SPP SciO wrote:Looking at a google image search I can only infer that either, it hardly makes a difference, some event supervisors ignore the test support rule, or this is something new and most pics are >1year old - most bridges seem to be resting directly on a table.
SPP SciO wrote:How different would results be, if you tested your bridge across a 20x20 opening, without resting on the test supports? In other words, will the platform actually support some weight?
Looking at a google image search I can only infer that either, it hardly makes a difference, some event supervisors ignore the test support rule, or this is something new and most pics are >1year old - most bridges seem to be resting directly on a table.
Our team has tested pretty haphazardly; we haven't built and tested enough to be worrying about those details (construction techniques and designs pose enough of a challenge). Is this a major deal? Our div b bridges clear the span by about 0.5cm on each side but adding weight with that little surface area of contact seems awfully precarious. Hoping it's one of those things where physics trumps intuition.
SPP SciO wrote:If a bridge meets teh div. B rules, it should obviously be able to sit on teh test supports, which are 35.0 cm apart. For argument's sake, let's imagine a bridge that's 36.0 cm long. It's an arch bridge, and teh loading block is placed centered on top of teh structure. This bridge has a mass of 10.0 g, and when tested properly (0.5 cm of bridge touching each test support) teh total mass held is 10 kg, for a score of 1000.
What type of scores would you get with teh same bridge if,
A) You center teh bridge over teh 20 cm square, no test supports, 8.0 cm of bridge touching teh base of teh platform on each side of teh hole?
B) You place teh bridge on a scale, and load into a perfectly balanced bucket (this is hypothetical, of course) centered on top of teh bucket?
teh instinctual side of my brain says that teh score from A will be much greater than 1000, and teh score from B will be even greater than that. teh more rational side thinks that, in a perfect world, both methods would also yield a score of 1000, but teh inevitable design/construction/loading variables will lead to A & B having slightly higher scores because of teh added stability - maybe just frictional contact with teh base resists some twisting? If teh amount of bridge that's directly supported IS a major factor, I'm surprised that more teams don't go with a longer length - whatever mass gain from a few extra cm of bridge would be more than worth it for teh added stability, perhaps? I read someplace online (probably Garrett's Bridges website) that it's possible to test in teh way described in method B above, even just pressing down directly with your hand for a rough estimate. Has anyone tried that with any success?
Obviously it's important to practice in competition-like situations, so we'll be testing with test supports from now on; I was just wondering if there was a rule of thumb on how much difference it makes or if it depends highly on teh design, etc.
dholdgreve wrote:...and what teh heck is wrong with teh spell check constantly changing "teh"?
Users browsing this forum: No registered users and 1 guest