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Sherlock Holmes: The Case of the Isolated Short - Solved!

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Posted by 7j43k on Sunday, September 9, 2018 12:31 PM

gmpullman

...black nail polish! *

*Don't worry about the looks you get from the cashier. Just tell her it is for modeling. She'll understand Confused

 

 

 

Yes.  I've seen photos of both female and male models wearing black nail polish.  

It's a different kind of look, but go for it!

 

Ed

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Posted by 7j43k on Sunday, September 9, 2018 12:29 PM

I added a two-wheel front pilot truck to my 0-6-0T.  No springs or added weight.  It worked fine.

If your truck works fine, as is, why mess with something that's working?

 

Ed

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  • From: Vancouver Island, BC
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Posted by selector on Sunday, September 9, 2018 12:04 PM

I have intentionally mangled more than one BLI drawbar in order to keep it from sliding over an axle or frame member of the truck, or against the bottom of the cab, or against the closest axle if there are more than one in the truck.  If memory serves, the original P1 Niagara and the PCM Y6b were up to some bending at least once.  However, only had to do that process the one time.  Thereafter, it always worked reliably.

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Posted by selector on Sunday, September 9, 2018 12:00 PM

Tom, I am happy for you.  You must really appreciate this fine item, and you were keen to see it cured.  Good work.

I sometimes wonder if a spring could be trimmed.  Snip off a coil or four, and see if that suffices (and actually yields a noticable improvement) and yet doesn't cause new problems.

Even so, if that front truck has a lot of play laterally and vertically, you'd need some real speed and some nasty joints, curved track or no, to get that truck to lift its wheels and flanges clear of the rails...no?  Or substantially uneven heights transversely across the rails.  Poorly executed superelevation would also possibly not help.  But the image shows a well-leveraged truck whose single axle would want to fall easily with gravity that far from the pivot point, especially with all that brass weighting it.

-Crandell

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  • From: Collinwood, Ohio, USA
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Posted by gmpullman on Saturday, September 8, 2018 11:55 PM

More than once, I've gone to the great photo repository at Brass Trains where you can find photos of every angle (almost) just to confirm how your locomotive compares to other examples.

If you look through this group you can see that this example pretty much matches what you have: (zoom or go to full screen).

https://www.brasstrains.com/BrassGuide/Pdg/Detail/23496/HO-Steam-Overland-Models-1453-New-York-Central-2-8-2-H-10B

I agree with Wayne that a little lead or tungsten putty inside that box enclosure might be some added insurance.

I'm presently working on a Westside B&O 2-8-2. The pilot wheels have no additional springs or weights and is, in fact, a bit skinnier than your assembly. My LMB H-10 Mike does have a tension spring attached to the frame.

https://www.brasstrains.com/BrassGuide/Pdg/Detail/23498/HO-Steam-L-M-Blum-Models-New-York-Central-2-8-2-H-10B-MIKADO

 

If it ain't broke... but keep in mind that you can add weight if it gives you trouble down the road.

Fun Stuff, Ed

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Posted by tstage on Saturday, September 8, 2018 11:54 PM

It's tracking just fine, Wayne.  The locomotive came with a cylinder-shaped lead weight that I will be installing soon.  My NJCB 0-10-0 switcher came with the exact same-size weight that's held in by a screw and it probably added an additional pound over the front drivers.  Wow! - Talk about tractive power! Surprise

Tom

https://tstage9.wixsite.com/nyc-modeling

Time...It marches on...without ever turning around to see if anyone is even keeping in step.

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Posted by doctorwayne on Saturday, September 8, 2018 11:24 PM

Not much room there for a spring, Tom, but you could add some lead into that lead truck's frame if it's not tracking well.

Wayne

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Posted by tstage on Saturday, September 8, 2018 11:17 PM

Having said the above, here's a mystery that I'm still trying to figure out.  The front truck on my OMI brass 2-8-2 Mike doesn't come with a compression spring to keep the truck pressed against the track:

I'm not experiencing any derailments.  However, is this normal for brass stream locomotives with front trucks?  (My other two brass steamers are switchers and don't have either front or rear trucks.)  Are sprung front trucks only generally found on plastic steam locomotives because brass steam locomotives are heavier?

There are two smallish springs that came in the OMI box with other detail parts but there's nothing included to say what they are all for. The springs is about the same OD as the screw in the middle of the above photo - maybe slightly larger.  Or, is this something I even need to be concerned with if the locomotive is tracking properly?

Thanks,

Tom

https://tstage9.wixsite.com/nyc-modeling

Time...It marches on...without ever turning around to see if anyone is even keeping in step.

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  • From: Collinwood, Ohio, USA
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Posted by gmpullman on Saturday, September 8, 2018 11:13 PM

I feel your pain, Tom! Welcome to one of the idiosyncrasies of brass.

One time I had a locomotive with a four wheel engine truck and finally narrowed down the pilot wheels as the culprit. As it turns out the original, thin fiber washers (as insulators) were missing from behin the wheel face causing a short to the stamped brass engine truck frame. Cab handrails touching tender parts are another common place.

I've used your kapton tape cure several times, too. That and black nail polish! *

*Don't worry about the looks you get from the cashier. Just tell her it is for modeling. She'll understand Confused

In DC days you could get away with minor intermittent shorts. Not so with DCC and even the stay alive won't help much since the short dumps anything the cap might be holding.

Might be worthwhile to build a database of "tracking down shorts — where to look" for handy reference.

Glad you're on your way!

Regards, Ed

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Sherlock Holmes: The Case of the Isolated Short - Solved!
Posted by tstage on Saturday, September 8, 2018 10:29 PM

I just spent the past 2 hours isolating a short on a brass 2-8-2 heavy Mike I picked up a few weeks ago.  The locomotive did fine on straight sections of track on my temporary layout but shorted on the R22" curves.

I first noted that the front trucks sparked so I isolated the wheels from the underside of the frame with two strips of Kapton tape.  While that eliminated the sparking, the locomotive still hesitated in certain spots on the curves and the MRC power supply definitely showed a short.

I next removed the front truck to see if that improved matters - it didn't.  I then removed the rear truck* and - voila! - the shorting went away.  Aha!  So the rear truck must be the culprit.  Just to be absolutely sure though, I re-installed the front truck and...there was NO shorting. Yes

*[I must say that a heavy Mike with both the front & rear trucks removed sure makes for one rugged-looking 0-8-0 yard switcher. Big Smile]

Now that I had isolated the short to the rear truck, I needed to find out exactly where the short was located.  After pushing down on the cab roof slightly, I found that I could get the locomotive to consistently short.  I surmised that the clearance between the rear truck and the underside of the cab was small enough that any slight vertical movement caused the two to contact one another.  Upon further investigation I found that the spring/screw combination that secures the coupler bar to the underside of the cab, as well as providing the electrical path from the tender to the drivers, was what was shorting to the top side of the rear truck.

The E-Z track is laying on carpet so it undulates slightly but noticeably at the track joints; more on the curved sections than the straight sections.  That would explain why the shorting primarily occurred on the curve sections.  Thankfully, the remedy was another piece of Kapton tape on the top of the rear truck bracket and now my brass 2-8-2 heavy Mike runs without a hitch...er, without shorting.

While these sorts of scenarios can be frustrating to diagnose, it is gratifying when you are able to figure it out by the process of elimination.

Tom

https://tstage9.wixsite.com/nyc-modeling

Time...It marches on...without ever turning around to see if anyone is even keeping in step.

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