I first tried removing the wheel sets and cleaning the metal internal diesel bogie side plate bearing surfaces as these are coated in something black (either chemically blackened or painted). This seemed to improve matters for a couple of years but then the problem returned.
Here is an example video of the issue, the Trainorama NSWGR 44 Class has clean wheels and the track is also clean.
After the issue returned I tried graphite powder and electrically conductive grease on the square bearing blocks and internal metal bogie side plate bearing surfaces with little change, due I think to not cleaning the bearing surfaces again..
So what is my theory?
I believe that due to the sloppy contact between the axle bearing blocks and the internal metal bogie side plate bearing surface, and also running under DCC, there has been sparking due to the higher current availability of DCC that has built up a layer of oxidised material that causes the conductivity to breakdown.
I have noticed this with diesel locomotives on other DCC layouts that get a fair bit of running as well.
I think that I have found a solution but time will tell of course.
Simply put, I have installed 0.0125" phosphor bronze pickup wires that rub on the axles, this takes the sloppy fitting bearings out of the equation.
The 0.0125" phosphor bronze wire is made by Tichy Train Group and is Product No. 1106. I bought mine from the Model Railroad Craftsman at Blacktown NSW.
The following process was done on a Trainorama NSWGR 44 Class but I have also done a Trainorama NSWGR 49 Class that is easier to remove the bogie side frames.
Removing the 44 Class bogie side frames is tricky but can be done. I used a pair of long nose pliers that have smooth jaws. I had previously used long nose pliers with serrations but they don't work. The smooth faces allow the small clips on the bogie to release where as the serrated jaws hold the clips so that they can't release. Place the locomotive upside down on a soft surface. There are four sets of small clips in the bogie side frame keeper plate in small cut outs. Place the ends of the pliers jaws into the cutouts on either side and squeeze. At the same time place a small screwdriver under the end of the keeper plate and lever against the chassis coupler mounting. With luck you will get the first clips to release and then work along the clips to the other end. Once you have done it the first time it is easier to do the next bogie. Yes, this is a three handed job.
The pick up wires are made by bending an angle of about 45 degrees on the end of the 0.0125" phosphor bronze wire and trim to no more than 4 mm. Make another similar bend in the same plane 52 mm along the wire and trim again to approximately 4 mm.
|Bogie and Pick Up Wire Ready to be Installed|
|Fine Black Decoder Wire soldered to the Pick Up Wire and the Bogie Side Plate|
The pick up wire is placed between the rear of the wheel and the bearing block on the axle. then it is first hooked over one of the outer end axles then under the middle axle and then over the other end axle. This over, under, over placement holds the pick up wire in place.
|Pick Up Wires In Place on the Bogie|
And here is the result, note that this is a different 44 Class that had the pick ups fitted than 4434 in the first video, it is next for the treatment.
EDIT: Please note that neither of these two locomotives are fitted with a Keep Alive. I doubt that a Keep Alive would resolve the issue as it would become discharged with the intermittent pickup.
I have recently found some Rosin Soldering Flux at JayCar Electronics which has very little corrosive qualities so clean up is not really necessary. I have always used rosin fluxes for all my model soldering due to the lack of corrosion. Some fluxes need to be cleaned off thoroughly otherwise corrosion will set in over the years and destroy the solder joint. I find that soldering wires needs no cleanup but if I am soldering an etched brass kit then I will use some Methylated Spirits on a pipe cleaner to remove any trace of flux.
|Rosin Soldering Flux|