Transition Curves Small Layout

[Sunshine Express]

I have an 8x4 Layout and naturally there is a tight squeeze for all the good ideas like switching tracks  etc.,but though most of my stock negotiates the worst of these,I am thinking of altering  some main line curves by the addition of a small piece of straight track,as in real railroads. Is there any rule of thumb for say 18" Curves ? Length of small piece of straight track,or just where it would fit without creating a bag alignment ?
My latest Loco,Spectrum Consolidation,does not like the Peco long curve point sections,but does not derail,though it needs relief here. Only run 4wheel Diesels,and 40 ft Box Cars etc. Think Small is the motto.

[Hunt]

See if info in this website helps you http://www.trackplanning.com/easements.htm

[robin]

For a layout on a 4x8 sheet, curve transitions are just going to require real estate you don't have.  I assume you're using some flex track.  If so perhaps some cardboard curve templates in 15 and 18 inch radii will help you lay out your ideas prior to cutting and soldering.  Using the shortest possible rolling stock that is properly weighted with well adjusted trucks will help a lot.  Forty foot long cars should be your maximum length and twenty-six foot long would be better.  Modeling the Civil War (or War of N. Aggression) would keep your rolling stock a workable length.  Switching to narrow gauge HO (HOn3) would also allow some very tight curves and still look good. 

Something to keep in mind:  Even if you could get 50 foot long cars to negotiate 15 inch radius curves; they would look very unrealistic doing so.  The shorter cars have more visual appeal on tight curves.

Robin
Whose first layout was a spaghetti bowl!

[rogertra]

Transition curves are not needed for reliable operation on model railways as physicis in the form of inertia and friction don't scale down.   This expains why you can run a loco at warp speed around 18" curves on a table top railway yet the prototype can't do that on curves of 250 foot radius.

On a model railway, transition curves are usually just put in for good looks.

[Sunshine Express]

Thanks to all. Yes I have  some 26ft Old Time stock,and small locos,and will stay with 4 wheel diesels and small stock. Transition curves out-  thanks again. Diesels and small box cars actually lull you into a sense of enjoyment and forgive  much of your planning errors. My main mistake was the Peco Long Curve  Set Track Points,they are deadly for  4-6-0's and 4-4-0's,yet the sme locos will go through crossovers on normal Peco track.
I will consider removing these,even though they have been great space savers.