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Re: I think the engineer was trying to make up time
Author: Dr Zarkoff
Date: 10-13-2020 - 20:50
>That sounds like the most likely scenario. Of course the intended advantage of the electro-pneumatic was simply to provide near instantaneous application through the entire consist, correct?
Yes, and the concept dates back to 1886. It wasn't practical until about 1907, when it was first used on Boston and NYC subway/elevated trains. It's first use on mainline trains was on the PRR in 1913.
> For SP 98/99, I believe this allowed better running times because you wouldn't need to start as far back with a set, saving a little bit of time at each speed reduction.
Yes, and without going into a lot of complex details, the 98/99 installation used a self-lapping straight air valve on the locomotive to operate the E part of the braking system. It is to be pointed out that in all E-brake systems, excpet that first one, applying the brakes electrically also reduced the pressure in both the brake pipe and auxiliary reservoir(s). This is for automatic air brake compatiblility should a set of magnet valves fail (or the E-brake circuits fail enroute).
> I'm not familiar with the NP situation, but perhaps someone decided that running hot and counting on a quick set with the electro-pneumatic, which then failed, contributed to the accident.
I think you're on to something, although this can also happen with systems which don't have E apparatus.
> In reality though, you can't really call a failure of the electro-pneumatic a primary cause, if someone was running so hot and diving into a speed restriction such that the extra time to grab the automatic made the difference in causing a wreck.
An old head once taught me that it makes no sense to speed where track speed is high, but if you go 30 in a 25 zone you can make up 1/2 minute per mile, and you won't derail going 30 around a 25 curve (BTDT myself).
Yes, and the concept dates back to 1886. It wasn't practical until about 1907, when it was first used on Boston and NYC subway/elevated trains. It's first use on mainline trains was on the PRR in 1913.
> For SP 98/99, I believe this allowed better running times because you wouldn't need to start as far back with a set, saving a little bit of time at each speed reduction.
Yes, and without going into a lot of complex details, the 98/99 installation used a self-lapping straight air valve on the locomotive to operate the E part of the braking system. It is to be pointed out that in all E-brake systems, excpet that first one, applying the brakes electrically also reduced the pressure in both the brake pipe and auxiliary reservoir(s). This is for automatic air brake compatiblility should a set of magnet valves fail (or the E-brake circuits fail enroute).
> I'm not familiar with the NP situation, but perhaps someone decided that running hot and counting on a quick set with the electro-pneumatic, which then failed, contributed to the accident.
I think you're on to something, although this can also happen with systems which don't have E apparatus.
> In reality though, you can't really call a failure of the electro-pneumatic a primary cause, if someone was running so hot and diving into a speed restriction such that the extra time to grab the automatic made the difference in causing a wreck.
An old head once taught me that it makes no sense to speed where track speed is high, but if you go 30 in a 25 zone you can make up 1/2 minute per mile, and you won't derail going 30 around a 25 curve (BTDT myself).
