True radius of HO 24" and 22" loops

[UncBob]

 My 22 is ok on my 48 wide

So 52 should be OK for your 24

I have run 4-8-4 on the 22 no problems but it looks funny from above

[Lee 1234]

RMorris

Since the radius of a loop or turn is actually the centerline of the track, can someone tell me how much extra need to be allowed for the extra width of track plus the overhang of locos or cars going around a turn?

 One end of my layout has to fit into a 52" wide cutout, so I am wondering how much off the walls I need to stay.

The outside of a circle of track is the radius plus the width of the track.
To calculate clearances get a NMRA gage and measure the length between trucks of the largest car you intend to use. You are going to buy a gage sooner or later, do it earlier and get used to using it.

[UncBob]

 I am running 2 inches from track center line to the edge of e table--no problem but I do have a plexiglass guard

 

One other possibilty is to run 2- 22 inch ovals and have a 4 inch plug in the middle of the arc in the outer  oval which will give you 2 inch centers on the straights and you could have a little less run on the inner straight say 5 inches less --

[cuyama]

For many types (and combinations) of equipment, concentric 22" and 24" HO curves will be too close to one another.

It's safer to separate them by 2 1/4" to 2 1/2", as described here:
http://www.nmra.org/standards/sandrp/s-8.html

Also as described on the NMRA site, the clearance from the centerline to an obstruction such as a wall should be just over an inch. With a curve, 1 1/2" is probably safer.
http://www.nmra.org/standards/sandrp/s-7.html

And if you need to reach in there, finger space might require a bit more.

So a typical situation like this would suggest:
(22" R inner curve)
24.5" R outer curve (49" centerline diameter)
1.5" to wall
3" to table edge at minimum

Which yields 53.5". Probably tight in 52" wide. Possibly workable if you put up a shield of some sort to keep derailed cars at the edge from plunging to the floor.

Of course, the question that you could ask yourself is if there is another alternative arrangement of track in the room that would work and not be quite so tight while possibly yielding better access.

Byron

 

[tomikawaTT]

RMorris

Since the radius of a loop or turn is actually the centerline of the track, can someone tell me how much extra need to be allowed for the extra width of track plus the overhang of locos or cars going around a turn?

 One end of my layout has to fit into a 52" wide cutout, so I am wondering how much off the walls I need to stay.

First, welcome aboard 

A 48 inch diameter (24 inch radius) curve will fit in a 52 inch wide space with plenty of outside clearance for anything - even an 'honest' Big Boy.  The problem will come if you are trying to put a 22 inch radius curve inside the 24 incher - long car on the outside plus Big Boy on the inside equals sideswipe.

You could probably get away with adding 10mm to that 24 inch radius without compromising outside overhang, but experiment first with some temporarily-laid flex track (nobody makes 620mm radius sectional track.)  On the other hand, if all you will ever run are short locomotives and short cars, nested 22 and 24mm curves will work.

Chuck (Modeling Central Japan in September, 1964)

[cowman]

Welcome to the forums.

It depends on the equipment you are running, how much it hangs over the outside rail on your curve.  You will have to experiment to see what your equipment does.  Don't forget clearance on the inside of the inner rail for longer cars.   Since 22" radius track will fit on a 4x8 sheet of plywood, you should have no problems if you have 52" to work with.

Good luck,

[RMorris]

Since the radius of a loop or turn is actually the centerline of the track, can someone tell me how much extra need to be allowed for the extra width of track plus the overhang of locos or cars going around a turn?

 One end of my layout has to fit into a 52" wide cutout, so I am wondering how much off the walls I need to stay.