How to add wire from tender roller to locomotive

I assume you just want to wire "hot"- center rail- to use an additional roller/contactor.   You could use a single-pin male and female receptacle, attaching the receptacle in the cab of the locomotive (better hidden). You want the smallest size wire for appearance reasons.

You should be concerned about ampacity- the ampere load that the wire and connectors can safely handle.  Wire ratings are based NOT on what the wire itself will handle but on what the insulation will take as the heat in the wire increases from overload.  This can happen almost instantly due to a derailment, voltage spike etc.  The wiring used on model trains is generally 18 - 16 AWG (gauge), and the circuit breakers  (on transformers) generally 10 amps, so the transformer breakers will trip at 10 amps overload. (Your locomotives will generally draw about 1- 2 amps in normal operation.)

Ampacity ratings- vinyl and nylon insulated wire and terminals (enclosed = insulated):

AWG              Rating max amperes

22                      5

20                     7.5

18                     10  Based on above the min. should 18 AWG wire and connectors

16                      13

14                      17

You could also use high temperature wire and terminals which use a higher temp resistant insulation, and therefore have a higher amp rating.  But the terminals will be harder to find.

I use #22 wire for my one-wire tethers.  I use heatshrink and machine-pins to make them.  MTH and Lionel locomotives are all wired with #22 wire for power.  The only time I've ever seen a heavier gauge wire in a locomotive is the extra ground that MTH included in some DCS steam that was added because of flickering lights.

The wire ratings mean very little here, that rating is for sustained use.  The tether between the locomotive and tender are only going to have any significant current flowing for brief periods of time.

Here's the raw material for the tethers.

Thank you for the reply.  The next issue is from where to purchase the pickup assembly.  I tried MTH parts and they do not have any pickup rollers.  I also tried an internet search with no results.  Any ideas from whom to purchase the pickup roller assembly??

Lionel usually has a variety of pickup rollers available on their parts site (you just missed their 50% off parts sale a couple weeks ago).

The trick is mounting it on the truck of your desired choice where it won't come in contact with any ground source, and finding one that'll have a good profile. Some trucks can be very easy to mount a roller to with the right roller. 3D printing has helped many with this, but for those who don't have one at their ready disposal tend to resort to alternative methods.

@waterlevel posted:

Thank you for the reply.  The next issue is from where to purchase the pickup assembly.  I tried MTH parts and they do not have any pickup rollers.  I also tried an internet search with no results.  Any ideas from whom to purchase the pickup roller assembly??

MTH Parts has a couple dozen pickup roller assemblies in stock. Here is a search for "pick up" I did on their web site.  Click the switch at the top to Show in Stock Only.  There are a couple dozen pick up rollers.  Scroll down on the search to listings that start with pick up.  Click on the little camera to see a picture.  BTW, if you are searching on Lionel's website, use the search term "collector".

Bob

@waterlevel posted:

Thank you for the reply.  The next issue is from where to purchase the pickup assembly.  I tried MTH parts and they do not have any pickup rollers.  I also tried an internet search with no results.  Any ideas from whom to purchase the pickup roller assembly??

Of course MTH has rollers.  Truthfully, the most common roller I use is the BD-0000042, it's short and fits easily between most tender axles.

Here's a whole page of in-stock MTH pickup rollers!

https://www.mthpartsandsales.c...00000&in_stock=1