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Post by fauxmaha on Nov 15, 2019 18:23:52 GMT -5
Jeff, can you sketch out "electric transmissions" for us -- is it just shifting voltage or something instead of shiting gears? I've never thought how diesel locomotives actually work, beyond the basic power system. Marshall might want watercolor, but you're getting crayon. Pretty simple, really: Bigazz diesel motor (two stroke) turns a bigazz electric generator (I think most US trains run AC) which power bigazz electric motors down by the wheels. The cool part is there is no direct mechanical linkage between the diesel and the wheels. It's an electric train that carries around its own power plant.
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Post by billhammond on Nov 15, 2019 18:25:51 GMT -5
So it's direct drive from the motors to the axles and never undergoes a transmission-like shift as it gains speed? Pretty much a golf cart with a diesel generator?
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Post by aquaduct on Nov 15, 2019 18:28:55 GMT -5
Jeff, can you sketch out "electric transmissions" for us -- is it just shifting voltage or something instead of shiting gears? I've never thought how diesel locomotives actually work, beyond the basic power system. Marshall might want watercolor, but you're getting crayon. Pretty simple, really: Bigazz diesel motor (two stroke) turns a bigazz electric generator (I think most US trains run AC) which power bigazz electric motors down by the wheels. The cool part is there is no direct mechanical linkage between the diesel and the wheels. It's an electric train that carries around its own power plant. And you can run the diesel engine steady state at the optimum speed/load point for fuel economy, leaving train speed control to the electric motors.
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Post by aquaduct on Nov 15, 2019 18:34:05 GMT -5
So it's direct drive from the motors to the axles and never undergoes a transmission-like shift as it gains speed? Pretty much a golf cart with a diesel generator? Yep. A big ass golf cart...
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Post by billhammond on Nov 15, 2019 18:36:35 GMT -5
So it's direct drive from the motors to the axles and never undergoes a transmission-like shift as it gains speed? Pretty much a golf cart with a diesel generator? Yep. A big ass golf cart... So why aren't semitrucks using that system? Wait, I know, cuz that wouldn't work in city traffic, only on interstate long-hauls.
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Post by epaul on Nov 15, 2019 18:46:41 GMT -5
Trucks don't have room for both motors. No one cares if a train is a few feet longer in order to accommodate two power sources. With trucks, length is a concern. Trucks want compact power with as much of the available length as possible devoted to cargo. Trains don't give a shit.
Trucks face design limitations (public roads) trains don't have to deal with (private tracks).
(this is the result of thinking on the fly about something I had never thought about before. There might be holes.)
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Post by fauxmaha on Nov 15, 2019 22:57:50 GMT -5
Yep. A big ass golf cart... So why aren't semitrucks using that system? Wait, I know, cuz that wouldn't work in city traffic, only on interstate long-hauls. I understand Paul has made am extensive study of this very question. I'm sure he'll be along soon to share his well formed thoughts. It's actually an interesting idea. Unlike Paul, I've never thought about it. (One thing I do know from close to personal experience is the average trucking company CEO would give his left nut for a quarter of a mile per gallon in efficiency improvement.)
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Post by aquaduct on Nov 16, 2019 9:25:49 GMT -5
So why aren't semitrucks using that system? Wait, I know, cuz that wouldn't work in city traffic, only on interstate long-hauls. I understand Paul has made am extensive study of this very question. I'm sure he'll be along soon to share his well formed thoughts. It's actually an interesting idea. Unlike Paul, I've never thought about it. (One thing I do know from close to personal experience is the average trucking company CEO would give his left nut for a quarter of a mile per gallon in efficiency improvement.) Don't know about Paul, but the reality is that engineering is a game of balancing constraints. Semis are fundamentally different beasts from trains. First there are vehicle size constraints (public roads vs. proprietary tracks). The semi rig can only be so long (about 65 feet if I recall) and so wide (8 feet-ish) and so heavy (80,000 lbs in most states, 120,000 in Michigan). So the game is maximizing product density as opposed to vehicle wizardry. There's also resale value. Trucks are typically modified 7 or 8 times for different applications in a lifetime (maybe 40 or 50 years or more). A yard jockey in a chicken plant in Arkansas has no use for a diesel electric powertrain. They want cheap parts, easy to repair and rebuild which only comes from variation on a common theme in the industry. That means that displacement and 18 gears rule, no matter what the technical engineer's wet dream might want.
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Post by millring on Nov 16, 2019 9:34:17 GMT -5
While riding on a train going west I fell asleep.
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Post by amanajoe on Nov 17, 2019 10:54:31 GMT -5
In the case of the Volt though, they went for full on being able to drive off of the electric generated by the engine. While that gives greater (basically unlimited mileage) it kind of defeats the purpose. [/div][/quote] Joe, isn't that the way diesel-electric locomotives have worked for decades? Do they defeat their purpose? [/quote][/div]
Sorry, drove to Rockford and back yesterday, so not here to defend myself. I think it has already been covered, but if the intent of EVs is to get you off of the evil fuels of the world, then yes, series hybrids (while more efficient in the locomotive application, since it is not a hybrid really) are not any more fuel efficient than anything else (and in some cases worse) after the first forty miles, and now you are hauling around the weight of the battery pack.
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