DB is thrilled to report:
It's alive!
The Kato turntable and DB Bodgy Track Wiring and Points Control seems to work pretty well, other than trying to take the DG off onto the little radial track by the foreman's office at 1:30. No go. A quick look under the layout and I've only wired one of the two rails here! D'oh.
So how does it operate?
There is a little black switch on the right side of the control box for clockwise', 'anti-clockwise' and 'idle' (centre-off). You move and hold that switch into the required direction, and the turntable unlocks from the current track and starts moving. When you are approaching the track you want the bridge to stop at, you release the direction switch back to centre-off. The turntable keeps going until it latches on the next track. I assume this simply 'releases' the long plastic pin under each end (see previous posts for pics of the disassembled turntable), which pops out of the bridge on a spring like a tortoise's head and locates into the next hole it finds under the track is is approaching. The can motor in the operators cabin probably keeps going until it hits stall current, then switches off.
As for track power routing, there is a feed into the control box that runs out to the turntable bridge. The problem with this is that when the turntable spins 180 degrees, the track polarity obviously needs to be reversed, so the way Kato have implemented this is a silver 'reversing lever' on the control box that you can flip to reverse the polarity to the bridge.
With DCC this might prove annoying, but the turntable bridge has little copper wipers underneath. These are probably intended to send power into the radial track from the bridge so that the radial tracks are unpowered until you line up with them. However this can work the other way too, so several DCC folks simply don't use any power feed and ignore the reversing lever, simply letting the bridge get power from the radial track it is aligned with. This means you'd need to power your radial tracks, but it also means you need to be careful about their polarities around the circle, and it means that any sound-equipped loco won't get any juice while spinning. This is of no concern to me, as I don't have any NZ120 locos with sound.
The alternative is to use an auto-reverser on the feed to the bridge, and I may do this at some stage to make the thing more bulletproof, although the built-in method seems to work OK so far.
I obviously need to finish laying and wiring up the fan tracks now.
My first attempt a video ended with a 'buggerit' moment when I ran the DG into a "DCC-friendly" point set the wrong way. Beep beep stall.
I've thought for a while that the real solution to making these completely DCC friendly is to isolate a further "loco-length" section out from the frog, which is only powered when the switch is set for that route. This would prevent a loco from coming into a point set against it. It would still stop, but that wouldn't call the whole DCC system to halt. I suppose this would require a three pole switch.
DCC friendly wired frog:
DCC really friendly with isolated approach tracks:
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