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Ybr poly bridge6/10/2023 ![]() ![]() In the 3rd gif, a single beam of wood hanging off the left box, tips the scales, the left hand side now has 9 nodes so is heavier, yet it has far fewer beams. On the right hand side is exactly the same box, with 8 nodes, and I have additionally put steel beams between every single node, you can see the density of steel is much much higher, yet both boxes weigh exactly the same. The 2nd and 3rd gifs demonstrate the "only nodes add weight" principle, on the left hand side is a rigid box with 8 nodes and the minimum number of beams to make it rigid. I don't have any engineering experience except software engineering, I am a programmer and have done game programming and (on a hobby level) simulation of physical systems. The strength of road with steel 'danglies' Here are some gifs demonstrating some of these points:Īll beams, whether long or short, strong or weak, are equal under gravity This fact is not reflected at all in the guide which gives the maximum strength of road as significantly less than steel, but no in fact road in a steel bridge is even stronger than steel. Adding up to 2 additional beams (of that material) will make it even stronger, in fact if you attach 3 beams of steel to road, the road will be about 10% stronger than steel. It works approximately like this: attach a wood beam to road, and the road becomes as strong as wood, attach cable and it's strong as cable, attach steel and it's strong as steel. If you make a new road between two existing road nodes (say you make a road triangle, so the 3rd road adds no new joint), the new road will add weight, but not nearly as much as adding a new road node would.įinally, it doesn't mention this in the guide, but the strength of a road is determined by what kind of material is attached to it. A "road joint" is much heavier than a normal joint (about 8x heavier), also a longer road is heavier than a short road - but not by much, the shortest possible road is about 2/3rd the weight of the longest possible road. You probably noticed the universal use of "except roads" in the points. Materials appear to have equal tensile and compressive strength, this isn't realistic but also isn't completely unreasonable.I tested how much steel it takes to break steel, and did some back of the envelope calculations, and came to the conclusion it's strength is comparable to steel in real life. Materials generally have a high strength to weight ratio.(In reality, under compression a long beam is prone to buckling, and under tension a beam can break under it's own weight if it's absurdly long, in Poly Bridge the beams are short enough to make these mostly non-factors). ![]() ![]() This closely approximates reality at least for beams of moderate length. Beam strength is independent of length.It would make steel arch bridges less extremely featherweight though. How different would the game be if the weights model matched reality? It is hard to say, because most of the weight which breaks a bridge is the roads and vehicles. In Poly Bridge, the more densely inter-linked a bridge is, the stronger it is. This does not apply to Poly Bridge, where you can add more beams without adding any weight at all. One of the challenges of the classic BridgeBuilder game, was that it was hard to make a bridge stronger by adding more metal, adding more iron made the bridge heavier. Curiously, the cost model is completely opposite, you don't pay anything for nodes, and pay by the inch for beams. We could call this a "heavyweight bolts and areogel beams" model, where the only heavy component is the "bolts" which join two beams. It's a simple and reasonably effective model. This also makes suspension cable heavy if you don't use the nodes.Įssentially the fundamental design of the physics engine, is that each node has a weight of "1" (lets call it "1"), the nodes are joined with "springs" of various strength, these "springs" don't have any weight. What I mean, is if you add a new beam between two existing nodes, it wont add any weight at all, only creating a new node will add weight to the bridge. Only nodes have weight, and the weight of a node is independent of how many beams are attached (except roads).This means longer beams are lighter per meter than short beams, and maximum length steel beams are featherweight, to say nothing of long cables. Beams weigh the same regardless of how long they are (except roads).Thus steel is stronger but not heavier than wood. Beams weigh the same regardless of material (except roads, also hydraulics are minutely heavier).I've been playing around with the physics engine, along the lines of building scales and weighing things, testing breaking strain and so on.
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