turntable on dcc layout

[tonystrains]

Hi I wish to operate, using a spare DC controller, a Hornby turntable on my DCC layout. Do I have to isolate anything so as not to create a short? I have looked on the forum but it is not clear to me. Thank you in advance

[Flashbang]

Hi

You will have to modify the TT to allow dc rotation and DCC track feeding.

 

You will need to feed the rotating bridge motor from the dc supply using the old dc controller. So locate the two wires that run to the motor and remove them form any

 

TT connections. Then connect them directly to the dc controllers 'Track' output terminals. This will allow independent rotation of the TT bridge by the old controller, giving forward/reverse and control of the rotation speed.

 

The TT bridge rails will

 

need to be isolated from the existing method of power collection.

You can follow the Hornby guide and pull off the wiper contacts https://www.hornby.com/hornby-dcc/decoder-installation-guides/turntable-conversion/

Or disconnect the two rotating bridge

 

rail feed wires under the TT and take them directly to the DCC bus pair of wires (if a bus is used) or to a connection on the main input DCC powered track. Then fit Insulated rail joiners to the ends of all the rails leading into / off of the TT. Add new rail

 

feeds to all tracks after the TT.

[Fishmanoz]

I agree with Flashbang - what he says is exactly the same as is included in various other threads here on TTs for DCC.

I'd jsut add that there are a number of people on here who caution against using the Hornby method of removing the brass connections

 

to the outlets and prefer using either isolated rail joiners as Flashbang says, or modified isolated outlet rais which used to be available on eBay.

[Blackbird]

The problem with using the R070 turntable with DCC has been raised on this forum for many years. (check the search function) There are many ways of overcomming this problem, (electrically shorting the DCC system when the T/T rotates) as previously listed.

 

 

Hornby advise mutilating the original turntable (removing bridge contacts) then lots of additional wiring is required to supply the outlets. The use of the 'DCC turntable adaptor track' is a 'simple' method for those not wanting the complication of all

 

the addition wiring.

I used to produce this 'adaptor', initially as a 'service' to model railwayers, but have found it financially unviable.

So, again (see previous threads) I will explain what is involved:

The X918, inlet track fitted to the inlet

 

to the turntable (the position with the under rail contacts) has the rails 'gapped' between the contacts and the outlet. The gap ideally 1mm, should be filled with plasticard (or similar) and filed to profile. the gap filling and outlet rails secured with

 

superglue. This allows the turntable to supply the (DCC) power to the selected track, as designed. If any other outlet tracks that are connected to the main, they will require insulating track joiners.

The rotation of the turntable can be under DCC control,

 

but require an additional DCC decoder, expensive and not practiable when a dedicated DC controller will suffice.

[Fishmanoz]

Blackbird, at last I understand the design of your adaptor track which I either hadn't found or hadn't understood previously. And I keep forgetting it is you who built it.

Hsving gapped the track, I take it you now connect DCC either straight to the

 

contacts or elsewhere along the bridge circuit?

And I'm assuming that no outlets can be connected elsewhere on the layout where there is reversed polarity, even with the insulating rail joiners? Unless these spots are connected to reversed polarity outlets?

(Note

 

to Newbies: half the Hornby TT outlets have reversed poarity via a slip-ring arrangement in the bridge wiring. There is a good explanation on the Brian Lambert site under DCC, Turntable menu item at http://www.brian-lambert.co.uk/DCC.htm#Turntables.)

[poliss]

You should sell your design to Hornby Blackbird. ;-)

[Fishmanoz]

I think poliss is onto something there Blackbird.

[Flashbang]

Hi

I think it more to the point that Hornby produce a new DCC friendly Turntable!

[Fishmanoz]

Seems to me that a DCC friendly TT is an R070 with a separate connection for bridge power rather than just the current contacts, Blackbird's adapted inlet track and some insulated fishplates for any outlet tracks that are to be connected elsewhere in the

 

layout.

 

The obvious weakness in this system is ensuring that the DCC connection to the bridge is the same polarity as the power on the inlet track, not to mention the outlets connected to the layout. Apart from clear instructions, the only fail safe

 

wat

[Fishmanoz]

To finish that post - the only fail safe way to solve it would be a reversing loop module incorporated in the TT and I don't think anyone would want to pay for that.

 

Or do I have all that wrong?

[Fishmanoz]

Another problem that occurs- sound locos sitting in sheds will be turned off when the bridge turns away from them, but they will fire up again briefly each time the bridge goes past. Can't think of an elegant solution to this one.

[minoo]

Hi Guys,

 

I have tried the following and it works. The total cost is ZERO.

 

My layout is DCC and i have connected a spare DC contoller to the turntable motor. Hence ease of operation of the turntable without the extra cost of a decoder or the

 

hassles of finding the TT decoder address on the controller while other trains are running. So no back and forth of addresses on the controller.

I have just applied electrical insulating tape to the bottom of the rails of the inlet track and left everything

 

else as it is.

What happens now is that the current from the inlet track goes to the bridge via the bottom contacts and the bridge stays live all through out. The other end contacts of the bridge conduct the current to the outlets and those tracks stay

 

live. When the bridge rotates, due to the insulation at the bottom of the inlet track, there is no short when the opposite rails pass each other. I also have not wired any of the outlet tracks since they are all dead end tracks of the engine sheds and sidings.

 

They get the current when aligned with the bridge.

The advantages are

The bridge is always live

The outlet track gets the current only when aligned with the bridge avoiding any unrequired movements on the sidings

The sound and lights of the locos

 

remain on while they are turning on the bridge

No shorting happens and resetting of the controller is no more required. This also assures non stop running of trains on the layout.

No removing TT contacts and hence no void warranties.

 

Hope this

 

will resolve a lot of querries about the DCC layout and Hornby turntable.

 

Regards

 

minoo

[Fishmanoz]

I'm confused minor. What contact does your insulation tape stop? How does this stop shorts as the bridge rotates?

[Fishmanoz]

Sorry, I meant minoo. It was this iPad misguessing what I wanted to say.

[minoo]

Dear Fishmanoz,

Sorry for my late reply.

I was refering to the TT contacts that touch the bottom of the rails when the bridge turns. The same contacts that Hornby recommend to remove.

 

minoo

[minoo]

Fishmanoz said:

Another problem that occurs- sound locos sitting in sheds will be turned off when the bridge turns away from them, but they will fire up again briefly each time the bridge goes past. Can't think of an elegant solution to this

one.

Once in their sheds, the locos should be sitting quietly and resting till their next roster.

[Fishmanoz]

minoo said:

Dear Fishmanoz,
Sorry for my late reply.
I was refering to the TT contacts that touch the bottom of the rails when the bridge turns. The same contacts that Hornby recommend to remove.

minoo

Thanks minoo, I

get it now. You get the sound loco fire up problem too as the bridge goes past don't you?

[minoo]

[reply]Fishmanoz said:

 

minoo said:

 

Thanks minoo, I get it now. You get the sound loco fire up problem too as the bridge goes past don't you?

Dear Fishmanoz,

If the sound function is not turned off, then momentorily the sound and lights

 

will come up as the bridge rotates and makes momentory contact. But i guess that if one has driven the loco to its shed with the bridge aligned, one would switch off the sound and lights and then rotate the bridge, as in real railways.

minoo

[Fishmanoz]

Thanks minoo, it makes sense.

[Blackbird]

The principle of the 'DCC turntable addaptor track' is to prevent short circuit when the T/T is rotated (the LH track contacts the RH) but track power is maintained to the bridge and the selected output. The polarity of the output is maintained by the

 

bridge and mechanically changed-over by the pick-up plate under the bridge, so any outlet (connected to the DCC main) will be automatically (electrically) aligned. No reverse loop module is required.

[Blackbird]

minoo said:

Hi Guys,

I have tried the following and it works. The total cost is ZERO.

My layout is DCC and i have connected a spare DC contoller to the turntable motor. Hence ease of operation of the turntable without the extra

cost of a decoder or the hassles of finding the TT decoder address on the controller while other trains are running. So no back and forth of addresses on the controller.
I have just applied electrical insulating tape to the bottom of the rails of the inlet

track and left everything else as it is.
What happens now is that the current from the inlet track goes to the bridge via the bottom contacts and the bridge stays live all through out. The other end contacts of the bridge conduct the current to the outlets

and those tracks stay live. When the bridge rotates, due to the insulation at the bottom of the inlet track, there is no short when the opposite rails pass each other. I also have not wired any of the outlet tracks since they are all dead end tracks of the

engine sheds and sidings. They get the current when aligned with the bridge.
The advantages are
The bridge is always live
The outlet track gets the current only when aligned with the bridge avoiding any unrequired movements on the sidings
The sound

and lights of the locos remain on while they are turning on the bridge
No shorting happens and resetting of the controller is no more required. This also assures non stop running of trains on the layout.
No removing TT contacts and hence no void warranties.

Hope

this will resolve a lot of querries about the DCC layout and Hornby turntable.

Regards

minoo

[GordonBigBoy]

Dear Hornby, are you planning a new TT which will be designed specifically for DCC - this would be very well received by the non electricians amongst us

[GordonBigBoy]

Can you please post a picture of where the insulating tape is?

 

Blackbird said:

 

minoo said:

 

Hi Guys,

 

I have tried the following and it works. The total cost is ZERO.

 

My layout is DCC and i have connected a spare

 

DC contoller to the turntable motor. Hence ease of operation of the turntable without the extra cost of a decoder or the hassles of finding the TT decoder address on the controller while other trains are running. So no back and forth of addresses on the controller.

I

 

have just applied electrical insulating tape to the bottom of the rails of the inlet track and left everything else as it is.

What happens now is that the current from the inlet track goes to the bridge via the bottom contacts and the bridge stays live

 

all through out. The other end contacts of the bridge conduct the current to the outlets and those tracks stay live. When the bridge rotates, due to the insulation at the bottom of the inlet track, there is no short when the opposite rails pass each other.

 

I also have not wired any of the outlet tracks since they are all dead end tracks of the engine sheds and sidings. They get the current when aligned with the bridge.

The advantages are

The bridge is always live

The outlet track gets the current only

 

when aligned with the bridge avoiding any unrequired movements on the sidings

The sound and lights of the locos remain on while they are turning on the bridge

No shorting happens and resetting of the controller is no more required. This also assures

 

non stop running of trains on the layout.

No removing TT contacts and hence no void warranties.

 

Hope this will resolve a lot of querries about the DCC layout and Hornby turntable.

 

Regards

 

minoo

[2e0dtoeric]

I don't know if it will help you - but what I have done is this -

The motor used to turn the table is driven from an old variable volts dc controller.

The wires from the track centre of the t/table are left disconnected.

All three spurs off,

 

and the entry line, (side by side on one side of the t/table) are wired to my DCC bus, all with the same polarity. (except one, which I have been using as my programming track).

So - the track section ON the turntable takes it's power from the spur it is

 

'facing', thus avoiding crossed polarity situations.

The down side of this arrangement is - while the table is rotating, the loco on it is not connected to the DCC data, so if it is a sound loco, the sound goes off.

[Flashbang]

2e0dtoeric said:

The down side of this arrangement is - while the table is rotating, the loco on it is not connected to the DCC data, so if it is a sound loco, the sound goes off.

All lights and sounds, if fitted will all go off.

They will also probably need their appropriate Function key re operating to restore them once power is restored. Sound fitted locos will have to go though their start up sequence before they can move off too.