NGG16 Instructions

This page constitutes as much as you are going to get by way of instructions as these parts weren’t ever intended for mass sales and were always meant as an aide to scratch building.  The result is that whilst I offer some guidance below how you actually assemble stuff is up to you. There are a few things worthy of note though.


I am sorry its taken longer than I originally forecast. A combination of this being more popular than I ever imagined, interesting dealings with Shapeways and the much greater quantity highlighting some opportunities to develop my own workshop equipment. Some detail for purchasers follows but a more humorous tale is on the main blog.

The Castings

On the original offer I proposed a number of separate castings ie what I had ordered for myself in the past.  What happened when I started looking to order in quantity from Shapeways they became very much more attentive and helped with suggestions of how to get the best out of their process whilst controlling costs.  They have a pricing structure that charges by volume in fixed steps such that to do this as, say, three separate castings would have cost 3X, at their suggestion the castings were regrouped to a produce a single casting per end of the NGG16 at a cost of 1X.

Quantities of the single item then climbed to the point where, by adding a few spares, we crossed one of their discount boundaries. The truth is that if I’d stuck to the original plan I’d have lost money. A further time was for them to produce a test item to the new design before series production.

Other Design Changes

When these parts were originally designed it was done with a few measurements and a lot of scaling off photos. Nick Dunhill reported a discrepancy with the length of the radius rod. An enquiry to a friend at Boston Lodge works produced this drawing and from it in these castings the length of the rod has been shortened.

You may find this drawing handy. Please do not share it around  WS-NGG-0255 Motion arrangement (Walschaerts) 122-15811

Things your should know about how the CAD/Castings work

If you have ever used Shapeways you will know that they have a selection of automated tools that check your 3D print to see if they can print it. One of these is a heat map.

It works pretty much as you would expect. Red doesnt work, green  is OK, (yellow is a bit iffy). What this is checking is material thickness. Now us railway modellers doing things to scale push the limits of this requiring some compromise.

Many of the holes for pins and screws in the castings are very undersized and you will need to open them out. Treat them as markers for where the holes go. If I had made the holes close to finish size then it wouldn’t have left enough metal to pass the above checks.

Similarly the square in the combination lever where the valve attaches needs to be filed out. Actually, a combination of filing the square out and thinning the valve rod end is needed.

What You Get

You will get

  • Two cast brass sprues
  • Four machined tubes for valves
  • Four handrail knobs as the end of the valves

What’s been done

No matter how much you ask Shapeways not to, they coat the finished castings in a shiny lacquer that defies soldering.

They come very very shiny but that doesn’t last long of you warm them up with  soldering iron.

I have put all of these through my abrasive blasting cabinet which removes the coating and removes the few vestiges of print layering. They have all had the holes through the valve guides drilled and reamed to 2.1mm.

This was finished by them all having a ten minute swim in the ultrasonic cleaner.



Valve Spindles – preparation

This was my biggest moment of madness with this. These are cut from 2mm OD brass tube. They are over length so you have some thing to hold whilst you work on then.

Each has then been in the lathe and had both ends countersunk with a centre drill and de-burred. One end has then been counter bored to a depth of around 5mm and a diameter of 1.45mm.  Less precisely that’s big enough and deep enough for a handrail knob to be inserted.

I did contemplate further assembling them but after machining so many tubes I realised this was the path to insanity.  Instructions for you to do it are below.

Valve Spindles – Assembly

What were trying to achieve here is something that looks like chromed steel (think digger hydraulic ram) with an end with an eye on it that is black from brass bits that don’t look anything like steel.

Here’s what I do. Feel free to ignore me and do your own thing.

You will need a soldering iron, a small blowtorch, paste flux (the stuff plumbers use), 145 degree melting point solder, kitchen tissue and a bit of wood. A pin vice and a pair of flat bladed pliers are also used.   In the image imagine I remembered to number them 1-5 starting at the top.

  1. Item 1 is a bit of the brass tube. Stick it in the pin vice holding just a couple of mm at one end with the counter-bored end sticking out.
  2. Smear the end with paste flux and apply solder with a soldering iron ensure the end 6-10mm is tinned.
  3. Heat it up until the solder melts in the flame of the mini blow torch. When the solder is molten wipe the surplus off with the kitchen tissue. Make sure there is quite a bit of tissue between you and it as it’ll be hot. You may have to do it a couple of times to get a smooth finish.
  4. Try the handrail knob in the end. In most cases it won’t go in because the solder has flowed round into the hole. This is good. In your right hand hold the handrail knob in your pliers by the knob. Add a little past flux to the shaft of the knob. Holding the pin vice in your left hand (having lit the blow torch) heat up the end of the tube and when the solder is molten push the handrail knob into the hole and let it cool.  An extra phase here to make sure its soldered is to heat it up again (without the pliers ) and then press it against a piece of wood.  The pliers can act as a heat sink preventing it from soldering, reheat and pressing against a block gets it all to the same temperature and pushes the knob home
  5. Having cleaned off all the flux make sure it runs in the gland casting and then dip the ball end in to blackening fluid


Well that’s it really. You’re on your own now.

I still plan to do my NGG16’s using these parts but lord knows if, or when, I’ll get round to them. If you are adding these parts to your STABLE* keep an eye on my newsletters and website as anything could happen. What is almost certain is that I won’t build them as standard.

Please do let me know how you get in with yours

* StaBLE – Stash Beyond Life Expectancy