Post by Paul Cutler III on Jun 21, 2012 8:10:47 GMT -8
It's pretty dead in here at the moment, and I'm bored here at work, so I thought I'd tell about the latest DCC install I did (sorry, no pictures).
It was a good friend's birthday and for a present for a guy who has everything I thought the best gift was a free DCC installation in one of his old brass steam engines that he hasn't gotten around to, yet. I looked through his collection, and managed to grab (don't ask how) what I believed to be last engine he'd ever do. It was a brass CNR 0-6-0 #7470...which happens to be the same engine now being used on the Conway Scenic in N.H. Later, I found out that my friend bought the model the same month I was born (January 1975). Yikes. Anyways...
So first I test it on straight DC...dead. Hmm...why is it dead? Upon going to take her apart, and I find a single wire coming from the tender through a hole drilled under the apron and wrapped around one of the mounting screws for the boiler under the cab. Turns out, it's the lead to the rear light on the tender, but that has nothing to do with why it's dead.
Open the boiler up, and one of the front ladders falls off. Epoxy that. Then I find a diode matrix for constant lighting inside. The wire from the drawbar is broken off the diode matrix...which would certainly explain the dead-ness. Another surprise? The boiler is one of my friend's "lead pours". Back in the day, he would routinely pour molten lead into the boilers of his brass steam to increase drawbar power. This is one of them.
I put DC analog clips on the motor brushes, and the open frame motor runs and the drivers all turn. Okay. Squeeking, but okay.
I examine the rubber tube connecting the motor to the worm. I appears intact, but looks cracked...and it looks like it's got wear marks...like it was rubbing against something. I look in the boiler, and sure enough, there's a black rubber mark on a small portion of the lead pour weight. Seems that this poor little 0-6-0 has had a dragging drive shaft for 37 years! Of course, it hasn't run at all in the past 13 since we went DCC...and probably some years before then, too. Anyways, I get out the Dremel and mill down the lead until it will clear the drive shaft.
I cut all the wires loose, get rid the matrix, and pull the motor out. As soon as I do, the rubber tube cracks right in half. Sigh. Like I couldn't see that one coming. I get some new plastic tubing (fish tank stuff) and clean off the old rubber hose (which was hard and stuck to the shafts). At this point, I clean and test the motor. The armature is very dirty, so I grab a pencil eraser and clean off the worst of it. I used a metal pick to clean the slots out of the armature, then used the eraser to clean the brush heads. Next I lubricate the armature with 2-26 electrical contact lubricant, and oil the motor bearings with light oil. I hooked up the motor leads again to DC, and spun the motor at top speed for 60 seconds in each direction. It runs great.
I go to put the new tubing on, and while it fits the motor shaft fits perfectly, the worm shaft is slightly smaller. Sigh. I have to get out the epoxy and glue it on. Before I do, I open up the gear box to look...and it's gummed up, too. I clean out the old grease, then re-lube and re-assemble the box. While I'm in there, I lube up all the axles.
I consider my DCC options. An N-scale decoder would fit, but I'm concerned about the 1amp (1.5amp peak) rating with the old open frame motor. An HO decoder has a 1.5amp (2amp peak) rating, which I like better, but no room in the boiler. I decide to use the tender instead where there's plenty of room, and use the HO decoder (DH123D).
I open the tender, and find another diode. Snip that out, and examine the tender. One side of the tender bulb is grounded to the frame (snip). The rear bulb appears to be a 12v bulb. I test with a AA battery, and sure enough, the bulb element barely warms up. It must be a 12v.
I check the tender trucks, and the bolsters are dirty. They are cleaned with a wire brush, and so are the tender bolsters. I took apart one truck, but the journals were very clean, so I just put it back together and didn't dissemble the other truck.
Next, I test wire the engine. Since the decoder is going in the tender, I need to bring a red wire from the boiler frame into the tender. I made a wire loop with solder and used the motor mounting screw to secure it. Then I soldered gray and orange wires to the motor brushes, and connected them to the decoder by twisting the wires. Next I soldered the black wire to the tender frame and connected that to the decoder. Over to the test track and...nothing. It does not work. Wha...?
I test the decoder. It works, but not in the engine. I swap out the wire harness. It makes no difference. I swap decoders...nothing. I use jumper wires to connect direct to the decoder while the engine is off the track...and it works! I put it back on the track and...nothing. No short, just nothing. I start tearing out my hair at this point.
Finally, as I look at the motor, I can tell it's grounded to the frame. Which is fine, because only the brushes matter. I look at the brushes. One of them has a little piece of orange insulation separating the brush tension spring from the brush. That makes sense, because the spring is one piece of metal that connects both brushes. Otherwise, you'd have a short. Then I notice that the brush tension spring is sandwiched between two metal washers on top of the motor. I think...that's not right. They should be plastic because otherwise...(imagine my face palm moment...thank you). Of course! The motor frame, which is grounded, is connected electrically to the metal screw holding the metal washers that's holding the metal spring that's connected to the metal brush! Duh!
So I put some pre-shrunk heat shrink over the end of the brush tension spring, and low and behold! The engine runs on the track. Whew!
Now it's time to do the final motor wiring. I put the decoder in the tender, and start thinking about plugs between the boiler and tender. And then I ask myself, why? Why use the plugs on an 0-6-0? The engine with tender is about the same size as a GP9, for pete's sake. And my friend doesn't use the original boxes, he uses A-Line boxes for transporting engines to the club. So why spend the money and waste the time? I decide to hardwire the decoder in place with no plugs to the boiler, and to use a black Sharpie to color all the wires black. The only trick left is that there are no holes for the wiring. I use the existing hole (see above) for the boiler frame lead (red wire), but I have 4 more wires to do (orange, gray, blue, white). I drill small holes in the tender floor under the apron to pass the wires though, and connect to the boiler (where there's plenty of gaps for wire).
Now it's time to test the lighting. I bring the engine to the DCC test bench, and try various resistors. I start with 680ohm...nothing. I have to go down to 270ohm before the light is bright enough. 220ohm is better, but the test bench is a Zephyr, which is only 12v. The club uses 14v, so I prefer a little dim on the Zephyr as they'll be okay at the club. I hook up the rear bulb, and it's super bright. That's not gonna last, I think. So I install a 100ohm, and that matches the headlight.
Back to the workbench, and I cut the wires close and heat shrink the connections. I go to close up the tender...and I've screwed up the front headlight wiring. I didn't run it around the tend frame like I should have, so I have to strip the heat shrink, de-solder the connections, feed them properly through the shell, then re-solder them and heat shrink 'em.
I assemble the tender and the boiler, color the wires with a black Sharpie, oil the valve gear, and I'm done. Whew. It only took about 5 hours, start to finish. It was fun to do, tho'. I love DCC'ing old brass. Every install is a challenge. I gave it to my friend, and he really liked it. It's one of those presents that just as much fun to give as to receive...
It was a good friend's birthday and for a present for a guy who has everything I thought the best gift was a free DCC installation in one of his old brass steam engines that he hasn't gotten around to, yet. I looked through his collection, and managed to grab (don't ask how) what I believed to be last engine he'd ever do. It was a brass CNR 0-6-0 #7470...which happens to be the same engine now being used on the Conway Scenic in N.H. Later, I found out that my friend bought the model the same month I was born (January 1975). Yikes. Anyways...
So first I test it on straight DC...dead. Hmm...why is it dead? Upon going to take her apart, and I find a single wire coming from the tender through a hole drilled under the apron and wrapped around one of the mounting screws for the boiler under the cab. Turns out, it's the lead to the rear light on the tender, but that has nothing to do with why it's dead.
Open the boiler up, and one of the front ladders falls off. Epoxy that. Then I find a diode matrix for constant lighting inside. The wire from the drawbar is broken off the diode matrix...which would certainly explain the dead-ness. Another surprise? The boiler is one of my friend's "lead pours". Back in the day, he would routinely pour molten lead into the boilers of his brass steam to increase drawbar power. This is one of them.
I put DC analog clips on the motor brushes, and the open frame motor runs and the drivers all turn. Okay. Squeeking, but okay.
I examine the rubber tube connecting the motor to the worm. I appears intact, but looks cracked...and it looks like it's got wear marks...like it was rubbing against something. I look in the boiler, and sure enough, there's a black rubber mark on a small portion of the lead pour weight. Seems that this poor little 0-6-0 has had a dragging drive shaft for 37 years! Of course, it hasn't run at all in the past 13 since we went DCC...and probably some years before then, too. Anyways, I get out the Dremel and mill down the lead until it will clear the drive shaft.
I cut all the wires loose, get rid the matrix, and pull the motor out. As soon as I do, the rubber tube cracks right in half. Sigh. Like I couldn't see that one coming. I get some new plastic tubing (fish tank stuff) and clean off the old rubber hose (which was hard and stuck to the shafts). At this point, I clean and test the motor. The armature is very dirty, so I grab a pencil eraser and clean off the worst of it. I used a metal pick to clean the slots out of the armature, then used the eraser to clean the brush heads. Next I lubricate the armature with 2-26 electrical contact lubricant, and oil the motor bearings with light oil. I hooked up the motor leads again to DC, and spun the motor at top speed for 60 seconds in each direction. It runs great.
I go to put the new tubing on, and while it fits the motor shaft fits perfectly, the worm shaft is slightly smaller. Sigh. I have to get out the epoxy and glue it on. Before I do, I open up the gear box to look...and it's gummed up, too. I clean out the old grease, then re-lube and re-assemble the box. While I'm in there, I lube up all the axles.
I consider my DCC options. An N-scale decoder would fit, but I'm concerned about the 1amp (1.5amp peak) rating with the old open frame motor. An HO decoder has a 1.5amp (2amp peak) rating, which I like better, but no room in the boiler. I decide to use the tender instead where there's plenty of room, and use the HO decoder (DH123D).
I open the tender, and find another diode. Snip that out, and examine the tender. One side of the tender bulb is grounded to the frame (snip). The rear bulb appears to be a 12v bulb. I test with a AA battery, and sure enough, the bulb element barely warms up. It must be a 12v.
I check the tender trucks, and the bolsters are dirty. They are cleaned with a wire brush, and so are the tender bolsters. I took apart one truck, but the journals were very clean, so I just put it back together and didn't dissemble the other truck.
Next, I test wire the engine. Since the decoder is going in the tender, I need to bring a red wire from the boiler frame into the tender. I made a wire loop with solder and used the motor mounting screw to secure it. Then I soldered gray and orange wires to the motor brushes, and connected them to the decoder by twisting the wires. Next I soldered the black wire to the tender frame and connected that to the decoder. Over to the test track and...nothing. It does not work. Wha...?
I test the decoder. It works, but not in the engine. I swap out the wire harness. It makes no difference. I swap decoders...nothing. I use jumper wires to connect direct to the decoder while the engine is off the track...and it works! I put it back on the track and...nothing. No short, just nothing. I start tearing out my hair at this point.
Finally, as I look at the motor, I can tell it's grounded to the frame. Which is fine, because only the brushes matter. I look at the brushes. One of them has a little piece of orange insulation separating the brush tension spring from the brush. That makes sense, because the spring is one piece of metal that connects both brushes. Otherwise, you'd have a short. Then I notice that the brush tension spring is sandwiched between two metal washers on top of the motor. I think...that's not right. They should be plastic because otherwise...(imagine my face palm moment...thank you). Of course! The motor frame, which is grounded, is connected electrically to the metal screw holding the metal washers that's holding the metal spring that's connected to the metal brush! Duh!
So I put some pre-shrunk heat shrink over the end of the brush tension spring, and low and behold! The engine runs on the track. Whew!
Now it's time to do the final motor wiring. I put the decoder in the tender, and start thinking about plugs between the boiler and tender. And then I ask myself, why? Why use the plugs on an 0-6-0? The engine with tender is about the same size as a GP9, for pete's sake. And my friend doesn't use the original boxes, he uses A-Line boxes for transporting engines to the club. So why spend the money and waste the time? I decide to hardwire the decoder in place with no plugs to the boiler, and to use a black Sharpie to color all the wires black. The only trick left is that there are no holes for the wiring. I use the existing hole (see above) for the boiler frame lead (red wire), but I have 4 more wires to do (orange, gray, blue, white). I drill small holes in the tender floor under the apron to pass the wires though, and connect to the boiler (where there's plenty of gaps for wire).
Now it's time to test the lighting. I bring the engine to the DCC test bench, and try various resistors. I start with 680ohm...nothing. I have to go down to 270ohm before the light is bright enough. 220ohm is better, but the test bench is a Zephyr, which is only 12v. The club uses 14v, so I prefer a little dim on the Zephyr as they'll be okay at the club. I hook up the rear bulb, and it's super bright. That's not gonna last, I think. So I install a 100ohm, and that matches the headlight.
Back to the workbench, and I cut the wires close and heat shrink the connections. I go to close up the tender...and I've screwed up the front headlight wiring. I didn't run it around the tend frame like I should have, so I have to strip the heat shrink, de-solder the connections, feed them properly through the shell, then re-solder them and heat shrink 'em.
I assemble the tender and the boiler, color the wires with a black Sharpie, oil the valve gear, and I'm done. Whew. It only took about 5 hours, start to finish. It was fun to do, tho'. I love DCC'ing old brass. Every install is a challenge. I gave it to my friend, and he really liked it. It's one of those presents that just as much fun to give as to receive...
