What is a Box?

Sorry, I was reading the How to Save Weight guide (http://www.chiefdelphi.com/media/papers/2220) and came across:

Replace 1/8th 1x1 inch Aluminum box with 1/16th wall 1x1 inch aluminum box. 50% weight reduction. Also good for ¼ pound/foot.
If using box as a tension strut try using angle or some stringer from aircraft spruce (at 11 oz. per 12 foot, it doesn’t get much lighter).

  1. what is a box?
  2. what is a tension strut?


  1. Box or square aluminum tubing
  2. I believe he is referring to a piece of tubing used as an off-vertical support for another structure.
  1. This is referring to square aluminum tube, i.e. the outer dimensions of the aluminum are a 1x1 square, and each side is 1/8" thick.

  2. Without context, I would guess that a tension strut is basically something being used to brace a tower or arm.

Edit: Looks like I was too slow.

  1. 1x1" square aluminum tubing and 1x1 box are the same thing in my language, though I can understand the confusion. These are aluminum extrusions and come often come in various thicknesses.

  2. A tension sturt is a type of brace that primarily works in tension. It is often a piece that triangulates 2 perpendicular members. If it works purely in tension, it can be as light as a strong piece of string. Check out old wooden airplanes to see some very clever use of string. Often I will see such a member made out of thicker than necessary material. In fact, one of the teams competing in Elims at Troy District this year had a piece of 1/8" thick 1x1 angle they were using as a tension strut. They were a pound overweight, and replaced it with 1/16" during the lunch break before elims. This in my opinion is a great way to loose a pound.

wait… a pound over weight, but were allowed to play anyway and didn’t fix it until right before elims…? who’s the inspector that made that decision…?

I suspect that this team made modifications to their robot throughout their competition that resulted in them being a pound overweight when elimination inspections rolled around.

Either that, or the scales ruled against them. They’ve been known to have an error margin of at least ±.25lb, if not greater.

Little known fact(at least in CT and possibly other new england area regionals):
When we do the reinspection prior to elims, we typically compare the current weight(with bumpers and battery on) to the original robot weight + the bumper weight(originally weighed separately) + 15lb allowance for battery

This gives teams roughly 2 lbs of leeway… if you’re still overweight, then you changed something that probably should’ve required that you get reinspected. If you didn’t get reinspected, and you should’ve, you get angry lead inspectors having “a little chat” with your team…

I was LRI at the event. This team weighed in perfectly fine initially (though very close), and likely gained a little weight during competition which is not terribly uncommon, but must be corrected when it is realized. Often LRI may give a little lee-way going into elims, but they are in a sense making their own rules on that. Usually when teams get this much over after qualifying, it is because they have been playing the weight swap game several times during the weekend. This is where they have removed something they want to put back on, and keep swaping out other parts to try to get the weight back. They bring individual parts and sub assemblies and place them on a scale (calibrated around a 100 lbs). If there is 0.1 lbs of error on the two parts, and they go in the opposite direction, they may end up with 0.2 lbs of error per change. While this is a bit on the extreme, it can happen. The other common weight gain I see is a team just a little bit over removing a dust shield for the elctronics or a couple of dust shields (0.2-0.4 lbs). Then a different pit crew member not present at the weigh-in re-installs those shields thinking someone forgot to put them on.

It is very easy to gain some weight during competition while making small changes. Technically if you are that close, you should re-weigh after changes, but teams are essentially on the honor system until they are re-weighed. The only time I have seen a team called out for competing overweight was when a they were considerably overweight (5+ lbs), and removed a major sub-assembly, and then re-attached it later without re-weighing.

I completely understand the concern that you have over allowing a team to compete with extra weight. Rest assured, they were competing overweight without my knowledge (and most likely without the team’s knowledge). As soon as they learned about the infraction, and accepted it, they worked their butts off to ensure that they would be competition legal for elims.

As people have said, it was probably modifications, but there have been countless incidents in which tools have been left on robots. Occasionally, tools will fall out onto the field during matches when they become dislodged from the robot. It’s actually quite common.

Well first, it’s very nice to meet you.

I agree completely that there are situations where that can happen, and know full well that exceptions are granted occasionally. I have been an inspector in CT for 4 years now, and Champs in 2010 and this year, so I’ve seen my fair share. I do realize that I don’t know all, and since I’m not an LRI, I’m not in a position to need to know all.

I wasn’t hoping to start an argument or anything here. I was just surprised to see the weight difference. I’m glad to hear that the situation was handled well.