Thread: Bridge CG and Inertia Data
View Single Post
  #1   Spotlight this post!  
Unread 21-01-2012, 20:56
Paul Copioli's Avatar Unsung FIRST Hero Woodie Flowers Award
Paul Copioli Paul Copioli is offline
President, VEX Robotics, Inc.
FRC #3310 (Black Hawk Robotics)
Team Role: Engineer
  
Join Date: Jun 2001
Rookie Year: 2000
Location: Rockwall, TX
Posts: 1,388
Paul Copioli has a reputation beyond reputePaul Copioli has a reputation beyond reputePaul Copioli has a reputation beyond reputePaul Copioli has a reputation beyond reputePaul Copioli has a reputation beyond reputePaul Copioli has a reputation beyond reputePaul Copioli has a reputation beyond reputePaul Copioli has a reputation beyond reputePaul Copioli has a reputation beyond reputePaul Copioli has a reputation beyond reputePaul Copioli has a reputation beyond repute
Bridge CG and Inertia Data
All,

Attached is a PDF file showing the center of gravity and inertia data for the bridge. It is slightly not symmetric due to the way FIRST designed the bridge. Additionally, the pivot points are each 3.5" away from the centerline and they are 4.5" above the ground. For the bridge in a neutral position this means the CG of the bridge is approximately 6" above the pivots.

Based on this geometry and cg info I did a quick calculation on the whole battery test. If I assume two batteries are 27 lbs total, then the distance the batteries cg would have to be away form the pivot for a right tip is 25.67". This puts the CG exactly above the pivot. The battery is about 6.6" tall so the CG for the battery is approximately 3.3" from that. Using the 30" to make the bridge tip from the video that means the battery CG is at about 26.7 in the video.

This is close enough for me...

Paul
Attached Files
File Type: pdf 2012 Bridge tipping analysis.pdf (529.4 KB, 117 views)
__________________
In full disclosure I am the President of VEX Robotics, a division of Innovation First International.