I have always been confused by this: I know that turnouts are labled #4, #6, #8, etc. based on the length of the turnout, but how do you know what radius the diverging curve is? Is there a chart e.g. #4 turnouts=18 inch radius diverging routes, or something like that? Also, what is a good price for wider radius, good quality, used turnouts in ho scale?
Check this out, scroll down and read. I’m sure this is not the only source of information, but a search had this at the top of the list, see if it answers your questions.
http://www.pcrnmra.org/pcr/clinics/Kolm-TurnoutsWhatYouNeedtoKnow-PCR2008-handout.pdf
Mike.
Yes, that was exteremely helpful. Just one question: The closure radius is the radius of the diverging route curve, right? Thanks so much for the PDF!
What the pdf calls the closure radius is the radius through the closure rail, between the points and the frog. On a standard turnout, much of the diverging route is straight through and past the frog, so the quoted figure isn’t necessarily a substitution radius (i.e. a smooth or constant curve that could be substituted for the whole turnout).
The approximate closure radius and substitution radius for typical HO turnouts is listed below.
#4 15"/29"
#5 26"/36"
#6 43"/56"
#8 67"/110"
The first number (closure radius) is from the pdf linked in the earlier post, while the second number (substitution radius) is from a list I found posted on another forum. There seem to be varying opinions on the actual numbers, so these are a rough guide only.
that’s not true. The turnout number describes the angle of the frog, not the length.
The lead-length, the distance between the switch points and the frog can vary. The diagram below illustrates how the lead and closure rail radius can vary while the frog number remains the same.
Ok, so say I was using 30 inch radius on my layout. Which turnout would I use for diverging routes off the mainline?
And here-in lies your confusion; you have assumed incorrect ‘information.’
The number of a turnout is an expression of the RATIO of diversion at the frog, or through it (…and beyond in the typical N. American turnout geometry where the route through the frog and beyond is essentially tangential to the curvature of the closure rails.)
Again, it’s a ratio. For every four units of movement along the ‘through route’, a #4 frog diverges one unit of length. A #6 turnout diverges one unit laterally for every six (6) units of travel down the turnout through the frog. What this amounts to is a wider divergence, or angle of divergence, for a #4 than on a #6.
It has virtually nothing to do with the length of the whole appliance, from points all the way through the frog and beyond, either route. On the whole, the higher the frog number, the longer the entire appliance will tend to be simply because the rolling stock must travel farther to exit beyond the frog, but that’s because the closure rails are longer.
Based on Rob’s list, the #4 has a substitution radius of 29 inches. That appears to be the closest turnout size you could slip into the 30 inch radius curve and diverge out from there.
Just one more suggestion, take a look at curved turnouts, they can buy you some more length on sidings or other situations. I have used several to overcome the problem of difficult turnout placements.
So it is physically impossible to make a perfect curve with turnouts unless you are using flextrack? That would explian all of the problems I have been having with gaps in sectional track joints when there was a turnout forming part of a loop.
Substitution radius is very misleading as to performance. Since the tightest radius through the #4 turnout is much tighter than the substitution radius, that is the limiting factor in the size and type of equipment that can operate. Probably not a great fit for the Original Poster’s desired large modern locos and intermodal equipment. Note that the Atlas “#4” Customline is actually a #4½, so it’s slightly better, but still might be a bit too tight.
Curved turnouts may help, but even curved turnouts used with flextrack will be slightly off from a true circle owing to the points and frog. The PECO Code 83 curved turnout, though broadly curved, is very compact relative to Walthers and some others.
you’re assuming that there is a smooth curve from end of the turnout near the switch points and at the end diverging route. That you can replace a section of a curve with the divering route of a turnout. This may be true for Atlas snap turnouts, but not for standard turnouts.
The turnout is straight between the switch point and the end of the turnout, and straight after the frog on both diverging and non diverging routes.
It’s not even true for SnapSwitches, as there is a short straight section (1½") in front of the curve.
Conveniently though, Atlas makes short filler pieces of sectional track, so if you use the extra 1/3 curve section plus add one of those short straights on the opposite side, it will work without flex track.
–Randy
Trouble is there are really no exact standards in HO that manufactures follow, they cab be a little loose.
That wouldn’t work well at all. If the minimum radius of the layout is 30", putting a #4 in makes the minimum radius 15", that’s the ACTUAL radius in the switch. The cars and locomotives have to transit the actual closure radius. If you want to preserve a 30" min radius you have to go with a #6 switch, a #5 has a radius of 26" which is less than 30, the first switch that preserves a 30" minimum radius is a #6.
My Walthers/Shinohara #4s have a radius of 25"≠ through the frog as measured with Ribbonrail 24" and 26" gauges. That explains why my 6-axle diesels can negotiate these turnouts.
Dante
Hello all,
Ahhh…I believe I now understand your question.
The diverging route is not a curve expressed in radius, it is an angle which can be best described in degrees.
As has been posted before, frog numbers are a ratio. A frog #1 would put the angle of the diverging track at 45º.
On the PECO website turnouts are described by Frog #, Nominal Radius and Angle.
If you notice the Nominal Radius of the #5 turnout does not directly match any sectional track manufactured.
Even when using sectional track it is necessary to modify the track beyond just cutting custom lengths.
Check out this thread…
http://cs.trains.com/mrr/f/11/t/256138.aspx
Now, that being said…
Curved turnouts are expressed in Nominal Radius and tend to match or approximate the common radi of sectional track.
Hope this helps.
Post Script:
As far as pricing on “previously owned” turnouts…
I was at a train show and made an offer to a vendor for used turnouts. I knew the price of the same units NIB at a local hobby store on my way home.
The vendor declined my offer. I thanked him for his time.
When I left the show went by the LHS and paid less than $5.00 difference for all the turnouts. New in box with all the little bits and a 30-day gurantee.
Caveat Emptor.
HTH- -JJ
Free, because generally speaking, unless the previous owner was super careful about how they were attached/removed, they will probably not be in perfect condition and may or may not work right. Buy in person where you can visually inspect the item (train show). Everything else is pretty much at your own risk.
I have 3 curved shinohara turnouts right now, plus 2 peco curved turnouts. Will try to post pics, unless someone already knows what radii they would be. Thanks for all the helpful comments!