Power pickup from track through rolling wheels is the prime cause of poor locomotive performance, firstly because of the obvious problem of dirty wheels and/or dirty track, but also since over time dirt and crud tend to collect at the points of contact between wheels and wipers and cause power interruptions. Trucks therefore need to be serviced from time to time.
Please note, however, that one should be be very careful with the trucks since incorrect reassembly will lead to binding wheels and very poor loco performance. So unless you're certain that my notes are clear enough to help you through this, don't disassemble your loco trucks! I added a few pictures to help clarify things.
The inner part of the truck assembly has four clips on the bottom that fit into slots on the bottom of the truck sideframe. Hold the truck in both hands with the gear tower away from you, your forefingers on the sides of the truck sideframe next to the wheelset on one end, and your thumbs on the bottoms of the same wheelset. Now press on the wheels with your thumbs until the clips that hold the two sections together disengage.
Turn the truck around and press on the bottom of the wheelset on the other end as well to unclip that end's clips. You can now take the truck apart. Remove the wipers on the truck sides if they did not fall off by themselves already when you took the truck apart, and the wheels. Do NOT remove the gears from the inner part of the truck - there's no need to and if you do, you'll find that they are extremely difficult to replace again!
The wipers have indentations into which the needle point bearings of the wheels fit, and the dirt and crud (and cat fur if your name is Jon) that collect in these indentations over time is the main cause of poor electrical pickup. Another less serious problem here may be incorrect (too narrow) wheel gauging, which causes too much free play between the axles and the wipers and can therefore also cause contact breaks. So clean the wipers and the wheel needle point bearings thoroughly, and check and reset the wheelsets' gauge as needed.
I've found that, when gauging loco wheels, it is better to err slightly towards the narrow side, rather than to set them spot on or wide. Spot on setting using the NMRA's "N Scale Mk IV Standards Gage" (sic) tends to cause the assembled truck to be too tight, with the wheels not turning freely. In fact, I have checked the gauge on several brand new out of the box Atlas locos and found that the wheels are all factory-set slightly narrower than the gauge. If I leave them like that, they run fine, but the moment I set them exactly according to the gauge, the locos derail on some of my my Peco insulfrog points/switches/turnouts.
Since I first posted this guide, I have discovered CRC 2-26, the magic potion of model railroading. After cleaning the wheel wipers, I use a paint brush to put a drop of CRC 2-26 into each axle indentation before I reassemble the trucks. I even apply some CRC 2-26 on the gear axles of the inner truck frame to lubricate them. (I use an empty pickle onion jar into which I squirted some CRC 2-26 since it's difficult to get just a drop at a time from an aerosol can! That way any unused liquid can be kept in the bottle for later use.)
To reassemble, first replace the wheelsets in the inner truck frame, and then the wipers on the sides. Be careful here - most four-wheel truck wipers can fit on either side of the truck, but some six-wheel trucks, like for example the SD50 trucksets I used in these pictures, are assymmetrical so they have different wipers on the two sides.
In the case of the SD50 and SD60, the marked wiper goes on the side of the truck away from the gears. The wipers clip onto little protrusions on the sides of the inner truck frame, and once they're in place, they hold the axles in position. (Although the wheelsets have plastic axles/gears, the weight is carried on the needle bearings in the wiper indentations, and not on the plastic axles.) With both wipers and all wheels in place, check that all wheels and gears can turn freely.
Hold the inner assembly between thumb and forefinger, with your fingers on the wipers to keep them in position, and carefully slip the assembly into the truck sideframe by inserting first one end from the top, until it is more or less in position so that the truck sideframe can hold the wipers in place, and then lowering the other end into position. Make sure that the gear holes in the bottom of the sideframe are on the same side as the gears.
Then squeeze the truck ends between thumb and forefinger until the clips snap into place, first on the one end and then the other.
Now check for wheel and gear binding. I've found that when there is any binding, it is usually either an axle gear that touches one side of its gear opening in the bottom of the truck sideframe, or the truck wasn't assembled 100% correctly with the wipers properly seated into their indentations in the truck sideframes.
If the wheels don't turn freely, check to see which wheelset is the culprit and which side of the axle gear touches the side of the opening in the truck sideframe. Then disassemble again, reset that wheelset's gauge in such a way that the gear will not touch the truck sideframe any more, and try again. For example, you'll find that when the wheelset is correctly gauged, there is a little gap between the plastic geared axle and one or both wheels. By closing the gap on one wheel and widening the gap on the other, the same gauging can be achieved, but with the gear itself in a slightly different position in relation to the two wheels. When the assembled truck is pushed along, all gears and wheels must be able to turn freely.
If anything about the procedure is perhaps still unclear, or if you used this guide and it worked for you, please drop me a note.
Good luck, and keep them on track!
The following pages contain decoder installation guides for some N scale diesel locomotives:
And the following page contains a guide to finally solve the power pickup problem that plagues N scale Life-Like SD7/SD9 N Scale diesel locomotives:
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Created in August 2001. Last updated on 11 September 2003.