US Gulf Coast · Balsa sticks, 1/16 to 3/8 in
18 in gap · a test vehicle on the deck where the judges choose · 150 g max
Official rules (PDF)(opens in a new tab)The rules don't mention AI tools. Check with your teacher or the organizer before you enter a design from this site.
Read it in the rulebook(opens in a new tab)Soon this page will show ready-made designs for this contest, each checked against every rule below, loaded until it breaks, and buildable with a hobby knife, with a printable build pack. For now, here are the rules in plain words.
Our summary of the official rules. If anything here disagrees with the rulebook or the organizer, they win.
Where a rule can be read two ways we use the reading the organizer most likely meant and show the other. Where ours is the looser one, ask your organizer before you rely on it.
The channel may be under any part of the span, so nothing may sit lower than 3 in anywhere inside the 18 in gap. The deck is carried on end legs or an arch.
The other reading: One 3 in channel at mid-span only.
'Out-to-out dimensions' means the bridge's width across the span.
The other reading: Some other overall dimension.
The roadway is level, and the vehicle's wheels run on stringers on wheel lines at +-1 in.
“span a gap of 18 inches, with a max length of 20 inches”
“clear path for traffic ... at least 3 in wide and 3 in high”
“Maximum out-to-out bridge dimensions are 6 in”
“vertical clearance of 3 in ... 3 in wide ship channel under any portion”
“Type 1 ... no greater than 3/8 in; Type 2 ... no greater than 1/16 in”
“cannot weigh more than 150 grams”
“shall stand freely on a flat surface”
“Judges may load the bridge at the point most likely to cause failure”
“Deflection of more than 1/2 in occurs”
The other reading: A sloped roadway the car can be pushed over; a full-width deck.
The bucket's bolts must pass through the deck. We require both configurations to fit at mid-span, and the judges pick the worst position where they fit.
The other reading: Only one configuration has to fit.
Built-up members are allowed as long as the whole section stays within 3/8 in; gussets come from 1/16 in sheet.
The other reading: Each piece, not each member, is limited to 3/8 in.