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Re: Bridge question
I just finished our bridge and here is what I came up with.
Looking at the game element drawings, the bridge pivots are 7" apart or 3.5" on each side of center. If you follow the low cost drawings, I think you will find your hinges end up 7" apart. Ours did.
Using the Youtube video the bridge is supposed to stay flat when 2 batteries are placed 28" from center and tilt when they are moved to 30". We weighed 2 batteries at 28 lbs. Working backwards from the 30" number you get:
Weight of the competition bridge (Wcb)*3.5 = 28 * (30-3.5)
or Wcb = 212 lbs.
Looking at our bridge, it began to tilt when the two batteries were at 18":
Wob *3.5 = 28 * (18-3.5)
Wob = 116 lbs.
Ballast required to bring our bridge into spec:
Wcb-Wob = 212-116 = 96 lbs. (equally distributed about the CL of course!)
It's very worthwhile to run through the excersise for the students. It's a very accessable and practical problem.
If anyone has any corrections to this, I'd be happy to hear them (especially if I've missed something!) and if you need any help with the equations or how I arrived at them, I'd be glad to explain what I did.
Thank you and good luck!
__________________
Dan Glenn
2015-16 FRC Chairman, San Diego Regional Planning Committee
2016 FRC Inspector, Orange County (LRI), Los Angeles, Carson Division
2015 FRC Inspector, Inland Empire (LRI), Central Valley, Los Angeles, Galileo Division
2015 FTC Mentor 10092 Green.Griffins; R&D Robotics Education
2014 FRC Inspector, Inland Empire, San Diego(LRI), Archimedes Division
2012-15 FTC Mentor Team 6565 Stuffed Dragons & 8489 Green Griffins Boys and Girls Club
2013 FRC Inspector, Central Valley, San Diego(LRI), Los Angeles, Inland Empire, Galileo Division
2012 FRC Inspector, San Diego, Los Angeles, Central Valley, Newton Division
2009-12 FRC Mentor Team 1622 Spyder Poway HS
2007-08 FRC Mentor Team 2658 Pedestrian Rancho Bernardo HS
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