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tender drive DCC fitting.





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#1 Atholl

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Posted 10 October 2011 - 12:54

Hi,
I have been trying to fit a DCC chip to a (Hornby?) tender drive Britannia loco.
Even with the 3 pole ringield motor brush plate fully isolated at the attachment screws I an getting an earth feedback to the earth brush holder via the armature spindle (shaft).
I am at a loss how to overcome this with the few (small) tools I have.
I will be very grateful for any advice.
Hopefully I have attached photo's of the set up, which does not seem like any Hornby I have traced so far.
Jim.

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Edited by Atholl, 10 October 2011 - 13:01 .


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#2 RedgateModels

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Posted 10 October 2011 - 13:46

Tricky .....

I'm assuming that you have the MKII tender drive that does not have traction tyres on all wheels and relies on the non geared wheels for power pickup.

this thread on the old forum details what I did to isolate the chassis from the brush holder
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#3 Atholl

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Posted 10 October 2011 - 14:50

Thanks Redgate,
You have quite elegantly done what I thought might be the solution - isolating the brush holder from the end plate, leaving no need to isolate the end plate itself.
If I had received no replies I would probably have attempted it off the cuff. Now after your tribulations I know where I am going. And it is going to save me hours of "suck it and see"!
Your pictures show a unit exactly like mine, but mine DOES have traction tyres.
One last question (I hope). IS this a Hornby loco? I bought it (used) as Hornby, but unusually I can find no markings except "SU" on the loco. chassis above the front bogie truck.
By the way, I fitted a chip to a 3 rail Hornby Duchess I had already converted to 2 rail years ago, by ( simply in that case) isolating the rear, earthed, brush holder.
Many Thanks Again, Jim.

#4 RedgateModels

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Posted 10 October 2011 - 14:58

Yes, although to be pedantic "Triang/Hornby"

just to clarify, the MKII unit has traction tyres on two wheels, the MKI unit had tyres on all six wheels and relied totally on the track feed from the loco - this was only used on the Evening Star loco as far as I am aware. All the Britannias had the MKII with removable tender and power feed from one side of the loco only.

#5 Atholl

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Posted 12 October 2011 - 14:52

Thanks again Redgate,
The Britannia (or tender?) is running fine on DCC.
As you said "Tricky". However everything was fine. The main hiccup was deciding that the red wire from the loco. needed to be connected to the black wire from the decoder. However, having slept on that - no problems. Perhaps the most frustrating bit was putting the brushes back in with my clumsy fingers. But I have to admit things like that were easier 50 years ago.
Regards, Jim.

#6 naugytrax

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Posted 15 October 2011 - 16:14

All the Britannias had the MKII

Er, not quite all of them. R.552 "Oliver Cromwell" had the tender with 6 traction tires and a permanent 2-wire connection to wipers on the loco drivers. The available tractive effort is quite impressive compared to later versions!

My sample has the anonymous chassis with the "SU" marking, like Jim's. I just got it out for a look, and I was reminded that originally the loco pickups only wiped the front and rear drivers. I added wipers for the center drivers, gaining an improvement in electrical connectivity. This might be significant in a DCC conversion.

Oh, and I don't think it is "Triang-Hornby". The box that I bought it in (from W&H Models, 9 pounds ninety-five) is marked "Hornby Railways Silver Seal Locomotive" and "Made in Great Britain by Rovex Limited" By the time the Silver Seal locos appeared, I'm pretty sure they had dropped the "Triang" identification.

#7 ColHut

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Posted 06 September 2016 - 05:57

Apologies for raising the dead with this. I have an old tender drive Bittern acquired by my son as a gift. It has the Mk II tender drive with pick up on the loco left side and return vis the chassis and axles to the tender right side.

Having now seperated the tender chassis from the motor, can I not replace the three Hornby live RH wheels with X1140 wheels insulated lh style wheels and then refeed the output power from the chassis/connector via wipers to the back of the tenders wheels to safely complete the circuit. The DCC chip can then be safely inserted into the circuit between the input wire from the tender connection to motor on one side and the chassis to wipers on the other?


Regards

Edited by ColHut, 06 September 2016 - 06:29 .


#8 ColHut

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Posted 07 September 2016 - 04:58

Ok wheels purchased second hand for $10 for 4, although I really only need 3. I will wire it up and see how it goes.

Regards

And it worked fine, completely isolated the axles from the track....

And then I realised that the keeper plate was plastic, and the only thing making the body live was a wire connecting one side of the motor to the body. I blush.

So by disconnecting that wire I can connect the chip in the usual way, and after re fitting the original conductive wheels on one side, the DCC circuit is complete.

Proof that one can re-invent the wheel.

Regards

Edited by ColHut, 07 September 2016 - 05:50 .

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