QCAD - getting started guides.

[Len Cattley]

Can you get the measurements from the drawing that has no measurements on it? If you see what I mean.

Len

 

[JimG]

Can you get the measurements from the drawing that has no measurements on it? If you see what I mean.

Len,

In such a case, you have to go for a measurement which is known - like the wheelbase measurement for a horizontal one, a wheel diameter for horizontal or vertical, or a known vertical dimension. Buffer centre lines were usually 3' 5.5" above rail level; the top of wagon and coach solebars was usually 4' 0". You want to try and work with as large a known dimension as you can find since you are always liable to incur small errors - like reading the width of a line on your original image. It might be pushing you luck to take a one foot dimension to extrapolate the length of a 57ft coach.

Jim.

 

[Len Cattley]

Ok mate I can use buffer centre line and one of wheel base's which is 8ft. According to Adrian I can import the drawing into Q-Cad but I,m not to sure how to line it up with the ft and inches on the drawing.
Len

 

[Len Cattley]

I tried to import a Tiff drawing but the web-site would not let me

 

[adrian]

Ok mate I can use buffer centre line and one of wheel base's which is 8ft. According to Adrian I can import the drawing into Q-Cad but I,m not to sure how to line it up with the ft and inches on the drawing.
Len

There are a couple of ways of doing it, both require you to rescale the drawing/layer.

First way - just import the drawing to a layer - create your drawing by tracing over the image. Once complete then scale the drawing layer.

Second - import the drawing to a layer, then scale the drawing layer prior to tracing over the drawing on a new layer.


The scaling factor to apply depends on which way you are doing the drawing, are you drawing it out at 12":1ft. or are you drawing 7mm:1ft. As mentioned previously I settled on drawing 12":1ft but 7mm:1ft is equally as valid.

So lets take the drawing I imported and see what the dimensions are. On the left hand toolbar there is a button with the image of a ruler. I can use this to take dimensions from a drawing. Lets take a look at the oval cut out in the tender side frame. On the drawing this is listed as being 4' 5" wide, however if I use the ruler, you can just see it in pale green, but at the bottom status bar it says 103' 10.75" which is massively over scale for what I want.



As mentioned I work in 12":1ft so I need to scale this down. The ratio will be 4' 5"/103' 10.75" which I work out as 53"/1246.75" or as a ratio 0.04251.

If I then use the selection tool and draw a box around the image file it comes up with the properties for the image. On the right hand side I have the property editor, this has a "width factor" and "height factor" which is currently set to one.



In this property editor I can change the factor to that required, in my case as shown this is 0.04251

If I enter these values into the height and width factor it shrinks my image file. Now in the image below I have used the ruler on the same oval cutout. It now says that my oval cutout is 4' 4.95537" wide ( see the distance: number at the bottom), which considering that I was just doing it freehand quickly is close enough to 4' 5" in my book.

So now I have my image accurately scaled to 12":1ft for tracing. Note also as I was doing it quickly the drawing is not quite square - one of the other properties listed is "angle" - if I was doing it properly I would tweak the angle first to get it horizontal before scaling the image.



Again I hope this helps.

Adrian

 

[Len Cattley]

That's helped a great deal mate, I need to learn to do angles as my drawing is not level. I really love these help files so helpfull, thank god you don't mind doing this.

Len

 

[SteveO]

Len, as an embellishment to the above, and as I just happen to be redrawing the Drewry artwork, I thought I'd offer what I'm doing at the moment.

Your first stumbling block will be finding an accurate drawing, as was mine. I eventually got myself a works drawing but even this is not totally accurate. I started with an absolute certainty – the wheelbase. I modified the axles to the diameter of 3/16", but the centres are accurate. By the way, this drawing is in 7mm scale so I can keep an eye on how small certain details are:


After that, you can import your drawing and scale it to your known absolute dimensions:


Then I start drawing in some fundamentals, like the frame, etc:


And after an hour or so you have most of the important reference points you need to build the rest of the drawing:


I must state that I use Adobe Illustrator for no other reason that I'm used to it and I know where everything is. While at uni I used CAD software every day and it wouldn't take long to get used to it again, but for speed I'm using Illustrator. This is it without the drawing guide:


It's no more that two hours old at this stage and will probably take me about a year to finish on-and-off.Good luck on your project.

 

[adrian]

Another quick video - showing how to import image, rotate and scale as required.

I hope it helps.

 

[SteveO]

The specifics are different, obviously, but the process is exactly the same as I do it.

 

[Len Cattley]

I tried twice to scale this drawing using 8' 0 as the measurement and both times it came out as 7' 4" . Not to sure what measurement I'm getting wrong.

Len

 

[adrian]

Have you converted the dimensions to inches?

List of tasks :

1. So you have imported the scanned drawing on to a new layer?
2. You have found a dimension on the drawing which says it is 8' 0"?
3. You use the point to point ruler and find out that in the layer it is for example 22' 7.5".
4. Convert the dimension from step 3 to inches, in this case 22*12+7.5 which is 271.5.
5. Convert drawing dimension to inches - so 8' 0" is 96"
6. So width and height ratio to apply is new length/original length in this example 96/271.5. Note you can type this calculation directly into QCAD, alternatively calculate it as 0.3536.
7. Measure the scanned drawing again - the dimension should now be 8' 0".

So what value did you get for point 3 and what did you calculate for point 6?

 

[Len Cattley]

Sorry Adrian I forgot to post that I scanned it in again calculated it again and found that was exactly right, I've been trying to draw the angle for the guards at the front of the frames as below.



This is for a Patriot, I'm doing a Rebuilt Scot but it's still hard doing the angles for the front guard irons (any ideas).
Len

 

[adrian]

This is for a Patriot, I'm doing a Rebuilt Scot but it's still hard doing the angles for the front guard irons (any ideas).
Len

That looks nice - the big parallel boiler and square firebox are always quite imposing.

I'm not too sure what you mean by the "angles for the front guard irons" as they seem to be already fitted. Are they wrong and you want to draw up new ones?

A couple of pointers then. First it's not a simple as reading it straight from the drawing as they have a joggle in to widen them out to the track gauge - so if you are drawing them out for etching you'll need to draw them out longer than that indicated on the side view. Either a front view or a little pencil sketch will let you work out the full length of the guard iron.

If you are then trying to work out the angle of the rear edge - then I would work out the width at the top and draw a line. Then work out the width at the bottom and draw a line. Finally draw a line snapping to the end points of the width lines you have just drawn.

The drawing you have probably doesn't the width marked on the drawing - in this case I use a set of spring dividers (or use a compass) on the original drawing. Then try to find another dimension on the drawing with the same spacing, or multiple of, by this I mean if you have a dimension on the drawing of 12" or 1ft. and you have the dividers set to the bottom width of the guard irons, if you spin the dividers three times and it matches then the dimension is 4" (12"/3) if you spin it 4 times and it matches then the dimension is 3" (12"/4). You will find that quite often the dimensions are rounded to the nearest inch so you can usually find an equivalent dimension that matches.

The other thing to note when looking at works drawings is that these were all drawn well before computers. So a lot of these drawings have been done by draftsmen on large A0+ drafting boards. When you are looking at arcs or circles on the drawing, if you look closely at the blueprints then you may well be able to see a mark or spot where the draftsman placed the origin of his dividers. Unfortunately a lot of the published drawings, using the Wild Swan books I have, have obviously tweaked the drawings for publication. I have a couple of works drawings from the NRM and the detail is much better than that published in the equivalent MRJ loco profile. WSP seemed to have "cleaned up" the drawings for publication and in doing so have lost some of this construction detail.

 

[Len Cattley]

Hi Adrian I have a A0 print of the pipe & rod plan from the NRM also photo's of Scot's and also a David Andrew's kit, I have taken some photo's of same.
On the drawing it has 2 3/4" inches from the rail head to the bottom of the guard iron I also think looking at the bends in the guard iron it would have been lower than the rail head when straight, I could make them separate from the chassis then solder them to it, what do you think?

 

[D G Williams]

Hello Aidrian. Many thanks for this thread, it has encouraged me to have another go at learning somthing about CAD, even if it's that I can't do it! Ive already hit a snag ...
I tried downloading QCAD from the link on page 1 of this thread but when I tried to 'run' it I got a security warning - the file did not have 'a valid digitla signiture.' I tried again, this time saving it instaed of runnning it, and scanned it with AVG and Malwarebytes. They both gave it the 'all clear' but when I tried to run it I got the same security warning as before.
Does this normally happen with QCAD and is it safe for me to run it?
David.

 

[Len Cattley]

Hi David, I was hoping you might get and answer to this question, I had to buy Qcad being only €42 it was not expensive, I was glad I did as I find it a very good programe. I would download it from the Qcad website it might run better from there.

Len

 

[Len Cattley]

Hi Adrian, any more updates on this?

Len

 

[adrian]

Hopefully in the next day or two.

 

[Len Cattley]

Hi chaps, how do I put an angle of 1:50 on my drawing as I need to show the angle of the cylinders?

Len

 

[JimG]

Hi chaps, how do I put an angle of 1:50 on my drawing as I need to show the angle of the cylinders?

Len,

Draw a horizontal line 50 units long. At one end draw a vertical line 1 unit in length from the end of the horizontal line. Join the opposite end of the horizontal line to the end of the vertical line not joined to the horizontal line and the line you have drawn is at a 1:50 angle to the horizontal.

Jim.