Our robot is on the edge of the weight limit [119-121lbs].
We do have pneumatic tires, 6 of them 10inches, would taking the air out of them help make a difference in weight? Also would that be legal?
If you deflate your tires to make weight, you must compete with deflated tires.
I doubt it will make any difference. Air is fairly light (hence the term light as air). Also if you do this and then re-inflate your wheels and that gets you over weight you are illegal, you may have passed inspection with your under inflated wheels but its still breaking the rules even if you don’t get caught. You are better off speed holing your bot in many places
Air is a low density form of matter. Unless you compressed the air to an extreme level I would find a solid piece of matter a lot better to take off for weight reduction.
Thanks of the replies, I guess I will get that hole drill warmed up…
1 word . . . helium. 
Why would you say this? Teams are encouraged to let all the air out of their pneumatic tanks when weighing, but can compete with them fully charged.
Is there a rule you can reference that verifies this claim?
FYI, at 35psi and room temperature, air weighs about 1/4 lbs per cubic foot (source).
So… …yeah you better plan to save weight someplace else.
Joe J.
This is why I think letting the air out of the tires is legal.
1/4 LBS for 1 sq foot.
6 Tires that are 10x3inches
Hm that might help.
Pneumatic tires are not pneumatics. (Blue box, [R71]).
The reason pneumatics are supposed to be empty when weighing (and all through inspection other than the power-on check) is for safety, so that something doesn’t go totally haywire. Pneumatic tires don’t have that problem.
Therefore, I can conclude that pneumatic tires, if deflated for inspection, must compete as inspected; i.e., deflated.
Oh, and Dr. Joe is right about air’s lack of weight savings. Just trust me on this (other than: I was dealing with about 3 IWC air last summer).
Is helium a legal robot building substance?
I didn’t see it as being illegal. However, keeping it from escaping is not easy. And to get much lift… well, let’s just say that you’d probably either have a structural failure or negate all of the lifting capability by adding strength to have any chance.
There are plently of ways to lose weight.
I whould try cutting holes or trinagles in your bot if possibale.
If we can see a pic of if we might be able to give some ideas.
I figured this thread had to be trolling…but then it was serious???
So ~0.13 lb total*, or about half the weight of the digital sidecar, [EDIT] or about the same weight as all of the data in the internet in 2007 [/EDIT].
*Assuming the wheel’s inner tube is a torus of R=3.5, r=1.5 in. Volume is V=2(pi^2)(R)(r^2).
The reason that they must compete with deflated tires has to do with the rule about robot configurations. The deflated and inflated states are 2 different configurations for the same robot, and the rule stipulates that both must be weighed at the same time.
Its well established on this insane thread that air is not going to make that much of a difference. However, I will offer up some tips from my experiences at competition on saving weight:
- go check your weight out at the inspection station as early as possible. The scales used at competition are of much higher caliber than what the average team has back at their shop, they are also calibrated specifically for the competition.
- Check your robot for bolts that aren’t used, dust that has accumulated, random screwdrivers just sitting on it. You’ll be surprised how many tools the field crew picks up over the course of 1 event. Most of that weighs more than air.
- My favorite weight reducer this year is high density foam, you can get it in 1" sheets and its mostly air. And does a much lighter job where people tend to use Lexan/Polycarb type materials. You can also find it easily a lot of places (just look up)
- After you do all of that, then try swaping out thinner pieces of metal/polycarb, you’ll save more weight there than other places
- Now you can proceed to the art of swiss cheesing.
*results may vary
#1 statement above is excellent… thinner lexan… 1/2 the thickness 1/2 the weight.
think about using rivets instead of screws and nuts… You would be surprised at how much weight you can save…
Of course you need to consider what strength you need and in areas where this is critical, rivets may not be a good choice as a direct replacement.
I would hazard a guess to say that EVERYTHING on your robot weights more than its own volume of air. If not it would float…in air…
buoyant force…
of course this year is the first year we have to add weight to our robot … low and to the front
The inflation of the tires is similar to the electrons of an atom, they are important, but weigh nothing (sort of). It shouldn’t be a problem and if it is I am sure you can have other ways of saving weight. Good luck though, hope you do well!
If there is more than one scale and you’re barely overweight, switch to the other scale and try weighing your robot. At the nationals in 2010, we were half a pound overweight on one scale and two-tenths underweight on the scale right next to it.