Page 20 - May June 2010

Extra Pickups for Brass Locos
It no longer surprises me to be working on older brass locos with insufficient wheels picking up current, usually two­truck loggers which only use one truck (two wheels) for each polarity. I fre­ quently add extra pickups to the insulated wheels, and I find it transforms the loco, especially on complex trackwork. DCC users will know this is even more important, as a break in current col­ lection can cause all sorts of odd problems.
However it was a surprise to find that an expensive modern model came with a similar failing. The Overland Big Blow turbine is a superb mechanism in all other ways but picked up from three wheels per rail only. The second unit and tender are unpowered and do not pick up power at all. The rather PA­like lead unit, fitted with two linked Mashima 1833 flat cans, and driving each axle through its own helical gearbox, would be an excellent performer but at slow speed, even on clean straight track, could occasionally stutter and in some cases stop. Lack of pickup was the only cause.
Oddly, the manufacturer had fitted wipers to one side of each truck, but these rubbed on wheels that were already collecting! It seems the makers might have thought this would enhance those wheels’ performance, and that otherwise the current would have to flow from wheel, through axle,
bearings and gearbox, into the centre gearbox casting, from which a wire went to the motor. But each wheel on the wiper side picked up current perfectly well when the wiper was not in contact with it, including the centre wheel which had no wiper at all! Anyway, I felt that the model deserved to have even the minor problems of power pickup overcome.
One way would be to use collec­ tors on the B unit wheels, but this would involve wiring between the units – not a big problem if a miniature two­pin connector is used, but I decided to keep all the extra collection “in house”, on the A unit. As this style of mechanism is used in a lot of Overland diesels, this fix could benefit quite a few other models.
The body removes very simply – four small screws, one in each corner of the chassis. Because of the provision of separate gear­
The Editor
boxes for each axle, there is no central “body” to the truck, and thus no keeper plate for it. I decided the easiest place to mount the pickup was on the underside of the centre gearbox, which has a small blackened cover like a miniature keeper plate.
Thin P/C board was cut to 1/8" × 3/8". This particular board is only about 1/16" thick and is metalled both sides.
The surfaces were cleaned, one side was roughened and the other side tinned. The gearbox cover was gently cleaned and roughened too, where the P/C board would be attached. The board was fixed with a small blob of Superglue Gel. It seems to be a very tough bond, but if you worry a lot you can use a small dob of old­ fashioned slow­setting Araldite instead. Leave it to set for 24 hours before continu­ ing, and it would be almost as tough as a weld!
Meanwhile, a suitable springy brass wire
is shaped and cut to length as per the sketch. A black, very flexible thin multi­strand wire is used to make the circuit. At the truck end I stripped about 1⁄4" of insulation, wound the wire several times closely around the centre of the pickup brass wire and soldered it there. Then this “joint” is placed on the tinned P/C board and soldered in place. All that needs doing after that is to gently adjust the wire pickups for correct placement and pressure against the back of the wheels. Make sure it can’t touch the axle or truck metalwork, and
is not to low, ie not too near the railhead.
Now the black wire is fed up through the truck and chassis spaces, and connected into the motor wiring. The easiest place for this is where the original wiring is soldered­tagged to the top of the centre gearbox castings. Each of your new pickup wires will of course go to the tag on the opposite truck.
Repeat the whole operation for the second truck. I then used some adhesive tape to keep the wires tidily secured on top of the motors.
Test the chassis then finally replace the bodyshell. I now found the loco ran smoothly at the slowest possible speed, without feedback switched on, and without the slightest hesitation.
20 ROUNDHOUSE