Q&A: Towers on an Elevated Bridge « Model Bridge Design

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Q&A: Towers on an Elevated Bridge

By Garrett Boon on October 12th, 2008 | Last modified: January 4th, 2009

This is the first in reviving my question and answer posts. When I receive a well asked question, I will answer it and post some of the dialogue here.

These two questions are dealing with making an elevated bridge, very similar to the Science Olympiad challenge.

1: I’m currently building an elevated bridge (for my physics class, not for scioly) and I have finished the two trusses and connected them and now only need to add the towers. Would it be a good or bad idea to make the towers slant outwards or should I just have them go straight up and down?

The only benefit to slanting the towers is that the main trusses can be a little shorter. This will reduce the weight of the bridge. The forces will increase on the towers if they are slanting, and then the towers will have to increase in weight. There is a balance to find. Since you have already built the main trusses, slanting the towers will not really help you. Also, it is significantly easier to build the towers so they are straight up and down.

2: For the bracing on the towers, I want to make X’s but I’m not sure how to do it exactly. Would I put one diagonal piece on one side of the corner and the other piece on the other side or put them on the same side and have one overlap the other?

Good question. I would recommend that you overlap the X’s. The X’s themselves do not need to be large pieces and thus won’t add a lot of weight. Rectangle shaped pieces work best. 1/4″ wide and 1/16″ thick should be more than sufficient. In one tower I built, the X’s were 1/32″ deep and 3/32″ wide. I never had a problem with the X’s breaking, it was always something else that failed.

Here is my Science Olympiad Tower.