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Got a question about this engine? I bought this engine the other day, all looks to be very little run time. So I put it on test stand and find out that the e-unit needs attention, fixed e-unit. put repaired engine on track works fine, except it runs really slow. I am running a ZW it works fine, but to get this engine to run I have to go full throttle, at half throttle it runs like it would be running on low throttle, sometimes it will just slow down and stop. the e-unit seems to be working right. I haven't checked the brushes yet or the commentator yet its on my list. It dose seem that there might be excessive play on the forward down force of the motor drive shaft, it looks to move about an 1/16 to an 1/8 of an inch from reverse to forward. I was just wondering if any one out there who has this engine has had this problem. Even thought I repaired the e-unit I'm still not real impressed with it. 

N&W J-class 4-8-4 6-8100 p3

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  • N&W   J-class  4-8-4  6-8100  p3
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Is this motor a clone of the PW 726 motor? Are there bushings or bearings on the worm gear end of the armature shaft? Is the motor secured to the chassis with two screws? Could something be loose with the screws, or missing/worn with the bushings or bearings? Did the gears and axles get fresh oil/grease when you were servicing it? You mentioned it looks new, so maybe the grease is 35 years old too?

Ok the first thing I done was put it on the stand, gave it a shake down. E-unit bad needed new drum. While I was inside I gave it a lube job inside and out. Part came in fixed e-unit, broke bottom finger on bottom board, need more parts. Fixed e-unit, again works but not like it should, it just doesn't sequence; the action isn't slick and smooth, but it works for now. Think I will change it to a Dallee later on. So test it on the stand runs well, it dose sound like a coffee grinder running, this leads me to thinking and from what I've read about some 4 drive wheeled steam engines, that it might need some shimming on the drive shaft. I'm going to pull it down off the track tomorrow and check it out.

I've rebuilt several 736/746 engines and there are some things you should take a look at. The 8100 is basically a remake of the 746 and is very similar to the Postwar version. The most common problem I've seen is excessive wear of the motor bushing on the commutator end of the armature, probably due to lack of lubrication considering the motor mounting orientation. This can cause poor gear mesh and may contribute to the famous Pullmor "growl". As previously mentioned, it is important to keep the side rods lubed as wear here will cause quartering issues and poor performance. I recently repaired a 746 where the shoulder of one of the drive axle bushings had disintegrated allowing the wheel to rub the cast frame.

 

 

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OGR Publishing, Inc., 1310 Eastside Centre Ct, Suite 6, Mountain Home, AR 72653
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