This was a query to the Marklin Mailing List and the resolution of the problem.

From ebcacsk at Wed Dec 6 12:20:00 1995
Subject: Very strange Z-scale problem

I have the track cleaning wagon (car, motor car/wagon or whatever is the correct term), the yellow one where some of the wheels clean the rails, Märklin no. 8802. By the way it works well for track cleaning.

A couple of days ago I decided to run it over switches (points?). The ones with one straight and one curved part are no problems, but the double curved ones are.

I hooked up (this was a test only) right and left hand double curved points (switches?) with a piece of straight track in between. The power is fed through a connection rail in this straight part. At the other end of both points I added some curved track. Not a complete loop. Impossible to draw but I hope you get the picture.

I drove the cleaning wagon back and forth on both the inside and outside track of both points - no problems whatsoever. I then turned the cleaning wagon around so it was pointing in the opposite direction. Outside track no problem, inside track on both points big problems - sparks and I think some sort of short circuiting, complete stop. This happened on both switches. When the wagon approaches the point from the left, for example, it does not stop at the same place as it would approaching from the right. There is a gap of 0.5 to 1 cm between these two cases. But the problem is irrespective of if it is a right or left hand point, as long as the wagon is pointing in the 'wrong direction'.

I've spent two evenings trying to figure out what is wrong, but I've not been able to.

Has anyone experienced the same problem? Are the electronics in it such that the polarity is important? I have no problems with other engines.

Thanking you all in advance.


From Jvuye at Wed Dec 6 16:20:51 1995
Subject: Re: Very strange Z-scale problem

I have never expereinced this type of problem in Z, although the track cleaning 'Schienenbus" really works well only in one direction (the big cleaning wheels in front) but the problems I had related to derailments, not shorts.

I will try to reproduce your experiment and see if anything comes out.

I won't be able to try that before the week end, though. Maybe someone will come up with an answer before then.

In the mean time, you may want to reproduce the problem with the Schienenbus body removed: when it stops on the short, you may be able to have a better look at the details of which shorts what. Since the only difference for this vehicle is these big cleaning wheels, I'd take a really close look there.

I gather from your message that you did not experience any trouble with other engines, right?

I'll let you know if I find anything.

Jacques Vuye
San Jose CA

From ebcacsk at Fri Dec 8 10:41:21 1995
Subject: Re: Very strange Z-scale problem now solved

The problem has been solved!!

I followed Jacques Vuye's advice (posted in a mail a few days ago) and removed the body shell. This way one sees all the wheels more clearly. I suspected, as Jacques did, that the large wheel in front was causing a short circuit somehow. A close study of the front wheels showed that they were not dead center on the wagon. So I placed a small piece of plastic between one of the wheels and the chassis to center the wheel pair. No luck, still sparks and short circuit.

I then looked very carefully and noted that the sparks eminated at the rollers just behind the large front wheel. By rollers I mean the second wheel pair without flanges. I removed the bottom plate, removed the rollers and then replaced the bottom plate. No longer any problems, back and forth in both directions with no sparks or short circuit.

From this I concluded that the problems were with the rollers. They looked perfectly o.k. Then I removed the bottom plate again and looked very carefully at the place where the rollers are sited in the chassis. On each side of the chassis at this point there is a short copper strip used for electricity pickup. These strips run from the top down. They are to be placed inside the roller wheels, where they press out and rub against the inside of the wheels, this is the correct positioning. But these strips are so short that one can place the rollers in the chassis with the strips pressing against the top of the wheel. When the bottom plate is in place the roller wheels are then pressed down, only a minute bit - a fraction of a millimeter, this is all the play/tolerance there is.

With the roller wheels sited properly the wagon ran like a dream.

The problem was caused by the following (I am making some assumptions). Current pick up at the center of a point should be from the wheel flanges only, this I assume from looking closely at a point and noting how the track and the small bits of electricity conducting metal strips are placed. With the roller wheel sited properly the roller wheels ride clear of the tracks at these parts of the point. Incorrectly sited they are pressed down and as they are much much wider than the flanges, they have caused a short circuit between two parts of the point. (At some place in the point the +ve and -ve current are separated by less than a millimeter, if my assumption on how the currect flows is correct). I assume that originally one side of the roller was sited correctly and the other not, this explains why it ran with no problems one way, but with lots of problems the other.

I hope I have not been too long winded, and that this may be of some help to Z-scale users.


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