Dynamic Brakes on Amtrak Diesel Trains

[MetraUPWest]

Amtrak's P42s (like almost all other passenger locomotives) are equipped with standard range dynamic brakes. Standard range dynamics brakes aren't effective at speeds below 25mph. At 15mph they are practically useless- they only have half the strength at 15mph that they have at 25mph. You wouldn't be able to hold the train to 15mph on a downgrade using only dynamics.

 

[NW cannonball]

Hoping then next-gen dynamic brakes are as good or better than those on the Prius. Maybe have to wait a while.

 

[Fan Railer]

I'm wondering if the OP knows what blend air dynamics are... as mentioned already, it's presumptuous to just assume that dynamics weren't used in this situation if you're not familiar with the operating characteristics of the locomotives themselves. It is additionally silly to make such a statement if you were not in the operating cab and able to observe the ammeter on the cab screen to see whether or not the dynamics were actually active or not. But I think the issue has been well enough explained within the last 27 posts that I don't have to repeat what was said already.

 

[John Bobinyec]

What I presumed was that there would be sufficient dynamic brakes in use to prevent having to stop part way down the mountain with overheated brakes.

It seems that in order to avoid an encore of that next year, those folks who match up the power to the consist might need to do something differently.

jb

 

[crescent-zephyr]

In order to prevent that next year, retainer brakes should be set, as was done when I rode the TVRM excrsion on this line a few years ago.

 

[crescent-zephyr]

Of course... That still requires stopping the train to set, and reset the retainers, so maybe the OP would still not be satisfied? Ha.

 

[xyzzy]

I rode the same excursion several years ago, basically the same consist. Eastbound we didn't stop to cool brakes or to reset retainers. I wonder if this year the brakes got stuck on one or two cars and that's the reason for the delay.

 

[John Bobinyec]

I rode the same excursion several years ago, basically the same consist. Eastbound we didn't stop to cool brakes or to reset retainers. I wonder if this year the brakes got stuck on one or two cars and that's the reason for the delay.

You're probably right. The head two cars were smoking quite a bit. Further back in the train - not so much.

jb

 

[John Bobinyec]

Of course... That still requires stopping the train to set, and reset the retainers, so maybe the OP would still not be satisfied? Ha.

To bring back service from Salisbury to Asheville sometime in the future, the schedule will be necessarily be a bit brisk - no time to set/reset retainers.

jb

 

[Agent]

This video was posted yesterday by Jacob Riley on YouTube. At the 12:15 mark, it shows the Blue Ridge Autumn Special going downhill at Mill Creek. Smoke can be seen coming from the brakes of the Baltimore & Ohio dome car when it goes by. I don't know what dynamic brakes sound like, so someone else will have to listen for them when the engines pass.

 

[xyzzy]

That's a smoking gun, pardon the pun.

 

[crescent-zephyr]

Of course... That still requires stopping the train to set, and reset the retainers, so maybe the OP would still not be satisfied? Ha.

To bring back service from Salisbury to Asheville sometime in the future, the schedule will be necessarily be a bit brisk - no time to set/reset retainers.
jb

That would also be a much smaller and lighter train, totally different animal. It may even be allowed 25 mph.

 

[Thirdrail7]

I have an idea. h34r: Perhaps all that is need is a little inspiration. :help: Next year, when this train reaches the top of the mountain, play this song as it descends and see if it helps:




I'm always happy to help! :hi:

 

[Fan Railer]

lmao

 

[Fan Railer]

This video was posted yesterday by Jacob Riley on YouTube. At the 12:15 mark, it shows the Blue Ridge Autumn Special going downhill at Mill Creek. Smoke can be seen coming from the brakes of the Baltimore & Ohio dome car when it goes by. I don't know what dynamic brakes sound like, so someone else will have to listen for them when the engines pass.



Note that in the video, the crash occurs at the 12 second mark, at which point the engineer dumps the brakes to emergency. This action calls for (I think) a full dynamic brake application with full air brake until dynamics drops out completely, and after the requisite 10-second delay, you do hear the dynamic brake fans spool up at the 22 second mark.

 

[MetraUPWest]

^In an emergency brake application, the locomotive will provide blended braking like normal.

Dynamic brakes, supplemented with air brakes. The locomotive air brakes are applied at speed where the dynamic brakes aren't effective.

This video shows perfectly how the standard range dynamic brakes work. Hear how much quieter the dynamics are as they get down to very slow speeds? That's because they have faded out.

As was covered before, they're not strong enough to hold a train to 15mph.