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2 of 12 locos short on mainline curve - why?

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  • Member since
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  • From: Moneta, VA USA
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2 of 12 locos short on mainline curve - why?
Posted by gdelmoro on Monday, June 8, 2020 11:23 AM

Can't figure this one out.

I have 14 HO Locomotives. Twelve of them (BLI, Athearn, Atlas, Bachmann and Rapido) have no problems in either direction on this newly installed 30" radius curve.

Track is in NMRA gauge and the fast-tracks gauge fits easily around the curve. 

Track is level in both directions.

1st loco = BLI Paragon 3 SD9, six axle.

2nd loco Atheran F3 A-B both powered with LOK Sound decoders in consist) four axle. 

The locos behave the exact same, start, go about a foot or two, trip the mainline breaker then after the breaker resets start again and repeat this.

 What makes this even more frustrating is they run fine on the rest of the layout on 30, 28, and 26" curves. 

Any ideas?

Gary

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Posted by rrebell on Monday, June 8, 2020 11:30 AM

Gauge of the wheels is slightly off I would guess.

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Posted by MisterBeasley on Monday, June 8, 2020 11:57 AM

Is this curve anything but track?  Any turnouts, guardrails?  Is there an insulated block, like for train detection and signalling?  How recently did you lay this track?  Is it part of a reverse loop or protected by a secondary circuit breaker?

If nothing else, closely examine the engines.  Fine pieces of wire or even track spikes could be stuck in the trucks, or there could be a single strand of loose wire, so remove the shell and check that carefully, too.  Remember, too, that two different engines could have two different problems.

It takes an iron man to play with a toy iron horse. 

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Posted by BigDaddy on Monday, June 8, 2020 12:05 PM

rrebell
Gauge of the wheels is slightly off I would guess.

If they don't derail, how would this cause short?  If they do derail, why doesn't it happen anywhere else.  Derail or not, why only one particular curve?

Henry

COB Potomac & Northern

Shenandoah Valley

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Posted by BATMAN on Monday, June 8, 2020 12:34 PM

I finally found that Kadee truck spring once it had caused a short and it had been missing for a long time. I had looked and looked for it.

Brent

"All of the world's problems are the result of the difference between how we think and how the world works."

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Posted by rrebell on Monday, June 8, 2020 12:44 PM

BigDaddy

 

 
rrebell
Gauge of the wheels is slightly off I would guess.

 

If they don't derail, how would this cause short?  If they do derail, why doesn't it happen anywhere else.  Derail or not, why only one particular curve?

 

Because it is just enough to squese against the rails causing a misinterptation of a short. Guages are great but they have their limitataions. Had this happen on DC once on a curve (not the same result but you get the jest). The electronics on DCC on on the lookout for very small shorts and the squeese could get two polls to be close enough to arch a short but not enough to shut down the power. And wiskers do grow in electronics.

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Posted by Wolf359 on Monday, June 8, 2020 1:02 PM

The fact that these two locos short on the same spot every time would suggest a track issue in my opinion, and that these two engines are particularly sensitive to it. I know most Athearns have an electrically hot frame, and I would guess that the BLI does as well. I know you said that the track is level in both directions, but have you checked any and all joints for a sudden dip or rise that may have escaped detection and might make these engines bottom out on one or two of their own wheels? I ask this as I have had it happen before. Check the underside of these locos for signs of the wheel flanges scraping the frame. If you find damaged paint anywhere the wheels could possibly scrape, then that's likely your problem.

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Posted by woodone on Monday, June 8, 2020 1:15 PM

Is it possible that you have one or more 1/2 axle wheel sets that are touching in the middle. The curve might be jut enough to move the 1/2 axle against the other and short-has soon has you remove there is no pressure on the 1/2 axle so the short goes away- same for running on a straight section/the curve you are having problems with-is it in gauge?
a slight tight section? Have seen 1/2 axle shorts make you pull your hair.

 

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Posted by selector on Monday, June 8, 2020 1:23 PM

It can't be the tracks.  They work fine electrically, and they work on most of your locomotives.  So, for me, there's something about the swivel/movement of trucks or axles, maybe on the pickup wires making contact and shorting across them...not sure, but the tracks are good.

Don't overlook Brent's post.

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Posted by gdelmoro on Tuesday, June 9, 2020 5:39 AM

Thanks all, no derails and no turnouts in this area. 

I'll check wheel gauge, vacuum track and look closely for debris.

another thing i noticed yesterday is that when it happens part of the train is in the yard which is a separate CB protected district. Could that have any impact? Rolling stock all have metal wheels And Kadee couplers.

Gary

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Posted by richhotrain on Tuesday, June 9, 2020 6:10 AM

gdelmoro

another thing i noticed yesterday is that when it happens part of the train is in the yard which is a separate CB protected district. Could that have any impact?  

Sure it could. 

Gary, how sure are you that this only happens with 2 of your 14 locos. Sounds like a short which should affect all of the locos, not just two of them.

Also, you mention that "part of the train is in the yard". This implies that there is rolling stock connected to the loco. What happens if you only run the loco through this track area?

Rich

Alton Junction

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Posted by wrench567 on Tuesday, June 9, 2020 6:37 AM

Gary.

 Newly ballasted section? I made the mistake of using screened sand once. Even dry anything with a dose of heavy electrical draw would trip the breaker. I had to tear it all out and start over. I failed to run a magnet through the sand first. I poured some into a plastic bottle with a neodimion magnet. That magnet looked like it had a shag carpet on it after just rolling the bottle back and forth.

  Check your feeders. You may have introduced a reversing section or a crossed over feeders.

    Pete.

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Posted by rrinker on Tuesday, June 9, 2020 9:11 AM

 Try to narrow down the exact spot - run the locos at a creep when close to the area the short occurs and carefully look at the wheels and track to see if yoou see anything. This may take several attempts to find the issue, a particular wheel, or the couplers, or whatever it is. Slow methodical troubleshooting is usually best.

Wheels out of gauge would not cause a short, they might cause a derailment and then a short because of that, but if the wheels were out of gauge enough so that the left wheel could touch the right rail on a plain 30" radius curve, it wouldn;t run on straight track. Too close together could have the stub axles touching inside, but that would cause a short either all the time or any time it went around a curve and the wheels got pushed closer together. And probably derail at every turnout.

 Loose wire or something touching when the trucks swivel seems unlikely as well, if the same locos can negotiate sharper curves just fine.

                            --Randy


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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Posted by gdelmoro on Tuesday, June 9, 2020 9:14 AM

Problem solved -you can't make this stuff up! Thanks to all who replied. 

Same two locos having the problem. Their tolerances must be tighter and more sensitive. 

there were three problems causing the shorting.

1) it seems that one of the turnouts exiting the yard (one I "salvaged" from the old layout) Confused had a loose point rail that was contacting the back of the six axle wheels.

2) There was about a 1" section of black crud on the curve. I thought it was clean because I had run my CMX car around about 5 times. Every time these locos hit this spot,it must have lifted the heels just enough to cause a spark/short. 

3) the same turnout with the loose point rail had the tortoise wire just slightly too high for one of the two locomotives causing the wheels to move toward the loose rail.

I temporarily fixed the turnout by supergluing the rail and cutting down the tortoise wire. New turnout ordered. Track mannually cleaned.

Luckly I took Rich's advise and did not do any scenery until all track was laid and tested so the turnout replacement wil be easy.

Gary

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Posted by richhotrain on Tuesday, June 9, 2020 3:18 PM

gdelmoro

Problem solved -you can't make this stuff up! 

YesYesYesYesYes

Alton Junction

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