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PostPosted: Thu Jul 30, 2009 8:23 am 
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Joined: Sun May 31, 2009 3:30 pm
Posts: 3
Since the code applies to the height of the rail, can I use code 40 in a 55 fixture, or does it the thinner width of the rail head draw the head of the rail out of gauge?


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PostPosted: Thu Jul 30, 2009 10:25 am 
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Joined: Thu Feb 23, 2006 4:51 pm
Posts: 84
Hello John,

It's true that the code number applies to the height of the rail but the rail base width for code 40 and 55 is also different. It's important that the rail fits snuggly in the assembly fixture to maintain the proper gauge and clearances. Code 40 rail would be too loose in a code 55 fixture whereas code 55 rail will is too wide to fit in a code 40 fixture.

A few customers have built turnouts in a fixture using rail smaller than it was intended for using track gauges to keep the rails in proper gauge and also using an NMRA track gauge to check that they have the proper clearances but this approach is not recommended.

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Customer Service - Fast Tracks HobbyWorks Inc.
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PostPosted: Tue Aug 28, 2012 8:02 am 
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Joined: Fri Oct 07, 2011 6:24 pm
Posts: 33
Interesting.

It's odd that the Micro Engineering code 83/code 70 rail base profile is the same, but the code 55/code 40 is not.


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PostPosted: Tue Aug 28, 2012 10:54 am 
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Joined: Sat Aug 13, 2005 10:48 am
Posts: 365
Location: East Texas - USA
The code 70 - 83 rail bases were not always closely the same. IN the early 1990's ME ran a custom 'pull' of code 83 rail for a client, who ended up failing to complete the transaction. ME sold off the rail by using their code 70 flex track molds, and discovered that the combination was cheaper but still effective for code 83 and continued with the new profile since then.

Code 40 and code 55 rails are significantly different in profile and always have been. In large part because they are targeted to different scales - though used often within same scales. Rial height alone does not mean identical (or even very close) rail profiles. The code 83 offerings in the market have very wildly different rail bases and webs as well as even the rail head widths.

Fixtures relying on rail bases for alignment require either custom per rail construction of the addition of rail gauges on the rail heads for compensation when constructing. While not recommended by Tim, many do in fact use the rail gauges and allow multi-rail use in a single fixture.

-ed-

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COSLAR RR - http://www.coslar.us/
NMRA Standards and Conformance Department
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I estimate I have about 5 pounds of coupler springs somewhere in the vicinity of my workbench.


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