radius

[ABC]

Yep, with flex track you can make any radius (but it gets tough once you try to bend it below 12" or so). No there's nothing wrong with 20" radius as long as you locos and rolling stock don't require a 22 or 24 inch radius or something like that.

[full maxx]

here's mine 18" and 22" on 4X8 

[Joe Satnik]

Dear All,

Using flex track (or sectional curves, for that matter), you need to keep in mind the minimum center-line spacing between tracks to avoid overhang crashes. 

http://www.nmra.org/standards/sandrp/s-8.html

(Scroll down to HO.)

One would not, for instance, put a 20" radius flex curve between 18"R and 22"R sectional curves, as it would need minimum 2-3/8" spacing, according to the NMRA.

Gomez Addams would be proud if you do, though.

Hope this helps. 

Sincerely,

Joe Satnik     

[jward]

one thing you may find helpful if laying flex track are the radius guages made by ribbonrail. these thin pieces of metal curved to fit between the rails of track laid at a particular radius, and they are available in a variety of sizes from about 15" up to 48" radius. you simply set the guage between the rails of your flex track, it will force the track into the desired radius, then you fasten the track down. using these is an easy way to ensure a smooth curve and eliminate the kinks and sharper curves that sometimes result when laying flex track. these can also be used for handlaid track (like i do) and to elimiante kinks between sections of sectional track.

[ABC]

I have two of those.

[tford]

jward or ABC were do you get these radius gauges?

[ABC]

The owner of my local hobby shop gave them to me about 5 or 6 years ago.
Here's the track gauge's that they make for HO scale:
5, 10, and 24 inch straight
and 5 and 10 inch gauges for 18 inch radius curves through 48 inch radius.
They are about $4 each.
Here's a pics

5 inch
Here'a link to walthers
http://www.walthers.com/exec/search?category=&scale=H&manu=ribbonrail&item=&keywords=gauge&words=restrict&instock=Y&split=30&Submit=Search
Here's what's in stock:
170-10    Track Alignment Gauges - Straight -- 10"    HO   
170-20    5" Track Alignment Gauges - Curved -- 20" Radius    HO            
170-25   5" Track Alignment Gauges - Curved -- 25" Radius    HO            
170-26   5" Track Alignment Gauges - Curved -- 26" Radius    HO            
170-27   5" Track Alignment Gauges - Curved -- 27" Radius    HO            
170-29   5" Track Alignment Gauges - Curved -- 29" Radius    HO            
170-31   5" Track Alignment Gauges - Curved -- 31" Radius    HO            
170-33   5" Track Alignment Gauges - Curved -- 33" Radius    HO            
170-1020   10" Track Alignment Gauges - Curved -- 20" Radius    HO            
170-1022   10" Track Alignment Gauges - Curved -- 22" Radius    HO            
170-1024   10" Track Alignment Gauges - Curved -- 24" Radius    HO         
170-1030   10" Track Alignment Gauges - Curved -- 30" Radius    HO            
170-1032   10" Track Alignment Gauges - Curved -- 32" Radius    HO         
170-1034   10" Track Alignment Gauges - Curved -- 34" Radius    HO       
 

[tford]

Thanks, looks like they would be easy to use.

[Joe Satnik]

Dear All,

Track gauges:

Pros: 

1.) The alignment gauges could come in handy where it is difficult to use a trammel, as in a corner of an around the wall layout.

Cons:

1.) Expense. 

2.) Not the exact radius or spacing of radii you or the NMRA had hoped for. 

You can easily make a trammel out of a cheap wooden yardstick, which will be good for radii up to about 34-1/2".   

Just drill a small hole (e.g. 1/16") for the center of the circle at 1", then drill another at 1" beyond your target radius.  Keep both holes at the same point on the width of the yardstick.  (e.g. both holes 1/4" in from the left side...)   

Use a marker to label the hole with the target radius, then draw a line through the nearby ruler "inch" numbers to avoid confusion.  (Don't ask how I know this...) 

Put a small nail through the trammel into the layout board at the center of the circle, then draw the circle with a pencil through the trammel hole at the target radius.

Longer radii, use longer thin strips of wood, marked and drilled at points measured with a tape measure.

This MR article (ask your librarian) shows the use of a trammel in an around the wall layout: 

Let's build the Wildcat Central
Model Railroader, January 2001 page 74
A room-sized HO layout for today's big trains
Article also published in the book "Basic Model Railroad Track Plans", page 56
(FOAM, "KELLY, JIM", LAYOUT, TRACKPLAN, CONSTRUCTION, HO, MR )
Trackplan is 10x12
- Layout construction details
- Center-operating plan
- Standard gauge
- Continuous operation
- Double track main

Jim uses a camera tripod to float the center point for the trammel out in space.

I highly recommend this article, as it packs tons of tips on building layouts...   
   
Hope this helps.

Sincerely,

Joe Satnik