Posted by ChrisH at 1/18/2001 6:41 PM EST
Engineer on team #330, Beach 'Bots, from Hope Chapel Academy and NASA JPL, J & F Machine, Raetheon, et al.
In Reply to: good idea or bad?
Posted by Rob DeCotiis on 1/17/2001 8:10 PM EST:
: is it a good or bad idea:
: if you're tight on weight, just drilling holes in all of your stuff so it doesn't weight as much, suck as drilling holes in the claw that picks up the balls, or something like that?(just in preparation...
)
If nothing else it's very labor intensive, esp. if you're doing it as a field "repair". If I was to suddenly find I was over-weight I would take the following steps:
1) discard any non-functional or marginally functional mechanisms
2) reduce protective sheet material to the bare minimum.
3) put large holes in sheet materials that can't be completely done without.
4) After 1-3 then think about putting holes in structure. When you do drill structure be sure you drill areas that are primarily in shear. Examples would be the webs of I beams and c-channels. Avoid the flanges as these are generally in tension or even worse in compression.
But first use step 0)
Weigh EVERYTHING. We have a guy we call the Weight Czar, who keeps track of estimated weight and actual weight for all of our parts. If the estimated weight of a system is too high we drop it or work it until it isn't. We don't have to drill holes because the extra weight never gets in in the first place. We also track estimated and actual CG.
We learned this in "Ladder Logic" when we showed up to our first competition (the Nationals) and found to our great suprise that our "lightweight" robot was actually 29lbs overweight. We lost those extra lbs in about 4 hours, but the last 2 or 3 were hardest to find.
Remember a good scale can be your best friend.
Chris Husmann, PE
Team 330 the Beach 'Bots
PS. the last two years our offical weight was within 0.5lbs of our estimates