Elevated Bridge B/C

[andrewwski]

has anyone tried loading there bridges on the bottom chord instead of the top? if u have, is it better or worse than loading on the top?

When you calculate the truss forces out, it only ends up changing one member on each bridge design. So it doesn't really seem to change much. Flips one member from compression to tension, but otherwise is basically the same. So it probably won't change much.

[bob3443]

i got 3rd place in divison B with an efficency of 770

[croman74]

i got 3rd place in divison B with an efficency of 770

And you said this was states on the scrambler thread. good job. 770 as 3rd place at states, so I hope 620 is good for me at regionals.

[gandhiji]

if you hair dry or bake a bridge, it loses weight from the water vapor evaporating, but does it in any way weaken the bridge at all??

[bob3443]

I forgot to mention that my bridge broke on the bus, so i had to glue it back with like 10 seconds, and it added a lot of weight.

[jazzy009]

if you hair dry or bake a bridge, it loses weight from the water vapor evaporating, but does it in any way weaken the bridge at all??

someone respond to this. i would also like to know. i was going to bake my bridge the night before but i was afraid because ive never tested that...i suppose it could help but wouldnt the glue melt? i guess it depends on the temp...

[Balsa Man]

Actually, over the years have done some testing/evaluation on drying.

The short answer is, the effect is short-lived; not really a way to pick up any meaningful advantage in competition.

A few specifics-

First - up to around 140F, should have no significant impact on wood or glue - you'll get all the effect you can see in 10 min
Second - with balsa structure, depending on starting humidity, weight right out of the oven will go down...maybe 5%. It will return to almost all its initial weight within 10-15 min
Third, with a bass structure, weight will go down for up to 15 min, and come back up in 15-20.

So, good thought, but....

BTW, Mike 4192, what was the efficiency of your bridge? Sorry 'bout the outcome; Rule #1 is know and follow the rules.

Len Joeris
Fort Collins, CO

[jazzy009]

thanks. now what do you think about putting it in a sealed box with grains of rice at the comp? we do that and its mostly superstition but i think it might help a TINY bit.

[bob3443]

mike4192, what team are you from? i was also at NJ states

[croman74]

thanks. now what do you think about putting it in a sealed box with grains of rice at the comp? we do that and its mostly superstition but i think it might help a TINY bit.

I put rice with the bridge even when it's not at competition. I believe it helps a "TINY bit", but it's not any significant difference. It just knocks the mass down by like .1 grams. It doesn't do much.