Building model bridges for competiton

[piku]

I signed up in school for a balsa wood bridge building club thing (you know, where you make those flimsy bridges that somehow hold like 80 pounds ). Anyway, I was wondering if anyone here could provide suggestions or where to check on the internet for information, because my friend and I plan on making an awesome one

 

[Farbio]

we did one out of toothpicks in school many years ago...ours held a whole set of encyclopedias w/ the first one stacked vertical across the middle of the bridge.

the ways we found to do it:
make the actual 'roadway' 3 layers thick and make each layer on about a 45 degree angle to what would be straight, w/ each layer alternating direction
under the roadway, between the supports, make some triangle supports that extend about 1/2" below the road way
make the supports like log cabins, remember how lincoln logs fit together? do it like that

hope that helps...if u need anything more, pm or email me

 

[cxim]

I do believe we have a mis-spelled user name here, Piker

 

[MrPALCO]

piku...triangulate every connection, in three planes......three is the ultimate strength of the Universe...

 

[piku]

Farbio - thats interesting. Ill have to play around with that design.

cxim - I... don't get it

 

[Viper GTS]

Piku... It's more than just interesting, if you've ever had a statics class you'll know that it's the ONLY way to go. A triangular pyramid is the strongest shape you can make out of rods, & triangular sectioning in trusses produces the most vertical strength. If I had a scanner that worked, I'd scan some diagrams out of my statics book. They might help you. Or, if you want, I can photocopy them & mail them to you.

[EDIT]I'm dumb, I thought your comment was in reference to MrPalco's statement. Still, my post applies.[/L]

Viper GTS

 

[DAM]

80 lbs ha ha ha, dude when i was in high school one of the groups in our school held 1500 lbs, yes thats right im not makins stuff up, this guys bridge held 1500 lbs, he had the record that year, but was broken the followin year by some other school holding nearly 1600 lbs


the most my group ever did was 1100.




dam()

 

[piku]

Viper - ya I know about triangles... who doesn't? (acctually I think octagons or pentagons or something are technically better but im not sure)

DAM - I think we are using VERY different rules. A 25 gram bridge could NEVER hold 1600 pounds

 

[Viper GTS]

But what are octagons & pentagons constructed of? Without the central pieces, they'd be VERY weak.

Viper GTS

 

[GreenBeret]

It's all about the triangles, Piku. Put 5 triangles together, and you have a pentagon... 8 and you have an octagon. Triangles baby!

 

[piku]

Well yes, a complete mesh creating them are better than a triangle. But stand-alone, just the outsides, a triagle cant be beat - you are correct.

 

[Viper GTS]

Piku...

The only reason that pentagons & octagons are strong is because they're composed of triangles. You don't gain any particular strength by forming triangles into those shapes, the strength comes from the triangles.

Viper GTS