Diesel Service Report, November 24th, 2020
Repair of USAF 1601
The repair and replacement of two of the four traction motor gear case assemblies under the locomotive is complete and they are almost ready for testing. Carl Pickus, Doug Newberry, Frank Kunsaitis, John Salvini, and Richard Berk, were able to complete the repair work and place the trucks back under the locomotive. Carl and Doug refurbished the brake cylinders using new cylinder cups and replaced broken springs. They then lowered locomotive back onto its trucks and reinstalled the side bearings and connected the brake rigging and air hoses.
Prior to the locomotive coming to the museum, previous owners had disconnected the high voltage wiring on the reverser switch to isolate traction motors 2 &3. That wiring has been reconnected to the terminals on the switch and the Motor Shunt contactors. The remaining task is to place the locomotive over the CB4 inspection pit and reconnect the traction motor wiring. After that is done, the locomotive is ready for testing.
Even though the above summary makes the job sound simple, it wasn’t. This project reinforces the fact that we learn as we go. In retrospect we would have done things differently, but we just didn’t know that earlier. We had assumed that the only damage to the gear cases and traction motors that came with the locomotive, was just the motor armature damage. GE switcher locomotive gear case and traction motor assemblies are unique designs, unlike any other locomotives that we have and we’ve had no experience with them.
Now we know they have a history of somewhat unreliable operation. And that was especially true with the double reduction GE747 series gear cases like we have under USAF 1601.
When 1601 first arrived at the museum, we inspected it and saw that the number 2 & 3 traction motors were damaged. We found that the brush holders had been removed from the motors and there was slight damage on one motor commutator and severe damage on the other one. Based on the inspection, it was our belief that the previous owners had not properly inspected the motor brushes and as the brushes wore out, arcing took place between the brush holders and the armature commutator. That arcing damaged the commutator segments. The previous owner then isolated the motors from the electrical system by removing the high voltage cables on the reverser switch. And that’s assumption and what we had for a number of years.
During the past few years, we searched for replacement GE747 traction motors and found a few places that would sell used ones that were guaranteed to be good. The prices for two motors ranged from $6,000 each, plus shipping from the east coast, to $8,000 each plus shipping and the return shipping of our damaged motors. That was still too expensive so we did nothing.
Then an Internet posting showed two complete trucks for sale in Kansas City. Each truck was priced at $10,000 plus shipping. What was intriguing with this offer was that it included two complete gear cases plus two operational traction motors plus all the brake rigging and the truck frame itself. At the time is appeared that is solved all our issues. We bought the complete truck.
Once it arrived, the two trucks from under the locomotive were removed and we were prepared to install the two new gear case traction motor assemblies in place of the two bad units that were under the locomotive. An inspection of the new motor commutators showed them to be in excellent condition, so we thought that all we had to do was swap the two gear case traction motor assemblies.
Unfortunately it didn’t work that way. The two new assemblies were installed in the trucks but when one of the trucks was being rolled back under the locomotive, Carl Pickus noticed that there was back and forth movement of one axle in the gear case output bearing. There should have been no movement there. But it was moving almost an inch. That meant the gear case and traction motor assembly, we call them combo’s, had to be removed. But that left us with another problem. We either had to fix that bearing or swap the traction motor from that combo onto one of the original combo’s from under the locomotive.
But before the motor swap idea went very far, Carl Pickus noticed that one of the damaged armatures wasn’t rotating when the truck was moved. That would be impossible if the ring and pinion gears are engaged. John Salvini opened up the gear case inspection port on that combo and found that the pinion gear teeth were totally missing. No part of the pinion gear was touching the ring gear.
After seeing that, he inspected the combo with the failed bearing and found that the pinion gear on that traction motor shaft was severely worn and very close to total failure. So that meant we couldn’t swap that traction motor into one of the original combo’s.
That left only one option. That was to remove the most severely damaged motor, that had a good pinion gear, and deliver the armature to a motor shop in San Diego. John made a continuity measurement of the armature and could tell that it was not shorted to the shaft. After many hours of machining, the motor shop was able to save the armature. That then gave us all the parts required to finally assemble four good combos for the locomotive.
Carl, Frank, Doug, Richard, and John, have reassembled everything for the final time, we hope.
We still aren’t experts on GE switcher locomotive trucks but we sure know a lot more now than we did four months ago.
This (left) is what a good pinion gear looks like.
This (right) is what a totally worn out pinion gear looks like. The teeth on the pinion gear are all sheared off. And we had no idea that pinion gears were the major source of problems in these gear cases. As the old saying goes, Live and Learn.
SF560 Fairbanks Morse H12-44 Restoration Project