Greynut Posted July 20, 2015 Share Posted July 20, 2015 I'm looking to add an R070 electically operated turntable to my DCC layout. I've read the 'how to' DCC conversion posts on the forum, as well as others elsewhere. I don't actually want to operate the TT itself by DCC, leaving it to turn under DC control from a separate 12v DC power source direct to the motor. I know it's suggested that turning it under DCC control is best but it gives me something different to fiddle with - plus if I hand it on to my grandson who has a DC layout, it will drop straight in. Well, it might, if what I'm thinking is OK to do - that is using it without removing the brass contacts at the end of the turntable bridge rails. My thinking is that instead of a power feed going into the bridge track, via the electrical contacts on the inlet ramp track spur, the bridge track feed will come from the track spurs going on and off of the TT, via the brass contacts on the bridge track itself - if they are left in place. I use droppers for each piece of track, so that as the TT bridge track lines up on a track ramp spur, the polarity comes from that spur - so no short as the loco moves onto the spur. Also, if a track comes off the opposite ramp, the polarity is kept as the TT bridge track is simply acting like an ordinary track piece when it all lines up. My further thinking is that if the bridge track is not directly being fed the constant DCC power it would get through the inlet ramp track spur, then, in itself, it's dead until it aligns with on/off tracks, so no polarity problems can occur. OK, when the table is turning, the bridge track is dead (I think) but I don't have sound and if lights go out I'm not too bothered. The thing is - will it work or have I missed something? Link to comment Share on other sites More sharing options...
poliss Posted July 20, 2015 Share Posted July 20, 2015 Not sure I fully understand and I don't have a Hornby turntable to check. If you leave the contacts on the ends of the bridge rails, and your spurs are powered, wont there be a short circuit as the left rail of the main track aligns with the right rail of the spur? Link to comment Share on other sites More sharing options...
St1ngr4y Posted July 20, 2015 Share Posted July 20, 2015 My thinking is that instead of a power feed going into the bridge track, via the electrical contacts on the inlet ramp track spur, the bridge track feed will come from the track spurs going on and off of the TT, via the brass contacts on the bridge track itself - if they are left in place. Hi,As far as I can tell, what you are suggesting would work with one proviso. Out of the box, the R070 bridge track is connected via a pair of wires underneath, to a pair of brass contacts located under ONE of the input roads. I think you would have to disconnect these wires from the input road contacts, if the input road has its own DCC connection, otherwise the bridge would be live constantly, which is not what you want.Ray Link to comment Share on other sites More sharing options...
Rog RJ Posted July 20, 2015 Share Posted July 20, 2015 No need to remove any wires from the brass contacts of the inlet track, just put some insulation over them to prevent them making contact with the track. Link to comment Share on other sites More sharing options...
poliss Posted July 20, 2015 Share Posted July 20, 2015 Checl? Oh for a spellchucker. :-p Link to comment Share on other sites More sharing options...
2e0dtoeric Posted July 20, 2015 Share Posted July 20, 2015 Or just don't use the second inlet, counting clockwise from the little hut over the motor, etc, with the metal feeds to the t/table bed, and make sure that you don't use the direct opposite tracks either, or, as stated earlier, as the t/t turns, at one point the rails just might diagonally connect and short-circuit.You can drive the t/t motor from a separate dc source, that's what I've done. (I used an old N gauge controller, rocking the switch for direction, and leaving the speed knob set at a reasonable level. The switch is sloppy enough to stay in the middle 'off' position, when not needed.) Link to comment Share on other sites More sharing options...
RDS Posted July 20, 2015 Share Posted July 20, 2015 ... plus if I hand it on to my grandson who has a DC layout, it will drop straight in ... Incredible! Grandfather has a DCC layout and Grandson has DC. Who would have thought? Get him converted!(I am a Grandfather myself) Link to comment Share on other sites More sharing options...
Greynut Posted July 20, 2015 Author Share Posted July 20, 2015 Many thanks for all of your replies! Ray - If I still go ahead with non DCC, the power feed to the TT bridge track would come from the on/off ramp tracks via droppers from the DCC bus - the one on the input road would not be used. 2e0 - If I go DCC, then I will use that input road ramp. As for diagonally crossing the rail polarity, as a result of what Poliss said, I did some tests (which I should have done a lot earlier) and I hope I've answered it a bit with my reply. Rog - I did think of that and I might well do it if I end up going full DCC on it. Poliss, you had me checking and double checking like a good 'un. I thought that you had come up with the killer blow to the idea ... and indeed you have to Plan 'A'. This was to leave all 4 of the brass TT bridge track contacts in place - i.e. one at each bridge track end. I admit I didn't even think about what happened when the bridge was turning - I was only thinking of how it might work when it was all lined up to an on/off ramp spur track section. If I didn't have some on/off ramp spur track sections on opposite sides of the TT, I don't think there would be a shorting problem. With an 'unopposed' on/off spur section, as the TT rotated, even though one bridge track rail contact touched the 'wrong polarity' spur rail on its travels, no circuit would be made as the other bridge rail would not be in contact with anything else in the track circuit at that moment. The trouble is that with on/off ramp spur track sections opposite each other on the TT, when the bridge rotates, the rail contacts on the bridge track do come into contact with an opposite spur track rail at each end of the bridge. One bridge end contact will contact the +ve spur rail, the other end will contact the -ve. Diagonally, as 2e0 said. To try to describe it another way - in my overall track circuitry, my +ve rail is the right hand rail. What happens is that, in rotating, the left hand bridge rail makes passing contact with that right hand +ve spur rail at one end of the bridge - and the right hand bridge rail makes contact with the left hand -ve spur rail at the other end of the bridge. If nothing was on the bridge this would have no effect as there is still no actual circuit formed as the non contacting ends of both bridge rails are waving about in fresh air. But putting a loco on the bridge could form a rather dubious circuitry situation. So I could take out the bridge rail contacts, add a decoder and DCC it all.Or, Plan 'B' - I'd still like to use it in non DCC form if I could. Take out both contacts at one end of the bridge. As all of the on/off spur track sections will have droppers, this would still power the bridge but without forming a circuit and reversing polarity when two spurs are opposite each other on the TT. Or am I still not getting my head round it (very probable is that). RDS - yup, I'm the family DCC merchant and much as I try, he won't take the DCC plunge. Youngsters nowadays - no sense of adventure! (Of course, this does not apply to younsters nowadays who do have a sense of adventure.) Link to comment Share on other sites More sharing options...
Rog RJ Posted July 21, 2015 Share Posted July 21, 2015 One possible option (I think) is to fit insulated rail joiners to all the tracks between the normal track and the special short turntable track pieces except for the inlet track with the brass contacts. This would mean that the turntable bridge rails are powered and will supply power to the short, isolated, approach tracks when lined up. Link to comment Share on other sites More sharing options...
Chrissaf Posted July 21, 2015 Share Posted July 21, 2015 Ray,I'm sure during your research, you will have looked at Brian Lambert's turntable wiring information page. But in case not, check it out here. May give you some alternative ideas.Chris.PS - I'm assuming you have also read Hornby's OWN guide for modifying the R070 located on the Hornby web site. In case not, it is here. Link to comment Share on other sites More sharing options...
St1ngr4y Posted July 21, 2015 Share Posted July 21, 2015 Ray,I'm sure during your research, you will have looked at Brian Lambert's turntable wiring information page. But in case not, check it out here. May give you some alternative ideas.Chris.PS - I'm assuming you have also read Hornby's OWN guide for modifying the R070 located on the Hornby web site. In case not, it is here. Hi Chris, I read Hornby's guide first, and got as far as removing the brass contacts at the ends of the bridge rails, before I realised that this was a bad idea. I didn't go to Brian Lambert's guide, but I have worked it out and it operates perfectly under DCC. The only "mod" I had to do to the original TT was to unclip the two bridge wires from the brass contacts under one of the input roads, and re-connect these directly to the DCC bus. After that, all that was needed was to place insulating rail joiners on the outside end of each input road. Simples :-) Ray I've just realised that the OP is also called Ray. Sorry if my reply has caused any confusion :-) Link to comment Share on other sites More sharing options...
Greynut Posted July 21, 2015 Author Share Posted July 21, 2015 Has the subject title of this thread has changed - or am I simply going mad (as the family has suspected for years)? I'm sure I put something along the lines that I was asking for advice on modding the TT for non DCC operation on a DCC layout. No worries though. Chris and Rog. I did originally look up Brian Lambert's piece and the Hornby guide, on modding the TT to fully DCC the beast. But then (for various reasons) I thought that I'd like to have it turn through a separate direct DC supply to the motor but to allow DCC to flow through the bridge track. This DCC input would not come from the inlet ramp connectors that are built into the TT to power the bridge track but would come in from the other on/off spur tracks which will be all DCC powered by droppers off the bus. To do this, I would need to retain some of the brass connectors at the ends of both bridge track rails. So the insulated rail joiners would not be needed although I can see that they might be a good idea in some DCC situations. As usual, I missed a few things that I should have thought of before I posted my OP but that's what I like about this forum - wise advice. As a result, the latest way of modding it to be DC/DCC operated would seem be to remove one pair of the bridge rail brass contacts at one end of the bridge track so that when it lined up to an on/off spur, the bridge would still be powered by the DCC spur trackwork. BUT ... where one spur was opposite another on the other side of the TT, when the bridge rotated, there wouldn't be a situation where a contact at each end of the bridge brushed past a reversed polarity rail forming a short circuit if a loco was sitting on it. With a set of bridge rail brass contacts only at one end of the bridge tracks, it would still brush past one reversed polarity on/off spur track rail but no circuit would be formed as the other end would have no contacts to touch the other opposing polarity rail. (Does my head in trying to word this.) Ray, my idea is that by not using the input ramp rail contacts, the reversing polarity problem would be avoided as the bridge track would not be internally powered through the TT. When the bridge rail lines up with any of the on/off tracks, if one set of the bridge track brass contacts are still there, the bridge track then takes its power from that on/off track - giving it all the same polarity. Generally, the problem which might arise with the 'keep a set of bridge rail contacts at only one end' idea is that if you want to swing a loco 180deg then:-a) the bridge rail contacts must be adjacent to the 'on' track the loco is coming in from to pick up powerb) but after the 180deg swing, the bridge rail contacts will be at the other endc) if there is no on/off spur at the other end - no power to the bridge to move the loco off. This would really mean that the only sensible way is to go for full DCC and mod it as per the guides. But I've never been accused of being sensible. Luckily, the only on/off spurs where I'd want to do a 180deg swing have on/off tracks opposite to them, so whichever way the bridge is round, it will still get power. So I can get away with it with my set up. I think if this was not the case, I would give a big sigh and go full DCC because to get over that problem would involve a heap of messing about. And ... OK ... there will be cases on other spurs where the TT has to swing right round but it's fun playing with stuff. The other Ray :-) Link to comment Share on other sites More sharing options...
Fishmanoz Posted July 21, 2015 Share Posted July 21, 2015 If you were to do a forum search on R070 or just turntable, you should turn up more then you can jump over on modding the TT for DCC. For a start, don't read the Hornby guide on the butcher's method of removing the contacts. There is a more elegant solution. Also, it matters not how you power the rotation of bridge, from a DC supply or DCC via a loco decoder, the same DCC problem occurs. And the problem is that, if the bridge is live via the brass connectors under the inlet track, you get a short as soon as you rotate it so that Track A on the bridge meets Track B on the inlet track, or vice versa. So the solution is to cut a gap in both rails of the inlet track between the contacts and the bridge. Then if all of your outlets go to sidings not connected back to the layout or the bus, nothing more needs to be done. These will be powered by the bridge when it turns to them and no shorts will occur. However, if any of the outlets are powered by connection back to the layout or bus, you will need to gap these too. And don't forget the reversed polarity of half of the outlets when connecting any of these back to the layout. Brian Lambert covers this under the slip ring TT design. Link to comment Share on other sites More sharing options...
Greynut Posted July 21, 2015 Author Share Posted July 21, 2015 Many thanks for your reply Fishy. I'm actually looking to incorporate the TT in a DCC layout but not to DCC up the innards of the TT itself. I know it sounds a bit odd but surprisingly, I do have my reasons. I'm not looking to power the TT bridge track from the built in brass connectors on the inlet ramp near to the hut bit. I'm looking at powering the bridge track through the contacts at one end of the bridge track itself. When it lines up to an on/off track, it will get DCC power from that on/off track as they will all be droppered to the bus, thus the track and bridge rails have the same polarity whichever way the bridge faces. As the bridge turns, the bridge track is effectively dead until it lines up on the next on/off ramp with laid track - which again gives the bridge the correct polarity. If I used the brass connectors on the inlet ramp making the bridge still live as it turned, then polarities would have to switch if it reversed direction. But with the bridge dead while it moves and current only coming from the lined up on/off tracks, the polarity takes care of itself. A short would happen if both sets of connectors (on both ends of the bridge) were still in place as when one bridge rail brushes the wrong on/off rail while it's turning, the other bridge rail would brush the opposite wrong on/off rail at the same time - on the opposite side of the table. A diagonal to both wrong rails would occur and a short would happen if a loco was on board to complete the circuit. Quite a big one, I would think. To avoid shorts with the bridge rails diagonally brushing 'opposite' on/off rails as the table turns, the contacts can only be at one end of the bridge. Although one of the bridge end rails will still brush an opposite on/off track rail, it's my reckoning that no circuit is produced, even with a loco on the bridge, as the other bridge rail is not in contact with anything without the other bridge contacts at the other end. Well, that's my theory anyway - if I've missed something or I haven't got it right, please fire away. The reason I posted originally was to see if it was possible as I couldn't find any real stuff on doing such a hybrid. Link to comment Share on other sites More sharing options...
RDS Posted July 21, 2015 Share Posted July 21, 2015 ... as I couldn't find any real stuff on doing such a hybrid ... and I don't think you will either. I have modified this model, using the ' cutting tracks method' mentioned by Fishy and it worked well but then again I only wanted to use it on DCC. Link to comment Share on other sites More sharing options...
Fishmanoz Posted July 23, 2015 Share Posted July 23, 2015 Your hybrid arrangement is quite irrelevant to DCC operation of the bridge and tracks, your DC supply to the motor is not connected to the track at all, with or without modding the TT. And your method not using the connectors under the inlet track will work too, unless of course you have powered tracks directly opposite each other. In this case as you rotate in either direction, one bridge rail will bridge between track A on one side and track B on the other. You would also have to be careful about correctly wiring your droppers on the reversed polarity outlets. If you operate sound locos, they will cut out when the bridge rotates too. All things considered, I think the gapped inlet track is the best way to go, together with gapped outlets if these are connected back to the layout and not just sidings. Link to comment Share on other sites More sharing options...
Greynut Posted July 23, 2015 Author Share Posted July 23, 2015 Sorry to confuse, I didn't mean the motor power supply as being part of the hybridity (is there such a word?). That will stay DC as I do like to do other things which don't involve the eLink and RM - I think fiddling is a good expression. The hybridisation (I know that's a word) was in supplying DCC power to the bridge without adding a decoder and using the inlet track connector. Basically using some method to power the bridge from the on/off tracks. My TT layout is having 3 on/offs on one side of the TT which link into the all round DCC layout. Then on the other side of the TT are 4 on/off engine shed sidings - and also another on/off linked to the overall layout. So perhaps not a usual scheme. As there were on/offs to the overall DCC layout on opposite sides, it just seemed best to have the on/off inlet track, that the bridge was lined up to, determine the polarity. I will have to isolate or take out the bridge rail contacts at one end of the bridge because, as you say, with both ends able to make contact, shorting would be the norm. But with only one end having contacts then a brushing connection when the bridge turns only occurs with one 'wrong' inlet rail, so no short. I don't have any sound locos as yet, so the bridge being dead when it revolves is no worry. If I do get one, I can always make the noises myself, I do half the time anyway (very sad really). Also, lights going out is OK - I'll just put that down to a driver who likes saving energy. Link to comment Share on other sites More sharing options...
RB51 Posted July 23, 2015 Share Posted July 23, 2015 I have absolutely no input to your query - but just wanted to say that your last post has given me the best laugh of the afternoon. Thanks. R- Link to comment Share on other sites More sharing options...
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