[MrBasse]

I don't know why people would consider there being risk to a robot under a bridge, if you build the frame so that it will hold the weight, all you need to do is ensure that your machine could hold up at least 120lbs or so and you'd be good. With thick axles and heavy duty wheels, I don't think there would be an issue. If the machine is less than 8" tall, I doubt anyone would have a weight issue to worry about.

I also feel the lexan would hold up just fine, the majority of the weight would be on the ground, there is one point where the lexan would be slightly off the ground that would see some strain, but probably not enough to break it. The key is making sure you know how high off the ground the mounting point is and building to ensure that you have no sharp edges that could possibly scratch or damage that lexan surface. We held a piece of lexan under stress for almost a year and the only thing that broke it was applying more force after bending it a full 270 degrees in a 2" radius curve. When it finally gave way it was exciting though...