Radius - how do I measure it?

CoggesRailway

Registered
25 Oct 2009
8,597
8
OK prepare for silly question(s)

When building a flexitrack bend how to a calculate it's radius? And what do I need to one day have a live steam garrett or similarly big/expensive toy....?

How do you state a radius in a generic way- not just in LGB language?
 

matthew

Registered
24 Oct 2009
954
1
Stoke-On-Trent, Staffordshire
Im not sure about what radius you would need, but i would say the easiest way would be to pick a point/pivot, and make sure the track is whatever radius you need away from that point at all times.

Think i confused myself there nevermind you :D
 

peterbunce

1880's Colorado Narrow gauge on 45mm track
29 Oct 2009
1,754
16
east of manchester
Depends, you could build the trackbase, assuming that it has not yet been laid, to the radii you want, or have space for more likely!

To hopefully work out an already laid radii you will need a stake/pin (piece of rod) and a piece of string or a wooden lath, with a hole at the end (for the stake/pin)and the take as many measurements as you can to arrive at a close guess - you may well have laid the track at several different radii! in one curve, again to get it into the (not enough) space that you have available.

Of course it should be done the proper way with lots of stakes set out in advance! <grin>
 

bobg

Registered
3 May 2010
20,141
25
Middle Earth
The radius of a curve is simply a measurement either in metric or imperial, being the distance from the centre point to the rail (or correctly the centre of the sleeper). One method is to work to a template cut in card or similar and adjust the rail to that. It can be a problem when there is something in the way of the template so inside and outside templates can help. Another way, if you have room is to scribe the arc from the given centre with a stick with a nail in, or a piece of string from a peg (a form of compass).

Having lived in the "Land of the Garratt" I have to say that they should be able to negotiate fairly tight curves and handle fairly rough track, that is what they were designed for, but as always, the advice has to be keep curves as large as you can, and the track as true as pos.
 

stevelewis

Registered
24 Oct 2009
2,480
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Buckley NR MOLD NORTH WALES
Simple way to plot a radius:

Say your MAX Rad will be 6'

Take a length of 2" x 1" or similar timber say 2.4Metres ( sorry to go metric but thsats how it is defined in B&Q etc)

Drill a hole a couplt of inches from one end sufficient diameter to put a thin bamboo can thro' THIS IS YR PIVOT.

Then measure from this Pivot point along your timber various lengths 3' 4' 5' 6' etc as required and drill holes at these points

By now it should be becoming clear???

Simply push the bamboo into the ground where you think the centre of curve may be and then use the required hole to mark the curve using a pencil or something else to make a mark.

one thing I would recommend with G scale flexible track id dont try to curve it like N or 00 gauge flex track,

Bend the rails seperately then thread them back on the sleeper web ( vaseline or grease helps the re threading process), G scale flexible track does tend to want to straighten itself out.

Hope this helps
 

Alec K

Registered
25 Oct 2009
1,192
156
The Vale of the Avon
The curves on my railway, currently awaiting a break in the weather for tracklaying, were laid out exactly in the way Peter has described, from my draft plan. To plot the curve on the ground, I used a metal earthing rod as the centre, and stout garden cane tied at the appropriate radius with garden twine. As the curve was laid out, I drove in 18" metal pins to mark its centreline (and for that matter the centreline of the transitions and straights).

As the curves are being laid with LGB sectional track to guarantee the radius selected, a double check was made with 'templates' of sections of curved track as the supporting woodwork was erected.

Alec
 

Neil Robinson

Registered
24 Oct 2009
9,554
555
N W Leicestershire
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If you need a fixed radius you may be better purchasing sectional track.
If you can use flexible track I suggest you vary the radius as per full scale practice. Start with a large radius 'transition' curve from the straight gradually tightening to the middle of the curved section and then easing again towards the end of the curve. This means that for the same site the middle bit will be a bit tighter than a curve of constant radius but running should be better.
e5c34eeda4f141f7b18e7c0367b88beb.jpg
 

CoggesRailway

Registered
25 Oct 2009
8,597
8
thanks guys as ever a wealth of info- interesing to understand neils point as well- not relly understood that before.
 

stevelewis

Registered
24 Oct 2009
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Buckley NR MOLD NORTH WALES
One thing to add though..........after many years of building garden railways I personally find that Garden Lines seem to :rolleyes: evolve rather than adhering to any pre determined plan
 

Sea Lion

Registered
25 Oct 2009
1,006
0
Isle of Man
I suppose you could almost say it doesn't matter a jot what you first put down because everyone rips it up and does it again at some time!

I would go for nothing under 4' radius then you should be able to run most NG offerings, and if you have space to make that 4'6" then I'd be hard pushed to think of any NG loco you couldn't run. Naturally if you want to run standard gauge trains (G1) then it is a whole different ball game and you will need some much bigger rdaius curves.

Happy steamings,

John
 

Gizzy

A gentleman, a scholar, and a railway modeller....
26 Oct 2009
34,341
1,775
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Cambridgeshire
www.gscalecentral.net
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Coggesy mate, are you using LGB Code 332 flexi track or similar from Piko, ART, etc?

I was sent a R3 template by Resin d'Etre of this forum (Jon), and you are welcome to borrow it.

R3 is around 4 ft radius....
 

CoggesRailway

Registered
25 Oct 2009
8,597
8
Gizzy it's LGB flexi- i got a bunch of rails and a box of the sleeper sections from grs...