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Radius help for a new guy

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  • Member since
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  • From: Oreland PA
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Radius help for a new guy
Posted by UncBob on Friday, March 20, 2009 4:30 PM

 Radius is measured --to the inside track--to the outside track --center line ?

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Posted by JWARNELL on Friday, March 20, 2009 4:47 PM

I have always assumed that it was the center line.

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Posted by Doc in CT on Friday, March 20, 2009 5:11 PM

 Radius is measured from the center point of the curve to the centerline of the track. HO track is 11/4 in wide, with standard cork roadbed just under 2in wide.

So a 18in radius curve needs a width of about 38in for a full circle. 

Checkout Beginners Page Consist from NMRA. 

BTW the NTRAK standard is  24in radius for mainline, 18 for branch.

Co-owner of the proposed CT River Valley RR (HO scale) http://home.comcast.net/~docinct/CTRiverValleyRR/

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Posted by UncBob on Friday, March 20, 2009 5:47 PM

 Many thanks

 

Since I have a 4 X 9.5 , I am going with a 22 outside oval and 18 inside oval with a cross over at the bottom

I will be close to the edges with the 22 but with a wall on the one side of the long dimension and a 2 'high plexiglass  on the exposed side I should be safe from catastrophic  derailments (kind that land on the floor0

 

Will run Mountains, Mikados and Consolidations on the 22 and Consolidations, Moguls and Americans on the 18 with ocassional crossovers --no cars longer than 40 ft

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Posted by dehusman on Friday, March 20, 2009 8:39 PM

UncBob

Will run Mountains, Mikados and Consolidations on the 22 and Consolidations, Moguls and Americans on the 18 with ocassional crossovers --no cars longer than 40 ft

Probably but chances are not well, especially the mountain.  Mountains usually like something in the 24-30 in radius range and look funky on small radius curves, below 30".

Dave H. Painted side goes up. My website : wnbranch.com

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Posted by UncBob on Friday, March 20, 2009 9:21 PM

 Been running IHC moutains on 22 and no problems  and they look great pulling 16 coal cars

 

Thing is I have had just a plain painted green homosote over plywood with one 22 oval for years and have decided to  expand and do scenery etc and get a little more serious with 2 train capability

 

Been using Bachman snap track and am converting over to Atlas 100 

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Posted by nw_fan on Friday, March 20, 2009 9:23 PM

 22" may not be optimal, but it will accomodate 95% of everything on the market.

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Posted by UncBob on Friday, March 20, 2009 9:43 PM

 Here is a pic I just snapped of the Mountain --I am testing my new track before tacking permanently and balasting

 

Testing Atlas track  

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Posted by tinman1 on Friday, March 20, 2009 10:20 PM

Radius measurements can be from any point on the track to the same point on the opposite side. Just watch you don't try going from outside to outside rails. It would be measured from left-most rail to left-most rail on the opposite side, etc.

edit- I would also clarify a little, if you are driving a nail in the center of the circle and drawing the circle, it would be the centerline.

Tom "dust is not weathering"
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Posted by Texas Zepher on Friday, March 20, 2009 11:31 PM

tinman1
Radius measurements can be from any point on the track to the same point on the opposite side. Just watch you don't try going from outside to outside rails. It would be measured from left-most rail to left-most rail on the opposite side, etc.

That would be the diameter.  To get the radius one would have to divide by 2.  And this method only works when the track turns 180 degrees or more.

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Posted by duckdogger on Saturday, March 21, 2009 5:01 AM

 Aren't we speaking of an arc (a segment of a circle's circumference) when we discuss radius issues?  It's a point of reference and what we actually incorporate into our layout.

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Posted by tinman1 on Saturday, March 21, 2009 6:45 PM

My error. Radius is from the reference point in the center, more useful than diameter, especially with less than 180 arcs. Diameter is great just to see if the track will actually fit , provided that one remembers to add the width of one track to it. (ie; a 18"r will not fit on a 36" table. In HO it needs 38"min, from edge to edge).

Tom "dust is not weathering"

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