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Class 850 / P1 Gauge O Works

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This model has been on the workbench for some time now, it's a Brendan Kelly/Hamill built model. Now that a number of projects are complete I can dedicate more time to get it finished.....






After having a good look a it and a bit of photo research a plan of action was worked out. The model has been prematurely painted as it's lacking a number of critical parts;- cylinders, valve gear, coupling rods, brake gear, cab opening details, cab roof rain strips, electrical pickup system, footplate frame details and buffers. Although it looks fine with paint on, there are a number of locations on the body that solder could be removed to improve the detail- so it was decided to remove the paint and start there.


Sand blasted


Bits were acquired and the electrical pickup parts are prepared.



Solder clean-up almost complete.


This is a screen capture of the CAD drawing, the drawing was done to work out how to make the cylinders, crosshead, rods, brakes, and a few other bits, the drawings of parts are extracted out to the right, for CNCing from metal sheet.


These bits are the tools for making up a new steam dome, there are tools for both Gauge O & OO. The long round bars are the boring bars for turning the base of the dome to fit on the boiler. The short round bars and screws are for mounting the dome in the lathe chuck to form the top curves. The square bars are for holding the carbide tools while sharpening them on the grindstone. There is another square bar yet to be made for holding the work piece in the lathe tool post while the base curve of the dome is being cut.

More later......



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1 hour ago, Galteemore said:

Interesting, Eoin. Stripping the paint off actually reveals that some good work has been done on the body - with some interesting omissions such as not rounding off the Belpaire edges.

Yes, Brendan does great work, but often gives the model to the client before its complete, this is where people contact me to do the completion- if I can!

The Belpaire edges are on the list.


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  • 2 weeks later...


I removed the dome, the chimney, handrail knobs, one short cab handrail, and the snifting valve. While assessing the model I had noticed that the chimney was off centre, I was going to leave it alone but when I had the model hot decided to remove it to correct it.



Again while the model was hot I did a few repairs to some of the soldering, this all had to be done on the outside as there was no access internally.


This is where the short n wonky cab handrail came from, the bottom hole is way off line so a solution is needed to fix this. That hole at footplate level will have to be filled with plastic filler when at the painting stage.


The body being cleaned up after repairs n parts removal.


The smokebox door had a raised number plate on centre, so that was filed off, new holes marked up for a dart handle and upper handrail.


While working on marking out the frames detail to be added to the front footplate I noticed that the right side buffer hole in the beam is off line by 3mm, when the frame pieces are installed this would be very noticeable so I reckon we need a new front buffer beam!



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  • 2 weeks later...
  • 3 months later...
Posted (edited)

Having a go at the new steam dome;-



After working out the sizes (I also decided to make a new chimney- slightly smaller then the one removed), two slugs of brass were cut from bar- 22mm dia for the dome and 15mm dia for the chimney.


The dome slug in the chuck just about to be tapped M4 for mounting in the toolpost bar to cut the boiler curve on the base of the dome. The radius is 17.5mm


Now mounted on the toolpost bar, set at 90 deg and ready to fly cut.


Cut- slightly out of focus! The mounting bar required 3mm packing to get the work-piece centred on the axis of the lathe. The first light cuts show if your on centre, then one packs out until the cut is centred on the tapped hole.



Checking fit.


A recess is bored out of the base for the work to be mounted lock-face on the mandrel.


Now the work-piece is mounted on the chuck mandrel.


Ready to cut the side.


I estimated the sides to be at an angle of 10 deg. so the topslide was set over to 10 deg and the cutting was done with the topslide to get the taper.


Taper complete.



This is the tool setup for cutting the top curve, it's a Ball Turning Tool mounted in the toolpost with the cutting tool set to cut a 19mm radius curve, the lathe is run backwards in this set-up as the tool is cutting on the backface of the work.


Curve done, cleaned up with files and emery paper.



Test fit.



M4 brass screw fitted.


I engraved a bead line around the base of the dome with the point of a calliper/divider.


Then back into the chuck to turn down the M4 screw to imitate a top nut on the dome. The screw is Locktited in first!


Next the chimney, this is my setup for threading on the lathe, the slug is in the chuck after being drilled through, I disengage the drive motor, mount that handle to the left in the lathe mandrill and rotate the work with the aid of the handle while pushing the tailstock along the lathe bed- tapping the work.


Fly cutting the curve base of the chimney. The radius is 19.5mm.


The work is then drilled through with an 8mm drill. One has to have a hole in a chimney.....


To turn the outside of the chimney the work is mounted on an expanding mandrel, it expands when tightened up and holds the work for light cuts.


Mounted in the chuck, the tail stock can be used here to support the work on the right but it gets in the way in what I'm doing, so light cuts are a must with so much overhang!



Rough cuts with a parting tool.


Finishing cuts with a round tool.


Filling down the sides, top one is done with the bottom yet to be.




Test fit.....


.......and comparison with he one that was removed.

More later



Edited by murrayec
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  • 1 month later...

Work on 850 continues;-



Parts cut out on the cnc machine and cleaned up.


When starting to set up the cylinders I realised that the chassis first needed its fixings to the body so I could work out the space I had to work with- the front of the cylinders are rather close to the front footplate down-turn. Also, the front valance parts need to be in place.



The front of the chassis will be held by a tab soldered to the underside of the footplate with a cross piece across the chassis frames to slide into the tab, the rear will be screw held to the body under the bunker.


The dodgy front buffer beam was removed.


One can see here, how off line the front footplate is.


A new buffer beam being setup in tin-plate and the footplate has been corrected.


Beam holes drilled and hook slot cut out, now ready to be soldered on.


Front valance pieces were made from OO track rail to match that on the body. I did cut brass parts out for this but decided to use the rail instead.


Footplate chassis frame parts are soldered on.


Same with the front valance parts.



Chassis mounting tab pre-thinned ready to be solder on the underside of the footplate.


Clamping arrangement for soldering.


After sorting where the rear screw will be, a hole was drilled in the floor of the bunker for a 6BA nut to be soldered in.


Chassis fitted.



Drilling holes for the boiler fittings- steam dome, snifting valve and chimney.


Done for now.......


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