Athearn Noise Problem Surprise
Apr 23, 2016 12:54:09 GMT -5
JNXT 7707, retiredalex, and 1 more like this
Post by mph on Apr 23, 2016 12:54:09 GMT -5
The M&SH RR recently acquired an Athearn Canadian National F-unit. Acquisitions of used equipment are common on the M&SH due to budget limitations and they usually always upset the shop foreman who has to get the units into running condition. There was hope that this unit would be delivered in running condition and would only require a clean and lube, but this was not to be. The second the unit began moving, the foreman started to cuss. The F unit was the victim of a major rubbing noise. The last time this happened was a bad motor mount on a used PA-1. The foreman was furious because this is the Athearn repair he dislikes. Off to the shop the unit went for a complete overhaul.
Once in the shop it was clear the motor mounts were fine. With the common cause of the problem gone, the shop performed a complete overhaul, except for pulling the motor from the frame. Everything was cleaned and inspected. While the axles did not show visual signs of cracks, the wheels slipped. Thinking this may be the cause of the mystery noise, all of the axles were replaced. The unit was reassembled lubed and sent to the track for testing, without the shell. Much to the frustration of the shop foreman, the noise persisted! It was obviously a rubbing noise, but visual inspection did not reveal any problem. The unit was run at length and the foreman noticed, the noise went away on right turns. With a few more passes, it was determined that the noise was coming from the rear truck. Back to the shop for a rear truck replacement.
As parts were being pulled for the work, the foreman noticed a design difference in the worm housing. The part in stock had tapered end, while the part on the locomotive had blunt ends. Could this be the cause of the problem? The shop replaced the worm housing, leaving the original truck in place and sent the unit back to the track for testing. To the foreman's surprise, the noise went away and he was left with the sounds of a typical blue-box Athearn F-unit.
The original worm housing ends were tapered and reinstalled. The shell was placed back on the frame and the unit was cleared for revenue service!
My apologies for taking the long way to share a problem that I had not run across with Athearns before, and I have worked on quite a few. The photo of the truck shows the area of the problem. The slotted coupling in the drive train, while visually appearing to have clearance, rubs against the worm housing when the motor is running. Considering that Athearn changed the design of this part (the photo with the 2 worm housings), this must be a known problem that I have been lucky enough to miss.
The photo of the unit is the shop foreman (me) being a proud father. I hope this helps someone.
Once in the shop it was clear the motor mounts were fine. With the common cause of the problem gone, the shop performed a complete overhaul, except for pulling the motor from the frame. Everything was cleaned and inspected. While the axles did not show visual signs of cracks, the wheels slipped. Thinking this may be the cause of the mystery noise, all of the axles were replaced. The unit was reassembled lubed and sent to the track for testing, without the shell. Much to the frustration of the shop foreman, the noise persisted! It was obviously a rubbing noise, but visual inspection did not reveal any problem. The unit was run at length and the foreman noticed, the noise went away on right turns. With a few more passes, it was determined that the noise was coming from the rear truck. Back to the shop for a rear truck replacement.
As parts were being pulled for the work, the foreman noticed a design difference in the worm housing. The part in stock had tapered end, while the part on the locomotive had blunt ends. Could this be the cause of the problem? The shop replaced the worm housing, leaving the original truck in place and sent the unit back to the track for testing. To the foreman's surprise, the noise went away and he was left with the sounds of a typical blue-box Athearn F-unit.
The original worm housing ends were tapered and reinstalled. The shell was placed back on the frame and the unit was cleared for revenue service!
My apologies for taking the long way to share a problem that I had not run across with Athearns before, and I have worked on quite a few. The photo of the truck shows the area of the problem. The slotted coupling in the drive train, while visually appearing to have clearance, rubs against the worm housing when the motor is running. Considering that Athearn changed the design of this part (the photo with the 2 worm housings), this must be a known problem that I have been lucky enough to miss.
The photo of the unit is the shop foreman (me) being a proud father. I hope this helps someone.
