Designs B/C

[dholdgreve]

WOW!!! Very well done!

[rschmitz]

Has anyone done any research on suspension bridges? I was thinking of 1/16th for the suspensions

[UQOnyx]

Thanks Bernard, that was very helpful. I thought thtat that was probably the way to go but I wasn't sure. It sounds good, but I'm still a bit troubled by this because there seems to be no wisdom behind those rules. However... I'm probably wrong. Anyways thanks for the help

[schuhler]

If you were to take a sheet of Bass wood and have it curve into a half pipe like shape with notches cut into the top where the loading block may rest how would that hold up against a typical square bridge?

Don't rules prevent you from doing that?

[rschmitz]

When building the Warren or Baltimore Truss design and placing the loading block on the top chord, Should the trusses go in the opposite direction, /|\ so they are supporting right below the loading block? or are most pictures I find correct \|/.
Also, should the trusses be at 45 deg angles?

[UQOnyx]

Another problem. I skimmed the forums, so I don't think anyone has asked this. When making the bridge, I begin by making two flat two dimensional sides of the bridges. I connect the tension member to the compression and glue on the trusses. Once I'm done with making the two sides, I don't have a jig and I probably won't be able to make or calibrate the jig in time for regionals which is in a week. So I assemble the two sides together by taking a bunch of 5 centimeter sticks and gluing them at right angles and connecting the bridge together. However, when I do this, the bridge has a tendancy to collapse in a different way. My compression and tension members are strong, and their joints are very sound. Instead, the bridge is unstable, with the top left side of the bridge moving towards the bottom right side, or vice versa. I know that the problem is because of the way I assemble the bridge. However, I don't know how to do it any other way. Any suggestions on how to fix this?

[retired1]

You probably need more X bracing on the compression members.
It is a bit hard to visualize your bridge from your description.
How much does it weigh???

[iwonder]

Another problem. I skimmed the forums, so I don't think anyone has asked this. When making the bridge, I begin by making two flat two dimensional sides of the bridges. I connect the tension member to the compression and glue on the trusses. Once I'm done with making the two sides, I don't have a jig and I probably won't be able to make or calibrate the jig in time for regionals which is in a week. So I assemble the two sides together by taking a bunch of 5 centimeter sticks and gluing them at right angles and connecting the bridge together. However, when I do this, the bridge has a tendancy to collapse in a different way. My compression and tension members are strong, and their joints are very sound. Instead, the bridge is unstable, with the top left side of the bridge moving towards the bottom right side, or vice versa. I know that the problem is because of the way I assemble the bridge. However, I don't know how to do it any other way. Any suggestions on how to fix this?

Yeah, it does't sound like you have any diagonal bracing on the sides with the 5cm pieces. Try using really, really small 5cm pieces to get it lined up, and then using the same wood you used for your trusses to go diagonally between the 5cm joints. That should stop the 'boxes' that are formed from the 5cm pieces from changing shape, which is what it sounds like it happening.

[UQOnyx]

Another problem. I skimmed the forums, so I don't think anyone has asked this. When making the bridge, I begin by making two flat two dimensional sides of the bridges. I connect the tension member to the compression and glue on the trusses. Once I'm done with making the two sides, I don't have a jig and I probably won't be able to make or calibrate the jig in time for regionals which is in a week. So I assemble the two sides together by taking a bunch of 5 centimeter sticks and gluing them at right angles and connecting the bridge together. However, when I do this, the bridge has a tendancy to collapse in a different way. My compression and tension members are strong, and their joints are very sound. Instead, the bridge is unstable, with the top left side of the bridge moving towards the bottom right side, or vice versa. I know that the problem is because of the way I assemble the bridge. However, I don't know how to do it any other way. Any suggestions on how to fix this?

Yeah, it does't sound like you have any diagonal bracing on the sides with the 5cm pieces. Try using really, really small 5cm pieces to get it lined up, and then using the same wood you used for your trusses to go diagonally between the 5cm joints. That should stop the 'boxes' that are formed from the 5cm pieces from changing shape, which is what it sounds like it happening.

Okay, I think I get what you mean. Basically I need, for example bracing between the top left cord of the bridge connecting to the bottom right of the bridge. Is this what I should do?

[iwonder]

Well, basically. But, if that's the part that's colapsing it's probably not a good place to brace since the brace would be in compression and wouldn't work too well. If the bridge forms a parallelogram when it collapses then you could brace from top right to bottom left, since that's expanding and would put the brace in tension.

Or just add a bunch and see which ones stretch or break first, and use those