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Brass Behavior

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Brass Behavior
Posted by dante on Thursday, July 29, 2010 7:01 PM

I have an "old" brass Doodlebug (Erie/Susquehanna rail motor car) that I purchased ostensibly unused a little while ago.  To check its operation I lightly lubricated accessible moving motor components and insulated (with nail polish) potential points of conflict between the trucks and body parts to avoid shorts on tight curves.

It operated very well in forward and reverse when oriented in one direction.  Changing rail polarity made no difference.  When I reversed its orientation, its behavior became erratic:  smooth running interrupted by hesitations and dead stops until prodded manually.  Switching rail polarity did not help.  This behavior occurred on tangent track as well as curves and turnouts.  Note that other locos operate smoothly on the same test track.

I am befuddled as to why this should happen!  Does anyone have any suggestions regarding cause and cure?

Thanks in advance,

Dante 

  • Member since
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  • From: Red Lodge, MT
  • 893 posts
Posted by sfcouple on Thursday, July 29, 2010 7:43 PM
I recently had a similar issue that turned out to be an intermediate short between the motor and engine shell. The locomotive run perfect on the test track, but in the process of picking the engine up from the test track and placing it on my layout caused a slight movement of a part (s) resulting in an intermediate short. You may want to consider checking the nail polish insulation as this may be creating the erratic behavior you are describing. Wayne.

Modeling HO Freelance Logging Railroad.

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Posted by dante on Thursday, July 29, 2010 7:58 PM

sfcouple
I recently had a similar issue that turned out to be an intermediate short between the motor and engine shell. The locomotive run perfect on the test track, but in the process of picking the engine up from the test track and placing it on my layout caused a slight movement of a part (s) resulting in an intermediate short. You may want to consider checking the nail polish insulation as this may be creating the erratic behavior you are describing. Wayne.

 

Thanks for the suggestion, Wayne; however, what puzzles me is that the orientation on the track seems to make the difference.  When I return it to its original orientation, it runs fine again.  As for the nail polish, that is only on a couple of low stirrups and steps that touch the truck frames only on tight (18") curves.

Dante

  • Member since
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  • From: Southwest US
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Posted by tomikawaTT on Thursday, July 29, 2010 8:32 PM

I ran into the exact opposite problem with a Tenshodo JNR EF-62 (Co-Co catenary motor) model.  It would run fine with one end upgrade (my layout has very few level spots.)  If it went over a summit and started downgrade it would buck and stall - but ran just fine back up the grade, only to turn prima donna once past the summit and headed down.

Turned out I had two problems:

  1. Deteriorated neoprene flexible coupling that would buckle and stall the motor when running downgrade.
  2. Cold solder joint that would open intermittently, breaking continuity between one rail and the motor.

Having two problems at once is unusual, and complicated the troubleshooting.  Once they were corrected, that catenary motor started living up to its potential as a heavy puller.

So, check for intermittent open circuits.  They have the same effect as shorts, except that the circuit breaker will never trip off.

Chuck (Modeling Central Japan in September, 1964)

  • Member since
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  • From: Red Lodge, MT
  • 893 posts
Posted by sfcouple on Thursday, July 29, 2010 8:42 PM
Dante, An interesting problem. Unfortunately I have no experience with this Doodlebug but I'm wondering if there is something unique with this particular model that might be causing the problem? Although it sounds like some kind of electrical short it is a mystery to me why it would run normally for a while and only display these issues when the orientation on the track is changed. Sorry I couldn't be more help to you but hopefully others here may have had a similar experience and can offer some ideas for you. Good Luck. Wayne

Modeling HO Freelance Logging Railroad.

  • Member since
    June 2010
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Posted by Forty Niner on Friday, July 30, 2010 12:03 AM

This is exactly "why" ever model railroad should have voltmeter and ampmeter guages, they will tell you instantly whether or not you have a short or an "open circuit"........aka no ground.

I have seen fellows fight and fight with an engine, then finally bring it to my house in desparation, we put it on the test track and the layout and determine immediately what the problem is, then it's just a matter of tracing it down.

The guages will get you 50% of the way there everytime and I don't know how a model railroad can be effectively run without them.

Mark

  • Member since
    December 2001
  • From: Pennsylvania
  • 709 posts
Posted by nedthomas on Friday, July 30, 2010 8:06 AM

Run the Doodlebug in the dark and look for arcing or flashes of light around the trucks and bolsters. If the electrical path to the motor is via the bolsters make sure they are clean. Sometimes leaning to one side will cause loss of contact.

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Posted by rrebell on Friday, July 30, 2010 10:50 AM

You have a short that is caused by the engine slightly leaning to one side. it works on the test track because that is dead level, on your layout one rail is higher than the other, it dose not take much and a regular level would not even show it.

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Posted by 7j43k on Friday, July 30, 2010 3:17 PM
Mark has a very good point

By finding out whether you've got either a short circuit or an open circuit, you will get some useful guidance.

You can probably get by with only a voltmeter, for now. Suppose you're running the item and the voltmeter says 5 volts. When the "event" happens, either the meter will say 5 volts (or slightly higher); or it will drop to a good bit lower. The former is an "open", the latter a "short".

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Posted by tinman1 on Friday, July 30, 2010 6:12 PM

An engine that is "stalled" will exhibit a drop in voltage and a spike in amperage, which should not be confused with a short. Try placing a second engine on the tracks at the same time (if you do not own an ammeter/voltmeter) and observe both engines running. If it's a dead short, neither will run. If an open, the second engine will speed up when the first one stops. If it's a stall, the second engine will slow down as the first stops.

I had an engine that acted similarly to what you describe. The problem I had was the wire, but I could not find a nick in the insulation nor could I verify a cold joint, but a new wire took care of it.

Tom "dust is not weathering"
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Posted by dante on Friday, July 30, 2010 10:11 PM

Thank you all for your suggestions which I will pursue.  Unfortunately, I will be away for a few days, so the investigation must be deferred, but I will return to it as soon as I can.  It is a vexing problem!

Dante

  • Member since
    April 2002
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Posted by dante on Monday, August 9, 2010 10:07 PM

All's well that ends well!  As is often the case, the simplest correction is the one that works.  I believe that I tried all of your suggestions (so even those that ultimately didn't apply taught me something) with the following results:

•  No loose parts.

•  No apparent cold solder joints.

•  No problem with motor's flex coupling.

•  No sparks in the dark.

•  No short, but an apparent intermittent open circuit when facing in one direction.

•  Track not level across its width but correction made no difference (leaning vs. no-leaning).

•  Ran it in static position, upside down with leads touching motor wheels and trailing truck wheels and/or bolster screw with no problem.

•  No problem with the only two wires-jiggling them made no difference.

•  So, although all the trailing pickup truck components looked clean, I burnished all the components with emery cloth:  the bolster, the screw, the body frame, the washer, even the ends of the spring and voila-it started to work just fine, regardless of direction or orientation on the track!

•  Delighted but still puzzled by the fact that this trailing truck was a problem when facing only one way, I remembered the story about the grade issue.  My test track is dead level according to the naked eye, but I placed a level on it and found a slight-VERY SLIGHT-pitch parallel to its direction.  I find it hard to believe that this almost immeasurable grade could affect the trailing truck in such a manner but it must be so.  (The only motive power I have that had this problem on this track.)

Thanks again, everyone!

Dante 

 

 

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