Bridge Designs

[SPP SciO]

Great points, thank you. I think I will have the students try the idea by building small hollow cubes, one from 12 sticks and one carved from a block - will post results if/when results come to fruition!

[brayden box]

Great points, thank you. I think I will have the students try the idea by building small hollow cubes, one from 12 sticks and one carved from a block - will post results if/when results come to fruition!

Last year at states, there was a team who had carved their bridge out of a block of wood with a laser. It looked awesome and really strong, but it performed terribly. (It also weighs a lot, because you can't change what kind of wood you use) The sticks and glue method works a lot better.

[andrewwski]

I've seen teams laser cut them from balsa sheets before - they generally don't seem to do well. The grain is the biggest issue - you want to load along the grain, but there's no way to do that when cutting all from one piece. It can also be harder to avoid imperfections in the wood.

[Unome]

I've seen teams laser cut them from balsa sheets before - they generally don't seem to do well. The grain is the biggest issue - you want to load along the grain, but there's no way to do that when cutting all from one piece. It can also be harder to avoid imperfections in the wood.

You're still active!

Back to the topic: the only time I remember hearing of a laser cut piece was at last year's Nationals (I think the picture is on the Best of Nationals page)

[JonB]

I've seen teams laser cut them from balsa sheets before - they generally don't seem to do well. The grain is the biggest issue - you want to load along the grain, but there's no way to do that when cutting all from one piece. It can also be harder to avoid imperfections in the wood.

You're still active!

Back to the topic: the only time I remember hearing of a laser cut piece was at last year's Nationals (I think the picture is on the Best of Nationals page)

That would be us. We laser cut tension pieces only. We do laser cut balsa for Wright Stuff, but I do not think we would ever laser cut any pieces of balsa for bridges. The balsa pieces are relatively short and easy to get right when cut by hand. Bass on the other hand is really tough to cut accurately by hand in really long pieces.

[Less_Incidence]

My method for cutting basswood is to tape a straightedge to the table, tape the straightedge to the sheet of wood, and tape the sheet of wood to the table, then make lots and lots of passes along the straightedge with a razor blade (assuming we're talking about making strips from a sheet). X-Acto knives do a horrible job and aren't sharp enough. The razor blades you can get from The Home Depot in cheap packs of 100 that are marked "009 RD" are my tool of choice. There might be a better way, but I've never done it any different because this works like a charm.

[brayden box]

My coach and I tried to do that, but no matter how many times we tried, the strips were always off and warped.

[Less_Incidence]

What do you mean "off and warped"? There's no such thing as a perfectly flat sheet of wood, so they're always going to have some small amount of warp to them. I understand it can be hard to keep the blade vertical; when I was developing my wood stripping technique I used a very straight 1/2"x1/2" square piece of pine set on top of the sheet as a straightedge so that I could keep the razor blade pressed against the side of the wood block and keep the cut as vertical as possible. Now I have a steady enough hand to do it with only a straightedge (It's quicker that way as it's easier to apply a little more downward pressure), but that took time to develop.

[brayden box]

what kind of laser do you guys use?

[bernard]

what kind of laser do you guys use?

For laser cutting wood, the laser from a laser cutter. But it's not hand operated as that would be extremely unsafe. Some schools with nice donations or funding will have them. But given how successful many teams have been without it, laser cutting isn't necessary to do well in this event.