Kato Engine Speed Mismatch

[rsauerbrun]

About a month ago I purchased a pair of Kato AT&SF PA-PB locomotives. They ran great at first and functioned as a single engine when paired PA/PB.

But now the A engine runs considerably slower than the B engine. I have confirmed this with tests running the engines at the same time on the same route, but not coupled. If I put the B engine ahead, it eventually runs away from the A engine. I have checked for damage and gunk buildup, but have found neither.

This is now causing derailment problems as when coupled they are either pulling or pushing on each other.

Does anyone have any ideas on how to fix this problem?

Thanks

[inkaneer]

DCC ers will tell you to switch to DCC but that will only mask the symptoms but not solve the problem.  From the inforamation given I would first suspect some resistance in the drive mechaism.   Possibly a driveshaft out of alignment or a bearing not properly seated.  There could be other reasons also. 

[rsauerbrun]

I am aware of the advantages of "speed matching" and building an A/B engine consist in DCC. I do plan to go there soon, but as you said, I would like to solve the baseline problem first.

I have no experience fixing these devices ... should I crack the case and take a look? Or should I take it to a train store?

[SecretWeapon]

Check for lint or ground foam picked up. This will screw up the gears & or the motor & drive shafts. Check for broken or missing teeth on gears.

[tokenbrit]

.. They ran great at first and functioned as a single engine when paired PA/PB.

But now the A engine runs considerably slower than the B engine...

How much run time have they had - are they both equally 'run-in'?
Is the speed mismatch the same fwds & bkwds, or just in one direction?
Is the slower one noisier?
Have you tried lube-ing the mech(s): gears &/or bearings?

[mmyers]

Those mechanisms are notorious for picking up dust and lint in the trucks. Check and clean the bearing cups on the side frames. It's amazing how much crap they hold.
After getting the two running properly, only then should DCC be considered.

Martin Myers

[railspike55]

quote..
"If I put the B engine ahead, it eventually runs away from the A engine."

I have run N track for long time. Before DCC.  As long as you run the faster loco a head of the slower one. Seams the difference is small following the above statement.

I belive the Pa Pb shells can be swopped around sence its the same chassis for both.

Untill you can determin the cause they should run fine this way.

Ron N.

[wm3798]

I don't have specific experience that the Kato PA/PB, but I've had enough engines apart to know that the symptoms are typical of gunk build up (a sure sign of this would be intermittent stalls and/or flickering headlight) or more likely, something binding in the drive.  I know that in older Atlas/Kato drives, the bearing blocks can be off-centered, causing a slight pinch in the drive worm.  The evidence of this is sluggish performance and extra motor noise.  If the bind is very slight, lubrication will do the trick.  If it's really noisy, the bearing block closest to the motor needs to be removed, or at the very least turned 90 deg. to correct the bind.

If you're not comfortable fooling around under the hood, take it to someone who is, but if you do dive in yourself, make sure you note where the parts go before you take it all apart.  A digital photograph of the guts before tinkering is a good idea.  Also, put a piece of towel, or foam or something down on the workbench before you get started.  It will surprise you how far a universal joint or a insulating washer can bounce... 

Good luck!
Lee

[Walkercolt]

I think it's gunk in the A-unit, too. I've got 4 F-3's I've had forever that I always run as an ABBA set, and I don't worry about what order I get them in, and they'll run 5" apart individually for 15-20 minutes on the club layout(make sense what I'm saying?). The needlepoint low-friction pick-ups gather glop and crud and dirt. Be sure NOT to over-lubricate...that makes things worse. If you can imagine just lubing by your breath, that's all you need. I put LaBelle 108 on and then use a Kleenex to remove almost every bit of it.

[slickwillie]

Thanks for the tip on checking for gunk build-up.

I have this problem on several of my Kato units. When they had their sale on RSC-2's, I bought one to match the existing one I have. I can't use them together, they are way, way apart in speed. I also can't double-head any two of my 5 Kato Mikes, their speeds are all over the map. The only units that stay together are the SD40/-2 (old versions) and Dash 9/AC/SD70's.

[AVR Mark]

I have bought new (old) Kato built locomotives which had been on the shelf, but never run for several years. In some cases, two locomotives of the same model type would not run at the same speed. I found that most of the time this was caused by the factory lubrication drying up on some of the locomotives. My usual cure is to oil the bearing blocks on both ends of the worm gears. This seems to eliminate the problem in most of the cases I have seen. If the motor needs to be oiled, it will be quite a bit louder than other engines of the same type. I have seen new (new) locomotives arrive with dry engine bearings.

Mark

[ednadolski]

Mark, what kind of lube(s)/oil(s) do you use?

I've had this sort of issue for a while now and not just with Katos.  Even the same kind of locos run at quite different speeds -- it's enough of a difference that some locos in a consist will slip esp. running up grade.   I thought that DCC speed matching would solve the issue and I even set myself up with the Trainspeed scale speedometer (a nice tool).   But the core issue is that even the same engine doesn't seem to run repeatably at the same actual speed for a given speed step, even with Back EMF enabled.  Also, the tunings seem to drift over time, I can tune a consist and then after a few weeks they need to be re-tuned again (and it's a bit of a tedious procedure to have to repeat that often even for a modest roster, tho programming from the PC w/ Decoder Pro definitely helps).

I see this with new engines so it doesn't seem to be related to gunk buildups.  It also seems that speeds vary as the mechanisms warm up with each use.

Ed

[AVR Mark]

I have been using Labelle 107 oil and 106 grease for quite a while now, with excellent results. As for the grease, a little goes a long way.

Mark