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| Re: Disabled New Jersey Transit train pulled into Penn Station (1305043) | |||
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Re: Disabled New Jersey Transit train pulled into Penn Station |
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Posted by Bill West on Thu Jul 31 01:45:33 2014, in response to Re: Disabled New Jersey Transit train pulled into Penn Station, posted by Joe V on Wed Jul 30 19:40:22 2014. MU's -have you ever found a technical explanation of whether it is the loco/MU concept or just the trucks/controls?ALP44/AEM7 weight -101 short tons is our ton, 2000 lbs. So the loco weight is 202,000 lbs, 2% over an ALP46 and within 1/2% of an ALP46A. Starting TE -TE specs are to do with loco weight, any current limits in the propulsion system and suspension/control methods. For 40 years diesels and the AEM7/ALP44 were uniformly rated and compared on 25% adhesion. The ALP46/46A was rated on 35% adhesion and some newer diesels are rated even higher. But the rails and dry weather haven't changed and I doubt that the wheels have become rubberized so why is the adhesion better? Because Bombardier thinks their better controls will let the engineer approach slipping more closely and they can demonstrate that in service. Having developed such controls they can be applied to any new loco or MU and one will see the same improvement. By way of comparison one of the arguments for 3 cylinder steam locomotives was that as the sum of cylinder thrusts is more uniform the loco can approach slipping more closely than a 2 cylinder engine whose thrust pulsates from 50 to 100% over each axle revolution. Its limiting TE is going to be much lower. Diesels/electrics don't have cyclic power in their motors but different control methods can introduce different ranges of pulsations while dealing with slipping and thus end up with the different useful ratings we see. Maybe the makers should be required to demonstrate TE performance, I venture that gently easing up to slipping the wheels would show the actual adhesion the trucks and controls can provide. More significantly I think it would vary widely from the arbitrary adhesion used in the specs. Because of guarantees the arbitrary spec adhesion is likely always lower than reality, but it will still vary with trucks and control methods Bill |
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