how do you scale up drawings

[Nigel HydeParticipant @nigelhyde97004]

Hi all

I have darwings of a 3 1/2 loco and i would like to build, but  in 7 1/4 .

so my question  is how do i scale it up? from 3.5″ to 71/4″

If i scale it up double the size it will only give me 7″

any ideas or am i being stupid  !!

thanks Nigel

[Nigel HydeParticipant @nigelhyde97004]

[JasonBModerator @jasonb]

Multiply the 3 1/2″ sizes by 2.0714285 and then adjust to suit standard metal and thread sizes.  You may also have to adjust the boiler dia to suit available tube size.

 

Also watch out for things that will be overscale, the 2″ Minnie traction engine is a good example as just doubleing up gives some rather bulky components.

 

Jason

[Paul BoscottParticipant @paulboscott25817]

Nigel
 
Considering the many hundreds of hours and pounds you will spend to make a good job of such a project I would suggest that you invest in a proven set of correct size drawings.
 
Paul

[Nigel HydeParticipant @nigelhyde97004]

thanks Jason and Paul

i am building Nick Feast Q1in 3.5″ and fancied a 71/4 one !!!

 

I have a good friend who is my clubs boiler inspector who would advise me on the boiiler

 

But as my dad said “one project at a time, son!” but i may build a 71/4 Q1 next

thanks all

Nigel

[Sub MandrelParticipant @submandrel]

Hi Nigel,

 

Your apparently simple question  has a complicated answer!

 

If you are making a true-scale model then mulitiplying by 2.xyz is fine. Fine for things like the size of frames/cab etc. But to make a working loco in a sensible amount of time you will want things like a boiler and various working parts to be made from stock materials (they don’t make copper tube in 1-thou increments!)

 

The problem is then that thicknesses and diameters are changing by different amounts to teh separation between components

 

Two 1/8″ components become 1/4″, but the distance between them becomes needs to increase by a little more to allow for the thickness not increasing enough. Essentially you have to re-draw the plans completely, or be prepared to check every dimension on the job.

 

Neil

[Nigel HydeParticipant @nigelhyde97004]

Hum i hadn’t thought of that !

not as simple as i thought

some serious food for thought

not sure i fancy re drawing the loco!!!

thanks Nigel

 

[JasonBModerator @jasonb]

You don’t actually need to redraw, just write the dims over the top in a different colour . BUT you need to calculate things carefully to arrive at those sizes.

 

Jason

[KWILParticipant @kwil]

Nigel, Have a look at photo No 3, one of these?

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