Noisy Atlas GP question

[shark_jj]

I am working on my Atlas GP9's.  Putting in Digitrax decoders.  Had to put solder on the contacts to get electrical continuity (annoying), however, now they run nicely.  Smooth and quiet, until I put the shells on.  Then they run noisy.  I have tried it with the shell only half on, so that I can see the flywheels and motor turning, so that there is no contact with the shell and I still get the noise.  It is like it is echoing inside the shell.  Take the shell off and it still runs smooth and quiet.  Has anyone else experienced this and if so is there a solution.

[Chris1274]

Ron Bearden found the solution to this. You have to remove the inner bearing blocks from each worm gear shaft. The details are all laid out here: http://trainweb.org/passengercars/Bearingblock.pdf

[shark_jj]

Chris, thankyou for reminding me of this.  I actually knew of Ron's solution but it has been years since I had encountered the problem and it had slipped my mind.  Appreciate the reminder.

[davefoxx]

Unfortunately, I cannot recall exactly and do not have a GP9 in front of me, but this may be one of the Atlas Classic locomotives that has a different bearing in the driveline.  If so, they're more like a doughnut with two small wings rather than the square bearing blocks.  You may not be able to Beardenize this type, but it's easy to put these in wrong, which will make noise.

Another problem can be overtightening of the frame halves, which can cause binding in the driveline enough to cause noise.  Also, it may make the shell fit a little looser, causing the shell to "rattle," explaining why the locomotive is quiet without the shell and noisy with the shell installed.  Maybe you could apply a piece of tape to the bumps that retain the shell to see if that tightens up the shell's fit and quiets the unit down.

Hope this helps,
DFF

[Chris1274]

I just had my own GP-9 opened up the other day and it has the square bearing blocks. Unfortunately the hex nut is on the worm shaft so tightly that I wasn't able to pull it off in order to remove the bearing block, at least not bare-handed. Hopefully when I try again with pliers I won't end up squashing it. In any event, the GP-9 will benefit from Ron's fix.

[Iain]

I just had my own GP-9 opened up the other day and it has the square bearing blocks. Unfortunately the hex nut is on the worm shaft so tightly that I wasn't able to pull it off in order to remove the bearing block, at least not bare-handed. Hopefully when I try again with pliers I won't end up squashing it. In any event, the GP-9 will benefit from Ron's fix.

I just cut them off; no need to pull the hex nut.

[MichaelWinicki]

I just cut them off; no need to pull the hex nut.

This.