DCC Turntable problem

[Lorrin]

Hi everyone,

I will start by saying I am not the most experienced person when it comes to Hornby stuff so please be patient with me :D

I have made a DCC layout for my 7 year old. Basic two track oval nothing too complicated which all works

fine.

He was asking about adding a turntable so I went ahead and got one.

I have fitted it using the guide on this site https://www.hornby.com/hornby-dcc/decoder-installation-guides/turntable-conversion/

Now I managed to get the turntable

to revolve using the Select controller first time no problem (Which really shocked me!!) but as soon as I put a loco on the track and it arrives at the turntable it stops when it gets half way on the turntable.

If I nudge the train on a bit it will

move again on the turntable rails.

I have noticed there is a small gap between the track rails and the turntable rails which I think may have been causing the issue but if I push them together so they touch it produces a short. If I turn the turntable

180 degrees it does the same so I don't think it is a polarity issue but as I said at the beginning I am no expert.

I have uploaded a 15 second video showing the loco aproaching the turntable and stopping when it gets part way on the turntable.
http://www.youtube.com/watch?v=l1Wzt1-KQ00

A

bit of extra info incase it helps. I have a bus wire going around powering the track and the turntable is powered by dropper cables to the same bus wires.

As of yet I have not powered any of the exit tracks from the turntable. Just wanted to get the

train to fully get on the turntable to begin with.

Is anybody able to give me any advice as to how I can solve this issue please?

Thanks for any advice in advance :D

Richard

[60157]

hi i think you will find that when you turn the turntable the tracks positive and neg feeds then become reversed thus shorting out and not letting the train go so you will need to put in a reversing box in one of hornbys dcc ones and wire it to the track

and the turntable and it shauld work then hope this helps
shaun

[poliss]

The loco wheels are causing a short circuit as it enters the turntable. Try swapping over the dropper wires to the turntable.

[Brightstar]

Hi Lorrin,

Have you allocated a number for the loco decoder that operates the turntable?

Put Thomas on to the middle of the turntable and see which direction it moves to. If it moves backwards then you need to reverse the leads to the power

bus to the turntable. and check which direction Thomas now moves.

If it moves forwards, Stop Thomas and put it on the Rails leading to the Turntable and see what happens, when it reaches the turntable. Hopefully, all should be OK.

[Brightstar]

Hi Lorrin,

The turntable is treated by the controller as another loco, so when you select it , the speed control on the Select Controller moves it clockwise or anti-clockwise depending in which dirction you move the knob.

The two wires from

the decoder to the bus wires decides the polarity of the turntable track, which is isolated from the spurs to and from the turntable, by the removsal of the copper strips on the turntable tracks. If the polarity of the turntable track is different from the

rests of the layout than a loco will not be able to cross onto the turntable and the Select safety feature will cutout the power supply to the tracks on the layout

All the spurs to the turntable, must have the same polarity as the rest of the layout,

otherwise the loco will not move on or off the turntable.

[FinnerZ]

I was thinking that if you just switched the polarity of the turntable track it would short circuit when it turns through 180 degrees which would defeat the purpose of having the turntable. I may be wrong (I don't actually have a turntable) but I agree

with 60157 that a reverse loop module could be used - all the track feeds run to the bus but the turntable track is connected to the output of the module - this allows such short circuits to occur and automatically reverses the current where needed. Also,

I seem to remember that with DCC even if you switch the power feeds around the train will still move in the same direction, but this may be only some locos. Good luck with your turntable.

[poliss]

The polarity of the wires has no bearing on which way a loco moves on DCC.

[Brightstar]

Hi All,

By removing the brass contact strips under the turntable rails you are stopping the approach/spur rails from making contact with these rails, go to this link for the turntable service sheet:

http://www.modeltrains.net.au/hornby/service_sheet_details.asp?sheetid=212

You

must therefore provide some method of powering the rails on the turntable. We must therefore ask Hornby how this is done when the contact strips have been removed.

I assumed that the decoder was providing this power, but looking at the service sheet

I can see that the tracks on the turntable are not powered and cannot be powered without some connection between the spur rails and the turntable rails.

I am send an e-mail tocustomer care asking for clarification.

[Lorrin]

Thanks for the replies. Can't really read them all properly at the moment as I am in work. Will read them tonight and post suitable replies. Many thanks

[Brightstar]

I have been looking at the service sheet for the turntable and I find that there are two spring contacts under the rails that rub on a printed circuit board above the gear that rotates the table. This disc is attached to two wire under the turntable, which

probably supply power to the rails, unfortunately there is no indication where these leads go to, see:
http://web.blissett.me.uk/house/hornby-service-sheets/ss-178-back.jpg

[FinnerZ]

It seems most likely that these are to be fed by the bus wire (as Lorrin has done) but this presents the issue of turning the turntable through 180 degrees and meaning the tracks don't line up. What's interesting is that Lorrin's turntable has the same

problem when turned through 180 degrees. This seems to me to be one of those issues where an idea was though up (ie powering the turntable track by the bus wire) without realising the problem (short circuits when the turntable is in a certain position. Again

if this is the problem I would expect the reverse loop module to do the trick. The only problem is that it is quite costly!

[Brightstar]

I found this information on another site:

"All the tracks into and out of the TTable are connected to the powerbus.( powerbus:- two cables that run below the baseboard around the layout. Feeder wires are soldered to the side of each rail and drop

through the baseboard and soldered to the powerbus. The DCC controller output is then connected to the powerbus)

Underneath the Turntable you can see two wires from the centre going out to the track infeed, I have disconnected these and soldered them

again to the powerbus. This means the rails on the turntable bridge are always live. I just made sure that in the position where the engine enters the TTable the bridge rails are on the same powerbus wire as the infeed track.

This allows the engine

to be driven onto the bridge.

All works perfectly, as the turntable rotates, once it gets past 180degress the polarity reverses, this does actually reset the sound though on a sound chipped loco, but no short circuits and no need for a reverse module

or track adapter."

Has anyone any other thoughts or suggestions?

[Rog RJ]

What I've done is to only remove the contacts from one end of the turntable bridge track and either don't use the inlet track (the one which has metal contacts) or put some insulation over the contacts. You then need to provide a power feed to all the

exit tracks that you use as well as the inlet track.

This allows the turntable bridge to get power from whichever track it's lined up with but won't cause a short circuit.

The bridge will lose it's power as soon as it starts to rotate which may

be a problem if you have a sound equipped loco on the turntable but stops the short circuit from happening
-

[FinnerZ]

The idea of the taking the track feeds off one end seems to be the cheapest solution. I was wondering though if there was a problem with cutting off the power to the loco like that because insulated sections are not suitable for DCC - I don't know if such

sections damage the decoder but if so then this could also be a problem with the turntable.

[Rog RJ]

FinnerZ said:

The idea of the taking the track feeds off one end seems to be the cheapest solution. I was wondering though if there was a problem with cutting off the power to the loco like that because insulated sections are not suitable

for DCC - I don't know if such sections damage the decoder but if so then this could also be a problem with the turntable.

There is no problem with having isolated sections on DCC. It can be useful for "storing" stock such as lighted Pullmans

to reduce power consumption or for any other reason. If a DCC equipped loco happens to run into an isolated section it simply stops, with no damage resulting.

[Brightstar]

Here is a Utube video of someones DCC layout with a working turntable, so it can be mmade to work. There are 4 video clips in total including one where he has converted the turntable to DCC operation.

http://www.youtube.com/watch?v=8AidE6YuJlI&feature=mfu_in_order&list=UL

[Lorrin]

Thanks again for the replies.

Here are a few bits of extra info for the various replies.

The loco is set to 3
The Turntable is set to 10

underneath the turntable are two wires that link to the entry track. I also found this (As

Brightstar posted earlier):

"Underneath the Turntable you can see two wires from the centre going out to the track infeed, I have disconnected these and soldered them again to the powerbus. This means the rails on the turntable bridge are always live.

I just made sure that in the position where the engine enters the TTable the bridge rails are on the same powerbus wire as the infeed track."


and connected the wires to the bus. So the rails on the turntable are powered. If I put the loco straight

onto the turntable rails it can move forwards and back just as would be expected.

looking at Rog (RJ) post, I dont have the connectors that I removed any more to try that. Also to get the rails to meet one of the entry/exit tracks you have to push them

to one end meaning that one end would never touch the other entry/exit track.

Not really sure what to try next

Thanks again :D

[Lorrin]

For those that were giving me advice many thanks. I have managed to get it working :D

Basically had an idea in work this afternoon. All I ended up doing was swapping round the dopper cables that ran from the turntable rails (not the decoder) to

the bus wire. So what was connected to red now connects to black and vice versa.

What I would reccomend if anyone else has a go at doing this would be to leave the cables underneath the turntable as they are and not connect them to the bus wires directly.

Anyway

here is a quick video of it working for those that are interested:

http://www.youtube.com/watch?v=qewE1whVnIA

Once again many thanks to all those that offered advice.

[poliss]

You didn't read my reply on page one? :-(

[Lorrin]

Hi Poliss,

Yes I did but I thought you meant the ones to the motor of the turntable not the actual rails.

Managed to get there eventually anyway :D

Thanks for your advice :D Nice to know so many friendly and knowledgeable people around

here!

My son is made up now :D

[Brightstar]

Hi All,

Here is a copy of the information supplied to me by Hornby Customer Care:

"The rotating rail section of the turntable is fed power via the wires running under the item. These are then connected to the 'input' rail. Please refer to

our website, which explains how to convert the turntable to DCC:

https://www.hornby.com/hornby-dcc/decoder-installation-guides/turntable-conversion/

Also I think you will find Brian Lambert's website very useful, which has a extensive section

on DCC and the turntable (see following link).

http://www.brian-lambert.co.uk/DCC.htm#Turntables.

Hopefully this has solved your query."

I have looked at the Brian Lambert link and I find that it contains at lot of useful information

on setting up a dcc layout and a section of using a turntsble on the layout and the various options available
.

[Blackbird]

Post a new reply...

[Blackbird]

Hi Richard,
The 'problem' with the R070 Hornby turntable has been a subject on the forum for a long time (years). I published a simple solution over 2 years ago. Alas the forum has 'changed' and previous references are no longer available (Hornby?)
After

listing my 'solution' the question still kept appearing! so I decided to offer the requirement for sale on e-bay; a simple adaption of the inlet track to the turntable. All of my purchasers have been happy with positive feedback. I no longer produce these

adapted tracks, as a service, as the time involved in converting was not viable for the costs.
The simple solution involves gapping the powered inlet track between the bridge pick-up connectors and the T/T. This gapping prevents the short circuit which

occurs when the T/T rotates with DCC power on the rails. This allows the T/T to operate, as designed, supplying power to all of the outlet tracks when the bridge is aligned. The published Hornby requirement of removing the rail-end connectors means that all

of the outlets require additional feeds. The previous other suggested remedies all have merit but lack simplicity.
If wanting to be totally DCC then hard wiring with a busmain would be ideal and removing bridge contacts correct, Hornby advise, (but invalidate

Hornby's published warrantee!)
Again, unless wanting to be totally DCC, the fitting of a DCC decoder the the T/T motor is not necessary. Direct control fron a DC controller is, in my opinion, the preferred means. A dedicated controller means that the T/T

does not have to be; addressed from the DCC control, operated, then the loco involved, re-addressed. Also a basic DC controller can be obtained (S/H) for less than the price of a DCC decoder, if not already available as redundent from DC system.
However,

good to see that you have your system working.

[poliss]

Nice to hear from you again Blackbird. You've been missed.

[Blackbird]

I make this reply months after the initial tread date, but hope it is of interest to anyone concerned with the DCC operation of the Hornby R070 turntable.
The DCC operation of the turntable rotation motor has no relevance to the track DCC connections.

It is a direct an independent control. The track connection is the problem with DCC. Being permanently 'live', the track connection will 'short' the DCC system when the bridge is rotated. That is why Hornby advise the removal of the contacts on the bridge.

However, this means that the bridge will not supply the outlet track aligned as it was designed to do! Additional wiring is required. The simple method is to gap the inlet track between the under-rail contacts and the bridge connectors. (there was an adaptor

available on e-bay). This allows the bridge to supply the power to the outlet selected.