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| Suffix-H bues | |
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| Tweet Topic Started: Mar 31 2012, 01:28 PM (568 Views) | |
| TransitChuckG | Mar 31 2012, 01:28 PM Post #1 |
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Foamer
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Is this true? We were told by somebody who follows the SEPTA bus situation that the first order of hybrid diesel buses SEPTA bought are now running with the electric disconnected, as straight diesels. Supposedly the buses were so trouble-prone that it was thought easier to simply get rid of the electric drive. So now those buses, the ones the "H" attached to their numbers in the fleet, are running as plain diesel buses. Can anyone on the list confirm or deny? |
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| Septa_kid | Mar 31 2012, 01:57 PM Post #2 |
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What if...
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It's true that the Electric was disabled, but the reason is different |
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| TransitChuckG | Mar 31 2012, 04:50 PM Post #3 |
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Foamer
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Thanks! I guess we'll find out why, someday. |
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| Van2006ko | Mar 31 2012, 05:54 PM Post #4 |
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Foamer
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That is not true. Ok, let me break it down to you. I know you have experience with engineering in the past so you may somewhat understand the terminology. There's an total of three sources of power which the hybrid uses to accelerate. Two of these sources are aided by the battery on top of the bus. These three sources are Diesel, Motor A, Motor B. Once the bus starts off at 0mph, the electric motor A takes over for 100% of the acceleration. Once at 5mph, the clutch engages the engine which in term couple the engine to the drivetrain. at this speed, the electric is still doing 95% of the acceleration. At 10 MPH or so, the torque available to the traction motors rapidly drop off. The diesel engine starts blending in some of the needed power to supply to the generator. Once at 15 mph or depending on the terrain/load conditions, the hybrid will switch to its second mode using electric motor B. Electric motor B is most effective between 20-40 MPH, after 40mph, it starts to drop off, therefore the diesel compartment takes over and do much of the acceleration. The Diesel component is couple to an CVT transmission. If there is an improper matching, as in the computer is not compensating the acceleration of the bus with the diesel. And the diesel does not kick in time at the top of "1st mode" and if it were to shift to second mode, the bus will have an sudden torque jump because motor B has greater torque then motor A at 20mph. Now back to the question, does the first generation hybrids run fully on diesel, No. Even with no battery storage, electric power is being routed through its electric motors from the generator. However, if there is no battery storage, the diesel will do much of the work throughout the entire range of the transmission. The first generation Hybrids still start off in electric, otherwise the bus would be stalled out due to no power at the wheels. If straight diesel was engaged directly from 0 mph, then the engine will stall out then shut off. Now to prove if this is true, listen to the whines of the transmission, the whine will fade out after the bus reaches 10mph. Then once the bus shifts into mode 2, the whine will come back into play. Around 30mph, the whine is the most intense. This is most present on the Restyles through because the fans which keeps the hybrid system cooling are different. Source: Tons of research to simulate an hybrid transmission in a simulator. http://portal1.cdta.org/maintenance/eLearning/Allison%20Electric%20Drive%20Theory%20of%20Operation.pdf Edited by Van2006ko, Mar 31 2012, 06:03 PM.
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| frankl3217 | Mar 31 2012, 05:54 PM Post #5 |
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Advanced Transit Fan
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over the past week, i have ridden 5836H,5840H and 5844H on route 29. they rode and sounded like the typical first generation hybrid (seems normal to me). i cant speak for the rest of the 5601H-5612H, 5831H-5850H groups. |
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| Septa_kid | Mar 31 2012, 11:22 PM Post #6 |
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What if...
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To make things short simple and sweet, here's the story so around the time of the Southern fire, the majority of southerns buses went up to Midvale, inculding the first gen hybrids. While there, the hybrids were fueled with the wrong fuel thus voiding the warranty on the buses... So when time came around for them to be overhauled, they were re-done to the best of the abilities of the workers of course with some set-backs, including the "hybrid propulshion" becomming more of a hybrid transmission (remember that since they couldn't get parts for an Allison EP-40 at the time, they had to work with B400/B500) Pretty much so now, even though yea you're still riding a hybrid and the technology is still technically there, it's moreso a over-hyped diesel bus.... |
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| Septa_kid | Apr 3 2012, 10:22 AM Post #7 |
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What if...
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That's something completely different.... |
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