Overweight!?

[Jordan2389Diaz]

My team now is five pounds under weight and we still need to add some more parts to our robot. We are thinking of making swiss cheese of our metal in order to lessen the weight of the robot like we did last year when my team got to the competition we were fourteen pounds over weight.

How many teams are almost over weight - or going to be over weight when you finished your robot?

Lord is my Shepherd I shall not want.-Psalms 23

[Sunshine]

2.9 pounds over weight at the moment.

[dodar]

Our team is like right around 118lbs and thats what we usually end up at, it is good to guesstimate your weight for each object going onto your robot so you know how to fix it easier than making your robot holy

[Daniel_LaFleur]

Originally Posted by Jordan2389Diaz

My team now is five pounds under weight and we still need to add some more parts to our robot. We are thinking of making swiss cheese of our metal in order to lessen the weight of the robot like we did last year when my team got to the competition we were fourteen pounds over weight.

How many teams are almost over weight - or going to be over weight when you finished your robot?

Lord is my Shepherd I shall not want.-Psalms 23

Be very careful when swiss-cheesing your robot.

The Last few years, bumper-to-bumper contact was the only contact that was going to happen.

Not so this year. You will see hard impacts at various angles going over the bumps, robots driving on top of other robots at the bump, robots falling off of the bar ... possibly on top of other robots. This year will be very physical. Expect large forces in directions that we have not seen in many years.

In other words, build it robust. And if you do swiss cheese your robot, understand the weaknesses you create, where you have created them, and how you will avoid forces at those points in those directions.

[Ben Martin]

We are about 12 pounds underweight at the moment.

It doesn't really help at this point, but the best way to prevent this is to always be somewhat conscious about weight as you build it and don't create extraneous superstructure.

Take advantage of your bumpers -- they will help reduce shock loads you receive from the sides, so you can cheese your aluminum somewhat in that 5in of space.

[Jordan2389Diaz]

Do not worry my team is only drilling holes in the metal where the structure tension is not involved and hopefully we are under weight or right on the mark plus our robot is stable.

Lord is my Shepherd I shall not want-Psalms 23

[IKE]

Before Swiss-cheesing, please read the following paper:

http://www.chiefdelphi.com/media/papers/2220

That being said, "lightening" holes are not a bad idea, just plan them out. Last night we swiss-cheesed a set of components. to give you an idea of the effort, 48 1" holes through 1/8" aluminum was worth about 0.48 lbs This took a significant amount of time and made a huge mess, and as far as i know, that kid is still deburring the parts...

1" hole = (.5^2)*pi = 0.785 in^2
x1/8" thick = 0.1 in^3
Aluminum is 0.1 lbs/in^3
thus each hole is 0.1*0.1=.01 lbs
x 48 holes = 0.48 lbs.

Note that larger holes do have more area, but you can make fewer of them. a 1.5" hole would remove (1.5)^2 material or 2.25 times as much material, but you can only drill 2/3 as many holes. Thus for the components we were looking at, we could do 48 1" holes, or 32 1.5" holes. The 1.5" holes would have been worth 0.8 lbs (.28*2.25*(32/48), but would have reduced the structural integrity of the component too much. this exercise took 10 minutes to do and saved us from scrapping components that had 10+ man-hours in making.

Please drill responsibly!

[Ken Leung]

Yup, we are currently about 10-15 lbs overweight. We should be able to cut 10 lbs right off the bat, but it's questionable whether we will be able to keep all of our mechanisms at the moment...

[MrForbes]

Weight? good question. Last we checked we were at about 90 lbs, with more parts still to be added.

Our new wood electronics box has 6 lightening holes, the pieces we took out weigh almost half a pound. 3" holes in 1/2" plywood. It had more to do with moving the CG forward, than with reducing overall weight.

[Jon Stratis]

Overweight? With the increase to 65 lbs in the withholding allowance... we're planning on withholding our entire robot!


All joking aside... we've always planned for weight from day 1, and it's paid off. Every year we end up adding steel plates to add weight - in some cases, they're bolted onto the bottom to help adjust our center of gravity, in others they're used as optional structural members (we could have used aluminum, but since we had the weight...). This year, i anticipate being 10-15 lbs under. We'll only add weight if we need to move our CG - other wise, being lighter is going to help with the final hang.

[Jordan2389Diaz]

What kind of materials did your team make your robot out of for it to be so light.

Lord is my Shepherd I shall not want-Psalms 23

[thatoneguy23]

Our robot is going to go on it's swiss cheese diet pretty soon. We won't have too much other than frame metal that we can remove either. Just hoping that it works out well.

[Kage]

My teams robot is 99% done...and 15 pounds under weight
we are probably going to add some random chunks of metal low-down in the chassis to help with the CoG

[Tom Line]

It is far more efficient to start lightening any steel components you have first. For us, the only appreciable amount of steel we use is in the trannies.

After that, see what you have that you can simply remove or cut off.

After that..... well I hate cheeseholing. We burned through any number of hole saws and drillbits in '08 trying to get down to weight.

[The Megan 2207]

For once we're actually underweight! Last I heard, we were at 65 pounds, but we're expecting to be 80 pounds or so (and this year's robot will FINALLY be smaller than me! ).