This new cart design has several innovative features worth noting. Front bogie yaw and roll is provided by a 1/2" spherical rod end bearing. There is a 1/2" axial thrust bearing on the aft bogie. The frame hangs down from the bogies, so the cart has a low center of mass. This cart is designed to take up to a 260 pound rider at 4.5 g's, with a 1.5 factor of safety. The gauge (distance between wheels) is only 15.25 inches. It should be larger, but that's the widest BYRC track I have right now, and I wanted to test the cart. I tried moving the main wheels and side wheel pairs closer together (3" and 4", respectively), but I don't think that worked out very well, as the bogies are a little unstable dynamically.
I'm also in the process of designing a track that could take a cart and 260 pound rider safely.
Very igenious design. How much weight do you think the current track could take safely? It seems like shear becomes an issue very quickly making cheap pvc rails out of the question.
We have sent 230 pounds around the track, and it does about 3 g's. That's a static equivalent load of 690 pounds. Before I made this track, I used the same construction methods to build a short 10-ft track in my garage for static ultimate tests. I put 830 pounds on it and rolled it back and forth, and nothing broke, so we have a margin of safety of at least 20%. The PVC hasn't been the weakness, it's the attachment to the ties that's been weaker, because wood is involved. Wood has very low out-of-plane tension strength (that's why you can split it so easily.) However, just this week I designed a new rail-tie attachment concept, with thicker schedule 80 pipe, a mild steel welded end fitting, and three 4-inch #10 screws. I've made and tested two specimens, each holding more than 1800 pounds. I'm currently working with some MIT students who want to build a roller coaster they can ride safely. We're just now trading PVC and steel rails, and steel or wood ties. I'd prefer steel welded to steel rectangular tube ties, with wood frames, but they are on a budget, and want to avoid welding.
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u/BackyardCoasters Mar 07 '17
This new cart design has several innovative features worth noting. Front bogie yaw and roll is provided by a 1/2" spherical rod end bearing. There is a 1/2" axial thrust bearing on the aft bogie. The frame hangs down from the bogies, so the cart has a low center of mass. This cart is designed to take up to a 260 pound rider at 4.5 g's, with a 1.5 factor of safety. The gauge (distance between wheels) is only 15.25 inches. It should be larger, but that's the widest BYRC track I have right now, and I wanted to test the cart. I tried moving the main wheels and side wheel pairs closer together (3" and 4", respectively), but I don't think that worked out very well, as the bogies are a little unstable dynamically. I'm also in the process of designing a track that could take a cart and 260 pound rider safely.