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Re: Auxiliary Braking, DPU is better
Author: SP5103
Date: 02-11-2019 - 11:23
> On older BN power (SD40-2) you did indeed lose all
> dynamic after the independent pressure reached a
> certain point--a bit above 10 pounds as I recall.
> There was no automatic bailing of the independent
> brake in dynamic on BN engines then. I have
> handled non-BN power that had that feature and
> perhaps the newer power on BNSF does. Also BN was
> very late to the extended range and high capacity
> dynamic brake game. (Perhaps starting with the
> GP50s of the mid '80's.) So we had plenty of
> practice using air on mountain grades.
I was thinking that I had been told when I was working at M-K that the BN "GP39M" units we were doing had that setup - too much independent pressure kicked the dynamic brakes off on that unit. By contrast, the SP GP40M-2 units we were doing were set up for the DBI to reapply any automatic set on the engine (that had not been manually bailed off) if you got out of dynamics.
Early BN must have been a real mish-mash of power. I don't think many (or any?) NP units had dynamic brakes. And there also seemed to be plenty of power without mu, and a mix of 6BL, 6BLC, 24RL and 26L braking systems, some not compatible with each other. Not even sure how much of the electrical mu was standard.
> dynamic after the independent pressure reached a
> certain point--a bit above 10 pounds as I recall.
> There was no automatic bailing of the independent
> brake in dynamic on BN engines then. I have
> handled non-BN power that had that feature and
> perhaps the newer power on BNSF does. Also BN was
> very late to the extended range and high capacity
> dynamic brake game. (Perhaps starting with the
> GP50s of the mid '80's.) So we had plenty of
> practice using air on mountain grades.
I was thinking that I had been told when I was working at M-K that the BN "GP39M" units we were doing had that setup - too much independent pressure kicked the dynamic brakes off on that unit. By contrast, the SP GP40M-2 units we were doing were set up for the DBI to reapply any automatic set on the engine (that had not been manually bailed off) if you got out of dynamics.
Early BN must have been a real mish-mash of power. I don't think many (or any?) NP units had dynamic brakes. And there also seemed to be plenty of power without mu, and a mix of 6BL, 6BLC, 24RL and 26L braking systems, some not compatible with each other. Not even sure how much of the electrical mu was standard.
