anti-gravity-gas
 

alright, what are all you people injecting into your air tanks to make your robots 130lb? we are bordering on 130lb, and we barely have anything! our arms are fiberglass, our transmissions weigh 2.5lb. Then i see all metal robots with 6 wheels, big huge gear boxes, and 10' long arms. whats the secret?

Re: anti-gravity-gas
 

you just have to know were the weight is going to be and work around it we have put on more stuff this year and our robot is more complex then ever and we are still under weight we have 6 cylnders 6 motors and we ended up wiht like 129.5

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you could try helium. hidrogen would be lighter but you risk flamibility

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well our personal preference is hydrogen, but sometimes that can get rowdy.....

naa im just kidding. all you need to do is selct materials wisely. EX. if something that you are planning to make of 1/2 lexan can be made with 1/4 aluminum, go for the aluminum. (also see the reference on what is called a mill and thing that goes on mill to make big holes...hey im a programmer, what do you want?)

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Maybe your frame is the pest - light and less voluminous metal may help i guess.

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Wait, is an aluminum plate lighter than Lexan of the same size and thickness? What's the density of each?

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from inventor..

it was just an example.. not an actual scenario. i would use 1/4 aluminum and get it anodized cuz it looks uber-cool

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no no no, the trick is a well known trick among veteran teams. Its offical FIRST terminology is "Speed Holes". These are the mysterious large 1 to 2 inch holes you'll see scattered about a robot, usually made while standing next to the scale using a large hole saw. Our old engineer leader used to get a little speed hole happy with the drill, he's no longer allowed near a drill. Heh.

Re: anti-gravity-gas
 

Why not a vacuume?
Just evacuate your entire robot. Its less dense then helium or hydrogen.

Or better yet, why not raise the pressure in the building where the regionals are at. That way, if your frame is sealed, the air in your robot is less dense then the air in the stadium.

When you weigh, be sure to use a dead battery (remember electrons have mass)

If you're really adventurous, you could short the terminals on your battery and boil off some electrolyte.

Also, try to cut some weight out of the RC, works every time.

In addition be sure to sabatoge the scale. When the scale is zeroed, put somthing heavy on it, like a battery. Then the scale is "zeroed" at about 13.5 lbs.

Oh by the way, don't actually do any of this stuff, its not GP :D

Good luck yall!

-Andy

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Make sure your code has as many 0's as possible...Everybody knows that 0's are lighter than 1's :yikes:

-Scooter

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No, no, no! The weight of binary values goes against intuition here. Since the beginning of computer storage, 1's have been represented by holes in paper tape or punched cards, making them lighter than 0's. This has carried through to electronic memory, where a logical 1 is customarily represented by a higher positive voltage, meaning fewer electrons. :D

Re: anti-gravity-gas
 

Actually, if you did a vaccuum, you wouldn't get the upward force of helium (and other) gases. I can have a balloon filled with helium fly up, but a balloon with nothing at all in it just kinda sits there ;).

Of course, the amount of helium in your average balloon lifts a couple of grams, so you'll need a bit more than would fit on a robot to make any difference...

Re: anti-gravity-gas
 

First, you might change to ANSI 25 instead of 35 if you have chains and you can make the change. Second, watch out for steel. Some applications will require steel, but in most cases, find an alternative - aluminum is the choice of FIRSTers it seems. When you put things on your bot, always ask - can this be thinner or shorter? Chances are, the answer is yes.

Also, get creative! Go on down to Home Depot or Lowes or Menards for you Midwesterners. Look around and see what they have for you to play with. You'll find strong aluminum tubes that are very light and relatively cheap. You'll find things like wire mesh, PVC and wood - all of which can replace aluminum and lexan in certain applications. Just make sure you get the light stuff (i.e. NOT oak). Last year 1020 had two pieces of 30"x50" light weight wood on the bot. It weighed almost nothing and just before weighing in, we hit them with a couple hair dryers to get rid of the moisture ;).

Congrats to all on completing your bot (or sorta completing as is our case) and good luck in competition.

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Since the ban on exotic materials has been lifted this year ..Your world is opened up..

We use Unobtainium (tough to find though...)

It has a negative density...(-.0314 g/ml)

Works great to alleviate temporary Mid to late February bloating due to post kickoff stress syndrome.

You will, of course, need a prescription to get it

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The thing that weighs down our robot is the pneumatics. Our solution was to just drill holes in the rams and tanks. No actually we drilled holes in anything that didnt hold a lot of weight, and removed some pneumatics fittings (those are actually really heavy). Another thing was this giant chunk of 5/8 inch plexiglass, which we replaced with marine grade plywood.

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We didn't use any this year, but I've found the best stiff lightweight structural material if you don't need the strength is 6 ft. shower curtain rod that Home Depot carries - it's 1 inch diameter by about .015 thick if I recall. Makes really nice long mechanisms - you don't get the droop of PVC.

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when you're done drilling holes in the air tanks, and you're still over, make sure you take that proton-heavy lead out of your battery.

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Take a vacuum pump and suck all the air out of your pneumatic system. No air is lighter than H2.

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I often wonder the same thing. Besides the team secrets Andy leaked earlier in the thread, here are a few mostly obvious tips off ghe top of my head.

Not all aluminum frame materials are equal. Pick something that is light. This is an area that can make a big difference. Last year we made our bot out of 1.5 in welded aluminum square and we were overweight. This year our robot is at least 4 times more complex and was undereight. We used 1010 series 8020 extrusion. With square round, etc wall thickness is a big factor.

wheels suck weight There is no need for giamongous metal rimmed go-kart tires. Avoid anything with metal rims like the plague.

resist the hive As goofy as this may sound, wires do take up weight, several pounds of it. Avoid hivelike electrical panels, make things as short and neat as possible.

No need for overly beefy gears. I see alot of gears that look like they belong in a bus transmission. avoid gears with hubs. Use keyways, and spacer tubes. We have gearboxes that we direct drive out of with 12.5 in wheels that combine the chips and the drills. They use 8mm wide module 1 hubless steel metric gears and are plenty beefy. Don't be afraid of plastic gears and sprockets either. Timing belts can pften be lighter than chains.

swiss cheese it early you cna save alot of weight and frusteration if you lighten parts from the start. If there is any unnecessary, non-structural material on a part, remove it.

Stay away from oversized fasteners Fasteners take up alot of weight. Use ones that are the right size. IE: not too long not too wide. In some cases if you are really desperate, you ,ight consider going back and replacing things with plastic equivalants. IE: electrical components.

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Two words....Thinwall Aluminum.

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Bah, just use the battery that came with the EDU-Bot to run your robot!!! That sucker is so small and light... Alot lighter than than that passe' big battery you get in the kit!!! That battery is like so 5 minutes ago!!!

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Remember. Your RC is heavy. More specifically, the chips inside your RC are heavy because they contain data, and data is heavy. Open up the RC and drill a hole through each chip. Also, pneumatic tubing weighs a lot. It too can take many, many holes.

In all seriousness, tho, a charged battery weighs a noticable bit more than an uncharged one. 13.5 and 10 lb, respectively, if I remember right... Dosn't make sense to me, tho... Electrons arn't that heavy. Hell, you don't even know where they are/are going.

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Well, if you're really having problems with weight you can do what Greg did for our robot. Drive it backwards off a platform over a foot high and put a hole in the side of our compressor. That worked wonders. *shakes head*
:D

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Helium? A vacuum? Why not just use a little engineering ;)

our robot weighs in at 84lbs http://www.chiefdelphi.com/forums/sh...ad.php?t=26186

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I'm curious, have you actually weighed the same battery charged vs uncharged? Did you get this information from a source (if so, could you point me towards it)?

I'm not doubting you :) , I'm just trying to figure out what might cause this. Keep in mind that a charged battery has the same number of electrons as a uncharged one.


It is possible to lose quite a bit of weight by drilling holes, removing excess wires, and eliminating redundant fasteners. However, if you need to lose any substantial weight you'll probably need to redesign or eliminate a major component. Look at everything on your robot and ask yourself the question "Does this part add any value to my robot?" If you answer "no", cut that part off. It’s really disappointing to have to cut a major (and working!) subsystem off a robot but its often the only way to make the weight limit.

Greg