Elevated Bridge B/C

rman · Post by **rman** » April 8th, 2009, 9:44 am

wyu1229 wrote:does anyone know the tensile strength of basswood, with the stress applied parallel to the grain?

The honest answer is that the machanical properties of wood are highly variable, so much so as to be almost useless. We have measured variations of at least 10-1 in almost every specification (tensile, compressive, young's, density, etc.) of balsa wood. Bass seems to be a bit more consistant but it still varies hugely from peiece to piece. If you design based on some sort of textbook value of tensile strength og basswood, your bridge will probably be eith overbuilt of underbuilt. The only way to get the lightest piece of wood possible is to test the actual peice you intend to use.

bob3443 · Post by **bob3443** » April 8th, 2009, 12:42 pm

sewforlife wrote:
Bjsong wrote:Can you guys post what was the 1st place efficiency at your state for elevated bridge so that I could get an idea of what competition at national will be like.
770. not that great

your from NJ right? becuase i got a 769.6 and came in third place. 19.49 grams and held all the weight

hbk.showstopper · Post by **hbk.showstopper** » April 8th, 2009, 7:38 pm

the 1st place team in my state was about there too...

sewforlife · Post by **sewforlife** » April 9th, 2009, 8:43 am

bob3443 wrote:
sewforlife wrote:
Bjsong wrote:Can you guys post what was the 1st place efficiency at your state for elevated bridge so that I could get an idea of what competition at national will be like.
770. not that great
your from NJ right? becuase i got a 769.6 and came in third place. 19.49 grams and held all the weight

yeah. that was you. what was the efficiency of the 1st place bridge?

bob3443 · Post by **bob3443** » April 9th, 2009, 8:49 am

sewforlife wrote:
sewforlife wrote:
Bjsong wrote:Can you guys post what was the 1st place efficiency at your state for elevated bridge so that I could get an idea of what competition at national will be like.
770. not that great
yeah. that was you. what was the efficiency of the 1st place bridge?

oh, i thought you meant 770 was the efficiency of the 1st place bridge, i'm not sure what it was.

Bridges and Bots · Post by **Bridges and Bots** » April 9th, 2009, 9:11 am

Really only 770? I thought it would be at least 1000 for a state winner. Because I'm constantly getting efficiencies of 1000 and up.

sewforlife · Post by **sewforlife** » April 9th, 2009, 9:16 am

no 770 was teh third place bridge...
looking at who got first place, their bridge was incredibly light.
it was made of dowel rods.... and weighed about 8 grams.... wow. i wonder how much it held.
and bob3443, yeah i didn't get to see all the efficiencies so i assumed the highest one at the point was gonna take 1st place. which was urs...
the first placers tested their bridge close to last

sewforlife · Post by **sewforlife** » April 9th, 2009, 9:18 am

bob3443 wrote: oh, i thought you meant 770 was the efficiency of the 1st place bridge, i'm not sure what it was.

yeah, i did mean that. by accident.
are u from hammerskjold? or churchill?

bob3443 · Post by **bob3443** » April 9th, 2009, 9:36 am

sewforlife wrote:
bob3443 wrote: oh, i thought you meant 770 was the efficiency of the 1st place bridge, i'm not sure what it was.
yeah, i did mean that. by accident.
are u from hammerskjold? or churchill?

hammarskjold going to chuchill next year

sewforlife · Post by **sewforlife** » April 9th, 2009, 10:25 am

wow. nice. did u guys get 10th in regions?

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