Nostalgia & History > Is this train in dynamics while accelerating?

On 6-2-92 I shot video of this BN coal empty leaving Alliance, NE behind C30-7 5056 and it sounds as if they go into dynamics as the train accelerates out of town. This is the only time I have seen this. Is it normal? It sure did sound neat though!

Brian Ambrose
Renton, WA



Edited 3 time(s). Last edit at 02/18/18 12:57 by BrianA.

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Probably the cooling fans on the two EMD SD units in the consist. Obviously the fans were NOT the latest "Q Design", for Quiet, or quieter.

It does sound a lot like DB's.



Edited 1 time(s). Last edit at 02/18/18 13:11 by tehachapifan.

Cooling fans at full blast. Trains climbing Tehachapi sound just like that.

Scott Schifer
Torrance, CA
TinyTrains Website

The giveaway to this is the rich smoke from all four units, they're definitely in full power. The noise is the EMD cooling fans.
G

Unless there is a serious wiring problem on a specific engine, or in the MU cable between units, it is impossible to have some units in power mode and others in dynamics. The same lever on the engineers control stand controls either/or. Not both at the same time.

EMD cooling fans seems to be the answer here. What I find strange is I have never heard them on any other trains I have seen or photographed, this was the first and only time. What causes the cooling fans to start as they did in the video?

Brian

BrianA Wrote:
-------------------------------------------------------
> EMD cooling fans seems to be the answer here.
> What I find strange is I have never heard them on
> any other trains I have seen or photographed, this
> was the first and only time. What causes the
> cooling fans to start as they did in the video?
>
> Brian

Probably due to the fact that the units were SERIOUSLY accelerating a long heavy train, and as the engines came up to temperature, prior to the train reaching your location, all three AC cooling fans (one after the other, in sequence) came on in both of the EMD units.

As additional information, when an EMD unit is bell load-tested with the "self load test" feature, i.e. loading the prime mover & generator on its own dynamic brake grids, the cooling fans tend to make more noise than the DB grid blower motors/fans.

When the hill out of Trinidad was taken over by the early MACs it was interesting to listen to them. They'd come out of Beshoar in Run 8
making a few mph, the exhaust fairly muffled but the fans on full kill. That was much opposed to the GEs where you could hear nothing above
the engine and exhaust noise.

Out

There are two ways for coal mtys to leave Alliance, NE. West towards Edgemont it is uphill to the Nida sag just short of Hemmingford. South towards Guernsey, WY it is mostly uphill to Angora. There would be no need to be in dynamic braking for either of those mmoves.

My thought was the Db's were being tested leaving Alliance for the later descent of Crawford Hill. Still surprised I have never heard that sound from any train on Stampede, Stevens or the Montana mountain passes.

Brian

BrianA Wrote:
-------------------------------------------------------
> My thought was the Db's were being tested leaving
> Alliance for the later descent of Crawford Hill.
> Still surprised I have never heard that sound from
> any train on Stampede, Stevens or the Montana
> mountain passes.
>
> Brian

As LaryDoyle posted, above, there is NO WAY to have some of the units in an MU'ed consist in dynamic brake while other units within the same consist are in power!!!! Such simply can NOT be done.

I never heard of pretesting the db leaving Alliance and it would have brought the train to a full stop. West of Hemmingford there was a drop down into the Niobrara(?) River before the climb to Belmont where the db could be tested. Taking an mty coal train downhill on Crawford hill without db was not much of a challenge. Taking a grain train over the same territory without db was a serious challenge. That was a handful with db.

> I never heard of pretesting the db leaving Alliance and it would have brought the train to a full stop.

Dynamic brakes can't bring a train to a full stop for the simple reason that they cease to function when the train isn't moving. At best they can bring train speed down to 2-4 mph. "Stall braking" with AC traction motor units is a different process.

Like I pointed out, it was uphill leaving Alliance for all coal mtys. Take away the power and the train will stall to a stop. Those EMDX SD60s had extended range dynamics.

I worked out of Alliance for 7 years and we never went into dynamic braking leaving Alliance with coal mtys. SD60s were after my time there.

Many EMD's had a rough gear cut between the crank, cams, and turbo gear set, that they would scream, changing note up or down with the speed of the crank. Even SD70's have that once in a while. This info was from a 30 yr veteran machinist that worked on them in Roseville.

terexgm Wrote:
-------------------------------------------------------
> Many EMD's had a rough gear cut between the crank,
> cams, and turbo gear set, that they would scream,
> changing note up or down with the speed of the
> crank. Even SD70's have that once in a while.
> This info was from a 30 yr veteran machinist that
> worked on them in Roseville.

Except, in throttle 7 or 8, the turbo is OFF THE CLUTCH, and running totally off the heat of the exhaust gas. At higher altitudes, the turbo even comes off the clutch at throttle 6. Plus, the sound in that video, posted above, is certainly NOT gear train noise from the prime mover.