From what I understand, NECR can only run their 6-axle SD40s between St Albans, Vt and Palmer, MA. Is this true? Why can’t they run all the way south to New London, CT? If it’s due to curvature, couldn’t the newest EMD’s run the tracks with their radial trucks? If it’s a track condition issue, and CN still owned the CV (which they don’t, I know), and they had more money to invest in the track, would they be able to run their SD70M-2s all the way down to New London? I’m just curious as to why we don’t see more 6-axles on NECR, or even on the CV back in the day! Thanks in advance!
Heck, even VRS used SD90MACs due to their radial trucks! And NS 6-axle power is frequent on Bow coal trains on PAR - so track conditions must allow 6-axles in New England…railroads just choose not to use them. But if grades exist, why not cut down on the number of locomotives with bigger units?
If this is true – and I wouldn’t be surprised if it were – I suspect it’s one of the bridges on the south end; just at the moment, I forget which one. But one of them has a low load limit… there is a dickens of a sharp curve in Stafford Springs, too, which might be part of the problem.
Were there ever any 6 axles on the CV? I can’t remember any…
Three things to consider with a 6-axle locomotive is its greater weight, longer bogie wheelbase, and longer locomotive wheelbase. Weight can be a complete show-stopper on a bridge, either because it exceeds the safe bridge rating or it accelerates the bridge’s failure rate. The former is what most people think of but the latter is where the action is. It makes a big $$ difference whether you accelerate failure rate so much that you have a bridge renewal issue in a few years hence rather than maybe 20 years hence. Because bridge renewals easily get into the $500,000 range, accelerating the day when you have to replace a bridge is a one-way ticket to abandonment on a low-density line.
Weight, bogie wheelbase, and locomotive wheelbase are all track issues. If you have light rail and/or poor tie conditions and/or poor subgrade and/or poor drainage the six-axle locomotive will accelerate track wear and hasten the day when big $$$ are spent for track renewal. Radial trucks only get you so far, they are not a cure-all. Besides that’s a very expensive locomotive that requires that much more revenue to pay for.
Sharp curves have to be VERY sharp before they prohibit six-axle locomotives. There are main line 16 degree curves in heavy-haul service on UP, and main-line 20-degree curves I know of in junctions with coal trains screeching through them every day. It’s not hard to make it where the train doesn’t come off the track, it’s just expensive.
There’s an economic trade-off between the unit-reduction you get with six-axle vs. four-axle, vs. the track maintenance costs. On a branch line or secondary line with one or two trains a day each way the unit savings with 6 axle is pocket change, whereas the track cost is going to be very large. An experienced roadmaster already knows the answer.
Lines that prohibit six-axle power usually have both bridge and track issues. Railroads try
Thanks for the information on weight and bridge issues. I can see the cost issues associated with a new locomotive for the purpose of radial trucks.
As far as the NECR is concerned, they do operate SD40-2s on the northern part of the railroad. Why exactly can’t they go all the way to New London though? If it is a bridge issue, does anyone know where this bridge or bridges are located? What is the max loading for these bridges?