Tonnage Ratinds and weather Reductions for locomotives

Wed Dec 19 14:38:24 EST 2018

“P***ng away your air” as a consequence predated the use of diesel motive power.

The dynamic brake was a great help; in some uses it eliminated the use of air brakes on downgrades at all.  

Many steam locomotives had two of the very efficient cross-compound air pumps (N&W had nearly five hundred locomotives so equipped).  Some diesels used a six-cylinder air pump (the DM&IR engines leased by N&W in the sixties, for instance) – could all put a lot of air back in the train line, but it was limited by the amount of air that could pass through a locomotive’s feed valve and a 1-1/2-inch brake pipe propelled by a 75 or 80 pound feed valve setting.

Ed King

From: NW Mailing List 
Sent: Wednesday, December 19, 2018 2:05 PM
To: nw-mailing-list at nwhs.org 
Subject: RE: Tonnage Ratinds and weather Reductions for locomotives

Ed,

Understand.

Would steam locomotives be any more vulnerable to not recharging ‘in time’ than diesels?

And am I correct in assuming that a train could get trouble even faster after “a sequence of these” if the trainline air pressure on the rear of the train is hard to maintain due to very cold weather?

Just musing,  John Garner

From: NW Mailing List [mailto:nw-mailing-list at nwhs.org] 
Sent: Wednesday, December 19, 2018 11:42 AM
To: NW Mailing List <nw-mailing-list at nwhs.org>
Subject: Re: Tonnage Ratinds and weather Reductions for locomotives

John – Releasing the brake and then having to make a second application before the reservoirs are recharged requires a deeper reduction of the brake for the second application to have any effect.  A sequence of these can create a condition known in the vernacular as “pi***ng away your air”.  This can lead to nervous moments on a long downgrade, or worse.  Weather doesn’t have to be cold for this to happen.  

Let any engineer who hasn’t had this experience raise his hand . . .

Ed King 

From: NW Mailing List 

Sent: Wednesday, December 19, 2018 10:56 AM

To: nw-mailing-list at nwhs.org 

Subject: RE: Tonnage Ratinds and weather Reductions for locomotives

Jimmy, If the engineer releases this brake application and then needs to make a second application relatively quickly . . . can a leaking trainline fail to recharge the auxiliary reservoirs throughout the train in time? If so then what?

Thx,  John Garner

From: NW Mailing List [mailto:nw-mailing-list at nwhs.org] 
Sent: Tuesday, December 18, 2018 8:17 PM
To: NW Mailing List <nw-mailing-list at nwhs.org>
Subject: Re: Tonnage Ratinds and weather Reductions for locomotives

On 12/18/2018 12:55 PM, NW Mailing List via NW-Mailing-List wrote:

  3. And maybe decreased braking capacity due to leakage.

    There is no such thing, at least not on a normal train [weird, oddball occurrences or trains sitting without air for long periods of time don't count for this narrative]. Quite the contrary!

If you don't know, unless a steam locomotive has at least a 24RL brake system, it has no "Pressure Maintaining Feature". What that means is that once an automatic brake application has been made to control the train downhill, let's say a ten pound reduction from 75 lbs. to 65lbs, the system has no way to maintain that 65 lbs. in the trainline. Consequently, if there is any leakage in the trainline, the brakes will apply even more. And, they will continue to apply and slow the train even more than desired until a stop is made or the brakes are released by the engineer. So, you can see the importance of having a tight trainline.

Jimmy Lisle

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