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Tex Arcana
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Quote:
Originally Posted by [H]ard|On View Post
Kind of like an Abrams tank. Or a cruise ship. They have large GE turbines and electric motors.

It's pretty dumb for a small car though. It's pretty dumb for a tank too imho, not to mention annoying for the poor crew.

Dumbfuck, they use tiny turbines in prop aircraft almost exclusively now, and they're waaayyy more efficient than the pussrod recipro dinomotors they used to use. They can be set up to run unattended to keep charging, and shut down when done. And with a nice combo of caps and batteries, and regen braking, the car would have a nice seamless driveline that would keep working even when the batteries are dead.
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Old 08-08-2011, 11:58 AM Tex Arcana is offline  
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Tex Arcana
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Doesn't that thing guzzle down diesel like mad in comparison to its piston-engined peers?

Because it's heavier'n your momma times ten...
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Old 08-08-2011, 12:01 PM Tex Arcana is offline  
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they have a combination of batteries and massive capacitors, the caps for huge push of power for start-up and acceleration, the batteries/generator for steady-state cruising. And they have regenerative braking.
Pretty much all of north america's long haul rolling stock is pure diesel-electric. Diesel to the generator, through the rectifier, to the traction motors. Newer trains run AC traction motors and use inverters instead of rectifiers, and might sneak a capacitor or two in there for the reliability of the generator, but that's it.

There's really no benefit in a hybrid drivetrain on a long haul train because they don't do any starting and stopping. They climb and descend hills, but they slow down when cresting a hill and accelerate again on the far side, using elevation instead of a battery bank, keeping excellent efficiency.

They're using hybrid locomotives now in things like switchyards, but in that case they're only moving a few cars around at a time which reduces energy storage requirements to a practical level, and they're doing so much starting/stopping in a switcher role that the energy storage capability saves a decent amount of fuel.

Same reason that hybrid cars are great in the city, but you can't beat a TDI on the highway.
Old 08-08-2011, 02:16 PM gee is offline  
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I remember seeing & reading that diesel-electric locomotives use a huge resister array w/ fans to push the heat from slowing down. So they don't really use regenerative braking just a cheaper more cost effective form of friction braking. I imagine if all they relied on was friction pads they would burn through then like fuel.
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Old 08-08-2011, 08:25 PM Thermo1223 is offline  
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I remember seeing & reading that diesel-electric locomotives use a huge resister array w/ fans to push the heat from slowing down. So they don't really use regenerative braking just a cheaper more cost effective form of friction braking. I imagine if all they relied on was friction pads they would burn through then like fuel.

Only b/c there's no battery to charge - otherwise it IS regenerative braking. The resistor keeps the controller from exploding since there's nowhere for the energy to go.

It's not really friction braking either, unless you count the friction of the wheels on the tracks (which is always there) The resistance of the electric motors helps but a loaded locomotive is so heavy most of the braking is done with pads iirc

This is more passenger oriented but still cool

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Old 08-08-2011, 09:08 PM [H]ard|On is offline  
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There is several stages of braking to a train, the pads are only really used when you crank the brakes I believe. The resistors are to bleed off speed, like down mild slopes or when getting ready for a stop.
Old 08-08-2011, 09:19 PM gribly is offline  
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I saw this movie unstoppable once, now I know all about braking trains
Old 08-08-2011, 11:22 PM Fiah is offline  
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I saw a movie where the train couldn't stop.

edit: wait no that was a bus
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Old 08-08-2011, 11:26 PM [H]ard|On is offline  
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Very few mainline (big) locos use batteries or caps or regenerative braking. More common in low power yard switchers. For these, multiple small diesel gensets are preferred to one big one too.

Dynamic brakes, with very few exceptions, shed the generated energy as heat through a monstrous resistor grid
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Old 08-09-2011, 01:16 AM eighteen_psi is offline  
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edit: dynamic braking works well at higher speeds, does squat as you slow down and can't actually stop the train. Generally use a combination of friction/dynamic as needed.
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Old 08-09-2011, 01:16 AM eighteen_psi is offline  
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Tex Arcana
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Cool stuff... I know they were working on (likely still are) a braking system that uses eddy currents in a metallic disc to create the braking forces--iirc, they used something akin on ThrustSSC, where the wheels themselves were the brake discs, they would move either magnets or coil/magnet structures closer to the moving wheel, and the eddy currents generated by the moving wheel would generate a braking force, which expressed as heat generated in the disc (wheel); according to the ThrustSSC team (again, iirc), they could actually lock the wheel up completely.
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Old 08-10-2011, 06:31 PM Tex Arcana is offline  
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Quote:
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Because it's heavier'n your momma times ten...

What I meant is: doesn't it consume a lot more fuel than competing tanks (equal power/weight) that use Diesel-cycle engines?
Old 08-10-2011, 11:16 PM Fiah is offline  
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Tex Arcana
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What I meant is: doesn't it consume a lot more fuel than competing tanks (equal power/weight) that use Diesel-cycle engines?

What you mean is your momma is so fat, that to fuck her, I had to slap her ass and ride the wave in.
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Old 08-11-2011, 04:42 PM Tex Arcana is offline  
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What you mean is your momma is so fat, that to fuck her, I had to slap her ass and ride the wave in.

jesus christ you're old.
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Old 08-11-2011, 05:38 PM someone else is offline  
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Tex Arcana
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jesus christ you're old.

Your momma's so fat, I had to roll her in flour and look for the wet spot.
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Old 08-11-2011, 05:53 PM Tex Arcana is offline  
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