Maximizing Turnout Reliability (Mark G)

WHAT IS AN RELIABLE TURNOUT?

We all have our own personal definition of a good working turnout based on our limited personal experiences, observations of what others do, or asking questions.  But there are so many potential problems with turnouts it is hard to understand the complete problem.  We have gaps of knowledge that varies from person to person.

The person who does not know how to fix a given problem may choose to minimize the problem by operationally doing something unrealistic.  An example would be a turnout that causes engines to electrically stall.  The unrealistic solution is to run the train at unrealistic higher speeds to get through the troublesome turnout. 

When the question does pop up a discussion list, lots of people respond with anecdotal evidence about what one needs to do for a reliable turnout based on their own experience. 

"On my layout all I do is this and it runs fine."  and encourages other to do same. 

Unfortunately there is no discussion in the discussion of what the definition of a good electrically working turnout is.  The bad assumption being made by everyone involved in the discussion is that WE ALL HAVE SEEN THE SAME PROBLEMS and hence WE ALL HAVE THE SAME DEFINITION of what a properly working turnout is. 

The person who has seen the most problems will offer their advice which is not accepted by others because they have not seen the need for it.  This lead to no resolution to the topic and the person asking the question having to CHOOSE what he or she thinks is the best answer and implementing the BEST answer.  This all happens because there is no common turnout performance standard.

Is it not having the engine stall at main line speeds?
Is it not having the engine stall at slowest speeds?
Is it not having the engine's sound system reset?
Is it not having the engine's lights to blink at any speed?
Is it any combination of the above.

To set the standard of what a good working turnout is, one has to understand all the variables that contribute to the problems and what to do about them.  This leads to a BEST PRACTICE answer since the solution here will work for everyone.



UNDERSTANDING THE VARIABLES OF THE PROBLEM

1) What type of engines are you running.  More importantly, how many electrical wheel pickup are they?  Generally the fewer the wheels to more need more reliable pickup.  Two axel engine are best in finding electrical pickup issues.  Stated another way, if you run short wheel base locomotives, this topic should become very important.

2) What are the turnout sizes you are using?   This relates to the length of the unpowered frog and the length of the point rails.   A high number turnout will have a longer unpowered frog and point rails while a low number turnout will have a shorter frog and point rails.  Running a high electrical wheel count locomotive through a low number turnout will generally have less electrical pickup problems.  This is unrelated to the DCC friendly goal of preventing shorts on the back side of the point rails.

3) How flat is the turnout is laid on it roadbed?  Is the point rails in the same horizontal plane as the frog?  Over that same horizontal plane is the any vertical plane shifts between the two rails (AKA Twist)?  Vertical and horizontal twist or kinks play a role in electrical pickup relative to the type of wheel suspension/freedom movement a given locomotive has.    See #4.

4) How rigid it the engine wheel base?  This is model manufacture specific.  If the wheel base is to rigid vertically and horizonatally, the engine may not do a good job of keeping all of the wheels in full electrical contact with the rail in uneven track or turnouts.

5) How often does one clean the track or more specifically the turnout.

6) How often does one clean the wheels the have electrical pickup.  This may includes any contact wipers.

7) Does the locomotive support any form of Keep Alive electrical power reserves?

8) Does the locomotive have flywheels?

9) How fast do you go through the turnout?  Slow or at high speed.  Faster is very forgiving since since the loss of power is very short in terms of time that is starts to look like dirty track.

Hence there are all lot of variables that go into determine electrical pickup success of given locomotive passing through a turnout.  If one does not understand all of the variables, one cannot achieve consistent results.  Given this is happening a lot, this is turn leads to wide variety of public opinions as to action to take to make the turnout reliable.   Everyone is relating what they needed to do so solve their specific set of problems on thier layout which may or may NOT cover all problems one is having on a different layout.


RELIABLE TURNOUT GOALS

A reliable turnout consist of setting high standards in two areas WITH EACH BEING EQUAL IN IMPORTANCE

1) Reliable Mechanical installation.  This deals with everything from preparing the roadbed to the turnout throwing mechanism.

2) Reliable Electrical Operation.  This deals with addressing the electrical weaknesses of the turnouts related to both frog and point rail power issues.


From a pure electrical pickup point of view, the one thing you can say for sure is that a turnout with
1) no electrical dead spots (no insulated gaps)
2) no electrical mechanical connection that are required to carry current (rail joints)
3) no vertical or horizontal twist, bends or kinks
from the point rails past through the frog will be the most reliable electrical turnout.

RELIABLE MECHANICAL

A) Level Roadbed.
B) Track and wheel gauging.


RELIABLE ELECTRICAL

a) Dead Frog.  Focusing on the turnout itself, unlike the point rails which often can have intermittent electrical pickup, a dead frog is a dead frog.  There is no question no electrical current can flow in a dead frog meaning any wheel performing an electrical wheel pickup function will NOT work when it roles over the dead frog.   Stated another way, the remaining wheels performing the same rail electrical pickup will have to support the current.

If the goal is maximum reliable operation with any locomotive one encounters, then it is good practice to power the frogs in an effort to reduce the possibility of a stall due to the remain wheel failure to maintain electrical pickup.


Ignoring the roadbed issues, handbuilding turnouts like those from fast-tracks are a great example of great electrical performance possible. 

http://www.handlaidtrack.com/
 
If you not going to hand build such turnouts, then modifying commercial turnout to be as close to fast-track type of electrical design is what it is all about and what this website talks about in modifying the turnouts.  Maximum electrical reliability for any locomotive.






PART 2 Electrical Turnout reliability can be broken down into 4 categories.

1) Minimizing Short Circuits.
There is no such thing as a turnout specifically for DCC.  However there are lots of electrical issues related to turnouts that have always existed under DC operation but become more noticeable under DCC operation. 
To get a good background of the electrical problems and how to fix them, go here: DCC Friendly Switches/Turnout

2) Maximizing Reliable electrical Pickup.