Attention rookie teams (and other teams who don’t know). It is generally a good idea to not build your robot to exactly 38x28. I don’t want to see anyone have to bring out the “robot adjuster” (aka sledge hammer) to beat it into fitting into the box. A half inch under on each dimension is good to fit in the box, an inch under dimension is perhaps more wise, in case something gets bent or you want to bolt something onto the outside edge later.
Good point. I was just telling the CAD guy yesterday not to make the frame use the whole demension.
as much as this seems like it should be common knowledge it isnt. Pay attention to this. It is terrible to have to modify parts that are essential so you an compete.
i think this should be made a sticky
Good point. We try to stay around .5" smaller all the way around. For some reason things always seem to grow and never shrink.
Our bot this year will be 26.5"Wx34"L. Somewhat close to square, with lots of breathing room for inspection. People usually dont take bolts or other protrusions into account when designing their chassis, which always get you when you max out.
I think FIRST should have their dimensions square, like 38"x38". That way you could design a square chassis without losing a potential unecessary 10".
What good is a robot that you can’t get out of the room you’ve built it in? 
I would like to add that many teams build close to max and measure constantly only to forget that they need to add some lexan to the outside of the chassis and find that the mounting hardware doesn’t allow the robot to fit in the sizing box.
Being a rookie, I have a few of questions…
Per the rule book, the maximum chassis dimensions this year are 28" by 38", is this with or without the bumpers installed?
I plan to use the standard bumpers but I am also wondering, for these to be considered the standard bumpers, do I need to use that fabric that they specify or can I use something like naugahyde?
What overall chassis dimensions should we shoot for given our choice to build and use the standard bumpers per the dimensions listed in the 2007 rule book?
Please advise on the above questions
Thanks
Dimensions do not include the bumpers which you will bring to the inspection detached from your robot for weigh in and inspection.
The fabric must be the same or a very close equivalent, as shown in the manual, in fact the construction of the bumpers should be the same as shown in the manual.
Dimensions of 1/4" less than maximum on all 6 sides is a good start. Included in the test will be any attachment points for the bumpers and any folding attachments that can’t hold themselves inside the sizing box. You will be required to place your robot in a three sided box with a feeler guage that will pass down the fourth side. If the feeler contacts anything on your robot it doesn’t pass the size inspection. Often teams will have hardware or tie wraps that exceed the dimensions in this test. Those teams will be required to remove or modify the offending parts. Inspectors will work with you on fixing dimensional problems and are trained to recognize frame damage that normally occurs during competition. We are really good guys and we are fair to all but we aren’t pushovers. Before the first regional, FIRST will publish an inspection sheet so you can check the robot yourselves for compliance and will publish revisions throughout the season. Keep checking.
Thank you for the helpful tips!
And PLEASE… think NOW about how you are going to weigh your robot. Find a friendly shipping company or figure something out.
It is always so heartbreaking to see teams spending Thursday of the competition trying to shed… in some cases… up to 30 pounds. But even coming in a quarter pound over can be a problem and stress that you don’t need at the competition.
Then think about what happens if one of your custom designed ultra cool ultra light weight parts breaks and you need to weld it up/bolt it back together/splint it/manufacture a quick replacement. Remember that you get re-weighed and re-sized prior to the playoffs.
Last year we passed tech in Toronto weighing 118.5… and passed tech for the playoffs at 120.0 after repairing a damaged part.
I would say weight limits cause even more headaches than size limits… you can see when you’re going over size, but weight just creeps up on you silently.
Jason
(currently 3-5 pounds over my personal weight limit… darn Christmas baking!)