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JMD---Z Boiler conversion for SSM/TMD J15 Kit

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Posted (edited)

I designed a fret for converting the SSM/TMD kit into the Z Boilered superheated version of the loco about 10 years ago.

I assembled two J15s from TMD kits during the 80s-90s picked up a part built kit at Expo EM about 20 years ago and bought a further two kits from Paul Greene shortly before he sold the business to Des Sullivan during the late 2000s.

Apart from the MM 201 and repaints of BR stock reasonable rtr models of Irish locos and stock were virtually unknown and apart from the SSM/TMD available kits were nothing to write home about.

Although mainly interested in the Midland I basically gave up on scratchbuilding during the 80s and I was planning to build a model of Kiltimagh and the J15 were the staple motive power on Burma Road goods trains so I ended up with 5 J15s and decided to build one as a superheated loco to add variety.


The original fret was very simple basically heavier main frames fitted to some locos by the GSR smoke box and firebox parts and a new spectacle plate. Additional parts were included to replace the fragile brake gear and reversing rods and Belpaire firebox formers similar to that used in the Y Boiler version of the JMD 650 Class kit. Although I gained considerable experience in designing loco and rolling stock kits over the past 10-12 years, I ended up with a 12 item snag list after I completed the test assembly of the firebox, boiler and smokebox after I converted a 2D design into a 3D object.

The first boo-boo was forgetting to attach the half etched smokebox wrapper to the main fret and I appear to have "disappeared" a copy of the original fret complete with wrapper!


The main design change in design from the original fret is to include a former/jig  for forming the firebox and bolt together assembly of the three main sub assemblies.


I removed the center section of the former/jig once I soldered the wrapper in place.


I was reasonably satisfied with the fit of the wrapper, though those fragile sandbox rods are a pain!  The cab and running board for the loco were assembled about 10 years ago!


I have designed the firebox-boiler-smoke box to bolt together using 10BA bolts. There may be variation in the diameter of boiler wrapper in individual kits supplied by TMD and SSM, the kits supplied by Terry McDermott in the 80s-90s were supplied with boilers formed from brass tube, the boilers wrappers in the two kits supplied by SSM in the late 2000s were rolled from sheet brass and were marginally larger in diameter.


I will cover the smokebox assembly and modifications to the running board in a separate post.








Edited by Mayner
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Smokebox & Front Footplate


The smokebox former is designed in two parts to reproduce the distinctive extended smokeboxes fitted to some classes of locomotives re-built with superheated boilers.


The bolts fitted to the main section of the former are intended for bolting the smokebox to the boiler-firebox assembly and the running plate, the bolts fitted to the extended section are basically alignment pins.


Smokebox fitted to boiler-firebox                                                                                                                                                          Original 2013? smokebox fitted to boiler-firebox: It was necessary to remove a section of the wrapper that fouled the                                                                                                                                                                                                                                  driving wheels on the original wrapper one of the inherent problems when you are unable to scale down full size gauge and                                                                                                                                                                                                                        running clearances in a model.


Frames and running board compromises TMD/SSM J15


The frames on the SSM/TMD J15 are designed in two sections in order to reproduce the open section between the rear of the buffer beam and the front of the cylinder block at the front of the loco and to allow the model to be assembled to a narrower than prototype gauge and or compromise wheel standards. This feature was absent on locos re-built with new deeper mainframes by the GSR including the preserved 186.


I did not notice this feature when I produced the original fret, but included it on the revised version.


The revised mainframes are modelled full length and include a half-etch line (viewed from the rear) for modelers who intend to assemble the frames in two parts in accordance with the original TMD/SSM instructions.

The chassis is designed with half-etched lines for hornblock cut-outs and fluted coupling rods!


Work in-progress with Saturated J15 with McDonnell linkage reverse built 1860s-1900, Post 1900 Saturated "Coey" J15 with raised sandbox, revised cab and direct reversing lever, Superheated J15 original frames and linkage reverse.

I expect to complete the amendments to the fret and place orders for the production fret by late next week with a 6 week lead time to delivery.

From a personal modelling perspective next job is to complete the artwork for the large capacity Type B tender to run with the Coey J15 on the Limerick-Sligo goods and assemble a Type A tender to run with the Superheated loco, an even bigger challenge will be to sort through my stock of J15 parts for boiler fittings and buffers to complete the two locos and where required order replacement parts. 





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Posted (edited)

That looks excellent 👍

Are we able to determine exactly what type of large tender is paired with 186? It's very modern for an engine which is fundamentally very old. I thought it was something which might, at one stage, have been paired with a 400/500 class 4-6-0.

Edited by Horsetan
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