Dapol Class 73s…into traffic!

March 28, 2017

No. 73 108 in late condition, photographed at Eastleigh in 2002.
Faded, dirty but still doing its stuff on the SE TPO.

No. 73 108 is one of the locomotives I have chosen to model using one of the two new Dapol models to recently arrive on Folkestone East. Conversion to EM turned out to be the simple, involving the regauging of the split axle wheel sets which have a good profile on them – good enough to run smoothly through my hand built track.

There are many well-thought out technical features of this model. The body lifts straight off after releasing the retaining screws – no pesky clips to fight. Don’t loose the screws though or you will be scr*wed when it comes to putting the body back. There is a good space for both decoder (nearest) and a sound speaker. A 21-pin socket ensures all lighting features have power.

The circuit board makes contact with circuits in the body by means of a row of sprung contact pins which eliminates linking wires and plug and sockets. However, I did not want the cab lights illuminated and was looking to fit a decoder with ‘stay-alive’ (‘keep-alive’) . The only one I had to hand was a wired LaisDCC one which works well with this mechanism. 21-pin versions with stay-alive are also available. I also wished to work the head code lights independently using red LEDs, so decided to remove the circuit board and hard wire a LaisDCC decoder in place with its stay-alive capacitor. The lighting connections to the circuit board are easy to locate and desolder, so this hard wire DCC conversion is easily reversed – the circuit board being stored away safely.

The image above shows the hard wire installation, with the head light LEDs wired with 5k Ohm resistors to reduce the fierce light to something a little more realistic. Connections will be made with the head code box LEDs too.

A stay-alive unit is seen in this image. It was not quite powerful enough to power the Dapol Class 73 when it lost contact through those pick-up bearing rings. In the end, I built a new stay-alive unit with some higher Farad rated capacitors with great success. The higher rated unit was still connected to the same LaisDCC decoder. It is worth mentioning that even the smallest capacity stay alive unit will prevent light flicker in the most reliable models even if there’s not enough juice to deal with a serious stall. In many instances, the flywheels fitted to modern mechanisms will carry a loco over a minute dirty spot without interruption,. The only hint of a problem will be a flickering of LED head and tail lights. Stay alive units also smooth the operation of locomotives that otherwise seem to run well.

A final look at the DCC installation. It may seem strange to remove the convenient 21-pin DCC interface. However, wired decoders offer so much more flexibility in terms of organising lighting effects and this installation turned out to be quick and effective. The model is numbered 73 108 with an address of 3108 and is now hauling trains on Folkestone East. It is at this point I must admit to keeping two Lima EDs, stripped of drives and in the process of being reworked with Dapol detailing parts. One is No. 73 129 ‘City of Winchester’ which is used as a trailing unit in the SE TPO so the train can be top and tailed. Two Dapol EDs on this train is overkill. The second loco was also a regular on the SE TPO: No. 73 131 which will eventually be refinished in EWS livery.

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Stay Alive ‘Peckett’ – fitting decoder and ‘cap’ to the Hornby model.

January 22, 2017

There’s not a lot of room in the Hornby OO gauge Peckett W4 0-4-0ST locomotive model which comes as no surprise. To maximise pulling power, the saddle tank, boiler and frame assembly is entirely cast from metal – beautifully done but challenging should you wish to fit even the smallest ‘Stay Alive’ device or speaker for digital sound.

 

The challenging little Peckett - a beautiful runner, but interesting should you wish to fit something other than the decoder Hornby has designed for it.

The challenging little Peckett – a beautiful runner, but interesting should you wish to fit something other than the decoder Hornby has designed for it.

Hornby has fitted a non-standard 4-pin interface for an adaptation of its small loco decoder. However, not all of us use Hornby DCC equipment and for various reasons too many to mention here. Adding an alternative N gauge decoder such as a Digitraz DZ126 for example would require hard wiring – at least it will slot into the front of the motor cavity where Hornby intends its own decoder to fit. However, when it comes to adding a Stay Alive device or digital sound…there’s simply no room unless the 4-pin plug arrangement is removed from the side of the motor and some milling out of the inside of the die-cast body undertaken – tricky!

This project shows how I fitted an N gauge decoder and Stay Alive to the Hornby Peckett.

This project shows how I fitted an N gauge decoder and Stay Alive to the Hornby Peckett.

To take advantage of the lovely mechanism over the sharp and complex track of the Loch Dhu Distillery yard, Stay Alive is essential to smooth operation in a loco with just four wheels and four current pick-ups distributed over a short wheelbase. I decided to try one of the low-cost LaisDCC decoders with its Stay Alive unit which would provide something like 0.5 to 1 second of power when track supply is interrupted. More power time would be desirable, but there’s simply insufficient space in the loco for a larger capacitor circuit such as the TCS KA-series decoders! Anyway, this is how I tackled the project. The same approach could be adopted by those wishing to fit a digital sound decoder – a sugar cube speaker should fit at the front of the model where I fitted the Stay Alive device. The model’s wiring, TV interference suppression capacitor and decoder retaining bracket were removed first.

Two screws hold the body in place - one is concealed behind a NEM coupling box.

Two screws hold the body in place – one is concealed behind the NEM coupling box at the front of the model.

There it is!

There it is!

For this project, soldering cannot be avoided. You will need heat shrink sleeve, a soldering iron and electrical solder, Kapton tape, double-sided adhesive tape, wire strippers, tweezers, mini-drill, milling tool for a mini-drill, wet and dry paper, screwdriver set, fine nose pliers, modelling knife and somewhere comfortable to work with plenty of light. It’s a long job!

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The wiring is simple including the rather large 4-pin socket arrangement. Interestingly enough, this is the start of fititng a decoder to the side of the motor to leave the front area clear for the Stay Alive unit (or speaker for a sound decoder).

Die-cast metal all round in the motor cavity - all of which can cause a short and kill a decoder if care is not taken over insulation and making enough room for the decoder.

Die-cast metal all round in the motor cavity – all of which can cause a short and kill a decoder if care is not taken over insulation and making enough room for the decoder.

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Yes, there is potential for attaching a decoder to the side of the motor. Some further space will need to be ‘created’ by milling away some of the inside of the loco body. There is also enough room to run wiring across the top of the motor mount but not around the back.

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Wiring and brackets are stripped away. Heat shrink sleeve is used to insulate the soldered connections between loco wiring, Stay Alive device and the decoder harness wires.

The decoder wiring has been shortened to fit the model. The unwanted lighting function wires have been trimmed short and insulated from everything else with 'Kapton' tape.

The decoder wiring has been shortened to fit the model. The unwanted lighting function wires have been trimmed short and insulated from everything else with ‘Kapton’ tape.

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With the decoder positioned on the side of the motor, it is now a simple task to work out how much metal to remove from the inside of the body.

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Around 2mm of metal was removed from the inside of the body, on one side only. This shows progress after 30 minutes of very careful work.

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Once the body will easily slide on and off the chassis without the decoder catching anywhere, you are finished. Clean up rough edges with wet and dry paper and insulate the inside surfaces of the motor cavity with insulation tape. When test fitting the model, do not force it over the decoder – crushing and scraping will damage it. If there is even a hint of the body catching the decoder, remove it and slowly mill away some more metal. There’s plenty to go at without piercing the saddle tank!

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Final assembly with Stay Alive ‘cap’ taped into place and Kapton tape used to secure wiring in place. The body now drops straight on to the chassis without touching any components.

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A time consuming installation but well worth it. The value of CV29 was set to 34 to switch the analogue operation off so the Stay Alive unit will function correctly (also for 4-figure addressing). I hope the close proximity of the die-cast body will act as a heat sink for any heat generated by the decoder, not that this loco will be under much load!

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The installation has resulted in a smooth running engine. The effect of using a low power Stay Alive is to make operations smoother in such a small short wheelbase engine. If the track is truly contaminated, it won’t work as well as a TCS KA-series ‘Keep Alive’ device, but there’s no fitting one of those in a Hornby Peckett without seriously milling away a great deal of the die-cast metal with the consequent loss of adhesion.

Examples of the TCS KA-series decoders and 'Keep Alive' units - too large for this project!

Examples of the TCS KA-series decoders and ‘Keep Alive’ units – too large for this project!

The Hornby Peckett at work at the Loch Dhu Distillery interchange sidings.

The Hornby Peckett at work at the Loch Dhu Distillery interchange sidings.