Thread: Bridge building help!!
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Unread 08-01-2012, 12:58
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Senior LRI NC District
AKA: Lee Barger
FRC #0587 (The Hedgehogs)
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Join Date: Dec 2005
Rookie Year: 2001
Location: Hillsborough, NC
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Re: Bridge building help!!
I have an issue with the low cost version of the bridge as supplied by FIRST. I have already contacted them about it ans supposedly the information was forward to their engineering team.

The main issue is the deck of the bridge is supported only by 4 3/4" wide ribs all in the same plane. As long as the bridge experience loads in the vertical direction or along it's length that is fine. By if it sides a strong side load (unsupervised hyperactive students or mentors) there is very little to keep the four ribs from simply folding over. For our kickoff event we added blocking between the outer and inner ribs. This took the form of a 6x15" piece of plywood that we attached between two vertical ribs, the top deck and the 2x4 on the bottom.

Also, I believe the plans call for the deck to be attached to the ribs using glue and staples. Use screws instead the staples. After a day of use at our kickoff volunteers were helping to pack up the field. Grabbing the first one by the deck (and not the underlying ribs) the volunteer promptly lifted the deck and left the rest of the structure sitting in place.
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