Scaling drawings.

[ferny]

Hi all

I have some drawings for a scratch build project, they have the dimensions on them but i dont know what scale they are.

Is it simply a case of working out the scale size and then trial and error with the photo copier!

In need them to scale as want to use them as templates for the build.

TIA

Jon

[pigsty]

Is it simply a case of working out the scale size and then trial and error with the photo copier!

Yes, it is. If you have the dimensions written on the plans you have, just measure the drawings as accurately as you can and divide that into the given dimensions. That tells you what scale the drawings are. Then divide that into the scale you actually want to model, and that will tell you by how much the drawings need to be changed to turn them into templates.

An example of the latter. Let's say the drawings come out at 1/48 and you want to model in 1/72. 1/72 is two-thirds the size of 1/48 (48/72 = 2/3) so you need to copy them at 66.67% to reduce them to the size you need.

[ferny]

Thanks Sean

How do you work out the copy ratio?

[Okdoky]

Ferny

As Sean says

Take a measurement (I use Wheelbase where possible as it is normally easy to get the real dimension from data sheets and or the drawings).

Say your dimension is 125mm and your real measurement is 3000mm

3000 divided by 125 = 24

therefor the scale is 1/24

If the dimension was 41mm and the real dimension is 3000mm

3000 divided by 41 = 72

therefor the scale is 1/72

To enlarge a 1/72 drawing to 1/24 scale

existing scale divided by proposed then multiply by 100 which in this case 72 divided by 24 multiplied by 100

= 300 Therefor you have to enlarge your drawing by 300 %

if you need to reduce a drawing

existing scale (say 1/10) divided by proposed (say 1/24) would give 10 divided by 24 multiplied by 100

= 41 Therefor you have to reduce your drawing by 41%

The same process works for whatever scale your original drawing scales out at.

It is always worth checking your photocopied drawing on a known dimension to see that the enlarged or reduced scale has been achieved. Always write on your copy the scale you have made it to so that you know it has been copied to the right scale.

[thx6667]

This may also be of use:

http://jbwid.com/scalcalc.htm

[Martin @ RAM Models]

I sometimes design radio control model aircraft and many years ago used to scale up small drawings to the size I desired with a calculator and ruler using numerous ref lines.

Modern technology now makes things a lot easier and I head straight down to the copying shop.

I have a choice of two local's to use, both are equally helpful. Being rather lazy I explain what size a key dimension needs to be and let them work it all out for me.

Never failed so far

[ferny]

Cheers Guys

As luck would have it i did some calculations and the drawing I printed off was exactly to scale! More by luck than judgement!

Regards

Jon.