DCC Loco Conversions - 18 - Dublo Early Stanier 8F

Straightforward conversion as both brushes can be isolated from the chassis with insulating sleeves on the brush springs, finding space for a large decoder is the tricky part.

This loco was already configured for 2 rail operation, probably as manufactured.





In this early conversion (2016) I have retained the original interference suppression parts which did not impede operation of the Lenz Standard 10231-02 decoder. At the time I was still keeping to all Lenz whilst I was getting to grips with DCC.

The build quality of Lenz decoders is very good but it has much more functionality than I need. This meant it is quite large and has a naked PCB (printed circuit board) which needs to be kept away from loco metalwork, which is not easy in a Dublo loco whose chassis and body are both made of metal.

I decided to put the Lenz decoder in the tender, which meant running two pairs of wires to the tender, track power to, and motor drive from. These were taken in pairs parallel to the draw bar into the front hole in the tender chassis used for the pickups on a 3 rail version as can be seen in images 2 and 3.

The wires are guided by tape past the loco footplate and anchored at the tender using braided nylon lacing cord.

The wire used for the connection between loco and tender was arranged to look like flexible pipes so they are black and have coloured markers of heatshrink sleeving to denote red, grey or orange at each end.



Once in the tender the cable loops around so that the loco-tender wires can be joined to the wires attached to the decoder. Despite the size of the tender the mounting holes for centre rail pickup and the body retaining screw leave very little space. The decoder wires take a tight turn upwards before being routed to the rear of the tender.





The decoder is fixed to the tender chassis with the provided double sided adhesive pad.

Would I do it the same way again?

Probably not, if I was to do this conversion now I would probably remove the interference suppression parts and fit a RoS-6D in the loco body and greatly simplify the wiring, however if you use a large format decoder then the tender is your only real option.


Discussion always

Jim

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Thanks Paul

Regards TCS decoders I must admit that I have not actually tried them, there are so many manufacturers out there, but my approach to power ratings is more based on the current when the loco starts to slip rather than stall. Okay I take a little risk if a loco does jam when I am not aware of it but that in my experience is very rare in battleship build locos, but when it comes to modern models I have had two Hornby loco drive 9Fs trash their delicate valve gear for reasons unknown. Meanwhile I can use physically smaller and more easily fitted decoders at lower cost, this 8F would have been a lot easier to convert now than a few years ago.

It's much like the difference between horse power and brake horse power measurements on car engines, brake brings it to a standstill whereas maximum torque at optimal rpm seemed more relevant to me, but I digress.

In some respects modern decoders are excessively rated for modern motors which take amazinging little current, but a well serviced Dublo loco can stay well below decoder limits even with a re-magnetised original magnet, NEO magnets despite their high magnetic field strength only seem to reduce the current by about 20% compared with a healthy Alnico magnet.

I will be converting a Duchess too, however I have graded my Dublo locos into four groups of what I consider increasing difficulty :-

1) Discrete (non-Ringfield) motors - often all is needed is a piece of sleeving on the brush spring wire which is electrically connected to the chassis
2) Ringfield - covering these will continue when more decoders arrive from Rails of Sheffield
3) Semi-integrated motors, e.g. diesel power bogies, insulating short brush tubes - TBD
4) Integrated motors such as the Duchess and it's contemporaries, insulating long brush tubes - TBD

The difficulty of (3) and (4) is how to set up the chassis for accurate drilling to insulate the non-insulated brush spring tube, at least with the Ringfield motors the end housing was removable and easily setup on a simple jig to drill.

Two early Castles I will write up shortly includes an ex-3 Rail for which I have employed modern Hornby tender wheels with pickups on one side.

Jim

 

Yes the Ringfield motor such as in the West Country loco is quite possible to convert as I found and shown in my approach to performing the necessary surgery. It is also possible to drill out and insulate the brush holder by hand if you are steady enough, it is only about 3 to 4mm deep but alignment is important, I am not steady enough and did not want to do 10+ motors by hand.

But even that loco I believe does not need a heavy duty decoder either, I will verify that shortly when I receive more decoders from Rails of Sheffield.

Jim

 

Hi Paul.

3D printing an insulating bush for a Ringfield would be possible too, they do push out of the metal fairly easily and as i note in my article about Ringfield motors some just fallout. Even an old original resin bonded paper insulating bush from early Dublo locos is easily dislodged by accident.

Regarding drilling out the old non-insulated brush tubes on locos such as a Duchess, I was intending to drill them out sufficiently to weaken them to avoid damaging the chassis casting and remove them, followed by opening out the hole just enough to fit a new tube with heat shrink around it. That may be possible with a couple of reamers. Only a gentle to slightly loose fit so as not to damage the heat shrink and retain with a spot of super glue.

Another option I was considering was using a freezer spray in the tube to loosen it but not sure whether that would damage the chassis casting.

It is all made the more tricky by trying to avoid removing the loco axles, got some more thinking to do with the aid of a couple of scrap chassis.

Jim

 

This reply superseded by :-

https://platform1mrc.com/p1mrc/inde...-conversions-22-brush-holder-extraction.6017/

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Hi Paul.

Just found a simple way of removing a non-insulated brush holder from a Montrose chassis which I will detail in a subsequent article with photos.

But here I outline the basic principle which is to jack out the tube ...

1) the carbon brush tube bore is nominally 1/8 inch diameter, (3.18mm)
2) tapping drill size for 4BA is 3mm
3) run a 4BA tap all the way through the tube, if using a first tap (or taper tap) the thread will be tight at the armature end which is useful to prevent subsequent rotation of the studding within the tube.
4) insert a length of 4BA steel studding all the way through with 4mm or so exposed at the armature end
5) at the armature end temporarily attach a nut nipped up against the tube for the initial pull
6) at the open end attach a piece of metal tube of bore to accept the OD and length of the brush tube, a washer and a nut
7) tighten the outer end nut ensuring the studding does not rotate until the nut at the armature end touches the chassis, and then remove that nut
8) carry on tightening the nut at the open end until the tube is loose
9) extract the studding with the brush tube attached
10) job done

By threading all the way through the tube it is gripped over a long length.
The removed tube shows that the tap almost cuts through it, it looks ribbed, which probably reduces the friction between the tube and the chassis.
The shorter brush tubes in the diesel bogies are similar, so the same approach should be possible.

The resulting undamaged hole in the chassis should now be able to be opened up with a reamer to fit a new tube wrapped in heat shrink sleeving.

Similar other screw sizes e.g. metric could be used, but BA is what I have a lot of.

Jim

 

Well you still could, as the next stage is opening out the hole correctly to fit a new tube in whichever form you go for.

I am relieved to have found a way that did not require a complicated jig to secure a wheeled chassis to a machine bed for drilling, Jim

 

Hi Paul

I have started work on my old Montrose and refined the extraction process to make it slightly simpler but maintaining the required result, photographed the stages and will now see about fitting a new insulated brush tube.

A new article specific to brush tube extraction and replacement will (should ) follow shortly.

Here it is :-

https://platform1mrc.com/p1mrc/inde...-conversions-22-brush-holder-extraction.6017/

Jim