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HO Scale #4 turnouts and 6-axle locomotives

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  • Member since
    January, 2011
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HO Scale #4 turnouts and 6-axle locomotives
Posted by RJ Dio on Saturday, January 01, 2011 4:49 PM

Will an Athearn six-axle engine (i.e. an SD-40 or U30C) have any trouble navigating #4 switches without derailing?


I would like to use #4 switches for things like yards but don't want to build a model railroad that limits where certain engines can go.


I am modeling the 1970's so I am not concerned about newer engines such as SD70MAC or GE Dash-8 40CW types.


On a related note concerning prototypes, is it correct that #4 switches roughly correlate to yard and industry tracks, #6 correlate to main line tracks, and #8 correlate to high-speed main line track?


And, is it correct that code 83 track roughly correlates to 140 lb. rail and code 70 track correlates to roughly 100 lb. rail?  This is useful information to apply when I am modeling heavy-use main lines vs. light duty or older branch lines.



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Posted by lone geep on Sunday, January 02, 2011 3:07 PM

I know that bachmann SD40-2s will navigate #4 turnouts.

The Lone Geep

Lone Geep 


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Posted by jrbernier on Sunday, January 02, 2011 3:13 PM

  It depends on what brand #4 you are talking about.  The Atlas Customline #4 is really a #4.5 turnout.  A Walthers/Shinohara #4 is a true #4 turnout.  I would not want to run a train with 2-3 large/modern 6-axle engines at 'track speed' through either brand.  A # 6 is a much better option(if you can spare the room).  That said, I have Atlas Customline #4 turnouts in my yard and I have had no problems with small/medium steam and GP9/SD7 locomotives.  If you are going to use #4's, use the Atlas ones as they are not as sharp.

  On the prototype, you will be hard pressed to find a yard turnout less that a #9 in most modern installations!

  • A #4 is really sharp - but we are talking about layouts with finite areas - Right?
  • A #6 is pretty much the 'normal' turnout for most layouts bigger than a 4X8.  I use #6 turnouts for ends of sidings and cross-overs.  Our club uses #6's everywhere and has had no problems with all types of modern power/steam engines/long passenger trains.
  • A #8 is a nice large turnout.  If I had the space, all of my cross-overs would be a #8.  The Prototype use #20 or #24 turnouts a lot for ends of sidings or other powered turnouts.  A basic 'rule of thumb' is that you can double the # of the turnout to find out what speed is safe through the diverging leg of a turnout.  Most TT/Rule Books limit trains to 35-40 mph through the diverging leg of such turnouts.


  • Code 83 trackage is about 132-136 lb in the prototype.
  • Code 70 trackage is about 100-112 lb in the prototype.



Modeling BNSF  and Milwaukee Road in SW Wisconsin

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Posted by Doug from Michigan on Sunday, January 02, 2011 5:47 PM

I have an Athearn SD40-2 that takes the Atlas #4's with no problem, even at considerable "greater than scale" speeds.  Don't ask me how I know this......

That being said, as my layout progresses I am still taking the advice learned here and in many books on layout design, and am trying to limit future uses of the #4's (4.5's) to yards only. 

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Posted by RJ Dio on Sunday, January 02, 2011 10:29 PM

Fantastic information and very helpful.  Thank you.  Yes, I am indeed using Atlas Custom Line #4's.

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Posted by ezielinski on Monday, January 03, 2011 2:39 AM

My whole 18x8 layout employs Atlas #4 turnouts - yards and mainlines.  Large Dash 9 and Dash 8 locomotives, SD40's, Geeps, SW's, even a 4-6-2 Spectrum steamer have no problems with them.

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Posted by richhotrain on Monday, January 03, 2011 8:16 AM

I don't know how you guys get steam engines and 6 axle diesels to negotiate Atlas Custom Line #4 turnouts, even at crawl speeds.

I just ripped out my two remaining #4s that accessed one track to my coal tower and replaced them with #6s.  I would ban the use of #4 turnouts altogether if I had the power.

I use #6s exclusively throughout my double mainline.


Alton Junction

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Posted by yankee flyer on Monday, January 03, 2011 11:26 AM

Hi Rich

I think it's all in how precise you lay the track. My yard is all #4s and I have a couple curves that gave my Alco PA1s, my heavy weight passenger cars, and the SD7 a fit. All problems were solved by a lot of fine tuning of the track. Some Atlas turn outs sit high in the frog and have to be pined down. #6s and above would be good if theres room. 

Smile, Wink & Grin Good day


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Posted by dante on Monday, January 03, 2011 4:52 PM

I have a Walthers/Shinohara #4 (DCC friendly with dead frog) on my test tracks being used to confirm criteria for the layout about to be built.  My 6-axle Proto 2000 E-8 and PA-1 and BLI heavy 2-8-2 take the turnout with ease, whether traveling fast or slow.  

The probable significant factor is that the radius of closure rail (RCR) is 26" as measured by Ribbonrail templates.  That is significantly better than the 15" and 22" indicated for a #4 and #4-1/2, respectively, in John Armstrong's book on track planning.  The frog is definitely a measured #4, as stated by Jim above. The track and turnout are spiked into a Homasote panel.

The obvious suggestion is to test your equipment on the turnouts you expect to use.


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Posted by Doug from Michigan on Tuesday, January 04, 2011 1:17 PM

I guess I just got lucky with mine, since I'm certainly no expert at laying track or fine tuning layouts.  BTW, I am using code 100.  I can't imagine why, but would the rail height make a difference with code 83?

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Posted by fender777 on Tuesday, January 04, 2011 3:40 PM

I use Atlas #4 all over and all my locos even my new ac6000 'DASH 9' ECT all work fine.Saves room.But if space is not a problem then #6 would be the best I guess .But my Altas #4 work fine.BOB

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Posted by wjstix on Tuesday, January 04, 2011 4:33 PM

A good compromise - if you're using a track line that offers it - is the no.5 turnout. I tried no. 4's in a couple places on my old layout but had some problems with a few engines, but no problems when I switched to no.5 or larger.

BTW in the real world, a no. 6 or 8 turnout would be pretty sharp, like yard trackage or industry spurs. Mainline turnouts are more like no. 20-22 range.

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Posted by rvos1979 on Tuesday, January 04, 2011 4:55 PM

I am currently building a layout with a paper mill theme, and have used several Shinohara code 70 #4 turnouts, there is even a #4 crossover.  I have intended this to be switched by a four-axle locomotive, but took plenty of time fitting the track together.  I have run an Athearn RTR SD45 through the crossover with no problems at slow speed, but it does look funny going through such a sharp turnout.....

Randy Vos

"Ever have one of those days where you couldn't hit the ground with your hat??" - Waylon Jennings

"May the Lord take a liking to you and blow you up, real good" - SCTV

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