Track Repair and Turntable Polarity Test

In my excitement after securing the turntable motor last night, I turned the module over and knocked it against my knee (I tend to work on the floor). Normally that wouldn’t have been an issue, except my knee struck the excess rail that extends beyond the module surface, where the fascia will eventually lengthen the module a bit.

That made for a big mess. The rails popped right off the ties and bent upward, severing forty or fifty plastic “rail spikes.” There was nothing I could do except replace that length of track. Here’s the damage:

So tonight I pulled out the soldering iron and desoldered the feeders. Then I pulled the track up to the first turnout and laid a new length of Flex-Track in its place. After gluing it down, putting some weights on, and soldering the feeders on, it looks like new.

After that repair I needed to do something a little more exciting, so I temporarily wired the turntable up.

I was afraid the locomotives would get hung up on the gap between the approach track and the turntable deck rails, and I was also afraid that the polarity of the tracks wouldn’t switch when rotating the deck.

For those who are unfamiliar with Peco’s turntable, I may need to explain this “polarity” piece a bit. The reason I opted for Peco’s turntable instead of another plug-and-play turntable is because it has a genius system for switching the polarity of the rails whenever the deck makes a full rotation.

This system depends on two separate brass collars beneath the turntable deck. Two spring-loaded brass plungers move across the collars when the deck rotates. Each plunger conducts electricity up to one of the two rails, and after both rails pass over the gaps between the collars, the polarity reverses (i.e. the positive rail passes over the negative collar and vice-versa). If this didn’t occur the layout would short out every time the deck made a full rotation.

Another benefit of the polarity changing is that a locomotive moving forward onto the deck can be turned 180 degrees and continue to move forward off the deck. It doesn’t matter that it just came from that direction; with the reverse in polarity, the locomotive still registers as moving forward.

Good news all around: the locomotives can get on and off the deck with no extra effort, and the polarity changes as it ought to.

Here’s a video of the turntable in action. Pretty soon, my hands won’t be needed except to push a button on the DCC controller. Next up, I hope to begin working on the software and hardware that will allow me to do just that. On that note, my brother-in-law sent me some documents and instructions earlier today, so I have some reading to do.

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