DCC Loco Conversions - 38 - Tri-ang L1 R.350 1961

Relatively simple conversion, but attention is required to two aspects of the chassis which is applicable to some other Tri-ang locos of the sixties.

As vintage 4 coupled with additional pony or bogie chassis models go this is one of the best IMO, it is well balanced and will run well for pickup and traction using just its coupled drivers.

However it requires some attention to the chassis for power collection to be reliable enough for good DCC running.

1) the omega collector wire can be very unreliable where it makes contact with the metal bush on the collector plate, I prefer to substitute a phosphor bronze strip soldered to the bush, less discrete but is 100% reliable.



2) this caught me out until recently after I originally converted it to DCC a year or two back and has always been an erratic runner. A sister loco much more battered from previous owners always ran well so what was the difference?

It turns out that early models had a composite chassis, two or more mazak blocks sandwiched between (in this case) two blackened brass chassis plates. These were held together it appears by riveted over stubs of mazak passing through the brass frames which over time can loosen.

This can be seen in image 2 and Tri-ang service sheet 29.

The chassis connection for the originally un-insulated brush spring wire is attached to one mazak block which in turn was loose relative to the brass sideframe used to deliver power from the un-insulated drivers.

To get around this I found there was just enough space on the brass frame to drill and tap an 8BA hole to attach a solder tag directly to the brass chassis plate. The cut end of the screw needs to be flush with the plate, tricky but necessary to allow the chassis extension plate to be re-fitted correctly.

I used a countersink head screw for two reasons, lack of clearance for a cheesehead screw between the body and chassis and the screw head would bite into the tag easily without straining the limited thread in the chassis plate.

Alternatively a soldered connection could be made as the side plates appear to be brass.

This modification means there is a solid connection for the power to be delivered from the uninsulated driving wheels to the decoder regardless of the chassis rivet state.





Fitting a RoS-6D Decoder

Suppression components removed and both arms of the brush spring are insulated with sleeves, decoder wires are soldered to the brushes.

Black heat shrink sleeves are shrunk onto the wire connections to the decoder pins to provide strain relief and insulation, shrinking is necessary for this conversion as the decoder floats free in the bodyshell. Pins 5 and 6 are cropped off as not required.



The decoder is a loose fit into the forward part of the boiler and smoke box, the decoder is inserted into the smokebox area during body fitting.



Summary

A straightforward DCC conversion so long as the collector wire and chassis electrical connections are sound.


Discussion always

Jim

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Update 19/08/22: Added to "Fitting a RoS-6D Decoder" above

"Black heat shrink sleeves are shrunk onto the wire connections to the decoder pins to provide strain relief and insulation, shrinking is necessary for this conversion as the decoder floats free in the bodyshell."

 

Thanks Chris

Even if you could get a tester faults can develop after conversion such as in a Dublo City, the armature failed shortly after conversion and blew the decoder, unfortunately there is rather too much current available at the track unlike pre-DCC power supplies when only one loco was driven (except when double heading) which limited the damage.

The alternative as paul_l does after conversion is to test with a cheap decoder and then fit the expensive one, however as I do not fit sound decoders and most are hardwired in that becomes less effective for me.

Split chassis types and Hornby Ringfield drives are the trickiest to convert due to their concealed chassis connections which need to be identified and modified accordingly.

Ultimately all you can do is be thorough with a multimeter and ensure all connections are sound and always check on the programming track (e.g. read the assigned DCC address) after any changes to the wiring, I tend to do that even if I have removed the body and refitted it again especially metal body shells that are live.

Jim