"Ron Calls on his years of experience....and freezes at the controls" (internerdstuff)
12/11/2013 at 07:46 • Filed to: None
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"Ron Calls on his years of experience....and freezes at the controls" (internerdstuff)
12/11/2013 at 07:46 • Filed to: None | 0
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Does anyone have a simple explanatation why the diesel elctric design has been the most common for the last 50+ years?
I have an idea its because it gives very fine control over starting/accelerating?
I've always wondered why they dont just use some kind of manual transmission with a torque converter/lock up clutch combo.That would give far better fuel economy while still retaining the gentle acceleration.Caterpillar did something very similar with their big ore trucks and it definitely paid off there
xx45xx
> Ron Calls on his years of experience....and freezes at the controls
12/11/2013 at 07:58 |
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choo choo
Mattbob
> Ron Calls on his years of experience....and freezes at the controls
12/11/2013 at 07:59 |
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having an electric drive allows you to run the diesel right where it is most efficient. This combined with the controlability of an electric motor is hugely convenient. The conversion from mechanical to electrical energy is very efficient. There really isn't much in the way of loss, so the total efficiency is good. Having the electric system also allows you to implement things like regenerative braking. I am more curious as to why there aren't more hybrid cars that use this setup. Also, I would imagine the torque converter needed to drive a train would be insane. Electric motors have the right, full torque at 0 RPM, characteristics to get a train moving.
Bad Idea Hat
> Ron Calls on his years of experience....and freezes at the controls
12/11/2013 at 08:02 |
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From what I understand, railways are very conservative companies, taking the maxim "if it isn't broke, don't fix it" to crazy levels, at least here in the US. There's always some sort of improvement to make things run better, but they seem resistant to change their ways.
davedave1111
> Ron Calls on his years of experience....and freezes at the controls
12/11/2013 at 09:35 |
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I'm not really sure, but I think a lot of it has to do with ease of building and maintenance. Certainly, diesel-electric is a lot better than diesel with a clutch and geartrain, and I think it's also less complex than using a transmission with a fluid coupling.
Don't forget, as well, that train rolling stock is one of those things that lasts for decades. With our modern fuel-conscious mindset it might make sense not to use diesel-electric if you're building new locomotives, but it would have to be a huge improvement to make it worthwhile getting rid of existing rolling stock earlier than planned. Sixty years ago, diesel-electric would have seemed like a nice modern system.
Sethersm
> Mattbob
12/11/2013 at 09:36 |
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One reason why we might not see cars with this type of setup is that when you pull up to a light, having the engine still spinning 3k rpm (or whatever) is quite unconventional. I suppose they could tie engine rpm to vehicle speed, but then you'd lose efficiency.
Also, weight. Locomotives are hugely heavy. Like 100+ tons. Not just because they have to be, but because they can be. Riding on rails and all, they've got at good base supporting them and they don't have to accelerate, turn or brake quite like a car does. It might be difficult to construct a diesel electric hybrid car which has a weight low enough to be practical. You've got the weight of the engine (which diesels tend to be on the heavy side I think), you've got the weight of the generator, then the weight of the motor(s), and for a car I'd think the weight of a battery bank as well.
Slave2anMG
> Ron Calls on his years of experience....and freezes at the controls
12/11/2013 at 10:09 |
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Diesel Hydraulics were very popular in Europe and were tried here in a couple of fashions in the 1960s. The European diesels tended to be higher speed beasts (relatively speaking) turning 1400-1500 rpm vs the US typical 900-1100.
The transmissions were more maintenance intensive as well with the U-joints and gearing. The transmissions were also more precision devices and required more precision care than the electric transmission - just not as forgiving as the electric transmissions. A real problem that was found here was that the wheel diameters had to be almost perfectly matched for the hydraulic units to function properly - I seem to recall that if the diameters were more than 1/8th" out from wheel to wheel that the transmission would shudder violently or something like that. Electrics don't have the wheels geared together and are not affected in this way.
And hydraulics seem to have fallen out of favor in Europe as well...probably for the maintenance reasons but I'm speculating there...