Overweight!?

[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.

[nitneylion452]

Originally Posted by eagle33199

Overweight? With the increase to 65 lbs in the withholding allowance...

Could you point out where the WITHHOLDING ALLOWANCE has been increases to 65 lbs? <R38> still states 40 lbs.

[Jon Stratis]

http://frcdirector.blogspot.com/2010...-year-and.html

After discussions with the Game Design Committee I decided that, although Robot Ship Day must remain February 23rd, this year, all FRC teams will be allowed to hold back 65 pounds of their robot’s weight on Robot Ship Day. (That’s roughly half of the total weight of an FRC robot.) Teams may continue to work on the items they hold back and then hand deliver the items to their event. Watch for a team update coming soon.

As Bill just posted that yesterday, i expect the game manual will be updated with 65 lbs in today's update.

[Dick Linn]

I can well remember seeking out free machine shop services to put steel chain sprockets on a diet. Or a couple hours with an angle grinder and a cutoff wheel to spider-web a pair of 60 tooth #35 steel sprockets. Eventually, you try to get in the habit of weighing and estimating as you go.

[Peter Matteson]

Originally Posted by Dick Linn

Eventually, you try to get in the habit of weighing and estimating as you go.

That's never stopped us from going overweight...

[Dick Linn]

Originally Posted by Peter Matteson

That's never stopped us from going overweight...

But then you can at least estimate the size of the drills you need to hog out holes.

[rsegrest]

91 lbs with battery...when we weighed the battery it listed at 14 lbs so we figure we're at 76 - 77 lbs...first time we've EVER been this far under Kind of scary though when you think about possible shoving matches!

[Jon Stratis]

We weighed ourselves tonight - 82.5 lbs. We still need to add:
- cRio
- kicker assembly
- hood/roll bar

We figure with all that, we're still going to be 10-20 lbs light. Which just means we get to use some steel plates again to help position our center of gravity (when the battery is included, we suspect it will be slightly to the back as it is now).

[HazzardFuzzBomb]

Weirdly we are at about 65pounds, we were so shocked when we read it. Looks like someone's robot is getting a nice shiny steel exoskeleton lol

[dodar]

haha we weighed in around 118lbs