Trains.com

Subscriber & Member Login

Login, or register today to interact in our online community, comment on articles, receive our newsletter, manage your account online and more!

how can 6 wheels not be making electrical contact?

1966 views
14 replies
1 rating 2 rating 3 rating 4 rating 5 rating
  • Member since
    July 2009
  • From: lavale, md
  • 4,455 posts
how can 6 wheels not be making electrical contact?
Posted by gregc on Thursday, May 18, 2023 7:21 AM

gotta assume this is a no so uncommon problem

a club member found a spot on the layout where his 6-axle locomotive had no power.  this loco had no problem going thru the diverging route.  his other 3 locos had no problems

yes it happened to be on a switch, approximately between the points and frog.  it had power < 1/4" in either direction.

i don't thing i've ruled out it not being a short, but i believe he said when consisted, the other locos push this loco thru.  (he's an experienced modeler who notices such things)

i checked for voltage on all the track segments: points, closure rail, frog, non-diverging rail from frog and stock rail (please forgive me if i'm using the wrong names)

i tilted the near (reachable) side of the loco up, up off the stock rail, and the loco lights came on when i bridged a wheel (?) on each truck with the rail.

what could the cause of this problem be: wheel contacting the rail, pickups between the decoder and wheels, track, ???

i should have measured the voltage between the opposite rail and wheels

greg - Philadelphia & Reading / Reading

  • Member since
    April 2021
  • From: saskabush
  • 127 posts
Posted by wvgca on Thursday, May 18, 2023 7:51 AM

it -can- be a combination of several things ... assuming the track and wheels are nice and clean ....

first of all the combination of track and turnout may not be level ... all locos are not built the same and may have differing amounts of give or flexibility to conform to uneven surfaces ...

secondly if the frog is an unpowered one [at the time] there is a spot even if the wheels were touch it may not pick up power ...

 

all of the above ideas can go out the window if the track is dirty, the wheels are dirty, or if there is a poor or nonexistant contact between the loco wheelsets and the loco frame ...

  • Member since
    December 2015
  • From: Shenandoah Valley
  • 8,981 posts
Posted by BigDaddy on Thursday, May 18, 2023 8:27 AM

Seems like more than one engine would have a problem if it were track related.

I think the fact that it is good in the diverging route and bad in straight line travel means that the rotation of the truck or lateral forces are improving the electrical pathway.  I suspect the wiring coming from one or both trucks.

Same disclaimer as above about dirty track/wheels

 

Henry

COB Potomac & Northern

Shenandoah Valley

  • Member since
    March 2011
  • 1,880 posts
Posted by NVSRR on Thursday, May 18, 2023 10:24 AM

I agree. Something is going on in the contacts and wiring from the contacts to the decoder.     When you tipped it to a side to test, you might inadvertently closed the offending gaps.   Giving false impression it was ok   The rotational forces through the crossovers would be doing the same .     

shane

A pessimist sees a dark tunnel

An optimist sees the light at the end of the tunnel

A realist sees a frieght train

An engineer sees three idiots standing on the tracks stairing blankly in space

  • Member since
    November 2013
  • 2,525 posts
Posted by snjroy on Thursday, May 18, 2023 12:44 PM

The wire connections between the trucks and the circuit board of the Athearn/Genesis engines are not soldered - it's a press fit. I've seen in at least one case where this connection became loose and resulted in a power pick-up failure on one truck. I believe other makes also use the "press fit" approach to connect wires. I fixed mine by soldering all these connections. You can easily check if this is the problem by lifting one of the trucks (with the other sitting on the rail) and applying power. Each truck should power the engine independantly.

Simon

  • Member since
    December 2004
  • From: Bedford, MA, USA
  • 21,079 posts
Posted by MisterBeasley on Thursday, May 18, 2023 1:09 PM

Is the track flat and level all the way through the bad spot?  I had a spot where a big Hudson would stall, but no other locomotive.  I discovered the track was not flat and the engine would lose contact as it went up a slight incline and reached a kink where the track dipped before the wheels came back down.

In my case, I maintained power but the engine would jump the track because the wheels lost contact with the rails.

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

  • Member since
    July 2009
  • From: lavale, md
  • 4,455 posts
Posted by gregc on Thursday, May 18, 2023 2:04 PM

thanks for the comments

snjroy
I've seen in at least one case where this connection became loose and resulted in a power pick-up failure on one truck.

guessing this would be the problem if i can measure voltage on wheels on opposite side, but would need to take the shell off to see if power is reaching the decoder

MisterBeasley
Is the track flat and level all the way through the bad spot?

how would you measure flatness and is it along the rail or between the rails?

assume a straight edge can be laid on top of a rail.   have noticed Atlas frogs being slightly taller than the adjacent rails

not sure about between the rails.   then one rail could be tilted up toward the right and the other rails toward the left.    not sure if side-to-side level matters

greg - Philadelphia & Reading / Reading

  • Member since
    October 2005
  • From: Detroit, Michigan
  • 2,264 posts
Posted by Soo Line fan on Thursday, May 18, 2023 7:00 PM

What is the manufacturer / model of the locomotive having the issue?

Jim

  • Member since
    May 2020
  • 946 posts
Posted by wrench567 on Thursday, May 18, 2023 11:23 PM

    Greg.

  Just because there is voltage doesn't mean there is enough current. A bad solder joint or rail joiner too loose could have enough resistance to stall a motor. Could this be the problem? I don't think so.

   I've seen board replacement decoders where the installer reused the black plastic caps instead of soldering the wires. That's just asking for troubles later on. Without further investigation, we are just guessing.

           Pete.

  • Member since
    September 2014
  • From: 10,430’ (3,179 m)
  • 2,160 posts
Posted by jjdamnit on Friday, May 19, 2023 1:41 PM

Hello All,

You might check the wheel gauge.

I had a similar problem with a four (4) axle HO loco that has the axles pressed into the gears.

The gears were not cracked, rather the axles had been pushed too far into the gears- -narrowing the gauge.

When the loco navigated a curved turnout; either the straight or diverging route, the wheels would lose contact on the gauge sides, derail and short out the power district.

Checking the wheel gauge with an NMRA clearance gauge I discovered the wheels were too narrow.

Simply re-gauging all the wheels solved the problem.

Hope this helps.

Post Script: If the axles are press fit into the gears and the gear is cracked this could provide enough side-to-side play to cause problems when navigating turnouts. H.T.H. J.J.D.I. 

"Uhh...I didn’t know it was 'impossible' I just made it work...sorry"

  • Member since
    February 2005
  • From: Vancouver Island, BC
  • 23,297 posts
Posted by selector on Tuesday, May 23, 2023 10:39 AM

Pin down the extremities of the turnout, small holes and track nails or non-metal weights maybe on the ties.  If there is ballast, soften it.  Then, get a small screwdiver or skewer under the middle of the turnout, maybe a wee bit closer to the points and throwbar, and pry up gently, just a mm or two, with the affected engine sitting on whichever route doesn't work.  If it lights up, you have a sagging turnout, a dip. 

OR....your locomotives pickup wheels aren't able to accommodate the dip because of improper seating, missing springs if they're supposed to be there under the axles, that kind of thing.

If you set the locomotive on a shiny flat surface, say a countertop, or a handy mirror that can be laid flat on a counter, do all the drivers sit tight to the surface?  All flanges fully contacting, no daylight? 

 

  • Member since
    July 2009
  • From: lavale, md
  • 4,455 posts
Posted by gregc on Wednesday, May 24, 2023 9:13 AM

the frogs may have been dirty.   the tracks are cleaned frequently with ~6 cleaning cars using a combination of abrasive, wood and masonite pads.   but i ran a screw driver along the inside edge of the frog and it went from black to shiny.

i'm believe that the wheels primarily make contact with the inside corner of a rail, not really the top.

this still puzzle me because if the wheel on the front truck lost contact, why didn't power come from the wheels on the rear truck?

why particular locomotives?   

(if there were mine and we had time, we could take the shell off, determine which rail the decoder is not getting power from, see which wheels have track voltage and try to figure why neither truck is passing power from the wheels to the decoder

considering selectors comments, i noticed that the frog is bowed up, i can push it down, some nails can hold it down.

but its not clear to me why if the trucks can swivel slightly front-to-back and at the same time side-to-side why any rise or dip in the track should make a difference.

greg - Philadelphia & Reading / Reading

  • Member since
    March 2010
  • From: Sherwood Park, Alberta, Canada
  • 243 posts
Posted by CNR378 on Wednesday, May 24, 2023 1:53 PM

Put the locomotive on a good piece of track, hold and apply power. Put a piece of paper under the front, then the back to see if it still runs. I really suspect the pickups aren't working on one truck.

  • Member since
    July 2006
  • 294 posts
Posted by markie97 on Wednesday, June 7, 2023 6:33 PM

I had a similar problem with a Bowser 616. two of the three axles on each truck have brass pickups that weren't always making contact. I bent the brass pickups slightly so that the wheel axles would make better contact and this solved the problem. Took only a very slight bending.

Hope this helps

  • Member since
    January 2008
  • From: Big Blackfoot River
  • 2,770 posts
Posted by Geared Steam on Monday, June 12, 2023 1:53 PM

gregc

gotta assume this is a no so uncommon problem

a club member found a spot on the layout where his 6-axle locomotive had no power.  this loco had no problem going thru the diverging route.  his other 3 locos had no problems

yes it happened to be on a switch, approximately between the points and frog.  it had power < 1/4" in either direction.

i don't thing i've ruled out it not being a short, but i believe he said when consisted, the other locos push this loco thru.  (he's an experienced modeler who notices such things)

i checked for voltage on all the track segments: points, closure rail, frog, non-diverging rail from frog and stock rail (please forgive me if i'm using the wrong names)

i tilted the near (reachable) side of the loco up, up off the stock rail, and the loco lights came on when i bridged a wheel (?) on each truck with the rail.

what could the cause of this problem be: wheel contacting the rail, pickups between the decoder and wheels, track, ???

i should have measured the voltage between the opposite rail and wheels

 

What kind of turnout?  Turn off all the lights and look for sparking that might indicate a short circuit, possibly the turnout is out of spec and the wheels are shorting across both rails. I had this occur with Peco turnouts and certain locos, ended up putting nail nail polish in a small area to insulate it, worked like a charm. Had to add more as it wore off, but much easier that modifying the loco drivers or the installed turnout.  

"The true sign of intelligence is not knowledge but imagination."-Albert Einstein

http://gearedsteam.blogspot.com/

Subscriber & Member Login

Login, or register today to interact in our online community, comment on articles, receive our newsletter, manage your account online and more!

Search the Community

ADVERTISEMENT
ADVERTISEMENT
ADVERTISEMENT
Model Railroader Newsletter See all
Sign up for our FREE e-newsletter and get model railroad news in your inbox!