Grades

[loisj4912]

In Build a Better Toy Train Layout, John Grams indicates that at some point in time there will be operational problems with grades.  Please elaborate on this topic.  We are about to start benchwork for a 32' x 26' layout and have several grades planned.

[3railguy]

When your grades exceed 2% (1/4"/1 ft), you begin to experience problems such as traction, derailing on short radius curves, pilots shorting on the center rail when the grade transition is too abrupt, and speed control. Just too name a few. Not saying you can't exceed 2%. 4% is the norm for many toy train layouts and what I'm mentioning needs to be considered. Traction tires, superelevated curves, transition curves, and cruise control are some remedies to these problems.

[Buckeye Riveter]

When your grades exceed 2% (1/4"/1 ft), you begin to experience problems such as traction, derailing on short radius curves, pilots shorting on the center rail when the grade transition is too abrupt, and speed control. Just too name a few. Not saying you can't exceed 2%. 4% is the norm for many toy train layouts and what I'm mentioning needs to be considered. Traction tires, super-elevated curves, transition curves, and cruise control are some remedies to these problems.

I would suggest that you not use a super-elevated curve on a grade.  Yes, the actual railroads do have super-elevations on grades, i.e. Horseshoe Curve, but our "models" do not perform the same in super-elevated curves.  The location and magnitude of the center of gravity is not tit for tat between model and actual and that factor is only one of the variables that must be considered.

In fact, I met an HO modeler that was a proponent of a reverse super-elevation when his rolling stock traversed his helix between levels.   He claimed, as the model climbed the grade, that the reverse super-elevation counteracted the tendency for the model train to derail due to string-lining. 

A super-elevation on the level, or near level, will work for a model and it looks pretty cool, too. 

[palallin]

I had to super elevate curves on my grade--especially on the downgrade side--to keep  my engines from derailing  (Gargraves track, 60"+R curve, ca. 3% grade).  Once the super elevation was smoothed, my derailment problems disappeared.

 

YMMV

[3railguy]

"I would suggest that you not use a super-elevated curve on a grade.  Yes, the actual railroads do have super-elevations on grades, i.e. Horseshoe Curve, but our "models" do not perform the same in super-elevated curves."

 Super elevated curves work fine with O gauge. The angle has to suit the curve radius, average speed, weight, etc. If these factors are not worked out, then no, they may not work.

[Fred Bear]

By isolating blocks of track and using pieces of bicycle inner tubes for traction grabbers, I've been able to pull off some pretty darn steep grades. Good juice on the upside, almost nothing on the downside seemed to do it. I guess you just have to experiment. Jake

[csxt30]

Jake : how did you do it ? I like that idea & maybe I can try it !!

Thanks, John

[Fred Bear]

I got the tire idea from someone on here, can 't remember now. Just cut skinny pieces from a bike tire inner tube and glue them on the front drivers on the loco's, mine are 1666's. The train that now runs the grades is actually a Southern Crescent and has traction wheels anyway. Where trains start uphill, I've used 3 insulated pins on each end of the thing, at the start and at the end of the climb, and isolated that block of track so I could put a bit more power on it to make the climb. Once it makes the climb and starts down the other side of the grade, I use another isolated block area and put almost no power on it at all, just enough to keep it moving. Pretty simple, requires a ZW or a couple of other transformers, which must be phased if you are using different transformers, which amounts to turning the plug around in the receptacle if it's sparking! Jake

[Buckeye Riveter]

http://www.morop.org/en/normes/nem114_en.pdf

[lionelsoni]

What Jake is doing with his ZW is dangerous, as I have preached many times before.

[otftch]

Something I do that helps a lot is instead of raising one track over another is to lower one while raising the other.This cuts your grade in half and is very pleasing scenery wise.

                                                                                                                        Ed

[msacco]

What Jake is doing with his ZW is dangerous, as I have preached many times before.

 Yes, this has come up before and I'm one who operates this way with nary a problem. I guess I've been lucky and I hope I remain so.

 

Mike S.

[Fred Bear]

What the heck is dangerous with my ZW?????? I've not heard the preaching, but I've not been on here that long. Tell me, tell me, I want to know! And I'm not being a smart axx about it, I'm serious, Jake

 

[msacco]

http://www.trains.com/trccs/forums/901883/ShowPost.aspx

 

Here's an old post where Bob talks about fault current a bit. I'm doing what you are jake but with the new zw and all bricks have their own breaker so maybe that's okay. My electrical knowledge isn't that strong to know for sure.

 

Mike S.

[lionelsoni]

When the pickup rollers connect the two transformer outputs together, each will try to impose its own voltage on the other and a large current will flow through the pickup rollers from one transformer roller to the other.  The situation is very similar to a simple short circuit. If you connect a 5-volt transformer output across a wire, a heavy current, called a "fault" current, will flow, limited only by the capability of the transformer to supply current. The same kind of fault current flows when two transformer outputs set to differ by 5 volts are connected together.

If the transformers are separate, then each one has a circuit breaker somewhere in series with its output that can react to the fault current and shut it off before the transformer burns up. This doesn't help the arcing at the track; but it does prevent a fire.

If both transformers are really one ZW transformer with two outputs, things can get dangerous. Lionel took a shortcut in their transformer design by using only one circuit breaker per transformer. The fault current that we are talking about unfortunately does not flow through the circuit breaker. So, if a train should stop while bridging the gap, the transformer can just get hotter until it burns up.  I have a couple of examples burned (not by me!) in just that way.

(Thanks, Mike)

[Buckeye Riveter]

You might not want to take my suggestions as to grades,super-elevations, and curves, but I would certainly listen to Bob's posting about the transformer connctions. 

A grade screw up might be an operation aggravation, but an electrical problem can become something serious.

[lionelsoni]

Jake asked me by e-mail:

How do I remedy this problem with the isolated track? I guess it never occured to me that when one roller is on one side and the other is on a different voltage, it's receiving two different voltages simultaneously. Thanks, Jake

A simple, safe way to do it is to use a single transformer to power the entire track, but put a voltage-dropping element in series with the center rail in the places where you want less voltage.  Two possibilities for this are a power resistor, like a Lionel rheostat, or a series string of rectifier-diode pairs, each pair wired back-to-back in parallel.  The transformer would power the uphill part directly, and the level and downhill parts through these elements.  The nice thing about the rectifiers is that the voltage drop doesn't change with the load, as it does with the rheostat.  And you can use a single string, tapped in the middle somewhere for the level sections and at the end for the downhill.  In fact you can tap it in multiple places to handle a variety of conditions on the same track, not just up, down, and level.  Each pair gives you something like a half-volt drop.

You can use individual diodes or, my favorite, bridge-rectifier modules.  Wire the + and - terminals of each bridge together.  These become the middle tap between a string of two diode pairs whose ends are the ~ terminals.  So you get two diode pairs in each bridge-rectifier module.

There are other ways, using relays to switch among voltages; but the rectifier scheme is pretty simple.

[Fred Bear]

Ummm, that's just a tad over my head electrically, but I think I can figure it out. I'm not sure what components I actually need to buy, but again, I'll take this letter to radio shack or the train store locally, and see what they can tell me.

     Thanks for taking the time to write this down, I really do appreciate it, guys like you make this board a very informative place! Respectfully, Jake

[lionelsoni]

Jake, this is the minimum (4-ampere) module that I would recommend:

http://www.radioshack.com/product/index.jsp?productId=2062580&cp=2032058.2032230.2032269&parentPage=family

It's $2.  They have ones with higher current ratings (and higher prices) if you want to be conservative; but a higher voltage rating won't make any difference.

For this one, connect the two outer terminals (+ and -) together.  Then use the inner terminals to chain as many modules as you need into a series string between the transformer and the center rail.  You need only one such string, since you can tap the string anywhere between modules, or in the middle of a module (by connecting to its + - terminals) to get the track voltage you need for each section of track.  Assume that you will lower the voltage by about 1 volt per module (a little more for the first few closest to the transformer, less as you go down the string).

It's hard to know how much detail to put into these posts, since one doesn't know which things the other guy knows.  So just keep asking questions as long as it takes to get the whole thing explained.  I would hate to have someone abandon an inquiry when the goal is so close.