Edwardian Posted February 13, 2016 Share Posted February 13, 2016 Not sure if I have posted on the correct thread, but I wondered if anyone could give me some pointers in re-sizing scale drawings? My printer, on photocopy mode, has only a set of arbitrary percentage values, but, if I scan a plan to pdf, the printer driver will let me print a hard copy enlarged or reduced by one percent increments. I have recently scanned some 7mm scale locomotive drawings. My question is, what percentage of the original (7mm scale) size would achieve 4mm scale? While we're at it, I might presume further on your good natures and ask what percentage value represents 4mm when scaling up from a 2mm drawing. On the face of it, that would be to print at 200%, but, I am never quite sure as there seem to be different scales applicable to N, and I am ignorant as to whether a drawing stated to be to '2mm scale' is to 1/152nd scale or whether some minor percentage adjustment is necessary. I should add that, in the case of enlarging from 2 to 4mm, I am talking of architectural plans. I recently enlarged 2mm drawings of a station building using the photocopy function. This permitted me to enlarge to 198% of the original. Frankly, that looked good enough for me. In the future, there may be instances where I want to be more precise with a building's scale, and to use the pdf to acheive a more precise re-scaling. Link to post Share on other sites More sharing options...
Edwardian Posted February 13, 2016 Author Share Posted February 13, 2016 Not sure if I have posted on the correct thread, but I wondered if anyone could give me some pointers in re-sizing scale drawings? My printer, on photocopy mode, has only a set of arbitrary percentage values, but, if I scan a plan to pdf, the printer driver will let me print a hard copy enlarged or reduced by one percent increments. I have recently scanned some 7mm scale locomotive drawings. My question is, what percentage of the original (7mm scale) size would achieve 4mm scale? While we're at it, I might presume further on your good natures and ask what percentage value represents 4mm when scaling up from a 2mm drawing. On the face of it, that would be to print at 200%, but, I am never quite sure as there seem to be different scales applicable to N, and I am ignorant as to whether a drawing stated to be to '2mm scale' is to 1/152nd scale or whether some minor percentage adjustment is necessary. I should add that, in the case of enlarging from 2 to 4mm, I am talking of architectural plans. I recently enlarged 2mm drawings of a station building using the photocopy function. This permitted me to enlarge to 198% of the original. Frankly, that looked good enough for me. In the future, there may be instances where I want to be more precise with a building's scale, and to use the pdf to acheive a more precise re-scaling. Link to post Share on other sites More sharing options...
RMweb Premium Clive Mortimore Posted February 13, 2016 RMweb Premium Share Posted February 13, 2016 7mm is 1/43.5 4mm is 1/76.2 Divide what you have by what you want then times by 100, and you have your percentage. 43.5/76.2x100=57% Link to post Share on other sites More sharing options...
Edwardian Posted February 13, 2016 Author Share Posted February 13, 2016 Thanks, Clive, I was about to EDIT to include those precise scales, but I am such a poor mathematician and didn't know what to do with them! You have given the answer, for which very many thanks, and, of course, the answer is so simple that I should have been able to work it out. I seem to have managed to post this thread twice, for which apologies. Honestly, I've really woken up with my Stupid Head on this morning. Either that or blame the progressive educational theories of the past that left me so ill-equipped for the World. OK, I admit, I'm just thick. Link to post Share on other sites More sharing options...
micknich2003 Posted February 13, 2016 Share Posted February 13, 2016 Those of us who "Listened to Teacher" and fifty odd years on, have not forgotten the formula will be able to work out the percentage. Personally I have long forgotten so I do it by trial and error. For 7mm to 4mm start at 60% and work from there. Link to post Share on other sites More sharing options...
BG John Posted February 13, 2016 Share Posted February 13, 2016 Check the drawings you're starting from to make sure they're to scale. There's no guarantee they will be if they're not originals. Link to post Share on other sites More sharing options...
Devo63 Posted February 13, 2016 Share Posted February 13, 2016 I recently photocopied some side views from the Mike Sharman 'Portfolio Series' books. I copied them at 57% to rescale them from 7mm to 4mm scale. It should really be 57.14% but I checked the copies with a ruler afterwards and they seemed to be spot on scale. Something annoying when I'm making a straight photocopy 1:1 is that the copy always seems to be a very small fraction smaller than the original. Could be just my cheap printer. Dave Link to post Share on other sites More sharing options...
RMweb Gold Colin_McLeod Posted February 13, 2016 RMweb Gold Share Posted February 13, 2016 7mm is 1/43.5 4mm is 1/76.2 Divide what you have by what you want then times by 100, and you have your percentage. 43.5/76.2x100=57% Or, more simply 4/7 times 100 = 57% Link to post Share on other sites More sharing options...
RMweb Gold Colin_McLeod Posted February 13, 2016 RMweb Gold Share Posted February 13, 2016 There seem to be two threads on this topic. Link to post Share on other sites More sharing options...
RMweb Gold Colin_McLeod Posted February 13, 2016 RMweb Gold Share Posted February 13, 2016 There seem to be two threads on this topic. Link to post Share on other sites More sharing options...
Edwardian Posted February 13, 2016 Author Share Posted February 13, 2016 Locomotive Magazine Drawings, compiled by Mike Sharman, apparently reproduced to 7mm scale, published by Oakwood Link to post Share on other sites More sharing options...
Guy Rixon Posted February 13, 2016 Share Posted February 13, 2016 In the "2mm scale" drawings, the scale can be either defined as exactly 2mm per foot, which is a scale ratio of 1:152 to 3 significant figures, or "British N" which is defined as a ratio of 1:148 (NB not 1:144, which is a common scale for models of aircraft). The 1:148 ratio gives 2.05mm per foot to 3 figures. If you don't know which "2mm scale" has been used in a drawing, I suggest that you measure a known dimension on the drawing and work it out. I usually use a wheelbase. Even scans of original GA drawings may be inaccurately scaled, as the cloth of the originals can shrink or stretch. Bear in mind that, in proper engineering, one is not supposed to scale measurements off a drawing. All measurements that matter for manufacturing are supposed to be written on one of the drawings in the set. Of course, as modellers working with relict drawings we sometimes have an original GA but rarely have the detail drawings for the components. E.g., I'm currently stuck on the dimensions for an RCH self-contained buffer. Link to post Share on other sites More sharing options...
jetmorgan Posted February 13, 2016 Share Posted February 13, 2016 The thing to make sure is that your printer is set to Print Actual Size...rather than fit paper then it should come out at the correct size. You might lose a few mm of the edge but as long as things are in the centre of the page you'll be fine. Photocopiers I find do tend to distort the image, I don't know if it's the glass or the heat on the paper or whatever but when I tried to blow up plans from 1/72 to 1/35 I could not get the outlines to match up so had to make a best guess average. Many years ago I did have a table for the percentages of increase or decrease when re-scaling plans. This was from an old copy of Finescale Modeller and I did try to make one myself as there is a easy formula for working out the correct amount. I'll have a look to see if I still have it and try and send you a copy. I'm currently trying to go through lots of old copies of Model Railway Constructor & Railway Modeller and scanning various plans for my own use and some of those need reducing or enlarging. Link to post Share on other sites More sharing options...
edcayton Posted February 13, 2016 Share Posted February 13, 2016 It always has been a problem when drawings are copied. One reason why our drawings always had "do not scale" on them. Another reason was that the draughtsman may have drawn it wrong but put the correct dimension on tje drawing! Ed Link to post Share on other sites More sharing options...
Edwardian Posted February 13, 2016 Author Share Posted February 13, 2016 Yes, I don't know why, but my post has appeared twice, so we now have 2 sets of answers. Oh Dear! Dave, I am using these Portfolio series plans (as I have said on the duplicate thread!), so your comments are particularly reassuring. This is providing that the act of scanning the image has not slightly distorted the scale of the original! Link to post Share on other sites More sharing options...
RMweb Gold Huw Griffiths Posted February 13, 2016 RMweb Gold Share Posted February 13, 2016 Check the drawings you're starting from to make sure they're to scale. There's no guarantee they will be if they're not originals. There's also no guarantee that they will be to the same horizontal and vertical scales - I've come across a number of published drawings with this issue. Of course, this assumes they were drawn to scale in the first place - which some probably were. You also need to watch out for wrong details / bits missing / mysterious new "additions" in the published drawings. While I think of it, drawings aren't always placed "square", or even flat, on scanner beds when they're being scanned - and I've come across a number of drawings (often on the internet) which have been skewed. A while back, I also came across another strange issue with one set of drawings (on a sales leaflet for a proposed railbus - which one, now defunct, company had been hoping to sell). Even allowing for differences in scale, some "features" of their railbus were shown at different heights on side and end elevations. What I'm trying to say is this - published drawings can be very useful - but you need to keep your wits about you (checking dimensions - perhaps even having a slide rule handy, or a constant set up on a calculator). It's probably fair to say that most (or all) of us have been caught out by stuff like this over the years - that's right, this includes this engineer. Regards, Huw. Link to post Share on other sites More sharing options...
RMweb Gold Joseph_Pestell Posted February 13, 2016 RMweb Gold Share Posted February 13, 2016 Peco have a really good way of dealing with this. They have a rule alongside their templates which you can measure after printing to check that the printout is full size. So if you take your original drawing, draw a line on it with 7mm divisions, and after printing check if those divisions are now 4mm. Simples! Link to post Share on other sites More sharing options...
Edwardian Posted February 13, 2016 Author Share Posted February 13, 2016 Thanks, all. I should think that, for the purposes of my bashing and bodging, I shall be able to get close enough if I model in the best traditions of British precision engineering (half an inch either way)! Link to post Share on other sites More sharing options...
RMweb Gold Colin_McLeod Posted February 13, 2016 RMweb Gold Share Posted February 13, 2016 You need to do better than that in the shipyard. There even three decimal places is no good. You have to be dead on. Link to post Share on other sites More sharing options...
RMweb Gold Colin_McLeod Posted February 13, 2016 RMweb Gold Share Posted February 13, 2016 Yes, I don't know why, but my post has appeared twice, so we now have 2 sets of answers. Oh Dear! Edwardian you will have to take the "average" answer. lol Link to post Share on other sites More sharing options...
BG John Posted February 13, 2016 Share Posted February 13, 2016 You need to watch out for inconsistency in drawings too, especially where they are hand drawn. The doors and windows on the drawing of Ashburton station building I'm currently using have all been drawn individually, and vary a bit in size. This doesn't help when I'm trying to create standard sized computer printed windows to fit the holes in the model! I suspect it's due to inaccuracy in the drawing, rather than accurately recording differences in the real thing. Link to post Share on other sites More sharing options...
Nick Holliday Posted February 13, 2016 Share Posted February 13, 2016 As others have suggested it would make sense to add, if you can, some form of scaling bar so that you can check the theory. I would suggest a simple line equivalent to, say, 10 ft at the correct scale will be easier to check, ideally as long as your drawing allows. It might be worthwhile adding one at right angles as well. Some copiers/printers have a tendency to print at different ratios vertically and horizontally. This can be compensated for by splitting the enlargement into two similar ratios, and recalculating the percentage on the second stage having turned the new copy through 90 degrees. Sorry to add to the calculations, but it's nothing that a simple calculator can't handle. Some copiers actually allow you to select different ratios for the x and y axes, with double the calculations, I'm afraid. I'd be a bit wary of the actual scale your scan produces, as it may not be exactly 100%. Hence the need to put a scale bar on, or have a relatively long dimension that you can check on the drawing. A useful facility within some versions of Adobe is the ability to carry out measurements using the measuring tool, and you can enlarge the image on screen to get as close as possible. A bit of a faff to work out the scales, with a lot of trial and error, but once worked out it is illuminating how inconsistent many drawings are, and you can print the drawing out with the dimensions showing. PS Perhaps a message to the moderators can get these two threads knitted together? Link to post Share on other sites More sharing options...
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