The LifeLike SD7s and SD9s can be excellent performers, but they have one serious flaw. They have great little motors and are excellent pullers, but they often start displaying power pickup problems after a while, or as soon as one installs a decoder or fiddle around in their insides for any other reason. This can especially be a problem on DCC, where they can take all the fun out of the hobby!
The problem is with the little copper wipers that wipe against the copper strips under the loco's chassis. These wipers lose their springiness very easily and then they do not touch the chassis strips all the time, and when the other truck also loses contact, like on points, the loco stalls.
Each wiper is made in two parts, the axle wiper and the chassis wiper, and both parts clip onto the side of the plastic truck frame. The two parts just press against each other for contact - there's no solid joint. This contact spot is where DCC usually zaps these locos if your DCC layout does not pass Don Crano's coin test - it causes an arc effect between the two wiper parts that WILL melt the truck frame and, in bad cases, even the axle gears.
I've tried many ideas to tackle this problem before I finally solved it. The ultimate solution that solved this problem for ever on my fleet of eight of these locos was to remove the top wipers altogether and to hardwire the trucks to the loco's chassis.
Detailed instructions to disassemble the SD7 is in my decoder installation guide for this locomotive. (If the locos on the pictures appear somewhat shabby, keep in mind that they have all been disassembled numerous times before this problem was finally fixed! If the parts still look good, it's probably a picture taken while I modified a loco for Bill Stallard recently....)
The truck is held in position by the axle of the worm gear. I use a small jeweler's screwdriver to push the axle out. Once it's removed, the truck will fall out. Unclip and remove the truck sideframes by inserting a jeweller's screwdriver or a blade into any end of the truck from the top, and remove the wheelsets.
Use a knife blade or screwdriver to remove the axle wipers by inserting the tool between the metal and the plastic truck, and twisting the tool. The chassis wipers can just be pulled off and discarded into your spare parts box.
Solder 3" pieces of wire to the four axle wipers at the spot where they have a little indentation on their top sides, as shown. If you first slightly roughen the spot where you want to solder to with a piece of fine grit sandpaper, soldering will be made easier. Don't get solder into the axle grooves. Use a flexible wire in two different colours - offcut wires left over from decoder installations is ideal.
Replace the axle wipers onto the truck frames. If they refuse to stay put, use just one very tiny drop of super glue on two of the dowels on the truck that fit into holes in the wiper - not too much because someday you or someone else may need to remove the wipers again. Fit two different colour wires to each truck, and in such a way that the same colour is on the gearside of the one truck and on the opposite side on the other truck. This way, when the loco is reassembled, the same colour on both trucks will pick up power from the same rail. Then test fit the wheelsets to make sure that the solder blobs where the wires were attached don't snag the wheels. There's usually more than enough room, but if not, file the solder down some so that the wheels all have some room for side to side movement. If your soldering skills are like mine and a blob turns out to be way too big, rather desolder the wire, clean the solder off and start over.
Thread the wires down through the holes next to the gear towers, and then up through the gear towers on the side opposite the gears, as shown. Make sure it doesn't go around any of the gears or snag any gear along the route. Pull the wires taut.
Use a toothpick to apply some superglue into the corners of the gear towers opposite the gear side and glue the wires into the corners. Then check the wheel gauge of all six wheelsets and reassemble the trucks, including the worm gears in the gear towers. I always apply a drop of CRC 2-26 in each axle indentation before replacing the wheelsets - it does wonders to enhance power pickup, and it also lubricates the axles.
Test the truck by pushing it along, to make sure that all wheels and gears can turn freely without any snagging.
Before installing the trucks (Ignore the truck in this picture.....), use a Dremel or Proxxon cut-off disk to cut shallow grooves as shown in the loco's gear towers, to make room for the wires so they don't get in the way of the loco shell. On the short hood end of the loco the cut on the left is not needed since there is plenty of free space inside the loco's cab for the wire. Be careful - don't slip up and cut right through the tower!
Remove the worm gear axles from both trucks, leaving the worm gears in position, thread the wires up through the gear towers as shown, and fit the trucks to the loco by inserting the worm axle gears. Needle nose pliers may come in handy since it's rather tricky to get a good grip on the slippery axle with fingers.
Cut the wires to a suitable length to allow some slack and solder them to the positions as shown. Be careful since you're soldering to metal on plastic. Apply a little flux to the metal tabs first, then get the solder gun up to full temperature and, with a little solder on the tip, just touch it to the metal for a split second to leave a little solder blob on the metal. Then tin the wire end, hold it in position against the solder blob and just touch it again for a split second with a hot iron. The solder blob and the tinned wire end will melt together and the metal tab will not be heated up long enough to melt the plastic.
Insert the wire into the grooves cut in the gear towers as shown, leaving a little slack inside the gear towers so that the trucks can swivel freely. Make sure that the wire on the left won't rub against the flywheel or the drive shaft tube. You'll find that the trucks have much better up-down (nodding) movement than before the modification. Test run the loco, then reassemble the shell and enjoy your LifeLike loco that will now perform like a Kato!
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. And if you do not feel up to the task of doing this modification yourself, please feel free to contact me, and I'll do it for you for a small fee. (My arm twists rather easily - just mentioning a couple of sets of DeLuxe N scale containers can usually do the trick.....)
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 servicing the trucks on Atlas and Kato N scale diesel locomotives to enhance their power pickup:
To get to the rest of my website:
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Created on 5 September 2003. Last updated on 20 September 2003.