[ARC5] Locomotives

[Brian Clarke]

Hello Wayne,

In big cities, where there are more routes than roads, you need to know 
exactly where you are so you don't plough over points, damage other rolling 
stock or pass a signal at Danger. GPS is good for this when the roads can 
see satellites, but underground the trains rely on dead reckoning - which 
gets tricky when you realise that roads pass under and over each other and 
so have slopes that mean distance covered is not the same as the 
straight-line distance between way-points.

Re hybrid trains: It is unusual for engines to run entirely on batteries - 
they usually don't have enough capacity, even for yard shunting. An 8-car 
commuter train draws 2 MW at take off - and need to dissipate this is 
stopping - batteries able to deliver 2 MW would likely double the mass of 
the engine cars. The diesel-electric is far more effective in that a 
series-wound electric motor has highest torque at stall, and the diesel 
motor then drives a DC generator to power the motor. More modern motors are 
3-phase variable-Voltage-variable-frequency (VVVF) - so the diesel drives a 
DC generator whose output is then chopped to form the VVVF drive. Older 
drivers can tell the difference between an all-DC system and the VVVF 
system. But as you don't want so much grunt that you get wheel spin, the 
VVVF system gives better torque control - so the driver trainers tell me.

73 de Brian, VK2GCE.

On Thursday, December 20, 2012 11:04 AM, you said:


> Read a few years ago that they are building "hybrid" locomotives, hybrid 
> in the same sense that a Prius is hybrid.
>
> They replace switching engines in the yards and in fact use the running 
> gear and frame from the old switch engines.  They use a whole bunch of 
> batteries and a diesel engine such as would come in a large pickup truck. 
> The engine keeps the batteries charged, only starting when required.  The 
> batteries run the locomotive.  A disadvantage of conventional diesel 
> electric locomotives for switch engines is that they don't have to move 
> long distances but have to run pretty much all day and night so to be 
> handy as required.  The hybrid locomotive's engine only has to run as 
> needed and I guess this not only reduces fuel costs but helps satisfy 
> local air pollution requirements.  The hybrids actually weigh more than 
> conventional diesel electric locomotives but this is seen as an advantage 
> when assembling trains because it gives them more momentum.
>
> They are going to start using hybrid locomotives for some long distance 
> routes; I would guess these are for routes where the braking can be used 
> to charge the batteries.
>
> I have always thought it strange that the first major commercial user of 
> GPS, using it even before the system was fully deployed, was the 
> railroads.  While it is quite hard to get lost in a train, it turns out 
> that knowing exactly where you are on a route helps a great deal, since 
> you can apply or reduce power to handle changes in grade based on solid 
> data rather than "This Looks About Right."  Thus, fuel and maintenance 
> costs are reduced significantly.
>
> Finally, I was told that in 1955 the old steam locomotives were surplused 
> and sold for $500 each, and that included free use of the RR network to 
> get it to your destination.  Don't ya'll all wish you had bought one?
>
> Of course, in 1955 the USN's F8F Bearcats were surplused and sold for $500 
> each.  And I would rather have one of those!
>
> Wayne