In retrospect the connecting rods were easy to draw. Not only are they a fairly simple shape, but they are also the same on both sides, so the artwork for the back is the same as for the front. Also all four are obviously the same so you only need to draw one. The parts for the Hudson-Hunslet are a number of magnitudes more complex. Not only are some of the parts quite complex shapes (i.e. not a simple combination of rectangles and circles) but every single part needs different artwork for the front and back of the etch, plus some of the parts fold. The flat parts took a while but by far the most complex was the single piece that wraps right over the loco to provide the body panels at the drivers end.
I took a similar approach to designing this part as I have done metal pieces for previous models. I started by drawing out a part that I thought would work, then printed it out, stuck it to some brass, cut out and folded the part and then checked to see if it would fit. On the third attempt I ended up with this.
Designing this folded part was especially complex, as what I had was measurements for the inside of the part, but it is much easier to draw the part if you know the outside dimensions. It's fair to say that it was very frustrating trying to get this right. It seems to be a good fit, but I'll only know for certain when I try and fit the etched version. The final artwork measures out at 62.56mm by 35.02mm yet contains 15 different parts (some are spares and some are variations) so some of the parts are going to be devilishly small.
There will now be a bit of a pause in posts on this locomotive while I await the etched parts and the next set of prototype 3D printed parts.
By the inside and outside dimensions do you mean the thickness of the brass? I'm glad I'm not doing this. I'm very confused.
ReplyDeleteGood luck.
ReplyDeleteI admire your chutspah, Mark. Etched brass is always fraught with tiny measurements and nasty little calculations for creep and bite, which I always studiously ignore :-) You are obviously the man to do this and I admire your methodical m.o. How are you drawing out the artwork, is it in Illustrator? It's good, too, when you find an etcher you can work with, I have had experience of one supplier's service deteriorating, but in your case, it helps enormously that Steve is a respected model maker and supplier in his own right and knows what he's at.
ReplyDeleteYes there was an awful lot of maths involved in drawing out just that one part and it only has four folds! Even some of the flat parts involved some trigonometry to figure out the correct size to fit in the space.
DeleteI've been drawing the parts using Inkscape, although Steve then takes what I draw and merges it into a larger Illustrator file for the actual etching. It took me a while to figure out how to use Inkscape to produce what Steve needed but now I've got the hang of it, simple parts can be drawn up quite quickly. I certainly don't think I would have tried etching at all if it hadn't been for Steve. The idea of having to deal with the actual company doing the etches, and the cost of a full sheet would have put me off.
Nice to see some progress Mark. I like your approach with the mock-ups, probably easier and cheaper than just ordering and hopeing for the best. Of course the correct way is to draw everything out, get the etches done and then stick the kit on the market without doing a test build...
ReplyDeleteHaving ordered updated prints of the body and sent off the etches, I think I've already spotted something that might need changing, even having done the mockup. On the real thing the bodywork panel above the engine actually sits on top of the rear panel. When I designed the print I modelled that but forgot the thickness of the etch. So the brass panel sits at the same height as the top of the print when it should be a touch lower. From normal viewing distances it probably won't be noticeable and with the rest of the panels in place it might all look okay. After all if we assume that on the real engine the panel is probably no more than 5mm thick then I'd need to drop it no more than 0.06mm on the model!
DeleteI have to say I can now easily understand how you can end up with etched parts that don't fit as drawing them up is a lot trickier than I imagined. It must have been even worse when they were all hand drawn as altering them must have been a lot harder. As you say though how the parts of some kits ever made it past a test build I don't know.