Question for Hot Water, RE: EMD Troubleshooting

I have a trouble shooting question on an SW8 that seems to have stumped the panel here.

The amount the engine loads is prone to changing every time the throttle is opened. 

Specifically, if you are stopped, you release the brake, and go to Run 1, one time the amp meter may go to 200 amps and the engine starts moving slowly, with just enough power to move itself.  The next time, with the same scenario, the amp meter may jump to 1,000 amps, the engine takes off like a jack rabbit, the wheel slip buzzer goes off, etc.  A few moves after than, and it's back to low amperage starts again.

What gives?

Original Post

Kelly,

Boy, since I've given all my EMD technical publications to Mike Manwiller, CMO at the Heber Valley RR in Utah, I'll have to try memory.

1) Since it sounds like a main generator excitation issue, you might try checking the battery field excitation circuitry. Pay close attention to the tips on the battery field contactor. 

2) Make sure that all connections are tight on the load regulator, the commutator on the LR is clean, and the brushes are good.

3) Since the problem appears intermittent, it will probably take awhile to chase the cause down, until the problem finally stays consistent.

 

Keep us posted.

The ORS (over riding solenoid) in the governor is what allows oil flow to go to the load regulator increasing excitation. When it is energized the load regulator stays in the minimum field position, when it gets de-energized it allows oil pressure to flow to the load regulator, bringing it to maximum field. The power for the ORS is a rather simple circuit so you should be able to check it pretty easily. It should be a PC wire (positive control) going to a NC (normally closed) interlock on the BF contactor, then it goes to the governor, only making stops at terminal boards. Every time you pull the throttle out BF lifts, de-energizing ORS so the load regulator can start slowly coming around for a smooth increase in loading. If the interlock on the BF is starting to fail it can intermittently not make a good connection when it drops, therefore not giving juice to the ORS, therefore keeping  the load regulator at maximum field. A couple more cycles on the BF and the interlock makes a good connection and it all goes back to normal. That’s a typical EMD setup. Hope this helps!

Kelly for what it is worth on all the trouble we had with our 45 Ton.

Mostly it just came down to loose connections. The issue came up when we would have excitation go between the series and parallel mode. It was like the Loco fell into neutral and lost all power. 

We also had a broken internal overtravel spring in the throttle lever cable. This gave us a mismatch to RPM and the electrical control. They got way out of sync then became ineffective. Once we found that we were able to tighten up the linkage control and then pin down the electrical issue. 

CSX FAN posted:

Kelly for what it is worth on all the trouble we had with our 45 Ton.

Mostly it just came down to loose connections. The issue came up when we would have excitation go between the series and parallel mode. It was like the Loco fell into neutral and lost all power. 

We also had a broken internal overtravel spring in the throttle lever cable. This gave us a mismatch to RPM and the electrical control. They got way out of sync then became ineffective. Once we found that we were able to tighten up the linkage control and then pin down the electrical issue. 

Lets go back to the mid 60s,,, Full crew, train order territory.  SWs. CN 1200 and  13oo series..I had a post deleted or removed deleted when I mentioned  giving  the Electrical panel a good whack with a pipe wrench. I've probably been on a few hundred SW types  (maybe more) and I can assure you although somewhat  unorthodox  it occasionally  made the deference of clearing the main line, or sending out the flag  in both directions.  Some crews  may even  remember opening the electrical panel and tapping relays  (and other things)with a broom or flagstaff.  That one even made nervous,

Yep I know this is not  the fix the posted is looking for.  Just a memory from years ago,

Kelly Anderson posted:
toddstrick posted:

In notch 1 does the load regulator start moving to Max field? 

I can't answer that.  I have not been personally involved with any of the troubleshooting.

It is #8618.  #1235 is nowhere near being operable.

The load regulator moves with engine oil pressure, so even though the ORS is allowing oil to flow to the load regulator it may not move much in 1st notch. That’s why there is a whole additional system for 1st notch excitation which bypasses the whole load regulator and goes through the LRC relay and a resistor you can adjust to reach around 275 amps as soon as you pull out the throttle. If you want to watch the load regulator I suggest you throttle up to at least 2 or really 3 to see some action. 

Gregg posted:
CSX FAN posted:

Kelly for what it is worth on all the trouble we had with our 45 Ton.

Mostly it just came down to loose connections. The issue came up when we would have excitation go between the series and parallel mode. It was like the Loco fell into neutral and lost all power. 

We also had a broken internal overtravel spring in the throttle lever cable. This gave us a mismatch to RPM and the electrical control. They got way out of sync then became ineffective. Once we found that we were able to tighten up the linkage control and then pin down the electrical issue. 

Lets go back to the mid 60s,,, Full crew, train order territory.  SWs. CN 1200 and  13oo series..I had a post deleted or removed deleted when I mentioned  giving  the Electrical panel a good whack with a pipe wrench. I've probably been on a few hundred SW types  (maybe more) and I can assure you although somewhat  unorthodox  it occasionally  made the deference of clearing the main line, or sending out the flag  in both directions.  Some crews  may even  remember opening the electrical panel and tapping relays  (and other things)with a broom or flagstaff.  That one even made nervous,

Yep I know this is not  the fix the posted is looking for.  Just a memory from years ago,

I've keep'em going with a flag stick before.

Especially GP38's to hold the cam under the floor in place.

I've had the SD40's  fluctuate the amp like that before . Makes it hard to switch.

My regular job uses a SD40 everyday and it has tendencies to drop out in 5th notch ,at times .

Really hurts when your trying to kick cars.

Collin "The Eastern Kentucky & Ohio R.R."

By some chance does this particular engine have a 2-position switch for quick loading vs normal?  (Or did it ever, under previous ownership, have one?)  I have seen them on the small cash register control stands as well as the cylindrical ones.

Tom

 

Superintendent, High Plains Division (O Gauge) 

The Panhandle & Santa Fe Railway Co.

Lone Star Hi-Railers

Santa Fe, All the Way

My thought was that the problem could possibly lie in that switch. (?)  However, 1000 amps from an SW8 in Run-1 exceeds what the engine should produce if running light.  If coupled to cars and the 2-position excitation switch is defective and making the locomotive load fast regardless of switch position, then perhaps 1000 amps could be developed intentionally if the unit has not initiated movement.

Your concern, though, as I understand it, is not the amount of amperage, but rather the speed at which it is obtained.  If you can test to see if the 2-position excitation switch output does not change on its own when your high excitation occurs, at least you would know for sure whether it is the culprit.

Tom

 

Superintendent, High Plains Division (O Gauge) 

The Panhandle & Santa Fe Railway Co.

Lone Star Hi-Railers

Santa Fe, All the Way

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