This is how the schematic should look, if we follow Dale's suggestion, with no feedback on the middle part
of the turntable ( "B" ) and different feedback depending if the loco is on "A" or "C", or both "A" and "C".

I can see the advantages

However, your controlling software should be able to handle enter and exit both from the "A"-side and the "C"-side



Per.

Hello Fabrice/All,

It is possible to add stop sensor contacts to each end of the turntable bridge but there are a few caveats.
First the Marklin/Fleishmann bridge end of rail spring contacts must exist. If they have been cut off this method won't work.
My friend Vic users this method with TrainController to provide a stop contact at each end of the TT bridge with a brake contact between the two stop contacts and it works very well.
Before going down this path I would exhaust all options to improve the speed profile of the locomotives before making permanent physical changes to the turntable/bridge. I haven't found a compelling need to add the extra stop contacts to my turntable but on my transfer table I have added the extra stop contacts.



The photo above shows the TT bridge cabin end at the 9:0 o'clock position. On the Bridge you will notice both rails at each end of the bridge have been cut 55mm from the end of the bridge these small segments are shown in blue and have no electrical connection to them. The cutting of the rails is best done with a very small end mill to avoid cutting the plastic on either side of the rail(s).
The brown rail on the bridge is ground (O) shown on the cabin side and the brake contact is shown in green.

The stub tracks around the turntable is where the s88 contacts are joined up to form two groups (two s88 contacts) (you have to ensure that the stubs rails for each end of the TT bridge is in a different group) I have shown this to be the yellow rail. This yellow rail must be insulated from the connecting stall rail. The brown rail doesn't need to be insulate but must be connected to the ground (O).

As the turntable bridge rotates the bridge spring contacts complete the circuit for the ground (O) and the s88 contact for each end of the bridge.

This method allows 360 degree rotation of the TT bridge.

I hope you have found this useful.

Edit: I have spoken with Vic and the TT bridge extra contact length is 55mm not 30mm as I mentioned.

Edited by user 15 October 2019 02:04:47(UTC)  | Reason: Not specified

Hello Ross, All,

This is a nice concept. You have moved the problem of additional bridge wires outside of the bridge, i.e. on the spoke tracks.

However, I'm suspecting possible problems with automation... I must say I haven't experimented this kind of configuration until so far, and it may depends also of the software used, but this alerts me a bit.

For the following explanations, I've reused part of your drawings, with some addition.


Note: Not all wires are shown

Let's call the 3 sensors/areas of the bridge "enter", "brake", "in".
The "brake" can be ignored for the rest of the explanation.

If I understand correctly, one rail of half of spoke track set are connected together to the same S88 input (Enter) -I have marked them E0, E46, E44... to E26, and the other rail is grounded for the same set.
For the remaining half spoke tracks set, tracks are connected in the same manner, to another same S88 input : In. I have marked them I2 to I24.
If this is not like that, then I've missed something. Please provide more explanations.

Here is an example of questions I have in mind:
-Q1: A loco is entirely on the bridge (0-24), i.e. All sensors are up (enter, brake & in). Now you move the bridge to another position, for instance 46-22. When the bridge moves (without having reached the final position), enter & in disappear because grounded sections disappear, even if brake is still high. What is the behavior of the software when some sensors of bridge vanish while rotating ?
-Q2: same kind of question, when the bridge reaches the new position, i.e. the sensors enter & in are back.
-Q3: now a variant of Q2. The new position reached is such that enter & in sensors are swapped compared to the initial position, i.e. 2-26... What is the behavior ?

Maybe the answer is TC doesn't care to lose some sensors/ignore them while bridge is moving... Let's suppose this is the case also with Rocrail.

-Q4: More annoying, at least with Rocrail: A loco wants to enter the bridge coming from I2 side. It enters the spoke track and fires I2, thus "In" sensor, without having fired previously the "Enter" sensor -> Unexpected detection = Ghost Train = Emergency power off !

I'm sure TrainControler is extremely sophisticated and is (possibly?) able to deal with such stuff, but I'm not sure with Rocrail.

These considerations are theoretical and I would need to simulate a complete behavior in order to be sure it's OK with Rocrail, before going that way.

However, many thanks for your suggestion, but at the present time it raises many questions in my mind.

Cheers
Fabrice

Hi Dale,

I'm pleased you are finding the topic interesting.

X and Y directions isn't a problem. Note the directional markers.



In the form shown you can specify how the loco exits the turntable by pointing the TT bridge cabin end to the track stubs required then ticking the forward or reverse boxes. In the example the loco can enter the TT bridge in a forward or reverse direct but on the stubs marked orange the loco may only exit the bridge in a reverse direction. This can be overridden at the schedule level for automatic operation see below.