Minimum Turnout #?

Chuck,

Ross states their #5 is slightly larger than a 100" diameter curve.  That seems to be too tight for your design.

Ron

The articulated engines more than likely will not be your problem.  A ten coupled loco will be the issue.

FWIW, a SS Big Boy will go thru an Atlas #5 stand alone or in a crossover.

I like #6 as a minimum.

Thanks Tom and CAP. That is the answer I was looking for. The #5 in Armstrong's book has an "RCR" of 52" which is way tighter than my planned minimum however I wanted to hear how actual locos did through them. The book says the RCR Substitution is 80" for a #5 which seems like it would be plenty.

I'd like to use the #5's but will probably go with Tom's minimums of #6's.

Thank you gentlemen.

Chuck

Chuck,

Read what John showed in his table and figure as the definitions of RCR and the radius of substitution and note the difference.  Then you will have your answer.

Also, you might be interested in the other reference books I listed on the other Forum.

Ed

I've studied that chart for 20 years now and yet the RCR and R Subst. has always confused me.

If we have a minimum radius of 72" and there is an RCR in a #5 turnout of 52" that is way under our minimum. However he does say the R Subst is 102" for a #5 turnout.

Doesn't a locomotive or long passenger car still have to technically navigate the RCR of 52" even if only for a few inches? Does that short section of 52" cause any problems?

I guess that's what I'm trying to ask and also what others consider a minimum on their pike.

Thanks.

Chuck

Chuck,

"Doesn't a locomotive or long passenger car still have to technically navigate the RCR of 52" even if only for a few inches? Does that short section of 52" cause any problems?"

You are correct.

The RCR is the radius through the closure rail and can possibly cause problems with longer wheelbase locos and passenger cars.  I have an alleged #6 but a Mike can't negotiate the closure rail.  To be on the safe side, if your minimum radius is larger than the RCR you should go to a higher number switch.  The radius of substitution means that the switch can be substituted in that radius curve.  For example, I built a #6 and substituted it in an 89" radius curve and since I built the switch I could curve other parts of the switch as well.  It worked very well.

I have the room for a 72" minimum and use it.  My proposed double track helix will have a minimum radius of 69".

Regards,

Ed

Ed that's the answer I was looking for and I appreciate that. The R-Subst in the book has always thrown me and I've read the explanation dozens of times trying to see exactly what Armstrong was trying to say. That substitute is only if you incorporate the turnout as part of a curved section of track. The RCR is still the limiting number with regards to what can pass through.

You have confirmed what I suspected and that is if we build a 72" minimum radius layout we have to go with #6 turnouts to keep the RCR above 72".

Thanks again.

Chuck

One more comment:

Not every switch needs to accommodate every engine, e.g., you would not use a Big Boy to switch the furniture factory. So the furniture factory could be accessed by a #4 and serviced by an 0-6-0, a 2-8-0 or a four-wheel truck diesel, SW series, GP-9. etc.  Conversely, you would not use #4's on a mainline crossover.

A suggestion:  Use #8's for your mainline crossovers. Use #4, #5 or #6 elsewhere as the need and space permits.

Best of luck,

Ed

That replacement factor has a fudge factor IMO. 

When you are comparing a # switch against replacement radius you are primarily looking at the degrees of the circle sweep achieved in the frog angle.

The Atlas #5 switch, due to the over length of the assembly for the "Atlas snap track  System" I remove 3+ ties/rail off of each end.

If your track plan is so tight that you are hammering a numbered turnout into a curve consider having Brad make a radius switch for you.

I have a real tight location where a numbered turnout just would not fly so Brad made a 72" radius Lionel type of switch.  Purists  would scoff at it but it works just fine.  Worked so well I used one on a customer's layout.

You will find that different mfgs of turnouts will vary on their execution. 

One thing that makes the Atlas #5 work so well is the way it uses a curved point against the tangent stock rail. That way you get more curvature accomplished with in the same point tip-frog point than a conventional #5.  All function problems aside the Atlas #5 geometry works out well.

BTW, IMO,  Ed has a real good understanding of turnout design & function.

I use eights on the mainline as much as possible but I had to use sevens for one crossover.

I use sixes in storage areas and for access to yards and industrial areas.

Like Ed says, you can use tighter numbers for industrial switching. I have 2 fives in my mine area out of necessity and would have used sixes if I could have. I can't imagine those tight switches for mainline running.

What railroad do you plan to model?

Modern diesels (MTH 2-rail SD-70's, Dash-8's, etc.) with one full Atlas D&RGW California Zephyr pulled by a large steamer for show.

Thanks for the great inputs!

Chuck

There's a "radius" associated with numbered turnouts -- the points themselves. As I recall, the point radius on a #4 was 33"-36" depending on manufacturer (some fudging goes on). A #6 was 83" and a #8 was 132". A #5 would probably work with the diesel locomotives you're using; not sure how large steam (8-drivers) would handle it. The Atlas #7.5 or a #8 would probably be better. Experience with some of my 2-rail colleagues seems to indicate that #6 turnouts will work for you unless you go beyond a Northern (a 2-10-4 Texas or UP 4-12-2). Chris' recommendation for #8's is the safest approach.

For comparison here is a selection of "#6" turnouts.  Note the " ".

Also shown is the Atlas #5 and Brad Strong's special order 72" radius sectional style switch.

Left to right:  Atlas #5, OP, Roco, Peco, Marcway, Brad Strong 72" radius.

The points were all lined up on a straight edge.  The frog positions vary to the mfg.

The Brad Strong diverging route is all in curvature, not shown well in photo. tt

Nice info there Matt and Tom.

Good stuff.

Chuck

Matt,

With exceptions for special situations, the points are straight.  The radius you are referring to is the RCR, the radius of the closure rail.

Ed

The RCR will vary within the same category of turnout when the closure rail continues tangent.  Note the photos. Eshelman's later (not shown) , Peco and Roco have an extended straight portion of their closure rail.

Extending tangent in the closure rails will necessitate a tighter RCR due to reduced overall length to accomplish same.

An aspect most favorable in the Atlas #5 is where the entire closure length between the frog tip and point tip is in curvature, which allows for the widest radius.

I am NOT advocating toy train disciplines for scale modeling.  Just saying that it is an effective compression for switching on small layouts.  Which conversely sells track.  Like anything else, follow the dollar.

Lets face it.  Real RRs do not use 5' gauge #8 or #10 turnouts on a mainline. 

I don't think the issue for anyone here in this case is about what is prototypical. I think we are all viewing it as being about what is going to disrupt the flow of the train least or most on a nice curve and what is acceptable.

"I don't think the issue for anyone here in this case is about what is prototypical." 

Agreed, very freeing. tt

Side note:  Returning from Indy I stopped at Thurmond WV.  On the main I noted 41  paces from the point tips to the frog.   Some where around 28" in 0 scale.