, one might consider that "your" standards may not be "the" standards. Neither is right, neither is wrong. They are just different.

-dave




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Re: Contradicting dimensions?
 

I'd rather go by this picture taken at the NH kickoff that shows a field within tolerances. Last year we designed for tight field tolerances and got bitten by it in Atlanta when the fields sunk some due to weight on the layers of softer materials* which caused us to regularly get stuck in one spot. Never again will we design for tight field tolerances, ever. 17.5" or less, ftw.

*('regolith' on top of carpet on top of rubber on top of hard floor)

Re: Contradicting dimensions?
 

OK...lol...you got me...

Re: Contradicting dimensions?
 

In this case, FIRSTs drawings are right. It was the manual that got it wrong. That sort of cross documentation error is common no matter what you do, and I think it's pretty easy to imagine how that happens. Production drawings often enough aren't made with the benefit of having the entire design modeled in the same program. A lot of drawing sets are a collage of the output of several different programs and individual models. So it is possible to end up with two different dimensions for the same feature, and it happens surprisingly frequently at least before they get proofed (my job for a short while). This is slowly changing as individual programs get better at 'doing it all', but for the foreseeable future things get made with a mix of programs, each good at some aspect of the model.

The biggest problem is just plain ol' over dimensioning. It's a frequent cause of mixing up tolerance levels and ending up with a design that calls for two different levels of tolerance for the same feature. When that happens the dimensions are conflicting. Even though they 'add up' they mean very different things when it comes time to making the part.

Re: Contradicting dimensions?
 

My team is a little perplexed... We have looked at the update for the bump (update 2) and the file for drawings says that it was updated on the same date- however they do not match... I understand that alot of you posting are questioning the work done- I just want help with making sure that this is built right. Can someone please help decipher the difference between update 2 and drawing GE-10047.

Thank you