Locomotive Rewiring Tips:
Adding All Wheel Pickup
to an HO Diesel

I have an old brass Alco diesel switcher that has been converted to DCC. However, it stalls on every turnout. The reason is that it was designed to use the front truck's axle to pick up from the right rail and the rear truck's axle and wheel on the opposite side to pick up from the left rail, ie, the wheels on the opposing sides of each truck are insulated and are therefore "dead". If the engine passes over a "dead", insulated frog on a turnout it loses pickup. To solve the problem it is necessary to find a way to add pickup wiring to the insulated wheels and connect that wiring to the correct side. An additional challenge is that the motor must remain insluated from the wheels and frame for DCC.

Bill Payne, a model railroader friend and member of our Nottawasaga Model Railway club is a whiz at mechanical and electrical jobs like this. He taught me how to install phosphor bronze wires to act as additional pickups, thus turning the diesel into an all wheel pickup locomotive. Follow along as we explain the locomotive rewiring procedure.

Cover plate and one axle removed.
locomotive rewiring axle removal

The first step is to put the engine chassis in a soft cradle or on the foam from the box and remove the coverr plate from one truck as well as one axle. Note the orientation of the axle and wheels to check which side is picking up power and which is the "live" wheel.  Always place the trucks on the benchtop in the same position as they were on the engine so that you can keep track of the left and right sides. It is easy to mix them up. When in doubt, recheck with a meter set on continuity. Phosphor bronze wire is very flexible and solders easily. You may have to special order it through your local hobby shop becaue it may be difficult to find. Bill had a length of it from other projects. We cut off a couple of pieces from his stock of phosphor bronze wire.

The original pickup wiper wire
locomotive rewiring original pickup

The idea is to cut a length of wire long enough to rub against the wheel tread or the back of the metal wheel. Both solutions are acceptable. Many newer locomotives have contacts rubbing against the back of the wheel. (This is also where dirt and hair can collect. If you have all wheel pickup and it seems to have disappeared, this is the first place to check.) Bill eyeballed the length and cut the wire slightly long. You can also measure it! There is some play here so a precise length is not necessary. To be safe cut it slightly long. You can always shorten it.

The wire will rub against wheel
locomotive rewiring bending phosphor bronze wire

Isolating the pickup wire

This is vital. We used a small square of thin circuit board. 

Bending and cutting phosphor bronze wire
locomotive rewiring soldering phosphor bronze wire

We mixed up a bit of 5-minute epoxy and epoxied the pad to the underside of the truck frame's metal bolster. Check to ensure clearance above the track if attaching to the underside of the bolster. Sometimes it is better to attach the pad to the top side. it depends on the thickness of the pad. Fortunately we had a very thin piece of double-sided circuit board. The epoxy helps to keep the edges from touching the metal bolster. Before the glue has totally set check the isolation from the bolster with a metre and then let the epoxy cure.


Soldering the contact wire
to the pad.
locomotive rewiring contact wire

The phosphor bronze wire is now soldered to the pad. Be careful to ensure that the wire is parallel to the wheels when the axle is reset in the frame. You can bend the wire a bit more to make it align properly.

Add red pickup wire to the pad
locomotive rewiring soldering pickup wire closeup

The tricky part is to now solder a wire to the pad to route power from the wheels to the decoder. You need to be fast so as not to unsolder the phosphor bronze wire. You could use different temperature solders but we didn't. If the wire is pre-tinned and the pad was pre-tinned with a little coating of solder you should be able to do make the joint quickly. It is a good idea to retain the same colour of wires throughout the project: red wires for the engineer's side (usually right rail) and black for the other side. You want to correspond with the red and black pickup wires on the decoder harness. This is still a good idea even if you're just doing locomotive rewiring for DC. It helps to avoid shorts! Remember that each truck will have a red and black wire on opposite sides.  If you keep with the original convention the front truck will be the reverse of the back truck. Of course, you could put all the red wires on one side and all the black wires on the other side. It's up to you. If you decide to do the latter then make sure that all the insulated wheels are on the same side.

All wires soldered
locomotive rewiring all wires

Here you see all the wires soldered in place. The new contact phosphor bronze wires are shiny. The original wires are dark.

You can make out the red wire that goes to the decoder. You have to find a good path up through the chassis that won't get tangled with the motor shaft or flywheel if there's one installed. Try taping it to the chassis or roof to keep it out of the way. It can be spliced into the existing wire going to the decoder. Use a piece of shrink wrap tubing or electrical tape to isolate the splice connection. Here is a top down view of one side of the frame.

Top down view of side frame
locomotive rewiring top down view of side frame

Finally, here is a truck fully reassembled without cover plate. You can barely see the red wire at the top of the photo and the phosphor bronze wire extending to rub on both insulated wheels. 

Assembled truck
locomotive rewiring assembled truck

After we put the locomotive back together we checked it on the programming track to make sure we didn't have a short. Then we put it on the track and confirmed we had all wheel pickup by lifting up one end of the engine off the track and then the other end. All was well.  Except...

Split delrin spur gear!
cracked spur gear

As I said at the start, this was an OLD locomotive. Somewhere along during the locomotive rewiring project the two delrin spur gears cracked. This can happen to anyone at any time and had nothing to do with the locomotive rewiring. Electrically the diesel works fine. We tried to use AC glue to stop the spur gears from slipping but they still cogged and jammed at the crack. Oh well, that is now another project. We have to see if we can find replacement parts from North West Shortline or from some other source and rebuild the gearing. I'll put together another page when we figure that out.



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