A little TLC for an older loco...

[doctorwayne]

Recently, a friend asked if I would look at a newly acquired loco to see why it wouldn't run consistently - sometimes it wouldn't run at all, other times it would run a short distance, then stop suddenly, and on some other occasions it would run, then slow and finally stop, with the current draw increasing as it slowed. Control, like my own locos, is DC.
The loco was this Japanese-made brass 0-8-0 from United. I searched on-line for more info about the loco's background, but found nothing to indicate if it's a model of a particular prototype or strictly a free-lance creation.


The model appeared to be very well-built, with generally solid solder joints and most of the valve gear put together using screws rather than rivets. The few loose solder joints appeared to be from rough handling by a previous owner. It ran on my short test track, but locked-up after a couple of short back-and-forth movements. There seemed to be interference between some parts of the valve gear and the main rod, and some judicious poking with tweezers located the problem area.
Upon disassembly, the first thing I noticed was that the wire connecting the drawbar to the original open-frame motor was not only #16 gauge, but also that it was solid (not stranded) wire. Even slight contact with the wire lifted the brush to which it was soldered from the motor's commutator, so it was possible that re-installing the boiler onto the mechanism would have a similar effect. I changed this out for some smaller gauge stranded wire, then placed it back on the track, only to have it run, then lock-up again. Time to find the bind in the valve gear/side rods.
I soon discovered that the problem lay with the reverse link: it connects the eccentric rod to the rest of the valve gear. I forgot to take a specific photo of the problem area, but in the photo above, the eccentric rod is the smaller of the two extending forward from the third driver, while the reverse link is the vertical part to which its forward end is connected. It's mounted on a shaft within the valve gear hanger, along with another part, but both parts have enough room on the shaft that they can move laterally (inboard or outboard) in addition to pivoting. Because the shaft is the un-threaded portion of a screw, it was a simple matter to remove the screws (both sides of the loco) in order to insert a spacer which would prevent these parts from moving too far inboard, where they could be struck by the moving main drive rod. Because the valve gear parts are quite small, I didn't have a small enough, yet thick enough washer to do the job, so used a very short length of 1/16" brass tubing. Before cutting off the needed lengths (about .060"), I first drilled out the end of the tubing with a #55 bit to allow clearance for the screw threads. The tubing was then cut with a #11 blade in my X-Acto knife - simply place the blade in the appropriate spot, then, working on a hard and smooth surface and while applying moderately-light pressure, roll the tubing back and forth a couple of times. Remember to cover the part being cut off, as it will otherwise fly away.
After re-assembling the valve gear, I clipped power leads to the motor then ran the loco while holding it in my hand. This allowed me to turn the mechanism on its side, and thereby allow gravity to move the parts laterally within the valve gear hanger. This showed that there was no longer any interference, even at the extremities of the lateral movement.

An inspection of the running gear showed it to be in generally good condition, although rather dirty from over-lubrication and accumulations of fine brass particles, the latter evidently from filing or using a cut-off disc. Because of this, I decided to do a thorough cleaning, necessitating a more complete teardown. With the motor removed, the gearbox was removed, then coverplate was removed from the bottom of the frame, allowing the drivers to be dropped. Next, the valve gear hanger was was unscrewed from the top of frame, and by lifting it clear, the frame was withdrawn from between it and the drivers. When I had dis-assembled the gearbox, an examination of the worm gear (it's also the axle gear, and the only gear, other than the worm, being used) I noticed that there was hardened grease between most of the teeth on one side, probably as a result of having sat for a long time without being operated. It was so hard that I had to use the backside of a #11 blade to scrape it out. This was likely the cause of the loco slowing with the attendant rise in current draw, and it's fortunate that it wasn't damaged. I didn't count them, but there must have been at least 60 teeth on this gear, explaining it's nice low-speed performance. After a perfunctory wipe-down to remove the worst of the dirt, all of these parts went into a sinkful of hot water and dish detergent. This was followed by a thorough rinse and air drying.
I discovered one of the driver springs crushed due to having been mis-installed by the previous owner, so replaced it, then repaired any loose solder joints. The loco's original generator, now missing, was replaced with a Cal-Scale casting.

I wanted to improve the electrical reliability of this loco, and work shown by Steve (e-paw), Bernhard (modelsof1900), and Lutz (Schraddel) convinced me to add all-wheel pick-up.
Before starting, I wanted to re-familiarise myself with the usual set-up of wiring and insulated wheels on older models, and a quick check of one of my own revealed that the wire to the motor on this loco was installed on the wrong brush (as you recall, I had simply replaced the heavy, stiff wire with a lighter one, soldering it (more neatly ) to the same brush. By moving it to the other brush, the loco, of course, ran forward when it should have being going in reverse and vice-versa. Evidently, the previous owner had, at some point, removed the drivers from the loco, then accidentally replaced them with the insulated wheels on the right-hand (incorrect) side. Rather than dis-assemble it again, he simply moved the wire to the other (wrong) brush, then, to maintain proper pick-up, rotated the tender trucks in order to place the insulated wheels on the left-hand side of the tender, opposite of normal practice. I moved the wire to the opposite motor brush, then flipped all of the drivers to place the insulated wheels on the left (proper) side, but left the tender trucks with the insulated wheels still also to the left. This allowed me to add wipers to all insulate wheels, then wire them all to together and to the proper motor brush.
On the tender trucks, I used contact cement to affix a small piece of .060" thick copper-clad circuit board to each truck bolster, then soldered re-bent centering springs from Kadee #5 couplers to the copper.


Onto this were soldered flexible wires, which was then routed through holes drilled in the tender floor. Another piece of circuit board was cemented to the front left underside of the tender's floor, with the wires passing through another hole and soldered to the copper. On the right-hand side of the tender floor (remember, the photos show the bottom of the tender floor) I solder a piece of .060" sheet brass in place, then, after using a cut-off disc to make slots in the front member of the tender's floor, soldered two female mini plugs in place, one to the circuit board and one to the brass.


The photo below shows the two mini plugs in the front end of the tender, with the male counterparts on the ends of wires protruding from the rear of the loco. Each wire leads to one of the motor brushes, so that even with the loco's wheels not on the track, the motor will run with current collected only by the tender.


Here they are connected (the first step in hooking-up the tender to the loco):


...and here with the drawbar also connected (it also conducts current from the right-hand wheels of the tender, which is then fed to the motor via a separate wire.


For the loco, I also used contact cement to affix the circuit board material in place, but added 2-56 nylon screws from Kadee to ensure a solid installation. To perform the soldering, the screws were removed, then replaced when the solder had cooled.


Because of the gearbox on the second driver, two separate boards were required, with a jumper wire connecting the front one to the the rear one. This is the front one:


...and the rear one, with another wire leading off to the left. It's attached to one of the motor's brushes:


Continued....