I was looking at a track plan of either a model railroad or a prototype and noticed that a particular switch (turnout) was labeled Number 4. Is that the same size/shape/radius switch as say, a a large scale Aristo 4? And the same as an HO number 4? And a full-scale 4?
I’m asking because I have a bunch of Aristo number 4s–the 4-foot diameter kind–and thought they might be too sharp for protypical operation. But seeing this, I’m not sure.
Your answers?
Well sorta yes…the switch number means that the diverging route moves away from the through route a given distance in a certain amount of distance. Now what those units of measurement are are variable…
Yes - But I don’t think the Arsito 4Ft Dia. Switch is a number 4. I believe it’s much tighter. They are useful on mining spurs and industrial track where only small locos would go, but too tight for mainline passing sidings etc. I still have a bunch on my indoor yards but only short cars and locos use those tracks.
Yes, if it is a numbered switch. The system is used internationally and applies to any switch including curved, double-switch, wye etc. etc.
I agree with Jon. The shorty switches are very useful in spurs industrial track and I will add where space requires them.
If you will be running short smaller equipment sure use the #4’s on your main. Think about the type of trains that would look OK on the #4 switches, Trolleys, Mining, Logging, European trains. If you plan on running modern equipment like intermodals with a 6 axle engine like a SD45 I don’t even think they will make it through a #4 switch.
I started with all #4’s since they were relativley inexpensive and readily available. Since then I have slowly been replacing them with the next size up which I believe is a #6 the LGB 16000 series with the 8’ diameter convergence. I still use the shorties inside yards and spurs.
Happy RRing
They also work as functioning derailers, when torn apart.
LGB, Aristocraft, USA trains all make switches, points, turnouts that are designed to drop into a circle of track that is a given radius / circumference. 2 of them also make a switch, turnout, point, that is a numbered unit. That is a #6. It is Not to be confused with a 1600 radius circle. Nor is a 1400 radius switch a #4. Real world railways avoid radius type switches, points, turnouts like the plague if they possibly can unless there is just no other way.
Bart Salmons said:
Well sorta yes…the switch number means that the diverging route moves away from the through route a given distance in a certain amount of distance. Now what those units of measurement are are variable…
Bart,
May I politely disagree with your last statement. The “switch number” is a ratio, just like a gradient, (and could be expressed in % if you wanted!) It is the frog angle expressed as a ratio of number of units along the side to achieve 1 unit of separation. In other words, a #4 has a frog that is 4 units long and 1 unit wide at the end away from the point. Pick your own units of measurement but you will get the same result.
It’s elementary geometry
Empirically obvious to the most casual observer, Grasshopper.
A numbered turnout has a frog that forms a right angled triangle where the long side is the number of the switch, and the short side of the triangle is 1. That means that a number 6 switch has the long side equal to 6 units long, and the short side is 1 unit long. The diverging track leaves the switch as a tangent (straight track) not as a curve. Both Aristo and USA make a # 6 turnout. I think that Switchcrafters make a #4, #5, #6, #8, and a #10. They may make other sizes, and might make custom sizes, too.
Most of Aristo’s and USA’s switches have the diverging track leave in a radius of some sort. I know that their “Wide Radius” turnout corresponds to a 5 ft radius (10 ft diameter) I measured their frog, and it was about 3 and a half, but don’t let that confuse you, it is NOT a 3 and a half switch.
Hope this helps and is not too confusing.
This is a good primer on turnouts.
Turnouts and frog numbers are two different things…
Yes a turnout can have a #6 frog, but the lead of the turnout can vary from turnout to turnout.
Steve’s explanation about how to measure a frog is close, but slightly wrong…
Here’s a simplified drawing of a frog point.
(http://fbcdn-sphotos-a-a.akamaihd.net/hphotos-ak-frc1/311257_10150317836796912_1947829575_n.jpg)
The green line represents the rail. The angle of the frog is measured by taking the theoretical tip of the frog, splitting it in half and measuring right angles. If you measure at 6" the right angle on a #6 frog should be 1". As you move further down the frog say at the 12" mark, the right angle measurement is 2". Now this is 1" or 2" split in half, so if you measure from the theoretical middle of the frog to either rail you’ll get a 6:.5 ratio instead of a 6:1 ratio.
I mention a theoretical frog point because on the prototypes (and our models) we can not get a razor sharp point. Therefore MOW refers to the theoretical half point of the frog. Or the point were the frog actually begins.
By the way the prototype considers anything less than a #11 turnout a problem. Most model turnouts are way undersize in terms of both lead length and frog size.
Dear All,
These are the formulas that I found came closest to John Armstrong’s and NMRA’s charts:
frog# = 1/(2 tan[frog angle/2])
frog angle = 2 arctan(1/[2 frog#])
It’s easy to mess up on the math.
Careful with the brackets.
Careful that your calculator is in “degrees” mode.
On some calculators arctan is tan-1.
11.4 degrees gives #5
#4 gives 14.25 degrees.
Hope this helps.
Sincerely,
Joe Satnik
Edit: Removed * from formula for consistency.
As I said, “Empirically obvious to the most casual observer.”
My math professor used to say that as he skipped over three or more steps.
I hated that. Still do.
Paul Mallory’s “Trackwork Handbook” (Revised edition 1977) has a table with the degree equivalents from #3 to #20.
(http://www.rhb-grischun.ca/F-PIX/FrogAngle.jpg)
The above has been done in CADrail, compared to info available and found correct.
In addition to forgetting everything the G’mint taught me about soldering, I’ve also deep-sixed most of what the Jesuits taught me about math, so your explanations, while welcome and enlightening, are proverbial pearls cast before swine. Ya see, in my high school where most guys were studying to become doctors, laywers, senators and assorted movers and shakers (the school’s prime alum is/was Tim Russert), me and my gang were majoring in Molson’s, Labbatts, and Jennys, as well as Chevies, Olds and Buicks (the Century was a hot ride back then). No regrets, though. I’m still havin’ fun.
Pete Thornton said:
Bart Salmons said:
Well sorta yes…the switch number means that the diverging route moves away from the through route a given distance in a certain amount of distance. Now what those units of measurement are are variable…
Bart,
May I politely disagree with your last statement. The “switch number” is a ratio, just like a gradient, (and could be expressed in % if you wanted!) It is the frog angle expressed as a ratio of number of units along the side to achieve 1 unit of separation. In other words, a #4 has a frog that is 4 units long and 1 unit wide at the end away from the point. Pick your own units of measurement but you will get the same result.
YEAH!!! Ratio was the word I was looking for this morning… and thats eexactly how I thought it worked, just couldn;t get the the info outta my noggin into the fingertips…thanks Pete…thats what I get for trying to be helpful before the first pot of coffee!!!
