Wednesday, February 27, 2008

Dense- might learn one day

There is a saying that you can't teach an old dog new tricks. I'd suggest that sometimes you can't get an old dog to forget bad tricks.

I've been building some new turnouts. Let me set the scene. I've arrived at what will be Topton. That is on my second level of the layout. Track elevation is about 65 inches above the floor. For some folks that makes great eye level viewing. It also means that to be comfortable working on track I need to stand on something. No problem, I built a movable work station. I haven't fallen off it yet.

THe track in this area was originally some track from a previous layout. It was temporary just to run a few trains. Now I'm replacing it with smaller rail. Also I'm building my turnouts. I've built a few and I've learned from each project. The rails are positioned on he ties and about ever tenth tie is actually a strip of Printed Circuit board (PCB) that about .08 inches in width. The rails are soldered to this PCB. For electrical purposes the two rails cannot be electrically connected. So at some point a small "cut" must be made across the PCB through the layer of copper.

I started building these turnouts yers ago. I'd build the who turnout and then cut the PCB surface. I was doing this on my workbench and then moving the turnout to the layout. Now though I'm building all of my turnouts in location.

So last night I'd finished building two turnouts. They are on opposite ends of the siding for Topton. They looked good. the distance between rails was very precise. So I knew the next step was cutting the PCB surface. I grabbed my variable speed cutting tool, a bright work light and my optical headset. A few minutes later I'd cut the PCB surfaces on all of the ties. Wonderful.

Wrong. I hooked my continuity test device to the rails and it screeched like a banshee. THat meant only one thing. I'd missed cutting a tie. I looked. I didn't see anything amiss.

Oh darn. Now I have a problem. I started looking at my problem logically. Lets see the problem might be associated with earlier track (I was connected to that) It might be turnout one, it might be turnout # 2. Heck it might be the tack between the two turnouts. And smart old me had not built in any features to make diagnosis easier. I had no way to disconnect the various sub assemblies to isolate the problem.

So I set to work. First I tried cutting into a few suspect ties. The tester still screeches. Only one thing to do. Attack the trackwork and isolate the sub assemblies. I really didn't relish this idea. There is the chance that some rails might slip out of tolerance. But I had no choice.

The up-shot of all of this was that I finally located at least TWO ties (naturally one in each turnout) where the surface of the PCB wasn't cut completely. Even with my close-up optical viewer I couldn't see the error. I'm suggesting that the dimension of the offending copper is about the width of a piece of hair. It doesn't take much to allow electricity to flow.

So what have I learned? After all that's what I'm trying to do learn.

Build and test one turnout at a time. Check it VERY carefully. And then each time I add a bit more track, check it again. I should have learned this lesson years ago. But I'm an old dog and I don't un-learn old tricks very well. Besides, I swear it "looked" like I cut each and every surface completely on each tie.

Maybe I need to invest in bigger electrical electrons that won't travel the small traces I miss. Yeah, right. No I just need to test more frequently.

The only thing that really worries me now is there might be a gap lurking right now that will actually close and cause problems this summer when the rail warms up and expands. After all I'm talking about distances the size of a piece of human hair.

But Topton is nearing completion. Next the track needs to traverse the Topton tunnel area twist around and head for valley bridge. After that Andrews, NC. is the last stop. Andrews with logging railroad connections, a hidden reverse loop. But most of the heavy trackwork will be completed. I'll actually be able to run trains from one end to the other on permanent rail. Of course I still have miles of scenery to construct.