Tuesday, August 12, 2014

War Stories - Episode 25: The Tooth Fairy visits a GP15-1

The unfortunate case of CR 1625.

It was one of 100 GP15-1s bought in 1979 by Conrail.  The GP15-1s were new locomotives with a good sprinkling of parts from trade-ins.  They filled a niche for low HP locomotives suited for yard and local service.

In the mid-1980s, digital electronics started showing up on new locomotives.  They held great promise for being able to optimize and adjust locomotive performance through software rather than through wires and relays.

It was thought that tthat older locomotives might benefit from digital electronics.  That thought collided with GP15-1 CR 1625.

First, some background.  Woodward Governor of Fort Collins Colorado had been making mechanical flyball engine governors for locomotives since the dawn of time - maybe a bit before.  Their PG governor was a state of the art,  time-tested device, but its set-up was so tricky, railroads generally wouldn't let any field maintenance be done on them.  Screw up and you could make a big mess.

Woodward had developed an electronic governor called CLC, that not only did everything the PG governor did, but could also control other devises like cooling fans and the air compressor.  One of the interesting things you could do was to independently set the engine speed and load for each notch.  The PG governor was limited by the mechanical geometry of its design, notably a triangular plate with three solenoids acting on it.  You had some flexibilty to set the speed/load schedule, but it was always a compromise.

Why would you want to do this?  Fuel efficiency!  There was the potential to squeeze more out of the lower notches, particularly on roots-blown engines where the blower provided more than enough air flow in the current scheme.

In 1988, we decided to try one.

Mistake number one.  We chose a GP15-1.  Modular electronics.  Good.  Fairly new locomotive.  Good.  Able to keep it captive to one location for testing.  Good.  DC main generator.  Oops.  Should have chosen a GP38-2.  Having the CLC get control of the excitation for a DC main generator without a massive load regulator proved to be a big problem.

Mistake number two.  Too many interested folk involved in the installation.

Here's what the story:

We gather at Altoona.  Juniata is going to do the installation.  It involves placing a speed sensor on the camshaft gear, mounting a fuel rack actuator where the governor used to sit and wiring up the brains of the system mounted in the long hood near the AC cabinet.  There is a small group working on each part.  It all goes pretty smoothly.

The last step before firing it up is setting the speed probe so it can "see" the camshaft gear teeth.  We pull the probe out and bar the engine over until one of the teeth is right below the drilled and tapped hole.  Then we screw it in until it touches and then back it off a bit until it has exactly the right clearance. The electronics are loaded with decent default values to mimic the PG governor we took off.  It's time to crank it up!

Whirrr, whirr, whirrr....nothing.  Woodward guys start checking out signals coming into the box.  Nothing from speed sensor.   Start checking connections, etc.

Meanwhile, while nobody is looking, the local Woodward service representative, loosens the collar on the speed sensor and screws it in until it bottoms.  He's thinking the gap is too large. What he's doing is screwing it down between two teeth!

The electricians find a wiring problem and fix it.  Prime, Crank.  Whir.... then nothing.  The whole locomotive heels over a few degrees, hangs there and then the engine starts cranking.  Whir, whir, whir.... Still nothing.

What the heck was that rock and roll action?

Speed sensor now shows defective.  Unscrew it.  It's stuck.  Finally get it out.  The end is gone.  The business end is pretty much destroyed.  Hmmmm.  How'd that happen?  Get another one and install it.  Crank.  Whirr, Whirr, Whirr....Varoom!  Big cloud of smoke, then smooth, steady idle.  Success!

We get the engine speeds tuned to the original speed schedule and set the fuel rack accordingly and called it quits for the day.

Later that night, the Woodward guy confessed to what he did.  We thought briefly about what it would take to check and see what the damage was to the cam gears - and decided against it.  We'd have to pull the main generator...big job.  The locomotive was running okay, so, no harm - no foul!  We load boxed the locomotive the next day, got it running reasonably well and send the locomotive out to work.

A few months, the main generator has a ground and the locomotive is sent to Juniata.  They pull the generator, and laying on the cam gear housing is....

The gear tooth, not the golf ball....

The broken speed sensor had caused one tooth to sheer right off!  I take the broken tooth as a souvenir of the project.

The grounded generator appears to be unrelated to the cam gear problem.We get the generator replaced, some new gears on the rear end of the engine and the locomotive is on it's way back to Pavonia for a checkered career with it's CLC governor.

The CLC never could control the main generator well.  The controlling SCR fails.  Woodward replaces it with better one.  The loading rate doesn't tune well and the locomotive runs poorly ramping up and down between notches.  We try several things, but none work very well.

One Sunday morning I get a call from the Philadelphia Division.  The locomotive had a major case of exhaust sparking, probably a side effect from that CLC governor, and had set a brush fire.   It makes the "unusual occurances" report.  Lots of unwanted attention. Oops.

I take a ride on it, from Pavonia to Millville and back and later, from Pavonia to Mount Holly and back.  I monitor it with the plug in tuning device.  It works pretty well but even monkeying with the tuning a bit more, I can't get it to totally behave.

Finally, we surrender and send it back to Juniata to have the CLC removed.   However, on it's last day, I spend one long day - past midnight - with it at the test lab, running a bunch of steady state load and speed settings for each notch.  Extrapolating from those results, we find that we might be about to save about 2% of the fuel burned each year with an optimized load/speed schedule.  It would require a huge amount of further work to get all the way to the goal line, though.  So, we move on to other things.

The 1625 is living out the remainder of it's life as LTEX 1411, recently working on the Wiregrass Central in southern Alabama following a stint as NS 1411.

The tooth fairy might not have been nice to it, but, I have still have its tooth!

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