Calculating & Drawing Radii

[Stese]

Hi All,

I'm planning and designing a new layout. For many reasons, I want to ensure I have no curve no tighter than a 3ft radius.

I've got some tight spaces that i'm hoping to use, but need to see if I can fit a 3ft radius curve in, specifically to get the railway to turn 90 Degrees in one place.

to visually test this, if I created a template out of cardboard, starting with a 3ft piece of string and a pencil, and making a curve arc of 90 Degrees, and then marking 2 lines 8.25mm from the centre on either side... would this be accurate?

Regards,

Steve D.

[Walkingthedog]

Sounds OK to me. 3ft radius to the centre of the track. I’d be tempted to use a piece of wood with holes in it to take a pencil. String isn’t ideal, it can stretch and wrap around the pivot point.

[Stese]

Thats a fair 'point' to make. 3ft from a nail to a hole for pencil....

job done.

I'm wondering if I can get away with anything less than 3ft, I'm guessing i'm only going to be losing longer locos with fixed driving wheels such as a large steam engine... hmmmm looks like a rivarossi big-boy can just about squeak around 18inch curves, so I should be able to get away with 24" without an issue.

The area I want this for is hidden anyway, so as long as it navigates it without coming off the track...

i'm rambling now, lol.

[RAF96]

I just bought a cheap (£9.99) angle level from Lidl which also has a pencil and compass points in the ends of the adjustable arms making it into a large drawing compass.



Previous to this I have used the wooden lath with a centre hole for a screw and standard radius holes for a pencil.