Testing Tips

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There are several ways to test model bridges:

  • With a machine
  • By pouring sand
  • Textbooks
  • Pushing down on your bridge

Using a machine

Obviously, if a machine is being used to test your bridge, there isn’t a lot you can do. You can stand watching the destruction of your bridge. Or turn away and cover your eyes with your hands. I would not recommend the latter option. You miss out on the most exciting part of model bridge building.

After spending all that time and effort making your bridge, why not enjoy watching it being crushed? Don’t worry, the bridge can’t feel a thing. You can learn valuable information by watching your bridge break. And unless you happen to capture the event on videotape, you won’t ever be able to see it again.

Using sand

If you have to pour sand into a bucket to load your bridge, here are a few tips:

  • Pour quickly but steadily
  • Pour into the center of the bucket
  • Keep the bucket steady
  • Never stick any fingers, arms, feet, or legs under the bucket
  • Don’t bump the testing platform

Using textbooks

If you are going to test your bridge by putting textbooks on the top, like many people do for popsicle bridges:

  • Make sure the first textbook is perfectly centered over the bridge
  • Line up all the over textbooks with the first one
  • Put each textbook on the bridge gently

If you aren’t going to test your bridge with any of the above methods, here is another simple one.

Take a bathroom scale and place it on the top of your bridge. Simply push down on the scale until the bridge breaks. Of course, only use this method if you think the bridge is not going to hold very much. I will tell you from experience, it gets very hard to push perfectly straight down over 100 pounds. You can end up breaking your bridge pre-maturely by accidentally pushing to one side.

What is the best way to test a bridge?

Which is the best method? I can’t say for sure. I would say that if you had a machine that pushed down at a slow rate, that would be ideal. Most machines add force to your bridge very quickly, and you may or may not be able to see where your bridge broke.

The sand pouring method is slightly slow if you are using a cup to transfer sand from one container to the one hanging from your bridge. Also, it is hard to make sure that you are pouring correctly and watch your bridge at the same time.

The textbook method is great because of its simplicity. There is very little mess, and textbooks are readily available. However, you have to add the load in chunks, rather than a continuous stream. You won’t get an exact weight held by your bridge.

Using a scale to push down on your bridge is also very simple. But you won’t be able to load your bridge very much. This might be overcome by first putting a bucket on the scale, and filling that with sand or other heavy objects, and then pushing down with your hands.

4 thoughts on “Testing Tips”

  1. I just am curious how much “support” each side should have, perhaps like a percentage? For example, if I am testing a bridge that’s bottom beam is 10 inches long, should the “span” it crosses be, like, 8 inches, so that each side gets 1 inch (of 10%) of contact?

    • Not much is needed if you are careful with the loading process. For my Science Olympiad bridges, I focused on cutting as much weight as possible. Those bridges spanned 35cm and were only 37cm long total. That only gives 1cm of support on each end.

      The danger is that the bridge is easy to dislodge while testing it, so you need to be careful. If you aren’t concerned about weight as much, I’d make give yourself more buffer on each end.

  2. I am very thankful for your page. I really learned a lot and it helped me with a school project. I am very curious as to your age and what you do for a living. Also, what do you look like. Thanks, Broski!

    • Glad to help. After my unsuccessful presidential bid in 2008, I retired to a small island off the coast of Florida near the Everglades.


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