Atlas GP-38...what is this?

Hello

Taking apart an Atlas GP38 that is making some noise
Do you know what are those blue "things" in the flywheel?

 

Probably to balance it?

 

My guess would also be for balancing the flywheel. I am no expert but that flywheel looks as if it has been rubbing against something. Could that be your noise? Also, that frame looks like it has been in a vise ? ? ? Just curious did you acquire this loco off of eBay ?

 

Not off of Ebay, but yes....used
A gentleman was selling it (+ few other things) since his dad passed away
It was factory equipped with a NCE decoder....got it for $50

 

How would one go about balancing a flywheel anyway? As in, how would you know where to add weight?

 

Most likely done at the factory I guess...unless the previous owner took it to Belle Tire ?

 

I have never seen a N scale flywheel with balance in my many years of modeling. I would think that is something the previous owner did. The only time such a little flywheel gives issues is when it is not on the motor shaft correctly or the mount of the motor is loose allowing it to shift and rub on something.

 

Should I remove them then?

 

Being that I have never seen an N scale flywheel counter balanced in my life I would remove them if it was mine. Those flywheels are either cast and then milled out or a solid piece of metal is milled out, The only purpose for a flywheel is to keep the motor turning when you run over a small dead spot. Cut the power quickly and you will see a flywheel equipped loco coast a small bit. The usual problem with a motor fitted with flywheels is that the motor is not set right in its mounts which allows the flywheel to rub against a structural part. That creates noise and affects the loco's performance.

 

I have see this on a few of my engines..Just left it alone...might screw something up if you remove it.

 

I would leave it too. Looks like balance putty from the factory. Why remove it if it's not giving you trouble? Run the motor at full throttle and see if it vibrates. If not, you have your answer.

Those "scratch" marks are not from rubbing. Close up photography is showing the machining marks.

BTW, what era is that GP-38? Fairly new? If it has a NCE decoder (I'm assuming factory) then it would be fairly new. Atlas might have changed its manufacturing process. In the past all manufacturers would add balance putty to the motor core, where the windings are. Maybe now they are doing the balancing on the flywheel instead so they can (a) just churn out the motors quicker without balancing them and (b) won't have to rebalance again after installing the flywheel should the flywheel installation screw up the balancing in (a). Why do it twice?

 

I will leave that putty in place then
Here are some pictures of the frame and back of the decoder:

 

It still has the phosphorous bronze strip to the trucks instead of the very new chassis where they do the wires to the trucks. But it's still fairly recent given the NCE decoder. You can't really tell with the c.1997 as that's the year when the frame was designed and those haven't changed for eons.

 

Flywheel balancing aside, I believe this thread was in an effort to find the source of noise, yes? What kind of noise are you hearing? There are some common (and easily fixable) issues that can be mistaken for flywheel rub.

 

Well...my vocabulary may have its imitation to properly explain the noise: some kind of "grinding" noise (?), especially in reverse...
Like if something was stuck in the pinions/worm gear (this type of noise)

 

The little bushings in the worm gear and the truck gears do have a little light oil in them right?

 

I noticed some grease (white) in the truck's pinions, and also on the worm gears. I don' think there was anything "dry" (i.e lacking lubricant)
But I will buy some Labelle 108 and use a compressed air can to clean and then lubricate those parts...I hope when i put it back together, it will still work !!!

 

One other (unproven?) thing that comes to mind is the orientation of the bearing blocks. While I have not yet measured them with calipers, I suspect that they are not always the same dimensions in all orientations. I'm talking about the inner dimensions of the bearing block that the worm "fingers" (that are a molded part of the frame, not the brass fingers) insert into. I believe the outer flanges of the bearing block (what you see when you look at a side with the hole in it) are indeed square and may (incorrectly?) lead people to believe the inner surfaces are as well. You will notice that these inner surfaces are smooth on two opposing sides and sort of faceted on the other two opposing sides. While I'm not certain, I believe that, in many, most, all? Atlas models, the smooth surfaces go against the frame fingers and thus one of the faceted sides is then facing outward when the block is installed in the frame. I believe this faceted surface is possibly intended to help the brass spring fingers, on the other frame half, hold the block in place. My theory is, if one or more of the bearing blocks is orientated the wrong way, this can possibly cause a mal-alignment of the worm and/or a meshing problem with the truck tower gear resulting in noise and/or performance issues. I purchased several used Atlas models where one or more bearing blocks were installed differently, presumably from a previous owner during maintenance or perhaps a decoder install. Your mileage may vary. Hope this helps.

 

My store doesn't have the Labelle 108....
But they have the Woodland Scenic Hob E Lube Premium lite. I will try that....