Unusual Way To Break-in B'mann HO Diesel Engines

[K487]

All:

First, I posted this on another forum and thought it obviously appropriate for this forum.

Second, I have over 20 B'mann engines and use some almost daily, so my comments below about fixing a couple of B'mann products are not be taken negatively.
 
You might find the following interesting and possibly useful.  I get in moods to test things so here I go again.

A few days ago I decided to check further into two of my Bachmann engines – GP38-2 and GP40 (identical chassis, motor and drive train, but different shells) – that had issues out of the box (I had test run them, lubed them, then test run them again.)  One loco surged and both had gear growl/chatter = unacceptable.
 
After removing the shells I put one on a test block on my work bench and ran it with no load. In considering the loco I noticed that I had (as usual) a 15" x 15" piece of cloth under the block on the work bench.  So I set the loco on the cloth, held it, and ran it some (the cloth creating drag on the motor and drive train).  I then had THE thought.

I put the heels of my hands on the cloth at each end of the engine so the cloth wouldn't bunch, held the loco with both hands, turned on the power all the way up, then used my thumbs to push down on the engine while it ran in place.  I did this backward and forward, and periodically checked the motor temperature by touching its side with a finger.  I put enough down-pressure to lug the motor down to within 10% of its stall speed, and then turned the motor off after about 1 to 1.5 minutes when it became too hot to touch.  While the wheels were turning on the cloth, and even with my down-pressure, they never burned through the cloth.  I repeated this procedure for the second loco.

The results?  Both engines now run 100% quiet (and I'll admit I was surprised – I used no grit toothpaste or anything – except oil - on the drive trains).  Also, one engine runs smooth as silk, and the one that surged still surges a little, but when mu'd with another engine I can once in a while barely see the train (70 cars) slightly surging.  Both engines are now in the official operating fleet.  I call this procedure a success, and plan to do it again (to a Bachmann engine; not sure about other brands) as needed.

Was I concerned about breaking something in the drive train with this "torque test"?  No.  I figured the parts were tough enough and the small motor not powerful enough.  I was correct on at least these two locos.
 
Lastly, you might be interested in this addendum.  A peculiar problem came up when I first ran one of these locos (with the shell screwed on) after this unusual break-in.  When I ran the engine it hummed loudly, and after listening closely I found that the hum came from the cab!  My first thought was, "That's crazy.  The motor's back in the center."  So I removed the shell and checked for any metal flash around the front of the engine that might be touching the shell.  There wasn't any BUT the lower half of the all-metal, two-part chassis has a 1/4" wide horizontal lip molded on it at the bottom that goes all the way around.  As you know it is used to rest the shell on.  Well, on each corner of this lip there was a small tit molded on.  I don't have a clue what it is for, but a minute's work with the dremel tool with cut-off disk fixed the problem – no more hum at all.

K487

[Doneldon]

I removed the shell and checked for any metal flash around the front of the engine that might be touching the shell.  There wasn't any BUT the lower half of the all-metal, two-part chassis has a 1/4" wide horizontal lip molded on it at the bottom that goes all the way around.  As you know it is used to rest the shell on.  Well, on each corner of this lip there was a small tit molded on.  I don't have a clue what it is for

K-

I would bet they're left over from the casting process.

                                                                       -- D

[K487]

Doneldon:

I'll bet you're right. 

Probably nobody in the manufacturing chain sees any harm or potential problems with them.  As I mentioned they are an easy fix, but the problem is in knowing they are or could be the problem.

K487