# Locomotive internal wiring diagram



## nealt (Jan 22, 2015)

I was looking at some HO track plans from the 1998 to 2012 time period. They shoe joiners at various locations on one side of the track. I was wondering how locomotives with multiple trucks are wired i.e which wheels are active pickup and which are insulated? It seems to me that with some wiring solutions the locomotive could stall or short especially near turnouts.


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## 400E Blue Comet (Jul 11, 2014)

Could you take a picture of the locomotive you're asking about? Generally cheap HO diesels with multiple trucks have a motor in one of the trucks, with just one side having metal wheels, while the other truck has contact wheels on the opposite side. Sometimes the motor can be in the front or back, but good ones can have two motors. I've noticed on some of my diesels that both sides of one or all trucks have metal wheels, and there's contacts on each side touching the wheels, so I suppose they can be wired like that too.


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## mikek (Dec 29, 2013)

Nealt is a new poster, so I'll just list basics. Track polarity stays the same, even through switches.
Locos and tenders have one pole (positive) on one side, throughout the set, and the other pole (negative) on the other side. Some locos have both poles on the loco, some depend on the tender to supply the opposite pole. Lit cars supply their own power, usually using one truck for one pole, the other truck for the other pole for lighting the coach. That keeps it simple, since manufacturers make wheelsets with one wheel insulated from the axle. Power comes from the track to the wheel, to the axle, to the truck or a pickup that rubs on the wheel or the axle.


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## nealt (Jan 22, 2015)

Take a look at the attached diagram. The heave arrows are insulated rail joiners. There would be a short without them as the polarity of the inner rail changes when it meets the outer loop. There is power supplied to the rails of this insulated section. Depending on the loco wheel power pickup arrangement and the length between the trucks there could be a short or dead area as the loco passes over this section.


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## traction fan (Oct 5, 2014)

*Insulated rail joiners, placement?*

Nealt;

Saw your track plan with the big arrows. It looks like the insulated joiners are staggered.
Normally; they are directly opposite each other. This would hold off any possible short until the loco got right to the insulated joint, and make loco pick up arrangement irrelevant. Can you explain why the insulated joints are not directly opposite each other?

Traction Fan


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## nealt (Jan 22, 2015)

No. I just copied it from a Model Railroader book I got from the library.


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## DonR (Oct 18, 2012)

I agree with NealT.

That section is isolated obviously because it becomes a 'reverse loop'
in need of a controller.

However, the staggered insulated joiners would cause a short circuit
when the front wheel pair shorted and caused the 'reverse loop controller'
to invert the phasing (polarity) which would again be shorted by
the rear pair of wheels.

The insulated joiners should be directly opposite each other. I can
think of no advantage to stagger them. Even if the insulators are
'protecting' a block, they should be even, not staggered.

Don


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## CTValleyRR (Jul 26, 2014)

I wonder if the big / small arrows would indicate "primary" location for the joiner pair, and the smaller ones an alternate location. It certainly wouldn't run as shown if the arrows indicated the joiner locations.


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## nealt (Jan 22, 2015)

They are curved terminal tracks. This was an EZtrack layout. see attachment.


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## DonR (Oct 18, 2012)

nealt said:


> I was looking at some HO track plans from the 1998 to 2012 time period. They shoe joiners at various locations on one side of the track. I was wondering how locomotives with multiple trucks are wired i.e which wheels are active pickup and which are insulated? It seems to me that with some wiring solutions the locomotive could stall or short especially near turnouts.


Most contemporary HO locomotives use all wheel power pickup. That means
that there are wipers against all wheels on each side of the locomotive (or
tender in the case of Steamers). Anything less than that will invariably run into
insulated frogs at turnouts and crossings that will pause or stop a loco.
The wheels on one side of the trucks have tiny insulators where they connect
to the axle to make this possible.

I am currently trying to upgrade an old Mehano SW-1 for a friend. It came from
the Yugo factory with only unpowered rear truck power pickup, tho there were
slots in the powered truck for wipers. I added them to get all wheel power.
It would not have made it around the layout as originally produced.

Wipers can be added to most car and loco truck wheels for better power
pickup.

Don


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## DonR (Oct 18, 2012)

As to those 'staggered' insulated joiners in the layout drawing:

In another thread there has been a discussion where
an experienced train guy recommended staggering the
insulated gaps by a quarter inch or so. The OP was
experiencing shorting using his Bachmann Dynamis
system and Bachmann reverse loop controller. The OP
claims that using the staggered joints his shorting
problem was resolved. 

Something to be considered if a rare combination
of factors results in shorting at Reverse loop gaps.

Don


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## CTValleyRR (Jul 26, 2014)

nealt said:


> They are curved terminal tracks. This was an EZtrack layout. see attachment.


I did see the attachment. It is not intuitively obvious that it is an EZ Track layout, nor that the pieces in question are curved terminal tracks. And it is my experience that just because you copied a layout from a book or on-line plan, that is no guarantee that it actually works.

I was speculating that perhaps the small arrows meant something different, as they are not obviously located at a track joint, whereas the larger arrows are.

Looking back, I see that, if the track in the upper part of the reversing section is in fact a terminal track, is the input to this section wired through a reversing loop controller, and is there another terminal track outside the picture you posted, for the rest of the track?


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