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| Re: How Railroad Could Have Avoided / Ameliorated Fiery Crash (1339047) | |||
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Re: How Railroad Could Have Avoided / Ameliorated Fiery Crash |
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Posted by Jace on Mon Feb 9 16:43:45 2015, in response to Re: How Railroad Could Have Avoided / Ameliorated Fiery Crash, posted by AlM on Sat Feb 7 16:54:34 2015. "No way you can stop at 6 mph/sec without causing major injury to standing passengers."Let's look at some details: - Emergency braking is never jerk limited. You want the train to stop as quickly as possible. - A 3.0 mphps brake rate = 0.14g, 5.0 mphps = 0.23g. - Seats and interior fittings/attachments are designed to 4 to 8g loads. This indicates how mucher higher decelerations can be in a collision and which is exactly why you want the train to stop before it gets into a collision. - For comparison a Boeing 737-700 has four brake settings: 1 = 2.7 mphps (0.124g), 2 = 3.41 mphps (0.155g), 3 = 4.91 mphps (0.224g) and Max = 8.18 mphps below 80 knots (0.373g) and 9.55 mphps (0.435g) above 80 knots. Before someone makes the inevitable comment, the B737 rates are just for information since many here may experienced these decelerations before. I'm not suggesting anything else. And yes I know there are no standees on an airplane when landing. A few other fun facts: - Emergency brake rate on FRA equipment is friction braking only, no dynamics (they're not considered to be primary). - LRV emergency rates are friction plus dynamic plus track. - LRVs have their highest emergency rates below 30 mph, they taper to these rates from higher speeds. Another disclaimer: this is not an attempt to blame the railroad or the equipment. The train and the crew operated as they should have, with what they had. |
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