RedLantern wrote:NellieBly wrote:...it's not horsepower that moves trains, it's tractive effort. It's all fine to bat around 8,000 HP on six axles, but recall that tractive effort is limited by axle load and a concept called "adhesion factor". Axle load is limited to about 36 tons in US practice, so a six-axle unit would weigh about 288 tons, or 576,000 lbs. (a conventional ACe weighs about 425,000). Figure a 33% factor of adhesion, and you've got around 200,000 lbs. of tractive effort. The 8,000 HP only matters if you want to go fast. It's the tractive effort that starts the train. So you'll need two of these units to move a heavy train...
This gave me an idea, although this would require additional current, I wonder if hanging large electromagnets from the truck frame between each wheel could pull the wheels tighter against the rails. This would in theory allow a smaller locomotive since the trucks would be compensating for the weight of the prime mover. These magnetic coils would need to hang down as close to the rail as possible without making contact.
Also it might be a good idea to use welded rail bolted to the ties instead of spiked (imagine a locomotive pulling out all the spikes before it's train runs over it). There would also need to be some extensive sheilding to prevent the magnet from pulling in unwanted metal (cars at grade crossings, signal masts, etc.) or from adding stress on the axle by pulling it in the wrong direction (as well as ripping parts off the locomotive).
The only real questions for this would really have to come down to: Would the rail have enough mass/density for a strong magnet to be able to pull on it to any useful amount? Would it be possible to make a magnet with this kind of strength that wouldn't be too large to mount? And of course, how much extra power would be needed to power a magnet for this to work?
I'm thinking along the lines of either one giant locomotive with a bunch of axles, or even little single-truck steeplecabs with the same tractive power as a big diesel.
I think that any kind of magnet like that would just cause a world of problems - there are so many electronics on the new locomotives and now even around the tracks that something that would require that kind of magnetic force could just open up a tremenoudous can of worms.
Ive pulled some heavy (for a commuter engineer!) trains with an ALP44 and ALP46 - but whats sticking in my head is a certain train I had with a single ALP46 - which puts out about 8000 HP with 4 axles. I had 10 Multilevels, about 150,000lbs each, 6 MUs, also about 150,000lbs each and 3 dead locos, 2 ALPs - at 200,000lbs each and a diesel at about 350,000lbs or so, and of course, the weight of the single loco that was powering it, at another 200,000lbs. So the train was about 3.15 million pounds (1575 tons) not including the 200,000 of the loco I was in.
I know thats a baby for some of you freight guys, but hey hahaha Im using passenger geared stuff!!
But what Im getting at is the problems I had with the train - the loco was VERY slippery - computerized wheelslip controls can only do so much! I have noticed that the lower HP of the DC ALP44s actually helps out on these heavy trains because of the more consistant power delivery - it seems like with the power of the AC Locos, if you are at or close to the limit of traction, it just keep putting out power, causing you to slip.
the GG1s and Little Joes and even the E60s worked well because they are heavy, and don't have THAT much power. I would think that an electric freight loco for a US style operation would need to be VERY heavy, and not 7 or 8 thousand HP. - I would think that a similar problem would be faced by the RRs as with the SD90s and AC6000s - too much HP, and if you loose one, your done.
It would seem to me (not that I know a whole heck of a lot about freight running) that a 5000-6000HP 6 axle loco in the neighborhood of 400,000lbs would be good, it would be heavy enough that it shouldn't be too slippery, not too powerful that just 1 could power a monster train, allowing redunancy if one dies, there is another one, and maybe save some drawbars
With regenerative breaking, (sending power back into the wire when dynamic braking) that should be a big plus to the RRs as well
Is there any kind of compariable loco like that elsewhere in the world? If so, how do they perform, and could they handle the riggers of US railroading?