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.<\/p>\n
The Castings<\/strong><\/span><\/span><\/h3>\nOn the original offer I proposed a number of separate castings ie what I had ordered for myself in the past.\u00a0 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.\u00a0 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.<\/p>\n
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.<\/p>\n
Other Design Changes<\/strong><\/span><\/span><\/h3>\nWhen 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.<\/p>\n
You may find this drawing handy. Please do not share it around\u00a0 WS-NGG-0255 Motion arrangement (Walschaerts) 122-15811<\/a><\/p>\nThings your should know about how the CAD\/Castings work<\/strong><\/span><\/span><\/h3>\n![\"\"](\"http:\/\/ngtrains.com\/blog\/wp-content\/uploads\/2019\/12\/Heat-map-300x255.jpg\")
<\/a>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.<\/p>\nIt works pretty much as you would expect. Red doesnt work, green\u00a0 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.<\/p>\n
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.<\/p>\n
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.<\/p>\n
What You Get<\/strong><\/span><\/span><\/h3>\nYou will get<\/p>\n
\n- Two cast brass sprues<\/li>\n
- Four machined tubes for valves<\/li>\n
- Four handrail knobs as the end of the valves<\/li>\n<\/ul>\n
What’s been done<\/strong><\/span><\/span><\/h3>\n![\"\"](\"http:\/\/ngtrains.com\/blog\/wp-content\/uploads\/2019\/12\/1-Shiny-300x146.jpg\")
<\/a>No matter how much you ask Shapeways not to, they coat the finished castings in a shiny lacquer that defies soldering.<\/p>\nThey come very very shiny but that doesn’t last long of you warm them up with\u00a0 soldering iron.<\/p>\n
I have put all of these through my abrasive blasting cabinet ![\"\"](\"http:\/\/ngtrains.com\/blog\/wp-content\/uploads\/2019\/12\/Castings-300x200.jpg\")
<\/a>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.<\/p>\nThis was finished by them all having a ten minute swim in the ultrasonic cleaner.<\/p>\n
<\/p>\n
<\/p>\n
Valve Spindles – preparation<\/h4>\n
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.<\/p>\n
You may find this drawing handy. Please do not share it around\u00a0 WS-NGG-0255 Motion arrangement (Walschaerts) 122-15811<\/a><\/p>\n It works pretty much as you would expect. Red doesnt work, green\u00a0 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.<\/p>\n 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.<\/p>\n 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.<\/p>\n You will get<\/p>\n They come very very shiny but that doesn’t last long of you warm them up with\u00a0 soldering iron.<\/p>\n I have put all of these through my abrasive blasting cabinet This was finished by them all having a ten minute swim in the ultrasonic cleaner.<\/p>\n <\/p>\n <\/p>\nThings your should know about how the CAD\/Castings work<\/strong><\/span><\/span><\/h3>\n
<\/a>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.<\/p>\nWhat You Get<\/strong><\/span><\/span><\/h3>\n
\n
What’s been done<\/strong><\/span><\/span><\/h3>\n
<\/a>No matter how much you ask Shapeways not to, they coat the finished castings in a shiny lacquer that defies soldering.<\/p>\n<\/a>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.<\/p>\nValve Spindles – preparation<\/h4>\n
![\"\"](\"http:\/\/ngtrains.com\/blog\/wp-content\/uploads\/2019\/12\/Counterbore_1-300x200.jpg\")
<\/a>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.<\/p>\n![\"\"](\"http:\/\/ngtrains.com\/blog\/wp-content\/uploads\/2019\/12\/Stages-300x194.jpg\")
<\/a> 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.<\/p>\n