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Inchicore Class J10 Conversion From LNER J72

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Well on a busy Friday morning last in Greystones



617 setout from the shop with a light train for its first trials, things did not go well and the lads had to limp back to the shop. They did take in the sights and snapped a few shots while stopped at the Breeches waiting for the Wicklow Commuter to go by, and have a chat with Paddy- who has been working on that rock removal for the past year....





Back in the workshop with assessment made it was decided that the electrical pick up was the main problem for failure and I set about improving this- two PB strips were made up to push against the wheel boss from the underside, making contact with the wheels and the chassis improved the pick up immensely.





Springs n wheels in place and keeper plate about to go on.



Then off to the test track......





Looks fantastic Eoin. I'd say the signalman is sunburned with the light so bright in the signal box!

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I have really enjoyed watching this thread. To have taken the model as received and to have re worked it to this standard is truly great modelling, top work sir. I don't want to veer from the thread topic and I know I have no reason to need one, but I need to put cash aside and get one of these Darts. From what was announced at the beginning to what is being produced now it's a top model, I really like it.



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Looks fantastic Eoin. I'd say the signalman is sunburned with the light so bright in the signal box!


Hi Dave


He's going to be OK!


my phone is brutal with light and I pushed the picture a bit as it was quite dark which enhanced all the lights. We do have one of your light control units but we forgot to turn them down......



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  • 1 month later...


617 had its buffers painted red, SMM decal number added to the front buffer beam, new axle spacers and final drive gear installed which has improved the running- minimal lurch now. I sourced the replacement axle spacers from Peters Spares....


And a shot pulling a bit of freight out at Greystones yesterday morning59eb9ae39f010_GS-196IMAG3381.jpg.91ea092d26c535d7d7dbb4d58562ad9a.jpg


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  • 3 years later...

Westcorkrailway's post on converting the LNER J72 toJ26 reminded me of this current project, which has languished in the attic for the last five months while waiting for the new replacement motor for the mini lathe.

When things happen they usually happen in 2's- with the death of Adobe Flash my CNC machine control software gave up also as it was dependant on Flash to run the graphics for the program! Thankfully the program designers brought out a new upgraded version in the new year that now runs.

Also the motor for the lathe arrived yesterday and am currently installing it with a slight modification by adding a USB cooling fan! Hopefully this addition will protect the new motor from burning out like the last one.......

Anyway- the J10 is back on the workbench for a chassis upgrade! The old Branchlines chassis works fine on the test loop track with a few pushes at first it finally gets up and running, when the motor warms up the loco runs fine, shunting, slow running and all. Though on the Greystones Layout which is an 'out and back' layout its not so great, warming it up is a problem and the awful Knock foam track underlay we used doesn't stay still, nor the track on the foam, due to the temperature changes in the layout room!!

So last year at the railway company meeting it was decided that a new chassis would be fabricated, one with a Mashima motor and chassis compensation to the two front axles.

The design work was completed last October but while in the queue for turning stuff the lathe motor burnt out and the project was put back.

The chassis is also a test bed for future chassis- it's going to have full chassis width wheel bearing tubes that the axles will be threaded through. The tubes will have flats milled on their ends to slide in the chassis hornblocks to allow for compensation, ala Guy Williams design.

The design of the chassis frames allows for frame holes like the prototype, frame spacers have been designed to strengthen the frames and allow this, also nickel silver will be used with it's added strength over brass . The first test cut and assembly will verify if this is possible, if not strong enough we will revert to solid frames.

This is the setup drawing showing the main components, on the left are the axle bearing tubes with the x marking the flats, also the frame holes can be seen on the chassis side view.



Motor, gearbox, wheels, and crankpins were sourced from Scale Link, it's the first time I'm going to try their own manufactured wheels with NS threads and Romford type axles.



Once the lathe is up and running and the wheel bearings are turned the chassis cutting will commence....... there are a few other jobs in the queue first though!



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The lathe today, slightly dissembled with the front control box removed while installing the motor and fan modification.


The new motor, waited 5 months for this.


The guy I took the old motor to, to have it checked, advised me that although the motor has a fan inside it- an additional fan outside running full blast all the time would assist in cooling when the lathe is running slow, as the motors internal fan would not cool the windings at all at slow speed. This is the main problem with DC motors and is the most likely cause of failure.

This is a mock up of the fan housing with cardboard to get the rough shape of things and make a template for cutting the parts from aluminium sheet. The motor is in behind the fan and has it's own cover which I will make a new one, not wanting to cut it up to keep the original.


The control box.


The fan housing is angled away from the chuck to protect it from swarf and coolant getting in. The fan will be controlled with a temperature switch.


That part in the chuck has been there since the motor burn, not wanting to loose the setting as a taper bore was being cut in this blank for a Gauge G wheel. I will be able to finish this job now.....


I have done quite a few mods to this machine over the years, it's not standard any-more and quite precise now.



Edited by murrayec
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I have just read through this thread from the start, very interesting detail on what at first might seem like a straight forward project. I was particularly taken with the section on your notes, it just shows the amount of planning that’s done before you start. Am I correct in thinking that I even saw where you made a jig just to position the hole for the nut on the boiler dome in the correct place? What precision!

I’ll shall be following carefully to see how you progress with the authentic side frames with openings, will you be able to maintain enough strength? Your idea with the axle tubes is intriguing but I wonder will the bottom of the frames tend to splay outwards. I’m sure you have a solution to that, perhaps with the mounting for the pickups. 

In the photo of the prototype it looks to me that the centre axle is closer to the front one than the back one, are you building the new chassis to prototype dimensions (wheelbase) or sticking with the Mainline ones to match your superdatailed body? 


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Yes, you are correct on the dome hole drilling- I have drilled domes before without a guide and not getting it on centre makes the whole dome look off centre, so using a guide is now mandatory😀 I'm slowly building up a collection of these guides for future use.

On frame strength - if you look closely on the chassis side elevation you will see that there are four 90deg frame spacers planned (marked in red), also the one to hold the motor is actually a 'U' spacer on its side, allied with this there is a cab floor (marked in brown), and again the compensation beam on the front axles pivots on a tube which rotates on a brass .8mm pin soldered into each frame.


I reckon its going to be quite strong, the first test build will let us know?

And yes, the new chassis is being built as per the prototype with the front axles closer than the rear.


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Here are a few graphics that show the make-up of the chassis in 3d;-



The front wheel axle bearings go into the frame slots before the frame spacers are soldered in, there is a hole in the middle/front of the bearing tubes for oiling the axles.



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  • 3 months later...

Main chassis parts and the wheel bearings have been machined for the new chassis described above;-

Chassis frames being machined out of .45mm nickel silver sheet.


All the parts removed from the sheet and edges cleaned up. The coupling rods are in two parts and have been half cut for the overlap on the centre crankpin. The frames have been half drilled .5mm for embossing the rivets and a few .5mm holes drilled through for construction alignment pins. Also the front and rear frame spacers have tabs which fit in corresponding tab cuts in the frames which should aid construction.


The two front axles run in full frame width brass bearings, cut from 4.74mm (3/16'') brass rod.


The bearing rods are drilled and reamed to take the 3.1mm (1/8'') axles.


Flats are milled on the sides of the bearing rods which will fit into the slots in the frames to allow up n down compensation movement and stop the bearings from rotating. There is an old 3.1mm axle in the bearing to stop the vice pressure deforming the bearing.


Bearings complete with an axle test fitted. An oiling hole is drilled in the centre of the bearings and the centre axle bearing is 1.5mm shorter than the front to allow a bit of side-play for the curves!


Next will be a bit of riveting, folding, fitting & soldering.




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1 hour ago, David Holman said:

..... find precision work like this just fascinating.

Me to!

Every so often in the process when things fit one sits back and thinks 'did I really make that' These moments drives one on through the mundane repeat process for the next eureka moment!


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  • 2 weeks later...

I stuck the chassis together this evening.

A bit of riveting to the frames first.



The fire box sides have been soldered to the inside of the frames, the frame spacers folded, soldered, and nutted- 12BA nuts to hold the pick-up system on the underside. Also the laminated compensation beam was soldered, two 1.2mm ID aluminium tubes cut, which will be used to centre the beam on the 1.2mm brass pin soldered accross the frames.


The back and front frame spacers are soldered onto the alternative frames, these have tab n recess fitting which will keep the frames square....


Frames brought together, squared and clamped. The brass tube wheels bearings are now fitted after checking free movement in the frame slots.





Checking the fit of the rear axle bearings with an axle jig and the rear connecting rods- it's spot on!!


Inserted the compensation beam, brass pin and aluminium tube spacers- aluminium! because the solder wont stick to it when the pin is soldered to the frames which can wick in and solder the beam to the pin- that bit has to rotate. Wheels also on and setting up for motorising......




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The bearing tube and compensating beam arrangement was used in the locos built by Guy Williams for the Pendon Dartmoor and Vale of the White Horse layouts and is detailed in his book "The 4mm Engine".

The Pendon locos appear to have been mainly built using hand tools cutting out the frames with a piercing saw and turning the tubular axle ends in a lathe before forming the axle slots with a needle file (tricky).

Fitting compensation in a small loco is certainly worth while because of improved power pick up with all 6 wheels in contact with the rails at all times as opposed to the 3 legged stool effect with a rigid chassis.

Edited by Mayner
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